From waltah at earthlink.net  Mon Nov  7 23:48:00 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Mon, 07 Nov 2011 23:48:00 -0500
Subject: [HBR] The long, SLOW HBR project
In-Reply-To: <CAC25BFA.A65F%waltah@earthlink.net>
Message-ID: <CADE0C96.C154%waltah@earthlink.net>

The BFO temperature compensation seems to be okay: It started with a
downward drift of over 1 kc over an hour or so and after several tries is
now wandering in a 200 cps range around the starting frequency.   Could be a
bad part in there somewhere.  I will swap the tube first, then open up the
(rewound command set BFO) coil and make sure all is solid inside, ending
with making sure I actually did put nail polish strips on both sides of the
coil.   

It may well be just variations in the line voltage.  The BFO is the triode
half of a 19JN8 (pentode is the 1st audio stage) in a modified Colpitts
circuit so voltages matter and the plate voltage isn't stabilized.   It's
not really a problem.

Next I need to finish up the local oscillator stabilization, both for 80M
and 20M -- the two sets of coils I have wound.   Then, I think, 40M coils
would be in order. 

It's in pretty good shape.    Unfortunately the weather is about to force me
to put off a cabinet until next spring -- I do woodwork outdoors and other
fall work (leaves, gutters, cars ...) is keeping me from the important stuff
right now.

Walt
KJ4KV


From waltah at earthlink.net  Tue Nov  8 12:22:13 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Tue, 08 Nov 2011 12:22:13 -0500
Subject: [HBR] HR-10 to HBR project
In-Reply-To: <CACA2A42.AD35%waltah@earthlink.net>
Message-ID: <CADECF75.C228%waltah@earthlink.net>

In an effort to build up an HBR that:

1. Is based on an easily available set of basic parts, and,

2. Could be duplicated

I bought a somewhat tired Heathkit HB-10.   The first round of work was

> ... to relocate the calibrate and antenna trimmer capacitors so there'll be
> room for the antenna and mixer coils.   After that, it's into the front end
> with the wire cutters and nut driver ... "Strip to a bare chassis and lay out
> new holes as follows ..."   However it shouldn't take more than a couple of
> days to get the major chassis work done.
  
The front end has been rearranged, 80M coils wound, the new oscillator tube
added, the mixer circuit/tube changed, and the necessary new panel made and
installed: All of that went pretty well, though I may need to add one turn
to the mixer coil to get perfect tracking.   I did do these two coils
without trimmers and that seems to work okay.

I then started at the back end.  Things were more complicated there: To even
start the testing I had to replace the audio section because the 6EB8 audio
tube (two sections -- triode-pentode) socket was so loose that you couldn't
get all pins to make contact for more than a few minutes.   Rather than
clear out the whole area to allow building the new circuit I redid the
original circuit using new parts and a new socket.

Having shown that signals would go all the way through the set, I tackled
the other changes in that area: moving the BFO and giving it a tube
of its own, changing the detector circuit, and rewiring that part of the
panel using the new toggle switches.

Unfortunately I recycled the detector socket and got some of the same
trouble as with the audio tube so I now have to rebuild my own work starting
with a new socket.  If a tube socket in one of these sets doesn't grip
firmly it ought to be tossed right at the start.

The BFO -- now a 6BH6 --  was relocated over by the detector. With the BFO
tuning cap moved one hole to the left (on the panel) all the connections are
shorter and the tangle (both electrical and mechanical) of IF and BFO has
been eliminated.  This has to be better than using the triode half of the
2nd IF stage as a BFO and I'm hoping it will get me most of the way to being
able to use AGC and BFO at the same time.

The original HR-10 design, however, has NO decoupling of various stages:
Everything is on the same filament buss and most of the tube plate/screen
voltages come straight off one B+ line just as in an All American Five BC
design.  So it's not as simple as just replacing stages: The interaction
between stages has to be fixed at the same time.

The one-step-at-a-time approach may make sense for developing this project
but my guess is that if it gets to be possible to duplicate it, that should
be done from a bare chassis.  (Maybe just leave the power supply.)   Between
Heathkit compromises (like cheap sockets), worn out or failed parts, and
original builder mistakes and workmanship issues, there's a lot of waste
motion in a rolling rebuild.

It will be important to get the foundation receiver working first since
that's the easy way to smoke out parts and other problems.  So far I've
found one dead crystal, one rosin joint, one unsoldered joint, two bad
sockets, and a worn-out volume control.   Building these into a new set
(even as part of one step at a time with testing) would not promote builder
mental health. 

(The second set I had to buy to get a good pair of crystals came with a
near-frozen bandswitch and I've seen others complain of the same. Since that
part of the set is unneeded, that's not a problem.)

The current status is that all stages sort of work, either in the original
or as rebuilt but partly because I don't have enough AGC voltage and partly
for other reasons, it sounds terrible.   After I replace the detector socket
I'll start at the audio section and work backward just as with any new
receiver.  

Tube lineup:

6EH7 -- RF 
6BH6 -- 100 kcs calibrator
6BH6 -- LO (ECO) 
12AT7 -- Mixer 
6LM8 -- 1st IF & AGC bias rectifier
6LM8 -- 2nd IF & AGC detector
6BH6 -- BFO (ECO) 
12AX7 -- detector 
6LF8 -- 1st & 2nd audio
6X4 -- B+ rectifier

A gain of three tubes (to a total of ten) plus comprehensive changes to
both tubes and circuits.   The 6LM8's are one of just a couple of
pentode-triodes with a semi-remote cutoff characteristic so I'm looking
forward to seeing how they work out.

I think I've made all the parts of this work before but of course a new
chassis and 'details' mean that it'll take time to get them working
here.  

Pictures shortly.

Walt 
KJ4KV






From ke9xq at charter.net  Tue Nov  8 13:22:38 2011
From: ke9xq at charter.net (William Wood)
Date: Tue, 8 Nov 2011 12:22:38 -0600
Subject: [HBR] HR-10 to HBR project
In-Reply-To: <CADECF75.C228%waltah@earthlink.net>
References: <CADECF75.C228%waltah@earthlink.net>
Message-ID: <6900FBA2-DDE7-47C0-9E5F-942862D5298A@charter.net>

Thanks Walt
    Been looking and looking for parts, but only have a
small portion of what I need so far, maybe I too should
look for a receiver that might have most all the parts.
Thought that last E-bay HBR13 was mine for the parts,
but had a hard time justifying the $250 : )
    Not too sure of my skills and knowledge, so I think I
need to stick fairly close to the original schematic etc.
for the HBR 13C that has been my goal.  Not gone to
many ham fests this last couple of years, maybe I need
to change that approach : )
Thanks for everyone's updates like Walt's here,  lets a
guy know he's not alone and crazy : )
73 folks
Bill






On Nov 8, 2011, at 11:22 AM, Walt Hutchens wrote:

> In an effort to build up an HBR that:
>
> 1. Is based on an easily available set of basic parts, and,
>
> 2. Could be duplicated
>
> I bought a somewhat tired Heathkit HB-10.   The first round of work  
> was
>
>> ... to relocate the calibrate and antenna trimmer capacitors so  
>> there'll be
>> room for the antenna and mixer coils.   After that, it's into the  
>> front end
>> with the wire cutters and nut driver ... "Strip to a bare chassis  
>> and lay out
>> new holes as follows ..."   However it shouldn't take more than a  
>> couple of
>> days to get the major chassis work done.
>
> The front end has been rearranged, 80M coils wound, the new  
> oscillator tube
> added, the mixer circuit/tube changed, and the necessary new panel  
> made and
> installed: All of that went pretty well, though I may need to add  
> one turn
> to the mixer coil to get perfect tracking.   I did do these two coils
> without trimmers and that seems to work okay.
>
> I then started at the back end.  Things were more complicated  
> there: To even
> start the testing I had to replace the audio section because the  
> 6EB8 audio
> tube (two sections -- triode-pentode) socket was so loose that you  
> couldn't
> get all pins to make contact for more than a few minutes.   Rather  
> than
> clear out the whole area to allow building the new circuit I redid the
> original circuit using new parts and a new socket.
>
> Having shown that signals would go all the way through the set, I  
> tackled
> the other changes in that area: moving the BFO and giving it a tube
> of its own, changing the detector circuit, and rewiring that part  
> of the
> panel using the new toggle switches.
>
> Unfortunately I recycled the detector socket and got some of the same
> trouble as with the audio tube so I now have to rebuild my own work  
> starting
> with a new socket.  If a tube socket in one of these sets doesn't grip
> firmly it ought to be tossed right at the start.
>
> The BFO -- now a 6BH6 --  was relocated over by the detector. With  
> the BFO
> tuning cap moved one hole to the left (on the panel) all the  
> connections are
> shorter and the tangle (both electrical and mechanical) of IF and  
> BFO has
> been eliminated.  This has to be better than using the triode half  
> of the
> 2nd IF stage as a BFO and I'm hoping it will get me most of the way  
> to being
> able to use AGC and BFO at the same time.
>
> The original HR-10 design, however, has NO decoupling of various  
> stages:
> Everything is on the same filament buss and most of the tube plate/ 
> screen
> voltages come straight off one B+ line just as in an All American  
> Five BC
> design.  So it's not as simple as just replacing stages: The  
> interaction
> between stages has to be fixed at the same time.
>
> The one-step-at-a-time approach may make sense for developing this  
> project
> but my guess is that if it gets to be possible to duplicate it,  
> that should
> be done from a bare chassis.  (Maybe just leave the power  
> supply.)   Between
> Heathkit compromises (like cheap sockets), worn out or failed  
> parts, and
> original builder mistakes and workmanship issues, there's a lot of  
> waste
> motion in a rolling rebuild.
>
> It will be important to get the foundation receiver working first  
> since
> that's the easy way to smoke out parts and other problems.  So far  
> I've
> found one dead crystal, one rosin joint, one unsoldered joint, two bad
> sockets, and a worn-out volume control.   Building these into a new  
> set
> (even as part of one step at a time with testing) would not promote  
> builder
> mental health.
>
> (The second set I had to buy to get a good pair of crystals came  
> with a
> near-frozen bandswitch and I've seen others complain of the same.  
> Since that
> part of the set is unneeded, that's not a problem.)
>
> The current status is that all stages sort of work, either in the  
> original
> or as rebuilt but partly because I don't have enough AGC voltage  
> and partly
> for other reasons, it sounds terrible.   After I replace the  
> detector socket
> I'll start at the audio section and work backward just as with any new
> receiver.
>
> Tube lineup:
>
> 6EH7 -- RF
> 6BH6 -- 100 kcs calibrator
> 6BH6 -- LO (ECO)
> 12AT7 -- Mixer
> 6LM8 -- 1st IF & AGC bias rectifier
> 6LM8 -- 2nd IF & AGC detector
> 6BH6 -- BFO (ECO)
> 12AX7 -- detector
> 6LF8 -- 1st & 2nd audio
> 6X4 -- B+ rectifier
>
> A gain of three tubes (to a total of ten) plus comprehensive  
> changes to
> both tubes and circuits.   The 6LM8's are one of just a couple of
> pentode-triodes with a semi-remote cutoff characteristic so I'm  
> looking
> forward to seeing how they work out.
>
> I think I've made all the parts of this work before but of course a  
> new
> chassis and 'details' mean that it'll take time to get them working
> here.
>
> Pictures shortly.
>
> Walt
> KJ4KV
>
>
>
>
>
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

If the grass is greener on the
other side of the fence, then
maybe you ain't watering
your own lawn...

Favorite Yahoo Groups...

http://groups.yahoo.com/group/OTR_and_Music/

http://groups.yahoo.com/group/Radio_Library/

And check out Tennessee Bill's site at:

http://otrshareandtrade.com/in.php?ID=12
and his personal site at:

http://TennesseeBillsOTR.com

Don't forget

http://www.archive.org/index.php

and one or two that maybe don't
want to be listed : )
And two dozen or more others
I won't tell you about unless you ask.


From ke9xq at charter.net  Tue Nov  8 13:27:49 2011
From: ke9xq at charter.net (William Wood)
Date: Tue, 8 Nov 2011 12:27:49 -0600
Subject: [HBR] CD question 'again' : )
Message-ID: <EE9388AC-FC1D-4B2E-9F06-E095EDF98B75@charter.net>

Greetings HBRers
    I know I asked this before, but my procrastination
caused me to create an opportunity to lose the info
so would love to get this all over again.  This time
I'll send off for the disk right away...   : )   I would like
that other $10 disk one of you told us about.
I already have and love the other one.
The one be J F Helms W6HHT

Can I talk one of you fine gents to sending me that
info again???
Thanks
73
Bill




From ke9xq at charter.net  Tue Nov  8 13:35:54 2011
From: ke9xq at charter.net (William Wood)
Date: Tue, 8 Nov 2011 12:35:54 -0600
Subject: [HBR] One more quick question
Message-ID: <F9C5AB07-5712-49B1-AF9E-7139EDFF3863@charter.net>

IF you were to look for a parts receiver for your
HBR project, which one or ones would you be
looking for???

I'm sure there are a few out there we maybe should
NOT part out : )  But, which one/s would you be out
there looking for???  IF I don' start looking better,
I'll still be looking haphazardly for the next few years : )

73
Bill

From waltah at earthlink.net  Tue Nov  8 15:24:45 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Tue, 08 Nov 2011 15:24:45 -0500
Subject: [HBR] One more quick question
In-Reply-To: <F9C5AB07-5712-49B1-AF9E-7139EDFF3863@charter.net>
Message-ID: <CADEFA3D.C287%waltah@earthlink.net>

Bill wondered:

> I'm sure there are a few out there we maybe should NOT part out : )  But,
> which one/s would you be out there looking for???  IF I don' start looking
> better, I'll still be looking haphazardly for the next few years : )

You know what my answer's going to be, right?   But there's a longer story
...

I think the problem is that most good receivers -- either a good design to
start with OR a so-so design but excellent condition -- are uncommon to rare
and tend to sell for high prices.   Pretty much anything that looks like a
W6TC  HBR and has all coils for one band is going to be in that category --
$200-up, I'd say.   Of course you wouldn't want to part out a really nice
one.

Other receivers ... well, there just weren't many that have good homebrew
potential.   I've worked on FT-101 redos: these are transistorized-to-hollow
state conversions and (although I didn't do it yet) I think they could be
excellent.  BUT this is a bandswitching double conversion project: The set
doesn't have either the proper tuning cap or dial scale for an HBR approach.

Other relatively popular homebrew multiband sets ... gee there I can't think
of ANY of those.   Really ...

I got the dial and tuning cap for the 'Long SLOW ...' project from a
parts-only G3RKK designed set (appears in one or two of the RSGB
Communications Handbooks) but that's the only one of those sets I've ever
seen and nobody knew what it was until I got it here and was able to ID it
from the book.   

There's the G2DAF homebrew design -- a few thousand are said to have been
built -- but that's a UK set, most survivors probably are still there, and
it's another crystal converter/tunable 2nd IF double conversion set, like
the FT-101.   I've never seen one on eBay.

There are plenty of home use 'shortwave' receivers but they're general
coverage sets with el cheapo dials and the wrong tuning capacitor.   You
could perhaps prune the cap to something that would work, but it's the
cheapest possible cap and you've still got a crummy dial.

Lafayette and others made some ham band only vacuum tube sets. One of these
might be a possibility but I have no clue what to look for.

A vacuum tube FM receiver with a slide rule dial and three-gang tuning cap
(some were two gang) would have a cap and dial mechanism, also perhaps the
power supply, though the later models were series string.   However you
wouldn't get usable IFTs ... you'd have to search out either a crystal
filter and compatible IFTs or find the parts for the real W6TC approach of
double conversion. 

The reason I landed on the HR-10 as the foundation for my current effort is
that many thousands were made, they're single conversion (to a high IF)
bandswitching ham-band only designs but they were not great sets to start
with so they're not highly prized today.     If you set up your bidding
properly you'll get one on your front porch from eBay in less than a month
for under $100 total and with any luck all the essential parts will be
there.  

These sets have:

1. A decent dial mechanism with an already calibrated dial.   This setup is
infinitely superior to the National MCN (etc.) 5:1 dials used on the early
'authentic' W6TC sets -- you absolutely can tune in an SSB signal.  It's not
quite the equal of an Eddystone 898 but the whole set will cost you about
what that dial would cost and the Eddystone layout and metalwork is pretty
much the hardest such work I've done.

(The Eddystone dial has anti-backlash gear drive for the tuning cap -- no
string drive is going to fully equal that.)

My second HR-10 came with the plastic dial face glued to the front panel,
probably as a solution to the warping problem.  I'm guessing it can be
salvaged but there would be some extra work.

2. A good tuning cap.

3. A crystal filter -- although the first set I got came with a bad crystal,
forcing me to pay another most of $100 for a second set.

4. A full set of IFTs and matching BFO coil and BFO tuning cap.

5. An S-meter and scale.

6. A usable 11" x 13" chassis -- I didn't have to do any cutout/new plate
work at all and this is a good amount of room for this project.

7. A transformer and power supply stuff.  Even the 6X4 and filter cap are
okay in my two sets.

8, Miscellaneous parts -- An output transformer, panel controls (though the
volume control is probably shot due to Heath having put the ON/OFF switch
there), a fuse holder, two 21 mmf air variables for dial calibration and
antenna coil peaking, knobs (my second set came with a bunch of oddball
ones), most of the nuts and bolts you'll need, and some smaller parts,
including some silver mica and temp compensating caps if you cut up the
(cheap!) bandswitch to get them out.

If you get a set with items 1-4 in working order, you are good to go --
that's all the stuff you could otherwise spend a couple years hunting down.
(Remember that because there were multiple approaches to W6TC HBRs not all
the HBR parts out there are compatible.)  Add coil forms (but you can make
those) sockets for the same,  some tube sockets, the usual batch of small
parts, wire, a new cabinet and probably a new front panel and you have the
whole kit.   

>From what I know now, the HR-10 is the way to go.  Having done the basics,
I'm pretty confident that a decent HBR design can be built in that chassis;
I just haven't done it yet!   And anyway the first step after buying one is
to get it working as-bought because you want to be sure that all the key
parts are in good order before starting your own project.

If in the end you don't do the HR-10 to HBR conversion you can almost
certainly dispose of a 'seller refurbished' unit for more than you paid for
a 'used -- not working' one.   :-)

Walt 
KJ4KV



From ke9xq at charter.net  Tue Nov  8 18:25:27 2011
From: ke9xq at charter.net (William Wood)
Date: Tue, 8 Nov 2011 17:25:27 -0600
Subject: [HBR] HBR 13C progress
Message-ID: <897D26B2-8BA1-46A1-9B47-D9D8444628F8@charter.net>

Thanks Walt
    So far I have junked out several receivers, mainly
because they were worth more in the parts box then
on the shelf : )  I did get the Eddy-stone dial from one
from our group here, and the same with the three gang
tuning cap.  A bunch of caps that need checking, and
probably most of the resistors but did not even try to
catalog any as of yet, because I'm still looking for some
of the harder to find parts.
    I did find a decent cabinet and bent up two chassis'
one of which I like, the other to be saved for a different
project potentially 20 years from now : )  The faceplate
is cut to dimensions, but no holes drilled yet in case I
need to re-position things with the final parts being used.
    So, while I am making progress, it is so slow it seems
like a standstill : )  I did find some nice older IFs but they
are the larger style probably used with octal tubes : )  Not
sure of the frequencies yet, have a shed to replace etc
before I check them out, but don't think I want to use them
in this project...
73
Bill

From ke9xq at charter.net  Wed Nov  9 09:39:46 2011
From: ke9xq at charter.net (William Wood)
Date: Wed, 9 Nov 2011 08:39:46 -0600
Subject: [HBR] WTB  CD of the HBR series
Message-ID: <A2BCBEAA-5FBD-472F-BFA5-EED6159AE68C@charter.net>

Greetings O T ers
    I'm asking again, because the previous request
might have been missed by the right person.  : )
I have the Jay Helms W6HHT CD and love it, but
was told there is another collection on the HBR
series and would love to have that one too.  If
memory is correct, it was $10.  I looked on the
internet and found a lot of related goodies, but
either did not find the offer, or missed it while
perusing the sites.  It might have stared me in
the face and I did not recognize it : )
    Would you please send me that info???
    While I'm here, has anyone collected all that info
and put it on a disk?  I found several reflectors that
mentioned one of the HBRs and dealt with it briefly
then went on to other subjects.  It would be nice to
have all those tidbits in one location, because
unless you hunt, you might miss some good ideas...
Thanks guys
73
Bill






From wnichelson at gmail.com  Wed Nov  9 11:14:55 2011
From: wnichelson at gmail.com (William Nichelson)
Date: Wed, 9 Nov 2011 11:14:55 -0500
Subject: [HBR] WTB CD of the HBR series
In-Reply-To: <A2BCBEAA-5FBD-472F-BFA5-EED6159AE68C@charter.net>
References: <A2BCBEAA-5FBD-472F-BFA5-EED6159AE68C@charter.net>
Message-ID: <CAMuFHikZFhjNFke03qTvNLcD5ZL7WTwFMZKd-UucGtRttZjF1Q@mail.gmail.com>

Bill, do you have the DVD *HBR RECEIVER DATA AND MORE?*  It was done by
K5BCQ in July 2002.  He did charge $10 for it and it had to be a labor of
love.  Loads of history and information.
73
Bill W3KOC




On Wed, Nov 9, 2011 at 9:39 AM, William Wood <ke9xq at charter.net> wrote:

> Greetings O T ers
>    I'm asking again, because the previous request
> might have been missed by the right person.  : )
> I have the Jay Helms W6HHT CD and love it, but
> was told there is another collection on the HBR
> series and would love to have that one too.  If
> memory is correct, it was $10.  I looked on the
> internet and found a lot of related goodies, but
> either did not find the offer, or missed it while
> perusing the sites.  It might have stared me in
> the face and I did not recognize it : )
>    Would you please send me that info???
>    While I'm here, has anyone collected all that info
> and put it on a disk?  I found several reflectors that
> mentioned one of the HBRs and dealt with it briefly
> then went on to other subjects.  It would be nice to
> have all those tidbits in one location, because
> unless you hunt, you might miss some good ideas...
> Thanks guys
> 73
> Bill
>
>
>
>
>
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

From windy10605 at juno.com  Wed Nov  9 11:37:33 2011
From: windy10605 at juno.com (Kees & Sandy)
Date: Wed, 9 Nov 2011 16:37:33 GMT
Subject: [HBR] WTB  CD of the HBR series
Message-ID: <20111109.103733.6840.5@webmail53.dca.untd.com>

That would be me. Yes, I can still make you a copy and yes they are still $10 postpaid. I'm good in QRZ.
73 Kees K5BCQ

---------- Original Message ----------
From: William Wood <ke9xq at charter.net>
To: HBR Receiver List <hbr at mailman.qth.net>
Subject: [HBR] WTB  CD of the HBR series
Date: Wed, 9 Nov 2011 08:39:46 -0600

Greetings O T ers
   I'm asking again, because the previous request
might have been missed by the right person.  : )
I have the Jay Helms W6HHT CD and love it, but
was told there is another collection on the HBR
series and would love to have that one too.  If
memory is correct, it was $10.  I looked on the
internet and found a lot of related goodies, but
either did not find the offer, or missed it while
perusing the sites.  It might have stared me in
the face and I did not recognize it : )
   Would you please send me that info???
   While I'm here, has anyone collected all that info
and put it on a disk?  I found several reflectors that
mentioned one of the HBRs and dealt with it briefly
then went on to other subjects.  It would be nice to
have all those tidbits in one location, because
unless you hunt, you might miss some good ideas...
Thanks guys
73
Bill





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From ke9xq at charter.net  Wed Nov  9 15:36:43 2011
From: ke9xq at charter.net (William Wood)
Date: Wed, 9 Nov 2011 14:36:43 -0600
Subject: [HBR] CDs
Message-ID: <2C8A58F5-85EA-42A9-A202-742875097B34@charter.net>

Thanks William
    Kees
    I just sent the $10
I'm also good at QRZed dot com
Thanks ahead of time : )
73
Bill


From waltah at earthlink.net  Wed Nov  9 19:13:47 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Wed, 09 Nov 2011 19:13:47 -0500
Subject: [HBR] One more quick question
In-Reply-To: <CADEFA3D.C287%waltah@earthlink.net>
Message-ID: <CAE06A76.C427%waltah@earthlink.net>

> The reason I landed on the HR-10 as the foundation for my current effort is
> that many thousands were made, they're single conversion (to a high IF)
> bandswitching ham-band only designs but they were not great sets to start
> with so they're not highly prized today.     If you set up your bidding
> properly you'll get one on your front porch from eBay in less than a month
> for under $100 total and with any luck all the essential parts will be
> there.  
> 
> These sets have: 

I want to add one item to that list:

9.  The HR-10 was designed for construction by ordinary not-too-skilled
people -- even, perhaps, complete beginners.  That means there's more than
the usual amount of working room per stage and 'tricky' mechanical work has
been largely avoided.   In addition, practically all assembly is with
machine screws and nuts -- no rivets or spot welds to grind or drill out.

In other words a kit radio is a good foundation for a home brew radio!

Walt 
KJ4KV



From wrcromwell at gmail.com  Wed Nov  9 19:32:25 2011
From: wrcromwell at gmail.com (Bill Cromwell)
Date: Wed, 09 Nov 2011 19:32:25 -0500
Subject: [HBR] One more quick question - HR10
In-Reply-To: <CAE06A76.C427%waltah@earthlink.net>
References: <CAE06A76.C427%waltah@earthlink.net>
Message-ID: <1320885145.2173.18.camel@lancelot>

Okay Walt,

I'm convinced. I am going to use my HR-10 (not)B as the foundation for
my HBR. I am going to remove the xtal filter and do the dual conversion
with the 85 kc cans from the BC-453 type receiver (I have the cans). I
will be looking for another set of IF cans for the HR-10 to use with the
xtal filter and then I will be able to build *two* HBRs! The second will
go on the stripped down chassis I have from a Knight Star Roamer. 

My HR-10 does work. Yes I'm going to ruin it's resale value. We can then
layoff one division of U.S. armored cavalry and a legion of Roman
soldiers from protecting it. I offered it for sale (cheeep) several
times and no takers. Maybe that's why there aren't and more Roman
Legions. Or maybe they got used on search and destroy missions for Star
Roamers. <evil grin>

It may as well become something useful. I still think I am going to
export the power supply and audio output to a black box under the desk.

I bet I can take longer building mine than you are taking with yours!

73,

Bill  KU8H


From waltah at earthlink.net  Thu Nov 10 12:39:27 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Thu, 10 Nov 2011 12:39:27 -0500
Subject: [HBR] One more quick question - HR10
In-Reply-To: <1320885145.2173.18.camel@lancelot>
Message-ID: <CAE1767F.C502%waltah@earthlink.net>

Bill Cromwell said:

> I am going to use my HR-10 (not)B as the foundation for
> my HBR. I am going to remove the xtal filter and do the dual conversion
> with the 85 kc cans from the BC-453 type receiver (I have the cans). I
> will be looking for another set of IF cans for the HR-10 to use with the
> xtal filter and then I will be able to build *two* HBRs! The second will
> go on the stripped down chassis I have from a Knight Star Roamer.

I probably should not even offer suggestions about the direction of another
HBR-er's project:  I'm the guy who just spent the last five years or so
learning how to build a decent series string ham receiver, right?   (And for
my next trick, maybe I'll do something REALLY useful, like sketch the
circuit diagram on the head of a pin?)

But ... the great advantage of the HR-10 is that it is close to all the
basic parts for an HBR project, all compatible, and all there in one package
without a bunch of gritty metalwork and force-fitting.   The scheme above
keeps the dial and tuning cap but pretty much recreates all the other hard
parts of HBR construction.   In particular there's going to be a space issue
with those command set IF cans:  The usual plan uses four of them, plus two
IF stages and a second mixer so that's three tubes and four IFTs to be added
with at most two tubes, two (miniature) IFTs, and the crystals subtracted.
I don't have the receiver in front of me now, but I'm thinking 'maybe ...
but it'll likely need a cutout and plate so you can squeeze things
properly.'

(I've no idea what the difference between an HR-10 and a 10B is, but it is
slight.)

Resale value of an HR-10?   As a complete unbuilt kit, $500-up.   (Yeah
really ... personally I don't get it, but people collect the darndest
things.)   As a good original non-smoker working radio, perfect exterior,
maybe $100-$125?  'I don't know what this is, it lights up, probably just
needs a couple of tubes,' with non-original knobs $50 +/- a bit.   Those are
eBay prices; at a hamfest they'd be less.

(I expect we all know how to translate 'probably just needs a couple of
tubes.'  The phrase means 'you are going to spend a week finding all the bad
connections, frozen-solid controls, and other oddball problems in this
sucker ...')

These are not your father's Collins 51S for resale value.

The Knight Star Roamer is the next step down from the HR-10 and at $37.35,
just about half the price.   It's a contemporary, but only four tubes
(6BE6-6HR6-12AX7-6AK6 plus a selenium rectifier and solid state diodes in
the detector/AVC jobs) and pretty much along the lines of the S-38 and
similar sets.   There's an overview, here:

http://www.ohio.edu/people/postr/bapix/StarRmr.htm

I'd say this set was a better match to its intended market than the HR-10
was to its.   It's a very limited set, but at the price, probably okay for
the beginning SWL who might someday get interested in a ham license.
There's no sign of a BFO, so by 1970 it would have been obsolete.

I haven't looked at a diagram but with that description it'll have a
two-gang capacitor (not suited to an HBR) and no sharp filter in the IF.
Also, that transformer probably will NOT handle 6-9 tubes -- it has perhaps
1/3 the filament power and half the plate power needed.   As you imply, a
separate power supply would be required.

Thinking of the Star Roamer as project foundation might better start down a
notch from the HBRs.   Maybe something along the lines of the Simple-X
Super?  With a very high Q antenna coil (and very loose coupling to the
antenna) you might get an interesting set.   If using a separate power
supply then perhaps a beam mixer (with separate oscillator) and mechanical
filter?   That would be a very poor man's Miser's Dream.   Might not have
enough gain for a mechanical filter though.

I'd say do the HBR first.  That ground has been well plowed; lots of people
know what works and what doesn't.  My pipe dreams (in the previous
paragraph) might be no more than that.

Walt 
KJ4KV



From radioconnection at gmail.com  Thu Nov 10 13:06:08 2011
From: radioconnection at gmail.com (Peter Bertini)
Date: Thu, 10 Nov 2011 13:06:08 -0500
Subject: [HBR] One more quick question - HR10
In-Reply-To: <CAE1767F.C502%waltah@earthlink.net>
References: <1320885145.2173.18.camel@lancelot>
	<CAE1767F.C502%waltah@earthlink.net>
Message-ID: <CA+uDY2T8KLp_n6iKNo4-3377fvOhnAnKEiMOccNB6x3vRwyuQA@mail.gmail.com>

Since the HR-10 frequency doubles the LO on the upper bands (one reason it
sucked so much)  would it possible to preserve the dial calibration when
using
plug in coils?

Pete

On Thu, Nov 10, 2011 at 12:39 PM, Walt Hutchens <waltah at earthlink.net>wrote:

> Bill Cromwell said:
>
> > I am going to use my HR-10 (not)B as the foundation for
> > my HBR. I am going to remove the xtal filter and do the dual conversion
> > with the 85 kc cans from the BC-453 type receiver (I have the cans). I
> > will be looking for another set of IF cans for the HR-10 to use with the
> > xtal filter and then I will be able to build *two* HBRs! The second will
> > go on the stripped down chassis I have from a Knight Star Roamer.
>
> I probably should not even offer suggestions about the direction of another
> HBR-er's project:  I'm the guy who just spent the last five years or so
> learning how to build a decent series string ham receiver, right?   (And
> for
> my next trick, maybe I'll do something REALLY useful, like sketch the
> circuit diagram on the head of a pin?)
>
> But ... the great advantage of the HR-10 is that it is close to all the
> basic parts for an HBR project, all compatible, and all there in one
> package
> without a bunch of gritty metalwork and force-fitting.   The scheme above
> keeps the dial and tuning cap but pretty much recreates all the other hard
> parts of HBR construction.   In particular there's going to be a space
> issue
> with those command set IF cans:  The usual plan uses four of them, plus two
> IF stages and a second mixer so that's three tubes and four IFTs to be
> added
> with at most two tubes, two (miniature) IFTs, and the crystals subtracted.
> I don't have the receiver in front of me now, but I'm thinking 'maybe ...
> but it'll likely need a cutout and plate so you can squeeze things
> properly.'
>
> (I've no idea what the difference between an HR-10 and a 10B is, but it is
> slight.)
>
> Resale value of an HR-10?   As a complete unbuilt kit, $500-up.   (Yeah
> really ... personally I don't get it, but people collect the darndest
> things.)   As a good original non-smoker working radio, perfect exterior,
> maybe $100-$125?  'I don't know what this is, it lights up, probably just
> needs a couple of tubes,' with non-original knobs $50 +/- a bit.   Those
> are
> eBay prices; at a hamfest they'd be less.
>
> (I expect we all know how to translate 'probably just needs a couple of
> tubes.'  The phrase means 'you are going to spend a week finding all the
> bad
> connections, frozen-solid controls, and other oddball problems in this
> sucker ...')
>
> These are not your father's Collins 51S for resale value.
>
> The Knight Star Roamer is the next step down from the HR-10 and at $37.35,
> just about half the price.   It's a contemporary, but only four tubes
> (6BE6-6HR6-12AX7-6AK6 plus a selenium rectifier and solid state diodes in
> the detector/AVC jobs) and pretty much along the lines of the S-38 and
> similar sets.   There's an overview, here:
>
> http://www.ohio.edu/people/postr/bapix/StarRmr.htm
>
> I'd say this set was a better match to its intended market than the HR-10
> was to its.   It's a very limited set, but at the price, probably okay for
> the beginning SWL who might someday get interested in a ham license.
> There's no sign of a BFO, so by 1970 it would have been obsolete.
>
> I haven't looked at a diagram but with that description it'll have a
> two-gang capacitor (not suited to an HBR) and no sharp filter in the IF.
> Also, that transformer probably will NOT handle 6-9 tubes -- it has perhaps
> 1/3 the filament power and half the plate power needed.   As you imply, a
> separate power supply would be required.
>
> Thinking of the Star Roamer as project foundation might better start down a
> notch from the HBRs.   Maybe something along the lines of the Simple-X
> Super?  With a very high Q antenna coil (and very loose coupling to the
> antenna) you might get an interesting set.   If using a separate power
> supply then perhaps a beam mixer (with separate oscillator) and mechanical
> filter?   That would be a very poor man's Miser's Dream.   Might not have
> enough gain for a mechanical filter though.
>
> I'd say do the HBR first.  That ground has been well plowed; lots of people
> know what works and what doesn't.  My pipe dreams (in the previous
> paragraph) might be no more than that.
>
> Walt
> KJ4KV
>
>
> ______________________________________________________________
> HBR mailing list
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> Help: http://mailman.qth.net/mmfaq.htm
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>
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> Please help support this email list: http://www.qsl.net/donate.html
>

From waltah at earthlink.net  Thu Nov 10 15:01:49 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Thu, 10 Nov 2011 15:01:49 -0500
Subject: [HBR] One more quick question - HR10
In-Reply-To: <CA+uDY2T8KLp_n6iKNo4-3377fvOhnAnKEiMOccNB6x3vRwyuQA@mail.gmail.com>
Message-ID: <CAE1958A.C51A%waltah@earthlink.net>

Peter wondered:

> Since the HR-10 frequency doubles the LO on the upper bands (one reason it
> sucked so much)  would it possible to preserve the dial calibration when
> using plug in coils?

As I recall the HR-10 doubles on 15-10 but the HBRs do it on 20-15-10 so
there is some difference in the pattern.

When you think about how to tune a certain range -- say 3.5-4.0 Mcs or
21.0-21.150 Mcs (plus or minus the IF), the main thing that matters is the
capacitors involved: Specifically the fixed caps and the variable -- plus of
course the shape of the plates on the variable.   But using the variable
that came with the dial assembly you shouldn't have an issue with plate
shape.   

Roughly speaking, the coil is just 'whatever it takes to get the right
tuning range with the capacitors you have.'   So tuning 22.681-22.831 Mcs
(oscillator tuning range with 1681 kcs IF) is the same (requires the same
capacitors) as half that -- 11.3405-11.4155 Mcs: the COILS give you the
different ranges.  

However 'roughly' isn't the whole story.   The distributed capacitance in
the coil and elsewhere in the circuit IS NOT equivalent to a different fixed
cap across the coil (hence correctable by changing the fixed cap in your
design).   It is 'distributed' -- here and there inside the coil and around
the circuit.   Furthermore, things like transit time (electrons in the tube
...) affect the frequency and do so in different ways at different
frequencies.   

Additionally, the HR-10 used a triode oscillator while my HBR-ization of
that uses a pentode ECO: That introduces yet another frequency-dependent
variation.   (Using the exact same oscillator circuit might have saved some
bathwater -- slightly better dial tracking -- but tossed the baby -- better
oscillator isolation, hence, stability.   At least, that is my thinking!)

So an oscillator for half the frequency isn't the same fixed and variable
caps with 4x the inductance as the simple theory would say.   And that means
that it won't have precisely the same tuning curve, either.

HOWEVER ... the differences aren't large.   By tweaking both the coil and
fixed capacitance away from what the simple theory says the errors can be
perfectly adjusted out at the end points and the narrower the band, the less
error there'll be at mid band.   And of course 80M is the widest band,
percentagewise.   All the higher bands are quite a bit narrower:  10M seems
wide -- 2 Mcs -- but it's at 8x the frequency so it's only half the width of
80M.   

With the coils I've made (80 and 20 on the Long SLOW set and 80 for the
HR-10 to HBR) I have had NO tracking trouble caused by the factors above.

For the Long SLOW project I tried both half frequency and full frequency 20M
oscillator coils: I had no trouble getting both to track the existing dial
calibration on the Eddystone dial that came with the tuning cap I am using.

The HR-10 dial isn't quite the equal of the Eddystone unit: The scale is
shorter and string drive isn't equal to anti-backlash gear drive.  I think
errors of 2 kcs or less are probably what you can achieve on the lower
bands; somewhat more on the high ones.  (These numbers would be double those
for an Eddystone unit.)  In addition the HR-10 has a CAL control that might
tune 50kcs on 80:  These sets are plenty good for general ham use (and way,
WAY better than  you could do with a National MCN/ACN type dial) but they
simply aren't frequency meters.

(I think it would be worth adding a 6:1 vernier drive to the CAL control:
Not only would that make this control easier to set precisely but it would
tend to hold it in place.   I will look at this change.)

Bottom line:  I don't think tracking a new plug-in-coil oscillator to the
dial calibration on an HR-10 will be a problem.  The errors are likely to be
in the 'noise,' that is, not easy to separate from the other small errors
coming from using a dial, drive, and circuit of this type.

Walt
KJ4KV




From wrcromwell at gmail.com  Thu Nov 10 18:55:32 2011
From: wrcromwell at gmail.com (Bill Cromwell)
Date: Thu, 10 Nov 2011 18:55:32 -0500
Subject: [HBR] One more quick question
In-Reply-To: <CAE06A76.C427%waltah@earthlink.net>
References: <CAE06A76.C427%waltah@earthlink.net>
Message-ID: <1320969332.1929.23.camel@lancelot>

Hi Walt,

Thanks for your comments.

The HR-10 vs A certainly is a big change. The A model has a different
paint scheme. There may be some internal changes but I haven't looked.
Mine is not the prettiest but not too bad, either. Having already
offered it several times and no takers it is virtually worthless. Except
as an HBR mule. BTW - mine has the xtal calibrator.

Moving the power supply and audio off the HBR to a separate box (my
intent) should give some more room for the additional parts inside. I
haven't approached the layout yet. I only just got my shack and
workspace buttoned up against the approaching northwoods winter.

The Star Roamer did have a BFO function but it was a regenerative IF
kludge. The chassis I have is a bare chassis. It eyeballs out (to my
eyes) about the same size as the HR-10 chassis. If it turns out to be
too small I'll use it for something else. It's a metal box with holes
here n there and about the right size. The rest of the Star Roamer that
lived on that chassis is a long time *gone*. Perfect for patching,
punching, and massaging. Once again, external power and audio. I have
the tuning cap sets from a couple of those old FM BC receivers.

I put a 10:1 drive on the "bandspread" cap in a Star Roamer once upon a
time and it helped immensely. No...it didn't become a frequency meter.
You should get useful results doing that with the Dial Cal cap on the
HR-10.

About long and slow - I have a few grandkids and great grandkids that
need hugging now and then. A big, good, old dog that needs his ears
scratched and walks. There are a couple of musical instruments that need
my attention - jam sessions, practice, and gigs. There are radios here
that already work and need to be exercised. And lets not forget about a
long term XYL! Most of us have lots of things to slow us down. So the
long, slow race is ON! Ready! Set! Went! <evil grin>

73,

Bill  KU8H


From waltah at earthlink.net  Fri Nov 11 00:10:28 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Fri, 11 Nov 2011 00:10:28 -0500
Subject: [HBR] One more quick question - HR10
In-Reply-To: <1320885145.2173.18.camel@lancelot>
Message-ID: <CAE21874.C5C3%waltah@earthlink.net>

I went looking for a bit more on the Knight Star Roamer.   This is a pretty
good link:

http://www.antiqueradios.com/forums/viewtopic.php?t=156805

and includes this link to the schematic:

http://www.mcmlv.org/Archive/Radio/KnightkitStarRoamer.pdf

This is a pretty impressive piece of work for something at this price and
level of simplicity.   Three stages of audio -- two halves of a 12AX7
cascaded driving a 6AK6 so there should be plenty of gain, plus the last two
stages get negative feedback from the voice coil winding on the output
transformer so the audio should be unusually good.

The IF stage is a 6HR6.  That's a high gain semiremote cutoff pentode and I
wouldn't be surprised if the pot in the suppressor grid circuit (called
'sensitivity' on the panel) effectively adjusts regeneration and allows it
to break into oscillation so you have the equivalent of a BFO.

There seems to be a code practice oscillator function, though I can't tell
how it works just by looking at the diagram.

An interesting receiver, and for having nothing much in the box it seems to
have pretty good features.  As Bill indicates, however, it's pretty much
just a chassis for HBR purposes  There's not enough there to get you very
far into W6TC-land.

Walt
KJ4KV




From ianmwilson73 at gmail.com  Fri Nov 11 16:46:17 2011
From: ianmwilson73 at gmail.com (Ian Wilson)
Date: Fri, 11 Nov 2011 13:46:17 -0800
Subject: [HBR] 6U8 as mixer in heterodyne VFO
Message-ID: <CAEz8jcR3Cjt4BLpJ636KARZivSb6J-DNWtduw0ihaP=BD7-gvA@mail.gmail.com>

A VFO configuration that interests me for receivers and/or transmitters is
to
mix a stable low-frequency oscillator with a higher-frequency crystal
oscillator
take the difference, and filter. For example, 2.5 - 3MHz mixed with a 10MHz
xtal to get 7.0 - 7.5MHz.

I am thinking of reworking a homebrew whatsit I picked up somewhere. This
has a small PSU, pair of 6U8 triode/pentodes, xtal socket, triple variable
cap
(probably ARC-5 RX), etc.

Which of these schemes is likely to work better (or is there an even better
alternative?):

  a) pentode as mixer with both inputs to g1
     (using triode as xtal osc, other pentode as input buffer and other
triode as cathode follower o/p)

  b) pentode as mixer with one input to g1, one input to k
      (using pentode as xtal osc, triode cathode follower to mixer k, other
triode as cathode follower o/p)

I prefer to use an input buffer so that the xtal oscillator signal doesn't
get pushed back to
the input. And the cathode follower seems a good use for one of the triodes
and will allow a fairly low
impedance output.

73, ian K3IMW

From donmhaworth at gmail.com  Fri Nov 11 17:54:26 2011
From: donmhaworth at gmail.com (donald haworth)
Date: Fri, 11 Nov 2011 17:54:26 -0500
Subject: [HBR] Mixers
Message-ID: <CAMwEKFjSrNFzaA2BC-2DUYYnrSa=aPp65bW5rPng7jLivuDn_w@mail.gmail.com>

Walt and the group:
What is your favorite mixer, and why?   Do you see any advantage to using a
MiniCircuits Labs double balanced mixer?  All other active elements would
be tubes--conversion loss, of course, rather than gain, as with a 6be6, or
such, but would it have better noise figures?
  Then there is the Pullan Mixer.  Anyone have an opinion on that one?

I would like to here what experience you'all have had
Thanks
Don (wb0rai) Nashville

From ianmwilson73 at gmail.com  Fri Nov 11 18:07:34 2011
From: ianmwilson73 at gmail.com (Ian Wilson)
Date: Fri, 11 Nov 2011 15:07:34 -0800
Subject: [HBR] Mixers
In-Reply-To: <CAMwEKFjSrNFzaA2BC-2DUYYnrSa=aPp65bW5rPng7jLivuDn_w@mail.gmail.com>
References: <CAMwEKFjSrNFzaA2BC-2DUYYnrSa=aPp65bW5rPng7jLivuDn_w@mail.gmail.com>
Message-ID: <CAEz8jcR5wspf1gj78g+m+DfRi-bJ2JVDk=iFD+mkiBa4CxkY7g@mail.gmail.com>

For RF, I like the 6JH8 family of beam-deflection mixers. If you apply the
LO to
the deflection plates, I believe that their basic characteristic is that of
a pentode,
but with a balanced ouput (easy to null by adjusting differential bias).

I have used a Pullen mixer as a product detector using a Compactron triple
triode (I forget the tube number, sorry). This worked well - using a triode
with 1mA
of plate current allowed of a large plate resistor and get lots of
conversion gain as
a result (useful for audio-derived AGC).

73, ian K3IMW

From waltah at earthlink.net  Sat Nov 12 19:47:14 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Sat, 12 Nov 2011 19:47:14 -0500
Subject: [HBR] Mixers
In-Reply-To: <CAMwEKFjSrNFzaA2BC-2DUYYnrSa=aPp65bW5rPng7jLivuDn_w@mail.gmail.com>
Message-ID: <CAE47DC1.C79D%waltah@earthlink.net>

Donald asked:

> What is your favorite mixer, and why?

Anything that is non-linear is a mixer if you put in two inputs.   There are
a VAST number of such circuits and each has advantages.   Picking the best
one depends on your application.

Low noise mixers have a big payoff at 10M and up, perhaps sometimes as low
as 20M.  The Pullen circuit would be an example.  Below 20M, atmospheric
noise will overwhelm tube noise.  The basic paper describing the circuit can
be found with a Google for 'pullen triode mixer.'

High gain mixers can be very useful in simple designs.   Pentodes are a
common example and the W6TC designs all use them, as does the HR-10 and many
other (mostly lower end) ham receivers.  They are, however noisier than
triodes and easier to overload.

Balanced (and 'somewhat balanced') mixers have the virtue that some inputs
and certain mixing products are cancelled at the output.   These shine in
receivers for strong signal or very crowded band conditions, also for some
transmitter designs where spurious outputs are an issue.

Favorites?   In simple/low cost receivers, any of the common pentode
circuits.   Pentodes usually have both signals applied on the same grid so
oscillator isolation is an issue -- it's a good idea to use a buffer stage
or an ECO. 

Even the lowly pentagrid coverters -- 6SA7, 6BE6, 6BA7 -- have a place for
extreme simplicity when desired signals are reasonably strong and some
performance compromise is tolerable.

Triode mixers can be configured for low noise -- the Pullen configuration --
or good signal handling ability.   They also work at higher frequencies than
multigrid tubes.  

In the usual HF ham receiver I prefer a push-push dual triode mixer -- say a
12AT7, 6J6. or 6DJ8 with the plates and cathodes in parallel, the received
signal on one grid, and the LO on the other.  This is 'somewhat doubly
balanced' -- that is, both input signals tend to cancel in the output -- and
it handles large signals well.  This is a very simple circuit -- always an
advantage.  Mixing gain is relatively low and for sensitivity/low noise
operation it needs an appropriate RF stage.

The beam deflection mixers -- 6JH8, 6ME8, 6AR8, and 7360 -- combine
sensitivity with singly balanced operation with respect to the signal on the
control grid AND good large signal handling capability.   Output is
push-pull -- a slight complication -- and a relatively high signal level on
the deflection plates (usually the LO signal) is needed to get good
sensitivity.   Some of these tubes connect a signal electrode to one end of
the filament so they can only be used in a configuration where that pin can
be grounded.  

For 'the most ham receiver with the fewest tubes' I'd start with a beam
mixer and no RF stage.   A 12AT7 as a push-pull LO.  You might even get by
with a single IF stage by using one of the frame grid pentodes such as the
6KT6.  I believe you can use AGC on the beam tube control grid so that would
give you two controlled stages.

Solid state diode mixers have a place: They've been used in microwave work
since WW II because vacuum tubes fade away rapidly above 1000 Mcs or so.
The modern solid state mixer circuits are certainly excellent and easy to
use.

The choice comes down to what best fits what you're trying to do -- and of
course, what interests you.

Walt 
KJ4KV




From donmhaworth at gmail.com  Sat Nov 12 21:35:14 2011
From: donmhaworth at gmail.com (donald haworth)
Date: Sat, 12 Nov 2011 21:35:14 -0500
Subject: [HBR] Mixers
In-Reply-To: <CAE47DC1.C79D%waltah@earthlink.net>
References: <CAMwEKFjSrNFzaA2BC-2DUYYnrSa=aPp65bW5rPng7jLivuDn_w@mail.gmail.com>
	<CAE47DC1.C79D%waltah@earthlink.net>
Message-ID: <CAMwEKFjEA4fh85tDVinCLMWUXdgdSnVfZqNe=qoNgQfVNSfDGg@mail.gmail.com>

Thanks for all the info....about the only mixer I have not tried is the
push-push dual triode.  I built a one tube superhet using a 6me8 in a
double reflex circuit originated by Bob Weaver.  The results were
amazing...200+ stations logged --the beam deflection tube(s) really are
something!  Bob's radio can be seen on his web site.  The 6me8 was used in
a self-oscillating configuration.  My version was rock-stable-less than 500
cycles of drift from turn on----and this using a toroidal inductor in the
tank....and with rather high voltages 50+ for the deflector plates......on
an FT 140-61 core....never did try it on anything other than the BCB...
I mention the above because that was my first superhet-tons of regens in
the past 50 odd years-but that was my first foray into the world of
superhets.  And that, of course led to The HBR....
My LONG SLOW project is based on the Collins r392.  It is now in it's 3rd
iteration--the final one-I hope!
In the first and second versions I used a conventional heptode converter-no
problems, so I will probably use it in the final version......but Walt's
dual triode looks like something I would like to try.
-----maybe a 12u7 ?  I think Walt said plates and cathodes were in parallel
with LO to one grid and signal to the other....
---I am using 26 volt tubes (R392), so I would have only 26 volts on the
plates.
--So far the greatest challenge has been the coils.  All my coils are
toroidal.  I am able to wind them to within +/- 1 uh.  'Pruning' the coils
is done by spreading/compressing the windings and measuring with an LCR
bridge. The big problem has been designing a way to make the toroids
'pluggable',  so far that has taken more time than the rest of the radio!
--Just keep repeating....its only a hobby.....only a hobby.......only a
hobby....................
Don (wb0rai) Nashville

On Sat, Nov 12, 2011 at 7:47 PM, Walt Hutchens <waltah at earthlink.net> wrote:

> Donald asked:
>
> > What is your favorite mixer, and why?
>
> Anything that is non-linear is a mixer if you put in two inputs.   There
> are
> a VAST number of such circuits and each has advantages.   Picking the best
> one depends on your application.
>
> Low noise mixers have a big payoff at 10M and up, perhaps sometimes as low
> as 20M.  The Pullen circuit would be an example.  Below 20M, atmospheric
> noise will overwhelm tube noise.  The basic paper describing the circuit
> can
> be found with a Google for 'pullen triode mixer.'
>
> High gain mixers can be very useful in simple designs.   Pentodes are a
> common example and the W6TC designs all use them, as does the HR-10 and
> many
> other (mostly lower end) ham receivers.  They are, however noisier than
> triodes and easier to overload.
>
> Balanced (and 'somewhat balanced') mixers have the virtue that some inputs
> and certain mixing products are cancelled at the output.   These shine in
> receivers for strong signal or very crowded band conditions, also for some
> transmitter designs where spurious outputs are an issue.
>
> Favorites?   In simple/low cost receivers, any of the common pentode
> circuits.   Pentodes usually have both signals applied on the same grid so
> oscillator isolation is an issue -- it's a good idea to use a buffer stage
> or an ECO.
>
> Even the lowly pentagrid coverters -- 6SA7, 6BE6, 6BA7 -- have a place for
> extreme simplicity when desired signals are reasonably strong and some
> performance compromise is tolerable.
>
> Triode mixers can be configured for low noise -- the Pullen configuration
> --
> or good signal handling ability.   They also work at higher frequencies
> than
> multigrid tubes.
>
> In the usual HF ham receiver I prefer a push-push dual triode mixer -- say
> a
> 12AT7, 6J6. or 6DJ8 with the plates and cathodes in parallel, the received
> signal on one grid, and the LO on the other.  This is 'somewhat doubly
> balanced' -- that is, both input signals tend to cancel in the output --
> and
> it handles large signals well.  This is a very simple circuit -- always an
> advantage.  Mixing gain is relatively low and for sensitivity/low noise
> operation it needs an appropriate RF stage.
>
> The beam deflection mixers -- 6JH8, 6ME8, 6AR8, and 7360 -- combine
> sensitivity with singly balanced operation with respect to the signal on
> the
> control grid AND good large signal handling capability.   Output is
> push-pull -- a slight complication -- and a relatively high signal level on
> the deflection plates (usually the LO signal) is needed to get good
> sensitivity.   Some of these tubes connect a signal electrode to one end of
> the filament so they can only be used in a configuration where that pin can
> be grounded.
>
> For 'the most ham receiver with the fewest tubes' I'd start with a beam
> mixer and no RF stage.   A 12AT7 as a push-pull LO.  You might even get by
> with a single IF stage by using one of the frame grid pentodes such as the
> 6KT6.  I believe you can use AGC on the beam tube control grid so that
> would
> give you two controlled stages.
>
> Solid state diode mixers have a place: They've been used in microwave work
> since WW II because vacuum tubes fade away rapidly above 1000 Mcs or so.
> The modern solid state mixer circuits are certainly excellent and easy to
> use.
>
> The choice comes down to what best fits what you're trying to do -- and of
> course, what interests you.
>
> Walt
> KJ4KV
>
>
>
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

From waltah at earthlink.net  Sun Nov 13 11:17:31 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Sun, 13 Nov 2011 11:17:31 -0500
Subject: [HBR] Mixers
In-Reply-To: <CAMwEKFjEA4fh85tDVinCLMWUXdgdSnVfZqNe=qoNgQfVNSfDGg@mail.gmail.com>
Message-ID: <CAE51554.C7D7%waltah@earthlink.net>

Donald said:

> My LONG SLOW project is based on the Collins r392.  It is now in it's 3rd
> iteration--the final one-I hope!
> In the first and second versions I used a conventional heptode converter-no
> problems, so I will probably use it in the final version......but Walt's
> dual triode looks like something I would like to try.
> -----maybe a 12u7 ?  I think Walt said plates and cathodes were in parallel
> with LO to one grid and signal to the other....
> ---I am using 26 volt tubes (R392), so I would have only 26 volts on the
> plates.

While a 12AU7 will work as an oscillator with 26V on the plates I don't know
what sort of mixer it would make.   The gain of a triode as an amplifier
goes down pretty fast at low plate voltages.   And the 12AU7 is used in this
mixer circuit mainly when large signal handling is required: In a
transmitter or perhaps as a second mixer in a double conversion receiver.

At 26 plate volts I'd go with what has worked before.

Toroids are a very good way to go for compact high Q work.   Despite some
sources saying you can't wind to an exact inductance, my experience is the
same as yours: There's enough leakage flux that turns spacing can be used to
make fine adjustments.

Walt
KJ4KV


From waltah at earthlink.net  Sun Nov 13 11:17:31 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Sun, 13 Nov 2011 11:17:31 -0500
Subject: [HBR] 6U8 as mixer in heterodyne VFO
In-Reply-To: <CAEz8jcR3Cjt4BLpJ636KARZivSb6J-DNWtduw0ihaP=BD7-gvA@mail.gmail.com>
Message-ID: <CAE51A12.C7D8%waltah@earthlink.net>

Ian said:

> A VFO configuration that interests me for receivers and/or transmitters is to
> mix a stable low-frequency oscillator with a higher-frequency crystal
> oscillator take the difference, and filter. For example, 2.5 - 3MHz mixed with
> a 10MHz xtal to get 7.0 - 7.5MHz.

That's certainly the way to get a solid VFO on the bands above 80M.   It
also offers a very good way to key a TX without having either backwave or
VFO drift after standby periods:  Key the xtal oscillator and bias
subsequent stages so they'll be cut off with no drive -- or use a sequential
keying system.   

The configuration I'd think about is a push-pull VFO driving a dual triode
mixer in the cathodes with a push pull crystal oscillator driving the grids.
Tie the plates of the mixer together as mixer output is single ended,
amplify from there.

I have a receiver that uses that oscillator/mixer setup -- the input to the
grids is the signal from the antenna -- and it works very well.

The advantage of that scheme is that both oscillators are rejected in the
mixer output -- that is, they cancel out in the plate circuit, meaning less
chance they (or a harmonic ...) will appear in the TX output.

I would definitely fiddle with the VFO frequency as you would still not want
a harmonic to appear in any ham band on which you'll use the VFO.

Walt KJ4KV




From waltah at earthlink.net  Sun Nov 13 12:04:54 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Sun, 13 Nov 2011 12:04:54 -0500
Subject: [HBR] HR-10 to HBR project
In-Reply-To: <CADECF75.C228%waltah@earthlink.net>
Message-ID: <CAE562E6.C800%waltah@earthlink.net>

To recap: The front panel has been replaced and the front end is in pretty
good shape, the 80M plug in coils are done except possibly for tweaking, the
RF stage, mixer and oscillator are working fine.

About the only exciting part of that work was that the 6EH7 RF stage
oscillated when first built.   I had put a plate between the antenna and
mixer coils but testing with a scrap of tin here and there around the sides
showed that the plate was too small.   A new plate about an inch larger each
way solved the problem.

The audio section has now been rebuilt and converted to the 'sort of hi fi'
circuit I use in receivers:  Feedback from the voice coil winding to the
cathode of the 1st audio stage.  This required exchanging the plate and HV
connections on the output transformer to get the right feedback polarity.
(Couldn't swap the secondary connections because the secondary is 0-8-500
ohms.)   I kept this function in one tube but substituted a 6LF8 for a
saving of 0.15 amp of filament power.

A plate detector circuit has replaced the former diode -- actually this is
the audio version of the push-push mixer used in the receiver front end, but
with a 12AX7.    The BFO was relocated from its former home with the 2nd IF
and is now a 6BH6 ECO.   I have a temporary (1N4148) diode providing AGC for
testing.

The second IF (originally a 6EA8) has been replaced with a 6LF8: This has a
semiremote cutoff pentode.  When I replaced the socket -- none of the
sockets in this set can be trusted to make good contact! -- I left out the
tube shield as my experience is they're never needed.  OOPS!  Make that
ALMOST never needed: this stage oscillated until I shielded it.

I suspect there's more to learn here as this stage is not pushed very hard.
The IF coils are high-Q as such things go -- pi wound with adjustable
powdered iron cores -- but the cathode resistor is 470 ohms and the screen
voltage isn't very high.  I did explore bypassing issues but nothing jumped
out.  ???

With this stage straightened out the receiver works decently, although the
gain is low and the AGC isn't much help.   There's very little drift as the
LO coil is in the former accessory calibrator socket (at the right rear
corner of the chassis) and doesn't warm up much at all and the 6BH6 ECO is
mounted 1/8" above a 9 pin socket hole so some air flows up around it,
minimizing heating of connected parts.

I'm working now on replacing the 6BA6 1st IF stage with another 6LF8.   When
that's done the triode in this tube will be diode-connected as a rectifier
to supply -100V or so for the AGC circuit and the (now unussed) triode in
the 2nd IF stage tube will become an AGC plate detector.   This will give
far better AGC, though I may have to raise the overall gain somewhat.

The advantage of this AGC system (compared to the usual diode) is that you
can run the signal in the 1 volt range at the IF output, rather than needing
10-20V for AGC.  That means better linearity (less distortion) in the IF
stages and ultimately, cleaner sounding signals.   The disadvantage is
slightly fussier design and the need to adjust what amounts to a DC
amplifier, namely that AGC detector.   Furthermore, that adjustment must be
redone whenever the line voltage changes significantly: This is not an ideal
design for portable service.

The adjustment could be eliminated by adding another IF stage driving ONLY
an AGC diode but that requires an additional IFT; there's really not room in
this project.  

Part of the reason the AGC is weak now is that the original design depended
on that:  With the 1940s SSB/CW detection scheme (BFO coupled into the IF)
it is necessary to use the RF gain control to control volume when the BFO is
on: It wouldn't work well to have good AGC fighting your volume control
efforts and/or the BFO driving the AGC!   Modernizing (by isolating the BFO
and coupling it in at the audio detector so the AGC can't see it) allows
better AGC.  

Credit where due:  The audio and AGC detector arrangement was largely stolen
from the Tempo ONE, aka Yaesu FT-200 transceiver, ca 1970.   This was surely
the best price performer of all the commercial vacuum tube sets and beat the
contemporary solid state rigs all ways from Sunday.

Lots more to do but this is going well so far.   It is easier repeating
established circuits and using a transformer-type power supply, no doubt
about it!

Walt 
KJ4KV 





From ianmwilson73 at gmail.com  Sun Nov 13 12:10:59 2011
From: ianmwilson73 at gmail.com (Ian Wilson)
Date: Sun, 13 Nov 2011 09:10:59 -0800
Subject: [HBR] 6U8 as mixer in heterodyne VFO
In-Reply-To: <CAE51A12.C7D8%waltah@earthlink.net>
References: <CAEz8jcR3Cjt4BLpJ636KARZivSb6J-DNWtduw0ihaP=BD7-gvA@mail.gmail.com>
	<CAE51A12.C7D8%waltah@earthlink.net>
Message-ID: <CAEz8jcS=0SekviSUBW3ZnD1Cwm3njO1hyrYz3b-caJoiAfR8=A@mail.gmail.com>

Walt,

Thank you for the ideas. My VFOs are single-ended but there's no reason I
couldn't insert a bifilar transformer between there and the mixer. Having
struggled
with filters in similar situations before, the idea of using balanced
mixers to
suppress some of the large unwanted signals is a winner.

In the context of hybrid receivers <warning: solid-state content>, I have
used
an Si570, which has differential outputs, driving a differential video
amplifier
(AD8138) as input to the deflector plates on a beam deflection mixer. This
is a wideband scheme, no tuned components used.

73, ian K3IMW

From donmhaworth at gmail.com  Sun Nov 13 14:44:15 2011
From: donmhaworth at gmail.com (donald haworth)
Date: Sun, 13 Nov 2011 14:44:15 -0500
Subject: [HBR] dual triode mixer
Message-ID: <CAMwEKFhB9GDx8Pd6ZVZtoQz35D5sdocbN8mDcqtE2OO9wmrF2g@mail.gmail.com>

Walt and all,
Thanks for your information.  Always a gold-mine to read!  On the dual
triode mixer, as I understand it, you have the cathodes tied togeter and
the plates tied together.  The LO is fed on grid one and the signal comes
in on grid two.  What cathode biasing is used(if any)?  Do you take the IF
output from the (two) plates via a small cap-50pf-or so? What is the load
circuit for the plate?
--I was thinking of using a 12U7....not a 12AU7,
-Thanks again for all the information.  I think I learn something with each
post I read
Don (wb0rai) in Nashville

From ianmwilson73 at gmail.com  Sun Nov 13 22:04:31 2011
From: ianmwilson73 at gmail.com (Ian Wilson)
Date: Sun, 13 Nov 2011 19:04:31 -0800
Subject: [HBR] dual triode mixer
In-Reply-To: <CAMwEKFhB9GDx8Pd6ZVZtoQz35D5sdocbN8mDcqtE2OO9wmrF2g@mail.gmail.com>
References: <CAMwEKFhB9GDx8Pd6ZVZtoQz35D5sdocbN8mDcqtE2OO9wmrF2g@mail.gmail.com>
Message-ID: <CAEz8jcQ0KU_EkWh4jFOqm0Kd_d-bbQ07NvhXftV9F1EtaEydgA@mail.gmail.com>

The scheme that Pullen used was to have devices with dissimilar gm. You
can achieve that with triodes just by selecting the operating point. Even
with similar dual triodes this is easy to do, for example by operating one
triode at much lower plate voltage than the other.

The original Pullen paper can be found by searching (sorry, not at home
so I don't have it to hand). He takes you through the calculations that give
good performance without exceeding the tubes' allowed power dissipation.

73, ian K3IMW

From waltah at earthlink.net  Mon Nov 14 11:16:50 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Mon, 14 Nov 2011 11:16:50 -0500
Subject: [HBR] dual triode mixer
In-Reply-To: <CAMwEKFhB9GDx8Pd6ZVZtoQz35D5sdocbN8mDcqtE2OO9wmrF2g@mail.gmail.com>
Message-ID: <CAE6A912.C8D5%waltah@earthlink.net>

Donald asked:

> On the dual triode mixer, as I understand it, you have the cathodes tied
> togeter and the plates tied together.  The LO is fed on grid one and the
> signal comes in on grid two.  What cathode biasing is used(if any)?  Do you
> take the IF output from the (two) plates via a small cap-50pf-or so? What is
> the load circuit for the plate?

You have the grids right -- one each to signal and LO.   I generally use
grid resistors of 100k or so but that's not critical.

The cathode goes to ground through 470 ohms or so;  you can experiment with
other values but this has given about the maximum conversion gain with the
tubes I've used -- 12AT7 and 6J6.   The tube must be biased more than for
use as an amplifier.

The plate goes to the usual plate tank circuit -- IF transformer or
whatever.  High Q is good since the nearer to a short circuit it looks like
to other frequencies the better the rejection of the (unmixed) input
signals.  

This is NOT a fussy circuit;   hook it up and it will work.   It isn't very
high gain but in many applications that's not what you want anyway and it
does deal well with strong signals.

(In fact, in the usual HF receiver design you really want to put as much as
possible of the gain in the IF section, AFTER the sharp filter.   This is an
advantage of putting a crystal filter in the mixer plate: You can put most
of the gain in the two IFs.)

Just as with other mixer circuits, this one can be used as a product
detector.   I've never seen a handbook circuit for that but use a 12AX7 with
a 3000 ohm cathode resistor and a plate circuit as follows:  From B+ 10k to
a filter cap of 47 mfd or more, thence to 100k: take audio here via .001 to
.005 mfd to your volume control and bypass this point with 100 mmf to 470
mmf to reduce RF getting into your audio, thence 10k from there to the plate
which is bypassed with another 100 mmf to 470 mmf.

With very low plate voltages you might want to use an RF choke instead of
the 10k resistor at the plate end but I've had good results at 140V or so
with the resistor. 

This circuit needs VERY pure DC to avoid hum -- that's the reason for the
extra filtering.

If you disable the BFO this circuit acts as a plate detector to deliver
audio from an AM signal.   The volume will be considerably less than from
the same signal with the BFO on, however that can be made up in the audio
section, either by manually increasing the volume control setting or by
changing the gain according to whether the BFO is on or off.

(In the HR-10 to HBR project I'm including the gain change in the BFO
switch.)   

An added advantage to this circuit is that you can pick off the LO or BFO
signal at the cathode (of the mixer) and it is well buffered at that point
-- ideal for connecting to a frequency counter or meter.   It may be
necessary to disable the signal input (unplug the antenna from the
receiver!) to avoid contaminating the count.   I'm now sticking a cathode
test point on the chassis to simplify tracking and drift testing.

Yet another advantage is that the BFO is isolated from the signal path,
making it simpler to to keep it out of the AGC.   However other product
detector circuits also give you this.

> --I was thinking of using a 12U7....not a 12AU7,

Ah yes.   I've never tried to use those 12VDC plate voltage tubes -- the
last gasp for vacuum tube auto radios -- so the number was a 'never seen
that.'   Thanks!

Walt
KJ4KV


From donmhaworth at gmail.com  Mon Nov 14 14:59:52 2011
From: donmhaworth at gmail.com (donald haworth)
Date: Mon, 14 Nov 2011 14:59:52 -0500
Subject: [HBR] dual triode mixer
In-Reply-To: <CAE6A912.C8D5%waltah@earthlink.net>
References: <CAMwEKFhB9GDx8Pd6ZVZtoQz35D5sdocbN8mDcqtE2OO9wmrF2g@mail.gmail.com>
	<CAE6A912.C8D5%waltah@earthlink.net>
Message-ID: <CAMwEKFgXb4WNCMm9Dsb76dmRu+M2a2eD7Xfwr4NLNLJZtZY57w@mail.gmail.com>

Thanks Walt.  As I understand it-both cathodes go to ground via a 470 ohm
resistor, and the plates are tied together and go to B+ via the tank ckt.
Unlike the Pullen which has different plate voltage on the two plates.  Is
that correct?
Thanks Don

On Mon, Nov 14, 2011 at 11:16 AM, Walt Hutchens <waltah at earthlink.net>wrote:

> Donald asked:
>
> > On the dual triode mixer, as I understand it, you have the cathodes tied
> > togeter and the plates tied together.  The LO is fed on grid one and the
> > signal comes in on grid two.  What cathode biasing is used(if any)?  Do
> you
> > take the IF output from the (two) plates via a small cap-50pf-or so?
> What is
> > the load circuit for the plate?
>
> You have the grids right -- one each to signal and LO.   I generally use
> grid resistors of 100k or so but that's not critical.
>
> The cathode goes to ground through 470 ohms or so;  you can experiment with
> other values but this has given about the maximum conversion gain with the
> tubes I've used -- 12AT7 and 6J6.   The tube must be biased more than for
> use as an amplifier.
>
> The plate goes to the usual plate tank circuit -- IF transformer or
> whatever.  High Q is good since the nearer to a short circuit it looks like
> to other frequencies the better the rejection of the (unmixed) input
> signals.
>
> This is NOT a fussy circuit;   hook it up and it will work.   It isn't very
> high gain but in many applications that's not what you want anyway and it
> does deal well with strong signals.
>
> (In fact, in the usual HF receiver design you really want to put as much as
> possible of the gain in the IF section, AFTER the sharp filter.   This is
> an
> advantage of putting a crystal filter in the mixer plate: You can put most
> of the gain in the two IFs.)
>
> Just as with other mixer circuits, this one can be used as a product
> detector.   I've never seen a handbook circuit for that but use a 12AX7
> with
> a 3000 ohm cathode resistor and a plate circuit as follows:  From B+ 10k to
> a filter cap of 47 mfd or more, thence to 100k: take audio here via .001 to
> .005 mfd to your volume control and bypass this point with 100 mmf to 470
> mmf to reduce RF getting into your audio, thence 10k from there to the
> plate
> which is bypassed with another 100 mmf to 470 mmf.
>
> With very low plate voltages you might want to use an RF choke instead of
> the 10k resistor at the plate end but I've had good results at 140V or so
> with the resistor.
>
> This circuit needs VERY pure DC to avoid hum -- that's the reason for the
> extra filtering.
>
> If you disable the BFO this circuit acts as a plate detector to deliver
> audio from an AM signal.   The volume will be considerably less than from
> the same signal with the BFO on, however that can be made up in the audio
> section, either by manually increasing the volume control setting or by
> changing the gain according to whether the BFO is on or off.
>
> (In the HR-10 to HBR project I'm including the gain change in the BFO
> switch.)
>
> An added advantage to this circuit is that you can pick off the LO or BFO
> signal at the cathode (of the mixer) and it is well buffered at that point
> -- ideal for connecting to a frequency counter or meter.   It may be
> necessary to disable the signal input (unplug the antenna from the
> receiver!) to avoid contaminating the count.   I'm now sticking a cathode
> test point on the chassis to simplify tracking and drift testing.
>
> Yet another advantage is that the BFO is isolated from the signal path,
> making it simpler to to keep it out of the AGC.   However other product
> detector circuits also give you this.
>
> > --I was thinking of using a 12U7....not a 12AU7,
>
> Ah yes.   I've never tried to use those 12VDC plate voltage tubes -- the
> last gasp for vacuum tube auto radios -- so the number was a 'never seen
> that.'   Thanks!
>
> Walt
> KJ4KV
>
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
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> Please help support this email list: http://www.qsl.net/donate.html
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From ke0mt at aol.com  Mon Nov 14 15:00:09 2011
From: ke0mt at aol.com (ke0mt at aol.com)
Date: Mon, 14 Nov 2011 15:00:09 -0500 (EST)
Subject: [HBR] Can you list a HBR -11 for sale on list?
Message-ID: <8CE711F25702652-1644-78CB9@webmail-d150.sysops.aol.com>


 

 

ke0mt at aol.com


From windy10605 at juno.com  Mon Nov 14 18:14:28 2011
From: windy10605 at juno.com (Kees & Sandy)
Date: Mon, 14 Nov 2011 23:14:28 GMT
Subject: [HBR] Can you list a HBR -11 for sale on list?
Message-ID: <20111114.171428.27004.0@webmail56.dca.untd.com>

Sure
73 Kees K5BCQ

---------- Original Message ----------
From: ke0mt at aol.com
To: HBR at mailman.qth.net
Subject: [HBR] Can you list a HBR -11 for sale on list?
Date: Mon, 14 Nov 2011 15:00:09 -0500 (EST)







ke0mt at aol.com

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From waltah at earthlink.net  Mon Nov 14 20:18:19 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Mon, 14 Nov 2011 20:18:19 -0500
Subject: [HBR] dual triode mixer
In-Reply-To: <CAMwEKFgXb4WNCMm9Dsb76dmRu+M2a2eD7Xfwr4NLNLJZtZY57w@mail.gmail.com>
Message-ID: <CAE727C7.C9AB%waltah@earthlink.net>

Donald:

> As I understand it-both cathodes go to ground via a 470 ohm
> resistor, and the plates are tied together and go to B+ via the tank ckt.
> Unlike the Pullen which has different plate voltage on the two plates.  Is
> that correct?

That's it.  Couldn't be much simpler!

Walt
KJ4KV


From ke0mt at aol.com  Tue Nov 15 14:13:43 2011
From: ke0mt at aol.com (ke0mt at aol.com)
Date: Tue, 15 Nov 2011 14:13:43 -0500 (EST)
Subject: [HBR] HBR-11FOR SALE
Message-ID: <8CE71E1D33AE138-1FA0-94235@webmail-d159.sysops.aol.com>


 
 FOR SALE HBR 11 clean good shape selling as is 20 and 15 meter coils 1- 80 M coil 1 -40 m coil the rest missing I bought this as a project but due to 1600 Broadcast nearby and lack of time gonna sell it as is $250 plus shipping US only KE0MT Jeff 303 819 4492 Denver CO

 

 

ke0mt at aol.com


From ke0mt at aol.com  Tue Nov 15 15:01:44 2011
From: ke0mt at aol.com (ke0mt at aol.com)
Date: Tue, 15 Nov 2011 15:01:44 -0500 (EST)
Subject: [HBR] HBR-11 IS SOLD
Message-ID: <8CE71E888A15F2C-1FA0-952BB@webmail-d159.sysops.aol.com>


 

 

ke0mt at aol.com


From waltah at earthlink.net  Tue Nov 15 20:45:17 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Tue, 15 Nov 2011 20:45:17 -0500
Subject: [HBR] HR-10 to HBR project
In-Reply-To: <CAE562E6.C800%waltah@earthlink.net>
Message-ID: <CAE87FDD.CB26%waltah@earthlink.net>

> I'm working now on replacing the 6BA6 1st IF stage with another 6LF8.

Done.  And that stage too needed a shield on the tube to keep it from
oscillating.  The 6LF8 was intended for use in TV color burst circuits and
-- though that's 3.58 Mcs -- I'm thinking that perhaps this tube doesn't
have the appropriate layout and/or shielding for high gain amplifier use.
Nothing is obvious from the basing diagram, though: It has an internal
shield connected to the cathode of the pentode and G1 is between K and G2 --
both standard provisions.

It does seem to work okay with a tube shield.

The most interesting thing about rewiring this stage -- if you can call a
mistake 'interesting' -- was the S-meter pegging when I turned it on.  Five
minutes of troubleshooting led back to an unsoldered B+ connection on one of
the lug strips I redid.   The good news is that because I don't wrap wires
(on lugs) there was no connection at all, rather than one that would be okay
until a little corrosion or dirt got in there, then stop working now and
then.  

I've never understood the obsession with wrapping wires around terminals.
The builder of this set did everything but tie 'em with square knots and the
result is that I sometimes have to destroy the lug in order to get the
connections off.   (Alternative:  When there's a bit of slack in a wire I
clip it against the lug, then clip/pry the wrap off a bit at a time.)

The military did this wrap stuff routinely but in the late 1950s the Navy
did tests that showed it did NOT make for more secure connections.  In fact,
it can conceal an unsoldered joint as happened once on this set.   Of course
most of my joints get taken apart anyhow, for one reason or another, and it
makes that far tougher.   I either stick the wires through a lug with a hole
or if that won't work, do a 180 degree hook in the end of the wire.  Then
when the joint is finished a tug on each wire/lead with the needlenose
confirms that it's actually soldered.

The next phase was tidying up loose ends before changing over the AGC
circuit.  The 3rd IFT had to be switched from a conventional winding and
single cap to a tapped configuration using two caps in series in order to
provide different (and reversed phase) voltages to the audio and AGC
detectors.   Unfortunately, I got the connections backwards so the AGC and
audio outputs crossed over each other -- bad idea if you want to keep the
BFO out of the AGC.  So the IFT had to be removed and pulled apart again (NO
fun with those clips),  then the caps removed from the very tight space, and
then reinstalled in the reverse positions.

It's the little stuff that eats you on these projects.

These are actually pretty good IFTs, though.   Litz wire, pie wound, and
looks like less than critically coupled:  They should do a good job (for
this frequency) of backing up the crystal filter.

Next was the realization that the 100 mmf filters on the detector output
were much smaller than could be used, leading to unnecessarily much BFO
signal traveling around the set.   Since the BFO was still adding about 2
S-units to the signal, I replaced these with 1000 mmf each.   Bingo ... AGC
leakage down to about 1/3 S-unit and no loss of highs on voice signals.

(The opposite phase of the AGC and audio outputs from the 3rd IFT allows for
neutralization of the BFO signal getting into the AGC by adding a cap of
about 1 mmf at the appropriate place in the circuit.  This fix too comes
from the Tempo ONE.   However I have found that it isn't always required if
you are sufficiently fanatical about controlling BFO coupling to other
circuits.

(You'll notice that in many sets with product detectors the BFO is in a
separate shield box with a coaxial cable to the detector.   That seems like
more work than the approach above and it doesn't retrofit very well to the
HR-10.)

When turning up the RF gain control there was a sudden scratching followed
by a hum right before maximum.  Signals, however, seemed okay ... bad
control?  No, wait -- that was a new control.   Checking the grid voltage on
the two stages controlled by that pot showed a sudden jump to -0.6V on the
grid of the 1st IF -- the new 6LM8.   Touching various things there with a
screwdriver showed this to be a VHF oscillation, fixed by adding a 100 ohm
resistor right at the grid.

Pretty much all the modern tubes will oscillate at VHF and require this fix.
The problem may be a bit worse in the HR-10 chassis because the tubes are
spaced about 1/2" to 1" more widely than would be normal practice so leads
are on the long side.

Lots of small chores to do.   Of course small means 'easy to troubleshoot
when it doesn't work ...'

1. Connect the 1st IF to the AGC line and change the AGC filtering to allow
for faster attack when the circuit is redone.   (The AGC time constants in
the HR-10 are based on AM operation; SSB and CW require quicker action.)

2. Delete the AGC switch.

3. Relocate the power switch out of the audio gain control to the already
installed toggle switch.   At some point the audio gain control itself needs
to be replaced.  

4. Redo the BFO switch to control the cathode rather than the HV so it can
also adjust the audio gain for equal volume on AM phone signals.

5. Provide separate HV filtering for the LO so its frequency won't be
affected by AGC action.

6. Wire the 100 kcs calibrator circuit.

7. Delete the existing RF gain control line; it'll be replaced by an AGC
threshold control when the new circuit is installed.   (I rarely use this
control: The AGC handles 95% of all situations.  However it's nice to have
for very noisy band conditions.

8. Study the remaining slight hum in the audio and decide what to do about
it.   The HV filtering is minimal ...

Many of these are messy because lug strips must be replaced (to get another
terminal) or existing wiring replaced because it goes the wrong place or is
too short.   

The set now plays beautifully with the RF gain full up and the volume
adjusted with the audio gain control.   When the above items are done it
needs the new (higher gain) AGC circuit and somewhat higher overall RF/IF
gain. 

Walt 
KJ4KV



From daileyservices at qwest.net  Tue Nov 15 21:20:40 2011
From: daileyservices at qwest.net (TC Dailey)
Date: Tue, 15 Nov 2011 19:20:40 -0700
Subject: [HBR] Wrapped wires
References: <CAE87FDD.CB26%waltah@earthlink.net>
Message-ID: <071FB063F4A84B3F8A2E0E3C048F6476@w0eaj>

Looking at (and disassembling) old tube-type Tektronix scopes, you'll find 
that they NEVER wrapped wires about terminals - they're run "through" lugs, 
then soldered, but NEVER wrapped around.  Last time I looked, this works 
just fine.

Tom - EAJ 


From waltah at earthlink.net  Thu Nov 17 00:31:47 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Thu, 17 Nov 2011 00:31:47 -0500
Subject: [HBR] Wrapped wires
In-Reply-To: <071FB063F4A84B3F8A2E0E3C048F6476@w0eaj>
Message-ID: <CAEA0673.CD70%waltah@earthlink.net>

Tom said:

> Looking at (and disassembling) old tube-type Tektronix scopes, you'll find
> that they NEVER wrapped wires about terminals - they're run "through" lugs,
> then soldered, but NEVER wrapped around.  Last time I looked, this works
> just fine.

Funny you should mention that.  I have a Tek 531A sitting awaiting
disassembly for parts.   Last time I took trash to the recycle place, there
it was ...  

I did open it up for a look and noted exactly what you say: No wrapped
wiring.   AND a lifetime supply of various excellent quality parts.

The 531A was the first really decent scope I used, back in grad school days
and it's not going to be easy for me to part it out.   It helps only a
little that I have a perfectly decent Tek 475 and when I applied power to
the 531, it emitted smoke from somewhere in what looks like a power supply
area.   

Geez, there must be a dozen 6DJ8s in there -- that's the tube that's a
better triode mixer than the 12AT7 and 6J6, if you can afford it.   (The hi
fi boys also like them so they are rarely cheap.)

Actually, this is the RM 31A -- the rack mount version.   (A 531A turned
sideways.)  Also what looks like an okay type CA plugin.   AND the manual.

Walt
KJ4KV


From donmhaworth at gmail.com  Thu Nov 17 01:26:36 2011
From: donmhaworth at gmail.com (donald haworth)
Date: Thu, 17 Nov 2011 01:26:36 -0500
Subject: [HBR] Wrapped wires
In-Reply-To: <CAEA0673.CD70%waltah@earthlink.net>
References: <071FB063F4A84B3F8A2E0E3C048F6476@w0eaj>
	<CAEA0673.CD70%waltah@earthlink.net>
Message-ID: <CAMwEKFhmqODnDyNShtPS=K=y_G9gGmZiCLNpef7QSLOfpDOpwA@mail.gmail.com>

Walt.  I have some questions about the dual triode mixer.  Is conversion
gain proportional to transconductance? And do you think a 6gm8 would make a
good mixer?
-thanks for sharing your expertise!
Don in Nashville

On Thu, Nov 17, 2011 at 12:31 AM, Walt Hutchens <waltah at earthlink.net>wrote:

> Tom said:
>
> > Looking at (and disassembling) old tube-type Tektronix scopes, you'll
> find
> > that they NEVER wrapped wires about terminals - they're run "through"
> lugs,
> > then soldered, but NEVER wrapped around.  Last time I looked, this works
> > just fine.
>
> Funny you should mention that.  I have a Tek 531A sitting awaiting
> disassembly for parts.   Last time I took trash to the recycle place, there
> it was ...
>
> I did open it up for a look and noted exactly what you say: No wrapped
> wiring.   AND a lifetime supply of various excellent quality parts.
>
> The 531A was the first really decent scope I used, back in grad school days
> and it's not going to be easy for me to part it out.   It helps only a
> little that I have a perfectly decent Tek 475 and when I applied power to
> the 531, it emitted smoke from somewhere in what looks like a power supply
> area.
>
> Geez, there must be a dozen 6DJ8s in there -- that's the tube that's a
> better triode mixer than the 12AT7 and 6J6, if you can afford it.   (The hi
> fi boys also like them so they are rarely cheap.)
>
> Actually, this is the RM 31A -- the rack mount version.   (A 531A turned
> sideways.)  Also what looks like an okay type CA plugin.   AND the manual.
>
> Walt
> KJ4KV
>
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

From daileyservices at qwest.net  Thu Nov 17 09:07:49 2011
From: daileyservices at qwest.net (TC Dailey)
Date: Thu, 17 Nov 2011 07:07:49 -0700
Subject: [HBR] wrapped wires & Old scopes
References: <CAEA0673.CD70%waltah@earthlink.net>
Message-ID: <C3D52BCDE20F4C85A33D5EEBE13AE763@w0eaj>

Absolutely, Walt - I worked part-time for GATEWAY Elec. when they had a 
store in Denver, and we had several old Tektronix scopes that I was asked to 
"get rid of" - as you know, not only do you end up with lots of really great 
parts, but they're all held in there by mil-spec screws, nuts, & 
lockwashers.  I've built more stuff from those scope teardowns than Carter 
had Liver Pills (dating myself, here).  Another bonus is always the really 
neat LABLED shields and covers for everything.  My FIRST scope was an 
ancient DuMont from a pawnshop; left it at the ham club on Treasure Island 
(SFRAN).

Tom 


From tshoppa at wmata.com  Thu Nov 17 09:17:08 2011
From: tshoppa at wmata.com (Shoppa, Tim)
Date: Thu, 17 Nov 2011 09:17:08 -0500
Subject: [HBR] wrapped wires & Old scopes
In-Reply-To: <C3D52BCDE20F4C85A33D5EEBE13AE763@w0eaj>
References: <CAEA0673.CD70%waltah@earthlink.net>
	<C3D52BCDE20F4C85A33D5EEBE13AE763@w0eaj>
Message-ID: <B136EDE3DF5EC441B6F08E0A7AB872450F4BF7B690@EX2K7-CMS-1.wmata.local>

The silver plated ceramic Tektronix terminal strips are the Cat's Meow.

-----Original Message-----
From: hbr-bounces at mailman.qth.net [mailto:hbr-bounces at mailman.qth.net] On Behalf Of TC Dailey
Sent: Thursday, November 17, 2011 9:08 AM
To: HBR Receiver List
Subject: [HBR] wrapped wires & Old scopes

Absolutely, Walt - I worked part-time for GATEWAY Elec. when they had a store in Denver, and we had several old Tektronix scopes that I was asked to "get rid of" - as you know, not only do you end up with lots of really great parts, but they're all held in there by mil-spec screws, nuts, & lockwashers.  I've built more stuff from those scope teardowns than Carter had Liver Pills (dating myself, here).  Another bonus is always the really neat LABLED shields and covers for everything.  My FIRST scope was an ancient DuMont from a pawnshop; left it at the ham club on Treasure Island (SFRAN).

Tom 

______________________________________________________________
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From daileyservices at qwest.net  Thu Nov 17 09:25:32 2011
From: daileyservices at qwest.net (TC Dailey)
Date: Thu, 17 Nov 2011 07:25:32 -0700
Subject: [HBR] wrapped wires & Old scopes
References: <CAEA0673.CD70%waltah@earthlink.net><C3D52BCDE20F4C85A33D5EEBE13AE763@w0eaj>
	<B136EDE3DF5EC441B6F08E0A7AB872450F4BF7B690@EX2K7-CMS-1.wmata.local>
Message-ID: <7BF4D68BA3AD4AEE9FED547D39A29761@w0eaj>

Oh yeah.. those are extremely COOL.

----- Original Message ----- 
From: "Shoppa, Tim" <tshoppa at wmata.com>


> The silver plated ceramic Tektronix terminal strips are the Cat's Meow.


From tshoppa at wmata.com  Thu Nov 17 09:37:02 2011
From: tshoppa at wmata.com (Shoppa, Tim)
Date: Thu, 17 Nov 2011 09:37:02 -0500
Subject: [HBR] wrapped wires & Old scopes
In-Reply-To: <7BF4D68BA3AD4AEE9FED547D39A29761@w0eaj>
References: <CAEA0673.CD70%waltah@earthlink.net><C3D52BCDE20F4C85A33D5EEBE13AE763@w0eaj>
	<B136EDE3DF5EC441B6F08E0A7AB872450F4BF7B690@EX2K7-CMS-1.wmata.local>
	<7BF4D68BA3AD4AEE9FED547D39A29761@w0eaj>
Message-ID: <B136EDE3DF5EC441B6F08E0A7AB872450F4BF7B6AD@EX2K7-CMS-1.wmata.local>

You know you're working with the cream of the crop when you open up the scope, see the silver plated ceramic terminal strips, and find the spool of silver bearing solder already in the scope as attached at the Tektronix factory.

-----Original Message-----
From: hbr-bounces at mailman.qth.net [mailto:hbr-bounces at mailman.qth.net] On Behalf Of TC Dailey
Sent: Thursday, November 17, 2011 9:26 AM
To: HBR Receiver List
Subject: Re: [HBR] wrapped wires & Old scopes

Oh yeah.. those are extremely COOL.

----- Original Message ----- 
From: "Shoppa, Tim" <tshoppa at wmata.com>


> The silver plated ceramic Tektronix terminal strips are the Cat's Meow.

______________________________________________________________
HBR mailing list
Home: http://mailman.qth.net/mailman/listinfo/hbr
Help: http://mailman.qth.net/mmfaq.htm
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From w4thq at cox.net  Thu Nov 17 11:47:22 2011
From: w4thq at cox.net (w4thq at cox.net)
Date: Thu, 17 Nov 2011 11:47:22 -0500
Subject: [HBR] HBR Wrapped wires
Message-ID: <20111117114722.RBCPE.2156.imail@eastrmwml108>

Group:

The Apollo Program NASA soldering spec required that wires to be soldered NOT be wrapped around a terminal.  The reason was that a wrapped wire could become intermittent and therefore hard to find.  A wire that was not wrapped would be off the terminal and easier to identify.  

J. Young  W4THQ

From waltah at earthlink.net  Thu Nov 17 15:48:35 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Thu, 17 Nov 2011 15:48:35 -0500
Subject: [HBR] HBR Wrapped wires
In-Reply-To: <20111117114722.RBCPE.2156.imail@eastrmwml108>
Message-ID: <CAEAAF42.CE28%waltah@earthlink.net>

J. Young said:

> The Apollo Program NASA soldering spec required that wires to be soldered NOT
> be wrapped around a terminal.  The reason was that a wrapped wire could become
> intermittent and therefore hard to find.  A wire that was not wrapped would be
> off the terminal and easier to identify.

Interesting!   

That has been my theory for a while.   Even if the wire doesn't come
completely loose -- maybe several other wires through the same lug are
holding it in place -- an unsoldered (non-wrapped) wire is likely to be
easily found when you start poking around and wiggling things.

However I just looked at the assembly manual for the HR-10 and it
specifically says that leads should be crimped around terminals before
soldering: "Crimp or bend the lead (or leads) around the terminal to form a
good joint without relying on solder for physical strength."

The manual I have is copyright 1967.   I wonder if Heath ever changed their
recommendation?

When you add to 'can find unsoldered wires more easily' the fact that most
home brew projects will require changes -- at least, mine do! -- this
becomes an easy question.

I have a Heath IO 4555 scope that has an intermittent trace; bet that's a
partially soldered joint.

Walt
KJ4KV








From daileyservices at qwest.net  Thu Nov 17 17:50:13 2011
From: daileyservices at qwest.net (TC Dailey)
Date: Thu, 17 Nov 2011 15:50:13 -0700
Subject: [HBR] HBR Wrapped wires
References: <CAEAAF42.CE28%waltah@earthlink.net>
Message-ID: <1C4178DC7643491B8475D3126256B75B@w0eaj>

I'm in the Commercial Fire Alarm business; each device on a data-loop or 
zone-string has "wires in - wires out", that is, each is on a terminal, but 
never more than 2 conductors per terminal - the idea being exactly as J. 
Young says - if any ONE conductor falls off, get broken, or is cut, the 
"supervisory" circuitry tell you there's a "trouble".  It's a principle 
that's worked for years, and I never knew that NASA used the same thinking.

Tom D - W0EAJ 


From wrcromwell at gmail.com  Thu Nov 17 20:32:03 2011
From: wrcromwell at gmail.com (Bill Cromwell)
Date: Thu, 17 Nov 2011 20:32:03 -0500
Subject: [HBR] HBR Wrapped wires
In-Reply-To: <CAEAAF42.CE28%waltah@earthlink.net>
References: <CAEAAF42.CE28%waltah@earthlink.net>
Message-ID: <1321579923.1933.6.camel@lancelot>

Hi,

Once upon a time I was taught to wrap and 'crimp' so that the solder
joint did not take the physical strain of holding the conductors
together. In practice I found the same thing Walt did, it needs to be
easy unhitching wires. I never have any problems with wires that are
"tacked" on and not bent/crimped. I have had bent/crimped wires break
off where they were stressed at the bend. 

Just my $5 worth. Two cents has been outmoded.

73,

Bill  KU8H


From rwfish at comcast.net  Thu Nov 17 21:01:49 2011
From: rwfish at comcast.net (Robert Fish)
Date: Thu, 17 Nov 2011 18:01:49 -0800
Subject: [HBR] HBR Wrapped wires
In-Reply-To: <CAEAAF42.CE28%waltah@earthlink.net>
References: <CAEAAF42.CE28%waltah@earthlink.net>
Message-ID: <4EC5BC8D.1090403@comcast.net>

I haven't been crimping wires just because of laziness.
It's nice, now I can act like I knew what I was doing all along.

Bob  K6GGO

> J. Young said:
>
>> The Apollo Program NASA soldering spec required that wires to be soldered NOT
>> be wrapped around a terminal.  The reason was that a wrapped wire could become
>> intermittent and therefore hard to find.  A wire that was not wrapped would be
>> off the terminal and easier to identify.
>
>
>
>
>
>
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>


From donmhaworth at gmail.com  Sat Nov 19 14:46:11 2011
From: donmhaworth at gmail.com (donald haworth)
Date: Sat, 19 Nov 2011 14:46:11 -0500
Subject: [HBR] dual triode mixer
In-Reply-To: <CAE727C7.C9AB%waltah@earthlink.net>
References: <CAMwEKFgXb4WNCMm9Dsb76dmRu+M2a2eD7Xfwr4NLNLJZtZY57w@mail.gmail.com>
	<CAE727C7.C9AB%waltah@earthlink.net>
Message-ID: <CAMwEKFjuAw9pdE0gpJoGWK5OoZaa6Of6MYmhjQEw61MFynxTPQ@mail.gmail.com>

Walt.
Can you tell me where I can find more info about the dual triode mixer?  I
am planning to use a 6gm8....Can you tell me what led you to using the dual
triode, rather than, say, a pentagrid type?
-Sorry for all the dumb questions....but it just seems 'to good to be
true'.  I really would like to know how the thing works.....I was also
thinking of using two 6gk5's-a very high gm tube-
-Your thoughts, please...
Thanks Don (wb0rai) in Nashville

On Mon, Nov 14, 2011 at 8:18 PM, Walt Hutchens <waltah at earthlink.net> wrote:

> Donald:
>
> > As I understand it-both cathodes go to ground via a 470 ohm
> > resistor, and the plates are tied together and go to B+ via the tank ckt.
> > Unlike the Pullen which has different plate voltage on the two plates.
>  Is
> > that correct?
>
> That's it.  Couldn't be much simpler!
>
> Walt
> KJ4KV
>
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

From pdulaff at embarqmail.com  Sat Nov 19 20:24:02 2011
From: pdulaff at embarqmail.com (Paul Dulaff)
Date: Sat, 19 Nov 2011 20:24:02 -0500 (EST)
Subject: [HBR] dual triode mixer - Pullen Mixer Notes
In-Reply-To: <CAMwEKFjuAw9pdE0gpJoGWK5OoZaa6Of6MYmhjQEw61MFynxTPQ@mail.gmail.com>
Message-ID: <1590713696.209443.1321752242259.JavaMail.root@md23.embarq.synacor.com>

Donald

I have attached a link to information on the Pullen Mixer. This is a dual triode configuration. The link contains information on theory of operation, correct design and biasing. Information is also listed for the reworked 1st mixer for the 75A-4 using this approach. I understand this implimentation works very well.

Paul - WB2NMI


----- Original Message -----
From: donald haworth <donmhaworth at gmail.com>
To: HBR Receiver List <hbr at mailman.qth.net>
Sent: Sat, 19 Nov 2011 14:46:11 -0500 (EST)
Subject: Re: [HBR] dual triode mixer

Walt.
Can you tell me where I can find more info about the dual triode mixer?  I
am planning to use a 6gm8....Can you tell me what led you to using the dual
triode, rather than, say, a pentagrid type?
-Sorry for all the dumb questions....but it just seems 'to good to be
true'.  I really would like to know how the thing works.....I was also
thinking of using two 6gk5's-a very high gm tube-
-Your thoughts, please...
Thanks Don (wb0rai) in Nashville

On Mon, Nov 14, 2011 at 8:18 PM, Walt Hutchens <waltah at earthlink.net> wrote:

> Donald:
>
> > As I understand it-both cathodes go to ground via a 470 ohm
> > resistor, and the plates are tied together and go to B+ via the tank ckt.
> > Unlike the Pullen which has different plate voltage on the two plates.
>  Is
> > that correct?
>
> That's it.  Couldn't be much simpler!
>
> Walt
> KJ4KV
>
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
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From pdulaff at embarqmail.com  Sat Nov 19 20:25:27 2011
From: pdulaff at embarqmail.com (Paul Dulaff)
Date: Sat, 19 Nov 2011 20:25:27 -0500 (EST)
Subject: [HBR] Fwd: Re:  dual triode mixer - Pullen Mixer Notes
Message-ID: <1937078359.209482.1321752327160.JavaMail.root@md23.embarq.synacor.com>

Here is the link:

http://aafradio.org/docs/Pullen.htm

Paul - WB2NMI

----- Forwarded Message -----
From: Paul Dulaff <pdulaff at embarqmail.com>
To: HBR Receiver List <hbr at mailman.qth.net>
Sent: Sat, 19 Nov 2011 20:24:02 -0500 (EST)
Subject: Re: [HBR] dual triode mixer - Pullen Mixer Notes

Donald

I have attached a link to information on the Pullen Mixer. This is a dual triode configuration. The link contains information on theory of operation, correct design and biasing. Information is also listed for the reworked 1st mixer for the 75A-4 using this approach. I understand this implimentation works very well.

Paul - WB2NMI


----- Original Message -----
From: donald haworth <donmhaworth at gmail.com>
To: HBR Receiver List <hbr at mailman.qth.net>
Sent: Sat, 19 Nov 2011 14:46:11 -0500 (EST)
Subject: Re: [HBR] dual triode mixer

Walt.
Can you tell me where I can find more info about the dual triode mixer?  I
am planning to use a 6gm8....Can you tell me what led you to using the dual
triode, rather than, say, a pentagrid type?
-Sorry for all the dumb questions....but it just seems 'to good to be
true'.  I really would like to know how the thing works.....I was also
thinking of using two 6gk5's-a very high gm tube-
-Your thoughts, please...
Thanks Don (wb0rai) in Nashville

On Mon, Nov 14, 2011 at 8:18 PM, Walt Hutchens <waltah at earthlink.net> wrote:

> Donald:
>
> > As I understand it-both cathodes go to ground via a 470 ohm
> > resistor, and the plates are tied together and go to B+ via the tank ckt.
> > Unlike the Pullen which has different plate voltage on the two plates.
>  Is
> > that correct?
>
> That's it.  Couldn't be much simpler!
>
> Walt
> KJ4KV
>
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
______________________________________________________________
HBR mailing list
Home: http://mailman.qth.net/mailman/listinfo/hbr
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:HBR at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

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From donmhaworth at gmail.com  Sat Nov 19 20:53:21 2011
From: donmhaworth at gmail.com (donald haworth)
Date: Sat, 19 Nov 2011 20:53:21 -0500
Subject: [HBR] Fwd: Re: dual triode mixer - Pullen Mixer Notes
In-Reply-To: <1937078359.209482.1321752327160.JavaMail.root@md23.embarq.synacor.com>
References: <1937078359.209482.1321752327160.JavaMail.root@md23.embarq.synacor.com>
Message-ID: <CAMwEKFiD-oebQ7L9_QZp4Ovt4RWE59jYn+BN0VHN=-6o6rZ-qg@mail.gmail.com>

Thanks, Paul.  I have read the Pullen information.  I had built the mixer,
as described for the Collins receiver, using a 6es8.  My results were
so-so.  I did not see a great deal of improvement over a conventional 6be6
circuit-note this was used in a home-built superhet-not in the Collins
radio.  Walt's mixer circuit differs from the Pullen in that the plates are
tied together-therefor at the same potential, the Pullen drops the plate
voltage to the second triode by about 1/3, one could almost say it looks
like a cathode follower, but the Keets Pullen reference shows otherwise.
-As I understand it, Walt is using a dual triode, cathode(s) to ground via
a 470 ohm resistor.  The plates are tied together, then to the IF tank.
One grid is fed signal, the other is fed the LO signal.  Each grid has a
100k resistor to ground, as well.  From what Walt has posted, it seems to
be a good mixer.  I would like to know just how the thing works.  I also
would like to know what would work best--lo mu-- high mu dual triode- if a
tube with high transconductance would work better......I was thinking of
using two 6gk5's--super high gm- but I can find very little info on 'dual
triode mixers'--other than the Pullen info...
-best 73's
Thanks for you response!
Don

On Sat, Nov 19, 2011 at 8:25 PM, Paul Dulaff <pdulaff at embarqmail.com> wrote:

> Here is the link:
>
> http://aafradio.org/docs/Pullen.htm
>
> Paul - WB2NMI
>
> ----- Forwarded Message -----
> From: Paul Dulaff <pdulaff at embarqmail.com>
> To: HBR Receiver List <hbr at mailman.qth.net>
> Sent: Sat, 19 Nov 2011 20:24:02 -0500 (EST)
> Subject: Re: [HBR] dual triode mixer - Pullen Mixer Notes
>
> Donald
>
> I have attached a link to information on the Pullen Mixer. This is a dual
> triode configuration. The link contains information on theory of operation,
> correct design and biasing. Information is also listed for the reworked 1st
> mixer for the 75A-4 using this approach. I understand this implimentation
> works very well.
>
> Paul - WB2NMI
>
>
> ----- Original Message -----
> From: donald haworth <donmhaworth at gmail.com>
> To: HBR Receiver List <hbr at mailman.qth.net>
> Sent: Sat, 19 Nov 2011 14:46:11 -0500 (EST)
> Subject: Re: [HBR] dual triode mixer
>
> Walt.
> Can you tell me where I can find more info about the dual triode mixer?  I
> am planning to use a 6gm8....Can you tell me what led you to using the dual
> triode, rather than, say, a pentagrid type?
> -Sorry for all the dumb questions....but it just seems 'to good to be
> true'.  I really would like to know how the thing works.....I was also
> thinking of using two 6gk5's-a very high gm tube-
> -Your thoughts, please...
> Thanks Don (wb0rai) in Nashville
>
> On Mon, Nov 14, 2011 at 8:18 PM, Walt Hutchens <waltah at earthlink.net>
> wrote:
>
> > Donald:
> >
> > > As I understand it-both cathodes go to ground via a 470 ohm
> > > resistor, and the plates are tied together and go to B+ via the tank
> ckt.
> > > Unlike the Pullen which has different plate voltage on the two plates.
> >  Is
> > > that correct?
> >
> > That's it.  Couldn't be much simpler!
> >
> > Walt
> > KJ4KV
> >
> > ______________________________________________________________
> > HBR mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/hbr
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:HBR at mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> >
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
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> Please help support this email list: http://www.qsl.net/donate.html
>

From Hopperdhh at aol.com  Mon Nov 21 14:05:14 2011
From: Hopperdhh at aol.com (Hopperdhh at aol.com)
Date: Mon, 21 Nov 2011 14:05:14 -0500 (EST)
Subject: [HBR] Fwd: Re:  dual triode mixer - Pullen Mixer Notes
Message-ID: <be9e.b84720.3bfbfaea@aol.com>



Great articles, Paul.  Thanks a lot.
 
Dan K9WEK
 
 
 
 
In a message dated 11/19/2011 8:25:30 P.M. Eastern Standard Time,  
pdulaff at embarqmail.com writes:

Here is  the link:

http://aafradio.org/docs/Pullen.htm

Paul -  WB2NMI

----- Forwarded Message -----
From: Paul Dulaff  <pdulaff at embarqmail.com>
To: HBR Receiver List  <hbr at mailman.qth.net>
Sent: Sat, 19 Nov 2011 20:24:02 -0500  (EST)
Subject: Re: [HBR] dual triode mixer - Pullen Mixer  Notes

Donald

I have attached a link to information on the Pullen  Mixer. This is a dual 
triode configuration. The link contains information on  theory of operation, 
correct design and biasing. Information is also listed  for the reworked 
1st mixer for the 75A-4 using this approach. I understand  this implimentation 
works very well.

Paul - WB2NMI


-----  Original Message -----
From: donald haworth  <donmhaworth at gmail.com>
To: HBR Receiver List  <hbr at mailman.qth.net>
Sent: Sat, 19 Nov 2011 14:46:11 -0500  (EST)
Subject: Re: [HBR] dual triode mixer

Walt.
Can you tell me  where I can find more info about the dual triode mixer?  I
am planning  to use a 6gm8....Can you tell me what led you to using the dual
triode,  rather than, say, a pentagrid type?
-Sorry for all the dumb  questions....but it just seems 'to good to be
true'.  I really would  like to know how the thing works.....I was also
thinking of using two  6gk5's-a very high gm tube-
-Your thoughts, please...
Thanks Don  (wb0rai) in Nashville

On Mon, Nov 14, 2011 at 8:18 PM, Walt Hutchens  <waltah at earthlink.net> 
wrote:

> Donald:
>
> >  As I understand it-both cathodes go to ground via a 470 ohm
> >  resistor, and the plates are tied together and go to B+ via the tank  
ckt.
> > Unlike the Pullen which has different plate voltage on the  two plates.
>  Is
> > that correct?
>
> That's  it.  Couldn't be much simpler!
>
> Walt
>  KJ4KV
>
>  ______________________________________________________________
> HBR  mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
>  Help: http://mailman.qth.net/mmfaq.htm
> Post:  mailto:HBR at mailman.qth.net
>
> This list hosted by:  http://www.qsl.net
> Please help support this email list:  http://www.qsl.net/donate.html
>
______________________________________________________________
HBR  mailing list
Home: http://mailman.qth.net/mailman/listinfo/hbr
Help:  http://mailman.qth.net/mmfaq.htm
Post:  mailto:HBR at mailman.qth.net

This list hosted by:  http://www.qsl.net
Please help support this email list:  http://www.qsl.net/donate.html

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Help:  http://mailman.qth.net/mmfaq.htm
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Help:  http://mailman.qth.net/mmfaq.htm
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From ke9xq at charter.net  Mon Nov 21 15:11:45 2011
From: ke9xq at charter.net (ke9xq at charter.net)
Date: Mon, 21 Nov 2011 15:11:45 -0500 (EST)
Subject: [HBR] Kees' disk came in  : )
Message-ID: <204462f3.b01e2.133c7c17a3f.Webtop.49@charter.net>

Greetings
    Thanks Kees,, your disk came in today, and thanks for the off topic 
goodies too, love your project car : )  I just bought a 76 Fiat Spyder 
Sport to start playing with...   Very rough shape and frozen motor, but 
got a spare engine (also frozen up) and 4 trannys, so I should be busy 
for the next couple of years : )
      Anyways, love the HBR goodies on the disk, just spent a couple of 
hours running through the files, a good addition to my HBR archiving.
      The Disk came in un harmed, but the cd case was busted in two, 
right down the middle virtically, very lucky and happy camper here : )
73
Bill

From windy10605 at juno.com  Mon Nov 21 16:04:06 2011
From: windy10605 at juno.com (Kees & Sandy)
Date: Mon, 21 Nov 2011 21:04:06 GMT
Subject: [HBR] Kees' disk came in  : )
Message-ID: <20111121.150406.13511.0@webmail52.dca.untd.com>

Glad you received it and like it. I see the Post Office is getting ready for Christmas. 
I did have a really nice multi color CD label for the front but can't seem to find the artwork.
73 Kees K5BCQ

---------- Original Message ----------
From: ke9xq at charter.net
To: HBR Receiver List <hbr at mailman.qth.net>
Subject: Re: [HBR] Kees' disk came in  : )
Date: Mon, 21 Nov 2011 15:11:45 -0500 (EST)

Greetings
   Thanks Kees,, your disk came in today, and thanks for the off topic 
goodies too, love your project car : )  I just bought a 76 Fiat Spyder 
Sport to start playing with...   Very rough shape and frozen motor, but 
got a spare engine (also frozen up) and 4 trannys, so I should be busy 
for the next couple of years : )
     Anyways, love the HBR goodies on the disk, just spent a couple of 
hours running through the files, a good addition to my HBR archiving.
     The Disk came in un harmed, but the cd case was busted in two, 
right down the middle virtically, very lucky and happy camper here : )
73
Bill
______________________________________________________________
HBR mailing list
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:HBR at mailman.qth.net

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Please help support this email list: http://www.qsl.net/donate.html


From donmhaworth at gmail.com  Wed Nov 23 20:06:44 2011
From: donmhaworth at gmail.com (donald haworth)
Date: Wed, 23 Nov 2011 20:06:44 -0500
Subject: [HBR] Pullen mixer
Message-ID: <CAMwEKFg6zj6JX+H2SwOiX0vXO75Dz=7fSZrNXwMBSr6=BM_Bmw@mail.gmail.com>

Some time ago I posted some questions about a dual triode mixer, as
described by Walt.  A very simple circuit, indeed, with the plates tied
together, a common cathode to ground via a 470 ohm resistor, and the signal
and LO fed on the grids.
-Long story, short--I built it and it worked, as  advertised.  Noise was
about same as the pentagrid convertor, however, and gain was much
lower-that was no surprise-but I did expect the noise to be a bit better..
I must add that I am running only 26 volts on the plate.(26d6).  The twin
triode I was using is a 6gm8.  I then tried it in a Pullen configuration.
One plate with 20 volts and second plate (with LO to grid)  2.2 volts--this
via a 50k pot so I could adjust the voltage.....WOW!!  What a difference!
All kinds on gain, NO noise---sounds like the antenna has been disconnected
-then you tune across a signal and it pops out.....!  Really impressive.
And the best part----no spurs --no birdies---I am using a N3ZI DDS for the
LO.  Injection is 250mv.  Antenna running into the other grid-no
tuning-nothing-and it blows away every mixer circuit I have tried, to
date.  I have found the best way to test a mixer circuit is to input a
signal to the (signal) grid--no rf amp-no tuning...this will show up a bad
/ good design in a hurry.  A good RF front end will cover a multitude of
mixers problems, so eliminating it will give you a good idea of how well
the mixer preforms.....
--I am now a believer.  All the things they say about the Pullen are
true---and all it took was three resistors added to Walt's dual triode
circuit!  I must say that the Plate voltage ratio is critical--it will make
the difference between no signal and Grins and Giggles-but a pot in a
voltage divider circuit to feed the second grid, and just tune for the best
output......for the 6gm8, I have 20volts on plate 1 and only 2.2 on plate
2............
----Give it a try!
---and a Happy Thanksgiving to all
Don (wb0rai) in Nashville

From waltah at earthlink.net  Wed Nov 23 23:39:27 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Wed, 23 Nov 2011 23:39:27 -0500
Subject: [HBR] HR-10 to HBR project
In-Reply-To: <CAE87FDD.CB26%waltah@earthlink.net>
Message-ID: <CAF334AF.D916%waltah@earthlink.net>

> Lots of small chores to do.

But before tackling them I discovered yet ANOTHER low level VHF oscillation,
this time in the 2nd IF.  This stage had a parasitic suppressor in the grid
but evidently that wasn't enough.  A 100 ohm resistor did the trick as
usual.

Connecting the 1st IF to the AGC led to an IF oscillation.   OOPS!  I had
used a metal film capacitor for AGC filtering and as I discovered on the
'Long SLOW ...' project, those have too much inductance for MF/HF bypass
service.  Replacing that with a disk ceramic eliminated the problem AND
further reduced the effect of the BFO on the S-meter reading -- now only
about a needle width.  That's tolerable, I think, so probably no need to
neutralize.

Other than having to run a wire from the S-meter all the way to the S-meter
zero pot on the back of the set, getting rid of the AGC switch was easy.
The AGC is now full time.

It's now possible to listen to the set.   The audio has just a bit too much
low frequency so that's a change in one or two capacitors.   It is also
slightly distorted: This is probably caused by my (rather casual) temporary
AGC circuit so I won't look into it until the permanent circuit is in place,
perhaps a week from now.

Transferring the power switch function of the volume control to the new
toggle switch was just the usual run-two-wires-in-an-awkward-place exercise.
The audio gain control may actually be okay -- the bad noises only happen at
very low settings and then only when you're actually turning it.

I replaced the BFO switch with a SPDT unit, grounding the center pole and
connecting the pole that's ON when up to the BFO cathode.   The other pole
goes to the feedback circuit in the audio amp where it shorts part of the
1st audio cathode resistor to raise the voltage gain from 10 (input grid to
voice coil winding) to 20 when the BFO is OFF.   The goal here is when you
zero beat an AM signal and switch off the BFO, the volume stays about the
same and this guess turned out to be roughly right.

I've been a remarkable long time coming up with this trick and will copy it
to the Long, SLOW project in the near future.

Giving the LO its own separate HV filter coming off the rectifier cathode
made no noticeable difference but since there's not enough AGC to cause much
change in the B+ load, that's not surprising.   When the AGC-controlled load
current (RF and two IF stages) is cut from ~45 mA to 5 mA on strong signals,
it'll be useful as that's a difference of 60 volts in the B+.

The filtering of the main HV in the HR-10 is just a 1.5k 10W resistor
between 20 mfd caps: There is no filter choke.   I could add the choke, but
the goal here is to keep things simple and require as few added parts as
possible.

Wiring the calibration oscillator was uneventful.   Well, except for a day
devoted to some kind of nasty stomach bug followed by Thanksgiving company.
I used the circuit of the Heath plug in accessory calibrator, HA-10-1 but
replaced the 6BA6 with a 6BH6 to save filament current.   I had to add 10
mmf in parallel with the 15 mmf trimmer I used across the crystal to get it
to zero beat WWV at 15 mcs but that's to be expected.   It's nice when
something works the first time.

Something about copying a well tested circuit ...

The first thing I discovered when I began looking at the full-volume hum was
that there was a loose connection somewhere in the HV filtering.  Gee ... it
took no time to notice that the filament winding ground shouldn't be via the
twist lug on the filter cap; wouldn't you think I'd also spot that the cap
itself wasn't well grounded simply by being twisted in place?   Wiring the
capacitor lug to a real ground got rid of the loose connection noise.

This appears to be a Heath design error and it would be surprising if it
didn't occur on some of the other kits.

The hum audible at full volume was coming from the detector stage.   I had
transferred the extra filtered B+ from the 1st audio (now inside a feedback
loop that takes care of a bit of hum) to the detector stage but completely
forgot that the BFO also needs pure DC.   The complication is that the BFO
is switched and draws about twice the place current as the detector.   Since
the detector operating point is somewhat critical the two do not share a
poorly regulated HV source very nicely.

There are two ways to go with this: Another separate RC filter for the BFO,
OR switching to a choke input filter with a second choke replacing the 1.5k
resistor.   I think either would be satisfactory: Adding another filter is
the quickest and cheapest but using filter chokes would greatly improve the
HV regulation (good for AGC action) and lower the power consumption
slightly.  There is enough space for a couple of the command set chokes.
For now, however, I'm going with quick and cheap!

On to increased gain/better AGC!

Walt 
KJ4KV








From waltah at earthlink.net  Thu Nov 24 23:46:01 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Thu, 24 Nov 2011 23:46:01 -0500
Subject: [HBR] Pullen mixer
In-Reply-To: <CAMwEKFg6zj6JX+H2SwOiX0vXO75Dz=7fSZrNXwMBSr6=BM_Bmw@mail.gmail.com>
Message-ID: <CAF487B9.D9E5%waltah@earthlink.net>

Donald posted:

> I am now a believer.  All the things they say about the Pullen are
> true---and all it took was three resistors added to Walt's dual triode
> circuit!  I must say that the Plate voltage ratio is critical--it will make
> the difference between no signal and Grins and Giggles-but a pot in a
> voltage divider circuit to feed the second grid, and just tune for the best
> output......for the 6gm8, I have 20volts on plate 1 and only 2.2 on plate.

Looks like you've found something that works.

I had written some of a post on mixers in general and triode mixers in
particular but none of it would be really new: "It depends on what you're
trying to do" ... 

I'll say only this: A (first) mixer implies a receiver and also the reverse.
Thus a 6GM8 in a Pullen circuit tweaked for maximum output at a very low
plate supply voltage implies certain kinds of circuits and operating
conditions on both sides.

Neither a lawnmower engine in a Maseratti or the reverse would be very
satisfactory.  So too with most of the circuits in a communications
receiver.   The challenge is to picture the entire mower when you are
building the engine and keep that vision in mind as you move from working on
the engine to the mower deck, the gas tank ...

You're working on a different lawnmower than I am and your vision for the
mixer is somewhat unlike mine.

Walt
KJ4KV



From pdulaff at embarqmail.com  Fri Nov 25 00:33:20 2011
From: pdulaff at embarqmail.com (Paul Dulaff)
Date: Fri, 25 Nov 2011 00:33:20 -0500 (EST)
Subject: [HBR] Pullen mixer
In-Reply-To: <CAMwEKFg6zj6JX+H2SwOiX0vXO75Dz=7fSZrNXwMBSr6=BM_Bmw@mail.gmail.com>
Message-ID: <21871254.356130.1322199200903.JavaMail.root@md23.embarq.synacor.com>

Don

Could you post details on the mixer circuit such as the plate load resistor values, cathode resistor value, etc.

Some literature states that the 6ES8 and the 6DJ8 can be substituted.

Best 73's

Paul - WB2NMI

----- Original Message -----
From: donald haworth <donmhaworth at gmail.com>
To: HBR Receiver List <hbr at mailman.qth.net>
Sent: Wed, 23 Nov 2011 20:06:44 -0500 (EST)
Subject: [HBR] Pullen mixer

Some time ago I posted some questions about a dual triode mixer, as
described by Walt.  A very simple circuit, indeed, with the plates tied
together, a common cathode to ground via a 470 ohm resistor, and the signal
and LO fed on the grids.
-Long story, short--I built it and it worked, as  advertised.  Noise was
about same as the pentagrid convertor, however, and gain was much
lower-that was no surprise-but I did expect the noise to be a bit better..
I must add that I am running only 26 volts on the plate.(26d6).  The twin
triode I was using is a 6gm8.  I then tried it in a Pullen configuration.
One plate with 20 volts and second plate (with LO to grid)  2.2 volts--this
via a 50k pot so I could adjust the voltage.....WOW!!  What a difference!
All kinds on gain, NO noise---sounds like the antenna has been disconnected
-then you tune across a signal and it pops out.....!  Really impressive.
And the best part----no spurs --no birdies---I am using a N3ZI DDS for the
LO.  Injection is 250mv.  Antenna running into the other grid-no
tuning-nothing-and it blows away every mixer circuit I have tried, to
date.  I have found the best way to test a mixer circuit is to input a
signal to the (signal) grid--no rf amp-no tuning...this will show up a bad
/ good design in a hurry.  A good RF front end will cover a multitude of
mixers problems, so eliminating it will give you a good idea of how well
the mixer preforms.....
--I am now a believer.  All the things they say about the Pullen are
true---and all it took was three resistors added to Walt's dual triode
circuit!  I must say that the Plate voltage ratio is critical--it will make
the difference between no signal and Grins and Giggles-but a pot in a
voltage divider circuit to feed the second grid, and just tune for the best
output......for the 6gm8, I have 20volts on plate 1 and only 2.2 on plate
2............
----Give it a try!
---and a Happy Thanksgiving to all
Don (wb0rai) in Nashville
______________________________________________________________
HBR mailing list
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:HBR at mailman.qth.net

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From donmhaworth at gmail.com  Fri Nov 25 03:07:03 2011
From: donmhaworth at gmail.com (donald haworth)
Date: Fri, 25 Nov 2011 03:07:03 -0500
Subject: [HBR] Pullen mixer
In-Reply-To: <21871254.356130.1322199200903.JavaMail.root@md23.embarq.synacor.com>
References: <CAMwEKFg6zj6JX+H2SwOiX0vXO75Dz=7fSZrNXwMBSr6=BM_Bmw@mail.gmail.com>
	<21871254.356130.1322199200903.JavaMail.root@md23.embarq.synacor.com>
Message-ID: <CAMwEKFjWKLxciGOi9gfueeCYcvbq=mh2Pg4oWAqSP2=3ADhjGA@mail.gmail.com>

Paul
The tube I am using is a 6gm8 dual triode which was designed to run with 30
on the plate(s).  IIRC, the transconductance is around 7800 @ 30 volts.  My
radio is based on the Collins r392, so my B+ runs at 25-26 volts.  Same for
the heaters.
As this was somewhat uncharted ground (at least for me), I was not sure
what The 6gm8 plates should run at.  The 6es8 calls for 150 on the 'signal'
triode and 50 volts on the "LO" triode.  I tried to keep the same 3:1 ratio
on the 'gm8.  I ended up with a 50k pot-wiper to the second plate.  Top of
pot to 25volt B+.  Bottom of pot to ground.  The 'signal' plate B+ was fed
via a 1.8k resistor, 20 volts on that plate, and the plate is at RF ground,
through a .01 cap.
The grid of the 'signal' triode has a 120k resistor to ground.  The 'LO'
triode grid has a 120k resistor to the CATHODES-not to ground-.  The
cathodes are tied together and go to ground via a 300 0hm resistor.
I forgot to mention-the output is taken from an IF transformer.  The
primary is between the plate (LO triode) and the B+ supplied from the wiper
of the 50k pot.  Secondary to IF stage. There is a .01 cap to ground on the
B+ side of the IF transformer.

With an antenna connected to the grid of the 'signal' triode (via a .01
cap), and a signal from a signal generator set to 5455 kc--assuming your
using a 455kc IF-tune the pot until you hear WWV!
As I mentioned, I am using a tube designed for low voltage B+.  I see no
reason why the pot voltage 'tuning' would not work with other tubes.  I did
find that .5 volt made all the difference in the world, so the pot was left
in the circuit.  The adjustment is rather critical-at least with the
6gm8-but once you find the 'sweet spot' it is very stable, however..........
TRY IT!!  I have yet to feed it with a tuned rf stage--RF stages can hide a
bunch of mixer problems--so if it works well-and it does! w /o any
tuning....it should really shine coupled with a good front end.
--let me know how yours works, and if I can answer any other questions.
Hope the above makes some sense....am full of turkey!
73's
de wb0rai Don

On Fri, Nov 25, 2011 at 12:33 AM, Paul Dulaff <pdulaff at embarqmail.com>wrote:

> Don
>
> Could you post details on the mixer circuit such as the plate load
> resistor values, cathode resistor value, etc.
>
> Some literature states that the 6ES8 and the 6DJ8 can be substituted.
>
> Best 73's
>
> Paul - WB2NMI
>
> ----- Original Message -----
> From: donald haworth <donmhaworth at gmail.com>
> To: HBR Receiver List <hbr at mailman.qth.net>
> Sent: Wed, 23 Nov 2011 20:06:44 -0500 (EST)
> Subject: [HBR] Pullen mixer
>
> Some time ago I posted some questions about a dual triode mixer, as
> described by Walt.  A very simple circuit, indeed, with the plates tied
> together, a common cathode to ground via a 470 ohm resistor, and the signal
> and LO fed on the grids.
> -Long story, short--I built it and it worked, as  advertised.  Noise was
> about same as the pentagrid convertor, however, and gain was much
> lower-that was no surprise-but I did expect the noise to be a bit better..
> I must add that I am running only 26 volts on the plate.(26d6).  The twin
> triode I was using is a 6gm8.  I then tried it in a Pullen configuration.
> One plate with 20 volts and second plate (with LO to grid)  2.2 volts--this
> via a 50k pot so I could adjust the voltage.....WOW!!  What a difference!
> All kinds on gain, NO noise---sounds like the antenna has been disconnected
> -then you tune across a signal and it pops out.....!  Really impressive.
> And the best part----no spurs --no birdies---I am using a N3ZI DDS for the
> LO.  Injection is 250mv.  Antenna running into the other grid-no
> tuning-nothing-and it blows away every mixer circuit I have tried, to
> date.  I have found the best way to test a mixer circuit is to input a
> signal to the (signal) grid--no rf amp-no tuning...this will show up a bad
> / good design in a hurry.  A good RF front end will cover a multitude of
> mixers problems, so eliminating it will give you a good idea of how well
> the mixer preforms.....
> --I am now a believer.  All the things they say about the Pullen are
> true---and all it took was three resistors added to Walt's dual triode
> circuit!  I must say that the Plate voltage ratio is critical--it will make
> the difference between no signal and Grins and Giggles-but a pot in a
> voltage divider circuit to feed the second grid, and just tune for the best
> output......for the 6gm8, I have 20volts on plate 1 and only 2.2 on plate
> 2............
> ----Give it a try!
> ---and a Happy Thanksgiving to all
> Don (wb0rai) in Nashville
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

From pdulaff at embarqmail.com  Fri Nov 25 16:29:52 2011
From: pdulaff at embarqmail.com (Paul Dulaff)
Date: Fri, 25 Nov 2011 16:29:52 -0500 (EST)
Subject: [HBR] Pullen mixer
In-Reply-To: <CAMwEKFjWKLxciGOi9gfueeCYcvbq=mh2Pg4oWAqSP2=3ADhjGA@mail.gmail.com>
Message-ID: <1924988469.368892.1322256592373.JavaMail.root@md23.embarq.synacor.com>

Don

Interesting stuff !

I was checking on pricing for the 6GM8. The audio folks have taken this tube since they can build tube preamps using low voltage and not hurt themselves. These folks are also seeing good signal to noise with these tubes.

Bad news is the audio folks have driven the price of these tubes very high.

The data I have so far has the 6GM8 at 2500 micromho's for transconductance. The 6ES8/6DJ8 has 12,500 micromho's. But, I think the key to low tube noise is low plate resistance.

I plan to get back into my HBR and my 75A-4 using the Pullen Mixer, but haven't gotten the time just yet.

I see that the 6ES6 is the low voltage pentode used for RF/If amplifier in the same car radio applications. May be a good mate for the RF amp to your Pullen Mixer.

Best 73's

Paul - WB2NMI



----- Original Message -----
From: donald haworth <donmhaworth at gmail.com>
To: HBR Receiver List <hbr at mailman.qth.net>
Sent: Fri, 25 Nov 2011 03:07:03 -0500 (EST)
Subject: Re: [HBR] Pullen mixer

Paul
The tube I am using is a 6gm8 dual triode which was designed to run with 30
on the plate(s).  IIRC, the transconductance is around 7800 @ 30 volts.  My
radio is based on the Collins r392, so my B+ runs at 25-26 volts.  Same for
the heaters.
As this was somewhat uncharted ground (at least for me), I was not sure
what The 6gm8 plates should run at.  The 6es8 calls for 150 on the 'signal'
triode and 50 volts on the "LO" triode.  I tried to keep the same 3:1 ratio
on the 'gm8.  I ended up with a 50k pot-wiper to the second plate.  Top of
pot to 25volt B+.  Bottom of pot to ground.  The 'signal' plate B+ was fed
via a 1.8k resistor, 20 volts on that plate, and the plate is at RF ground,
through a .01 cap.
The grid of the 'signal' triode has a 120k resistor to ground.  The 'LO'
triode grid has a 120k resistor to the CATHODES-not to ground-.  The
cathodes are tied together and go to ground via a 300 0hm resistor.
I forgot to mention-the output is taken from an IF transformer.  The
primary is between the plate (LO triode) and the B+ supplied from the wiper
of the 50k pot.  Secondary to IF stage. There is a .01 cap to ground on the
B+ side of the IF transformer.

With an antenna connected to the grid of the 'signal' triode (via a .01
cap), and a signal from a signal generator set to 5455 kc--assuming your
using a 455kc IF-tune the pot until you hear WWV!
As I mentioned, I am using a tube designed for low voltage B+.  I see no
reason why the pot voltage 'tuning' would not work with other tubes.  I did
find that .5 volt made all the difference in the world, so the pot was left
in the circuit.  The adjustment is rather critical-at least with the
6gm8-but once you find the 'sweet spot' it is very stable, however..........
TRY IT!!  I have yet to feed it with a tuned rf stage--RF stages can hide a
bunch of mixer problems--so if it works well-and it does! w /o any
tuning....it should really shine coupled with a good front end.
--let me know how yours works, and if I can answer any other questions.
Hope the above makes some sense....am full of turkey!
73's
de wb0rai Don

On Fri, Nov 25, 2011 at 12:33 AM, Paul Dulaff <pdulaff at embarqmail.com>wrote:

> Don
>
> Could you post details on the mixer circuit such as the plate load
> resistor values, cathode resistor value, etc.
>
> Some literature states that the 6ES8 and the 6DJ8 can be substituted.
>
> Best 73's
>
> Paul - WB2NMI
>
> ----- Original Message -----
> From: donald haworth <donmhaworth at gmail.com>
> To: HBR Receiver List <hbr at mailman.qth.net>
> Sent: Wed, 23 Nov 2011 20:06:44 -0500 (EST)
> Subject: [HBR] Pullen mixer
>
> Some time ago I posted some questions about a dual triode mixer, as
> described by Walt.  A very simple circuit, indeed, with the plates tied
> together, a common cathode to ground via a 470 ohm resistor, and the signal
> and LO fed on the grids.
> -Long story, short--I built it and it worked, as  advertised.  Noise was
> about same as the pentagrid convertor, however, and gain was much
> lower-that was no surprise-but I did expect the noise to be a bit better..
> I must add that I am running only 26 volts on the plate.(26d6).  The twin
> triode I was using is a 6gm8.  I then tried it in a Pullen configuration.
> One plate with 20 volts and second plate (with LO to grid)  2.2 volts--this
> via a 50k pot so I could adjust the voltage.....WOW!!  What a difference!
> All kinds on gain, NO noise---sounds like the antenna has been disconnected
> -then you tune across a signal and it pops out.....!  Really impressive.
> And the best part----no spurs --no birdies---I am using a N3ZI DDS for the
> LO.  Injection is 250mv.  Antenna running into the other grid-no
> tuning-nothing-and it blows away every mixer circuit I have tried, to
> date.  I have found the best way to test a mixer circuit is to input a
> signal to the (signal) grid--no rf amp-no tuning...this will show up a bad
> / good design in a hurry.  A good RF front end will cover a multitude of
> mixers problems, so eliminating it will give you a good idea of how well
> the mixer preforms.....
> --I am now a believer.  All the things they say about the Pullen are
> true---and all it took was three resistors added to Walt's dual triode
> circuit!  I must say that the Plate voltage ratio is critical--it will make
> the difference between no signal and Grins and Giggles-but a pot in a
> voltage divider circuit to feed the second grid, and just tune for the best
> output......for the 6gm8, I have 20volts on plate 1 and only 2.2 on plate
> 2............
> ----Give it a try!
> ---and a Happy Thanksgiving to all
> Don (wb0rai) in Nashville
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
______________________________________________________________
HBR mailing list
Home: http://mailman.qth.net/mailman/listinfo/hbr
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:HBR at mailman.qth.net

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Please help support this email list: http://www.qsl.net/donate.html


From waltah at earthlink.net  Fri Nov 25 16:36:46 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Fri, 25 Nov 2011 16:36:46 -0500
Subject: [HBR] HR-10 to HBR project
In-Reply-To: <CAF334AF.D916%waltah@earthlink.net>
Message-ID: <CAF5749E.DA78%waltah@earthlink.net>

Pictures of the project can be found here:

https://picasaweb.google.com/105255380483660395824/Walt2011Project

The first four (from upper left) are the original HR-10.   Then there are
two with the front end area stripped; the bandswitch assembly (coils ...)
have also been removed, though you can't see that in the pictures.
Finally, six pictures showing the HBR-ized version.   Points of interest:

1. The shield plate between the antenna and mixer coils.   It has to be this
large to prevent oscillation.

2. Relocation of the CAL capacitor from left of the ANT TRIM cap to below
it.  (Saw off the bracket, new hole in panel and new mounting holes in
chassis.)   This frees up the space just to the right of the tuning cap for
the coils.

3. Slide switches gone -- replaced with miniature toggle switches.

4. Large toggle switch does ON/OFF function, replacing the switch on the
volume control.

5. S-meter aligned with panel markings.

6. Three more tubes -- all 6BH6's -- for the three oscillator functions.

7. Extra holes for the 100 kcs calibrator function at the right rear of the
chassis are a mistake: This function is now in front of and just left of the
tuning cap.

8. Blocks of wood taped to top of power transformer (in some pics) allow the
set to be flipped over without resting on the shield plate.

9. In the new rear view you can see that the 3rd IFT (tall) and BFO coil
(short) have been exchanged.  The added BFO tube is visible between the
output transformer and the filter cap.

The BFO was formerly the triode half of the 2nd IF tube -- an impossible
location if you don't want the BFO getting in the IF and taking over the
AGC.   

10.  The coil in the 'accessory' socket at the right rear of the set is the
(Hartley) oscillator coil.   It stays cool enough there that there's almost
no drift.   The 6BH6 ECO LO is partly visible to the right of the oscillator
coil.   The tube between the 1st IFT and the rear of the tuning cap is the
12AT7 mixer.  

11.  The new power line connector and BNC antenna connection are visible on
the rear apron.  

12. Barely visible on the meter terminals are the two strings of 1N4001
diodes I use to protect meter movements on projects like this when the meter
is on the HV side so any short will cause loss of the smoke from some
part(s).   

I was pleasantly surprised at how little chassis hacking was required.
Holes had to be added for the new tubes and the new panel is a pretty big
job but most of the work wasn't too difficult.

There is one loose end in front panel layout.   The BFO TUNE variable cap
got moved to the former location of the RF/IF gain control.   (To shorten
the leads and thus reduce coupling into the IF.)  That worked okay as did
installing the power toggle switch in the former BFO control spot.   However
the RF/IF gain control really doesn't fit in the former bandswitch knob
location: It has to be wedged in forward of the drum for the tuning cap
string drive.  It works, but ... There needs to be a better answer to this.
Maybe right above the current phone jack hole?   NOT great human factors
there ...

Or move the ON/OFF switch above the phone jack hole and use the former BFO
TUNE control location for the RF/IF gain control?

Probably I will solve the RF/IF gain control location problem on this set by
using an extension bushing and a pot with a longer shaft so the pot itself
will be behind (clear of) the drum.  However unless you have a very well
filled junkbox, those extensions are probably unobtainium so another
approach should be found for any future build.

Bottom line: I think a satisfactory W6TC HBR design can be built on an HR-10
chassis provided that you use the crystal lattice filter and only the 1681
kcs IF instead of double conversion to 85 or 100 kcs.  The dial and tuning
cap are adequate, the plug in coils worked out fine, the selectivity is
pretty much perfect, there's plenty of room on the chassis ...

My set is close to an HBR-11 except for using the Heath 1681 kcs IF.   I
also used different second detector and AGC circuits but the W6TC circuits
would fit fine and are easier to build.  My version of the HBR-11
uses dual section tubes for the two IFs (eliminating the 12AT7) and omits
the voltage regulator tube; it thus gets the count down to 10 sockets,
counting the rectifier.   You could do it with 9 sockets by using a dual
section tube for the mixer and LO but there's plenty of room and I didn't
want to do that.  

At this point I can't fault any of the choices of tubes: The 6LM8 semiremote
pentode/triode IF stages are good, the 6EH7 RF stage can't be beat for that
job and the (lower powered) 6LF8 audio tube is plenty.

(FOOTNOTE: The 6LM8 IF tube seems to be rare:  I got four from Antique Radio
but they have no more and eBay lists a total of three: Two at $4 and one at
$18.   An alternative would be using the original 6EA8's and tweaking the
AGC circuit to apply a quarter to half voltage to these stages.  You can see
how this is done in the HBR-13C circuit.)

The best way to approach this project would be to get the project HR-10
working (to test all the parts) then strip it to a bare chassis.  The
oddities of original builder wiring, the fact that the original wiring
rarely has more than 1/4" of slack and that Heath recommended wrapping
connections, together with the extensive changes needed, make a rolling
conversion (as I did on this project) a time consuming and
not-too-satisfactory option.

> The hum audible at full volume was coming from the detector stage.

In the end I changed the HV filtering from resistors to a choke input filter
followed by another choke.   The improved regulation -- about 16V difference
from full gain to IF stages cut off, instead of 60V or so -- made a bit more
trouble seem worth it.   These are a pair of command receiver chokes;
they're rated 3H at 60 mA and the current doesn't go much over 70 mA even
with no signal so they should be fine.

With that change and just a bit more filtering for the BFO, the hum is GONE
and if all goes well I'll probably start the new AGC circuit in the next day
or so. It's easier to do that before working on the shortage of gain because
uncontrolled high gain causes so much distortion.

Also, the most obvious place to raise the gain is the 2nd IF which has the
original 470 ohm cathode resistor.   Changing that to a more suitable value
will likely require changes to the S-meter parts values since the meter is
in the plate circuit of that stage.   Unfortunately the S-meter uses a 2 mA
movement (800-820 ohms resistance) so it needs pretty high driving power.

The AGC change is complicated: It needs a negative HV supply, the RF/IF gain
circuit gets replaced, AND there's the AGC amp stage itself with a new rear
apron control.  

Walt
KJ4KV




From waltah at earthlink.net  Fri Nov 25 19:26:38 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Fri, 25 Nov 2011 19:26:38 -0500
Subject: [HBR] Pullen mixer
In-Reply-To: <CAMwEKFjWKLxciGOi9gfueeCYcvbq=mh2Pg4oWAqSP2=3ADhjGA@mail.gmail.com>
Message-ID: <CAF59C6E.DA94%waltah@earthlink.net>

Donald said:

> RF stages can hide a bunch of mixer problems

Mixer characteristics -- which may or may not be problems in a particular
application -- include internal noise, linearity on the signal path, and
gain.   An RF stage can make up for low gain (though usually that is better
done in the IF section), and hide the mixer noise.

An RF stage generally has three functions:

1.  Raising the signal level above mixer noise.

2. Isolating two signal frequency tuned circuits, thus simplifying their
design; and,

3. Acting as a controlled attenuator for signals much stronger than needed
to overcome mixer noise that would otherwise drive the mixer into the
non-linear range.   Generally this attenuator function needs both automatic
control (AGC) and manual (AGC threshold or RF/IF gain) control to cope with
the various situations.

Examples of ways this can play out are:

1.  The many 1940's designs with extremely noisy pentagrid and hexode mixers
that were nonetheless tolerable sets because of a high gain RF stage;

2. The G2DAF receiver with a 6ES8 RF stage for isolation and AGC purposes
operating at less than unity gain ahead of a very quiet 6DJ8 push-pull
triode mixer; and,

3. The Squires-Saunders SS-1R set with a beam deflection mixer (very quiet
AND able to handle very large signals) and no RF stage.

When you break new ground -- I'd guess that a Pullen circuit with ~2V on the
plate of the mixer scores as 'new ground' -- you get to figure out how the
rules apply to your creation.   I gather that the noise is low and the gain
ample but I don't see how it could handle very large signals while remaining
linear.  Maybe NO RF stage?   Donno ...

You can do the standard interference free dynamic range (IFDR) test with two
signal generators 20 kcs apart to get a number for this.   Or just set it up
and listen to 80M SSB in the evening traffic peak: If everything sounds just
as good then as it does at 2 AM local time, you don't have a dynamic range
problem.

(IFDR test: What is the signal strength that produces a chosen S/N ratio --
say 10 dB at 3800 kcs?  What is the signal from two (equal output)
generators when they are tuned to 3820 and 3840 that produces the same S/N
ratio at 3800 kcs?   The ratio of the two signals is the IFDR.

(There is some fussiness about connecting the two signal generators so they
don't see each other and cross-modulate in their own circuits.   There is a
fairly simple circuit to prevent this; the details are in the more recent
Handbooks.)

IFDR testing generally puts greatest stress on the last stage before the
really sharp selectivity.   That's because once you go through the
'knothole' the signals that are 20 and 40 kcs away from the desired
frequency are so much attenuated that they can no longer cause
non-linearity.  

In a set like the HR-10, the stress would be on the mixer because the
crystal filter is in that plate circuit.   In a 'true' HBR it could be in
the first or second mixer or even in the first LF IF because 20/40 kcs isn't
that far off for these stages and there is gain at each stage, as well.

Poorly designed RF stages -- too much gain, particularly if the tube itself
doesn't handle large signals well -- can also be the limiting factor in
IFDR.  The antenna coil Q is often limited by the load of the antenna so it
gives little help.   Basically an RF stage should have just enough gain to
cover the mixer noise and the mixer should have just enough to cover the
noise of the 1st IF.   If the 'knothole' is in the mixer plate circuit
you're home free after that and as much additional gain as needed can be
supplied in the IFs, detector, and even audio stages.

One question would be how the mixer job was done in the auto radios that
were designed around the space charge tubes.  Auto radios MUST handle large
signals so that ability should be a given with that tube/circuit.   And most
auto radios are reasonably sensitive as well.

The reason you found the push-push triode circuit to be high noise is that
it's not a good choice for use without an RF stage.  It does, however, have
a high dynamic range, meaning that if you boost the signal above the tube
noise you still have room before you drive the tube into non-linearity.

Somewhere I was hanging out a decade or so ago somebody was joking that an
833A might be an ideal receiver RF stage or mixer.  It wouldn't, really, but
that guy did understand that the ability to handle some power is a
requirement for HF receiver front ends.

My nominee for the least-well exploited mixer circuit is the beam deflection
tubes -- 6AR8, 6JH8, 6ME8, and 7360.   While there are some design hurdles
to get over they're not beyond anyone who could build a W6TC set from
scratch and you will have a radio with very few peers -- it should equal or
even beat the R390s for IFDR.   Unfortunately no ham design that I know of
made good use of these tubes.

The Miser's Dream and related sets (the Advanced Six Tube Amateur Receiver
in the '69 handbook) are the only ones I know of and the designer of the
Advanced Six ... really didn't get it: He turned out a single band receiver
(80M) using a 7360 mixer with no RF stage -- okay so far -- but used a 455
kcs IF, presumably so that he could use a Collins mechanical filter for
selectivity.   Great on 80, but images will be a problem if the front end is
tuned for higher bands.  Well, he knew that, so he put a crystal controlled
converter in front of it.   Image problem solved but the 1st mixer is now in
the converter and is perfectly conventional in design.

It's not bad as such things go but a showcase for the possibilities with a
beam mixer it isn't.   The SS-1R design is the one to follow:  If stripped
of all the complexity it will do the job and the circuit is out there.

General information on the SS-1R is here:
http://www.w1vd.com/SS-1R.html

Look at those performance numbers!   Yeah, the 0.5 uV sensitivity isn't
remarkable but it's all you need on HF and the numbers you do need, beat
everything including the R-390.

(My hat is off to anyone with the tools to MEASURE an IFDR of 94 dB!)

The schematics can be found here:
http://bama.edebris.com/manuals/squires/ss1r

In the five files with 'sch' in the file name.

There's probably some sort of beam tube HBR in the KJ4KV future.   Maybe on
the second HR-10 chassis?   Maybe three years from now?

Walt 
KJ4KV











From donmhaworth at gmail.com  Fri Nov 25 20:26:08 2011
From: donmhaworth at gmail.com (donald haworth)
Date: Fri, 25 Nov 2011 20:26:08 -0500
Subject: [HBR] Pullen mixer
In-Reply-To: <1924988469.368892.1322256592373.JavaMail.root@md23.embarq.synacor.com>
References: <CAMwEKFjWKLxciGOi9gfueeCYcvbq=mh2Pg4oWAqSP2=3ADhjGA@mail.gmail.com>
	<1924988469.368892.1322256592373.JavaMail.root@md23.embarq.synacor.com>
Message-ID: <CAMwEKFjtZLbRrSbcbjnbhywsUDyKLM1nWPFTF3gNMfXKetuFkA@mail.gmail.com>

Paul, Yes the 'gm8 is north of 20 bucks...might just as well be putting a
down-payment on a 7360 beam deflection tube.  I must have miss-read the
Gm--I thought the transconductance was 2500 with 6.3v on the
plate....increasing to about 8k or so at the max plate voltage (30
volts)...will have to go back and look again.
--The 6es8 is an interesting tube in its' own right, and I think I'll give
one a try-at 30 volts- Another tube to try is the 6gk5--two of them-- I
made a regen with one once that was hotter than anything I've ever come
across-and that with plate voltage of 18 volts....two nine volt
batteries...... I think (two) 6cw4's might be interesting.....
At any rate, build it with the pot so you can adjust for best operation.
It makes a HUGH difference between a good mixer and an outstanding one.
-The 6es8 was used by Eddystone in one of their receivers, as a cascode RF
amp in the front end.  It was also used as the front end in a lot of TV
sets.  Very good tube,  Frame Grid tubes are a cut above, no doubt about it.
best 73
Don

On Fri, Nov 25, 2011 at 4:29 PM, Paul Dulaff <pdulaff at embarqmail.com> wrote:

> Don
>
> Interesting stuff !
>
> I was checking on pricing for the 6GM8. The audio folks have taken this
> tube since they can build tube preamps using low voltage and not hurt
> themselves. These folks are also seeing good signal to noise with these
> tubes.
>
> Bad news is the audio folks have driven the price of these tubes very high.
>
> The data I have so far has the 6GM8 at 2500 micromho's for
> transconductance. The 6ES8/6DJ8 has 12,500 micromho's. But, I think the key
> to low tube noise is low plate resistance.
>
> I plan to get back into my HBR and my 75A-4 using the Pullen Mixer, but
> haven't gotten the time just yet.
>
> I see that the 6ES6 is the low voltage pentode used for RF/If amplifier in
> the same car radio applications. May be a good mate for the RF amp to your
> Pullen Mixer.
>
> Best 73's
>
> Paul - WB2NMI
>
>
>
> ----- Original Message -----
> From: donald haworth <donmhaworth at gmail.com>
> To: HBR Receiver List <hbr at mailman.qth.net>
> Sent: Fri, 25 Nov 2011 03:07:03 -0500 (EST)
> Subject: Re: [HBR] Pullen mixer
>
> Paul
> The tube I am using is a 6gm8 dual triode which was designed to run with 30
> on the plate(s).  IIRC, the transconductance is around 7800 @ 30 volts.  My
> radio is based on the Collins r392, so my B+ runs at 25-26 volts.  Same for
> the heaters.
> As this was somewhat uncharted ground (at least for me), I was not sure
> what The 6gm8 plates should run at.  The 6es8 calls for 150 on the 'signal'
> triode and 50 volts on the "LO" triode.  I tried to keep the same 3:1 ratio
> on the 'gm8.  I ended up with a 50k pot-wiper to the second plate.  Top of
> pot to 25volt B+.  Bottom of pot to ground.  The 'signal' plate B+ was fed
> via a 1.8k resistor, 20 volts on that plate, and the plate is at RF ground,
> through a .01 cap.
> The grid of the 'signal' triode has a 120k resistor to ground.  The 'LO'
> triode grid has a 120k resistor to the CATHODES-not to ground-.  The
> cathodes are tied together and go to ground via a 300 0hm resistor.
> I forgot to mention-the output is taken from an IF transformer.  The
> primary is between the plate (LO triode) and the B+ supplied from the wiper
> of the 50k pot.  Secondary to IF stage. There is a .01 cap to ground on the
> B+ side of the IF transformer.
>
> With an antenna connected to the grid of the 'signal' triode (via a .01
> cap), and a signal from a signal generator set to 5455 kc--assuming your
> using a 455kc IF-tune the pot until you hear WWV!
> As I mentioned, I am using a tube designed for low voltage B+.  I see no
> reason why the pot voltage 'tuning' would not work with other tubes.  I did
> find that .5 volt made all the difference in the world, so the pot was left
> in the circuit.  The adjustment is rather critical-at least with the
> 6gm8-but once you find the 'sweet spot' it is very stable,
> however..........
> TRY IT!!  I have yet to feed it with a tuned rf stage--RF stages can hide a
> bunch of mixer problems--so if it works well-and it does! w /o any
> tuning....it should really shine coupled with a good front end.
> --let me know how yours works, and if I can answer any other questions.
> Hope the above makes some sense....am full of turkey!
> 73's
> de wb0rai Don
>
> On Fri, Nov 25, 2011 at 12:33 AM, Paul Dulaff <pdulaff at embarqmail.com
> >wrote:
>
> > Don
> >
> > Could you post details on the mixer circuit such as the plate load
> > resistor values, cathode resistor value, etc.
> >
> > Some literature states that the 6ES8 and the 6DJ8 can be substituted.
> >
> > Best 73's
> >
> > Paul - WB2NMI
> >
> > ----- Original Message -----
> > From: donald haworth <donmhaworth at gmail.com>
> > To: HBR Receiver List <hbr at mailman.qth.net>
> > Sent: Wed, 23 Nov 2011 20:06:44 -0500 (EST)
> > Subject: [HBR] Pullen mixer
> >
> > Some time ago I posted some questions about a dual triode mixer, as
> > described by Walt.  A very simple circuit, indeed, with the plates tied
> > together, a common cathode to ground via a 470 ohm resistor, and the
> signal
> > and LO fed on the grids.
> > -Long story, short--I built it and it worked, as  advertised.  Noise was
> > about same as the pentagrid convertor, however, and gain was much
> > lower-that was no surprise-but I did expect the noise to be a bit
> better..
> > I must add that I am running only 26 volts on the plate.(26d6).  The twin
> > triode I was using is a 6gm8.  I then tried it in a Pullen configuration.
> > One plate with 20 volts and second plate (with LO to grid)  2.2
> volts--this
> > via a 50k pot so I could adjust the voltage.....WOW!!  What a difference!
> > All kinds on gain, NO noise---sounds like the antenna has been
> disconnected
> > -then you tune across a signal and it pops out.....!  Really impressive.
> > And the best part----no spurs --no birdies---I am using a N3ZI DDS for
> the
> > LO.  Injection is 250mv.  Antenna running into the other grid-no
> > tuning-nothing-and it blows away every mixer circuit I have tried, to
> > date.  I have found the best way to test a mixer circuit is to input a
> > signal to the (signal) grid--no rf amp-no tuning...this will show up a
> bad
> > / good design in a hurry.  A good RF front end will cover a multitude of
> > mixers problems, so eliminating it will give you a good idea of how well
> > the mixer preforms.....
> > --I am now a believer.  All the things they say about the Pullen are
> > true---and all it took was three resistors added to Walt's dual triode
> > circuit!  I must say that the Plate voltage ratio is critical--it will
> make
> > the difference between no signal and Grins and Giggles-but a pot in a
> > voltage divider circuit to feed the second grid, and just tune for the
> best
> > output......for the 6gm8, I have 20volts on plate 1 and only 2.2 on plate
> > 2............
> > ----Give it a try!
> > ---and a Happy Thanksgiving to all
> > Don (wb0rai) in Nashville
> > ______________________________________________________________
> > HBR mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/hbr
> > Help: http://mailman.qth.net/mmfaq.htm
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> >
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> >
> > ______________________________________________________________
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From donmhaworth at gmail.com  Fri Nov 25 20:59:22 2011
From: donmhaworth at gmail.com (donald haworth)
Date: Fri, 25 Nov 2011 20:59:22 -0500
Subject: [HBR] Pullen mixer
In-Reply-To: <CAF59C6E.DA94%waltah@earthlink.net>
References: <CAMwEKFjWKLxciGOi9gfueeCYcvbq=mh2Pg4oWAqSP2=3ADhjGA@mail.gmail.com>
	<CAF59C6E.DA94%waltah@earthlink.net>
Message-ID: <CAMwEKFiJD-UZzGNQCgGNoSXxp5VeUS1fX8Oa=gXRT2V8Aa7Asw@mail.gmail.com>

Walt
Good reading, as always.  I have always wanted  a SS-1r......the stuff
dreams are made of-to quote a famous movie line.....had both the R390 and
390a at one time, as well as a WJ HF1000.  Sold my HRO500 about 5 years
ago.....so now I have only the HQ180 to compare my homebuilt stuff to.
As to strong signal handling ability, the 6gm8 (Pullen) is able to hear a
signal on 630-with only minor noise from WSM on 650.  Same is true on the
other side of 650.  670 in Chicago comes in like a local with no shot noise
from WSM.  This with a long wire end fed at about 40 feet high, input on
directly on the grid.  WSM, with my tuned-loop antenna, measures 0.9 volts
p/p  with the scope hooked to the antenna-lots of signal!  So anything I
can hear  either side of 650, well, I know I am on the right track.....
I will try to get some 'real' numbers asap....
-Hope you had a good Thanksgiving
73 Don
On Fri, Nov 25, 2011 at 7:26 PM, Walt Hutchens <waltah at earthlink.net> wrote:

> Donald said:
>
> > RF stages can hide a bunch of mixer problems
>
> Mixer characteristics -- which may or may not be problems in a particular
> application -- include internal noise, linearity on the signal path, and
> gain.   An RF stage can make up for low gain (though usually that is better
> done in the IF section), and hide the mixer noise.
>
> An RF stage generally has three functions:
>
> 1.  Raising the signal level above mixer noise.
>
> 2. Isolating two signal frequency tuned circuits, thus simplifying their
> design; and,
>
> 3. Acting as a controlled attenuator for signals much stronger than needed
> to overcome mixer noise that would otherwise drive the mixer into the
> non-linear range.   Generally this attenuator function needs both automatic
> control (AGC) and manual (AGC threshold or RF/IF gain) control to cope with
> the various situations.
>
> Examples of ways this can play out are:
>
> 1.  The many 1940's designs with extremely noisy pentagrid and hexode
> mixers
> that were nonetheless tolerable sets because of a high gain RF stage;
>
> 2. The G2DAF receiver with a 6ES8 RF stage for isolation and AGC purposes
> operating at less than unity gain ahead of a very quiet 6DJ8 push-pull
> triode mixer; and,
>
> 3. The Squires-Saunders SS-1R set with a beam deflection mixer (very quiet
> AND able to handle very large signals) and no RF stage.
>
> When you break new ground -- I'd guess that a Pullen circuit with ~2V on
> the
> plate of the mixer scores as 'new ground' -- you get to figure out how the
> rules apply to your creation.   I gather that the noise is low and the gain
> ample but I don't see how it could handle very large signals while
> remaining
> linear.  Maybe NO RF stage?   Donno ...
>
> You can do the standard interference free dynamic range (IFDR) test with
> two
> signal generators 20 kcs apart to get a number for this.   Or just set it
> up
> and listen to 80M SSB in the evening traffic peak: If everything sounds
> just
> as good then as it does at 2 AM local time, you don't have a dynamic range
> problem.
>
> (IFDR test: What is the signal strength that produces a chosen S/N ratio --
> say 10 dB at 3800 kcs?  What is the signal from two (equal output)
> generators when they are tuned to 3820 and 3840 that produces the same S/N
> ratio at 3800 kcs?   The ratio of the two signals is the IFDR.
>
> (There is some fussiness about connecting the two signal generators so they
> don't see each other and cross-modulate in their own circuits.   There is a
> fairly simple circuit to prevent this; the details are in the more recent
> Handbooks.)
>
> IFDR testing generally puts greatest stress on the last stage before the
> really sharp selectivity.   That's because once you go through the
> 'knothole' the signals that are 20 and 40 kcs away from the desired
> frequency are so much attenuated that they can no longer cause
> non-linearity.
>
> In a set like the HR-10, the stress would be on the mixer because the
> crystal filter is in that plate circuit.   In a 'true' HBR it could be in
> the first or second mixer or even in the first LF IF because 20/40 kcs
> isn't
> that far off for these stages and there is gain at each stage, as well.
>
> Poorly designed RF stages -- too much gain, particularly if the tube itself
> doesn't handle large signals well -- can also be the limiting factor in
> IFDR.  The antenna coil Q is often limited by the load of the antenna so it
> gives little help.   Basically an RF stage should have just enough gain to
> cover the mixer noise and the mixer should have just enough to cover the
> noise of the 1st IF.   If the 'knothole' is in the mixer plate circuit
> you're home free after that and as much additional gain as needed can be
> supplied in the IFs, detector, and even audio stages.
>
> One question would be how the mixer job was done in the auto radios that
> were designed around the space charge tubes.  Auto radios MUST handle large
> signals so that ability should be a given with that tube/circuit.   And
> most
> auto radios are reasonably sensitive as well.
>
> The reason you found the push-push triode circuit to be high noise is that
> it's not a good choice for use without an RF stage.  It does, however, have
> a high dynamic range, meaning that if you boost the signal above the tube
> noise you still have room before you drive the tube into non-linearity.
>
> Somewhere I was hanging out a decade or so ago somebody was joking that an
> 833A might be an ideal receiver RF stage or mixer.  It wouldn't, really,
> but
> that guy did understand that the ability to handle some power is a
> requirement for HF receiver front ends.
>
> My nominee for the least-well exploited mixer circuit is the beam
> deflection
> tubes -- 6AR8, 6JH8, 6ME8, and 7360.   While there are some design hurdles
> to get over they're not beyond anyone who could build a W6TC set from
> scratch and you will have a radio with very few peers -- it should equal or
> even beat the R390s for IFDR.   Unfortunately no ham design that I know of
> made good use of these tubes.
>
> The Miser's Dream and related sets (the Advanced Six Tube Amateur Receiver
> in the '69 handbook) are the only ones I know of and the designer of the
> Advanced Six ... really didn't get it: He turned out a single band receiver
> (80M) using a 7360 mixer with no RF stage -- okay so far -- but used a 455
> kcs IF, presumably so that he could use a Collins mechanical filter for
> selectivity.   Great on 80, but images will be a problem if the front end
> is
> tuned for higher bands.  Well, he knew that, so he put a crystal controlled
> converter in front of it.   Image problem solved but the 1st mixer is now
> in
> the converter and is perfectly conventional in design.
>
> It's not bad as such things go but a showcase for the possibilities with a
> beam mixer it isn't.   The SS-1R design is the one to follow:  If stripped
> of all the complexity it will do the job and the circuit is out there.
>
> General information on the SS-1R is here:
> http://www.w1vd.com/SS-1R.html
>
> Look at those performance numbers!   Yeah, the 0.5 uV sensitivity isn't
> remarkable but it's all you need on HF and the numbers you do need, beat
> everything including the R-390.
>
> (My hat is off to anyone with the tools to MEASURE an IFDR of 94 dB!)
>
> The schematics can be found here:
> http://bama.edebris.com/manuals/squires/ss1r
>
> In the five files with 'sch' in the file name.
>
> There's probably some sort of beam tube HBR in the KJ4KV future.   Maybe on
> the second HR-10 chassis?   Maybe three years from now?
>
> Walt
> KJ4KV
>
>
>
>
>
>
>
>
>
>
> ______________________________________________________________
> HBR mailing list
> Home: http://mailman.qth.net/mailman/listinfo/hbr
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:HBR at mailman.qth.net
>
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> Please help support this email list: http://www.qsl.net/donate.html
>

From waltah at earthlink.net  Sat Nov 26 15:09:12 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Sat, 26 Nov 2011 15:09:12 -0500
Subject: [HBR] Pullen mixer
In-Reply-To: <CAMwEKFiJD-UZzGNQCgGNoSXxp5VeUS1fX8Oa=gXRT2V8Aa7Asw@mail.gmail.com>
Message-ID: <CAF6B197.DB4D%waltah@earthlink.net>

Donald posted:

> As to strong signal handling ability, the 6gm8 (Pullen) is able to hear a
> signal on 630-with only minor noise from WSM on 650.? Same is true on the
> other side of 650.? 670 in Chicago comes in like a local with no shot noise
> from WSM.? This with a long wire end fed at about 40 feet high, input on
> directly on the grid.

You are able to hear strong signals that you are tuned to in the presence of
off-channel strong signals.  This isn't the exact meaning of strong signal
handling as the term is used for mixers, receivers, etc.   It's a good
example of adequate selectivity -- that would be in your IF, since you're
feeding straight from the antenna.

'Strong signal handling' refers to the following issues:

1. You are listening to a weak one and suddenly the signal disappears and
the atmospheric noise drops too.   Your first thought is "what's wrong with
my receiver" but tuning around you discover an extremely strong station has
just come on, 20 kcs away.   When he's transmitting your receiver is
semi-dead over much of the band.    This is 'receiver blocking.'  The usual
cause is that some early stage -- RF amp or more likely the mixer -- is
being driven into grid current which drops the gain dramatically.

2. You are listening to a weak one on 3798.   There are strong stations on
3818 and 3838 and you can hear a distorted mixture of those transmissions
over the top of the one you are trying to listen to.   Of course this exact
combination is very unlikely but 3806 and 3814, 3791 and 3784, 3838 and 3878
-- and all the rest of such pairs -- work the same way, so on any busy band
there are bad combinations all the time.
 
This is 'intermodulation distortion.'   In a linear stage, 3820 and 3840 IN
will yield 3820 and 3840 OUT -- AND NOTHING ELSE.   But for every stage
there is a signal level that leads to NON-linear operation,  In that case,
3820 and 3840  IN yields the same two out PLUS the same two frequencies
modulated by the difference of 20 kcs.   So you get 3800 and 3860 as well.
Punch that stage with enough signal and you'll get 3780 and 3880 too ...
'second order intermodulation distortion.'   However the first order problem
comes first so that's the one we worry about.

Short story:  Good strong signal performance means being able to listen
without disturbance to a weak signal when there are strong signals elsewhere
on the band.   One of the best tests is 40M in the evening in the section
that is shared with broadcast.   Second to that, 80M in the evening.   A
really good receiver may get chatter from the guy only 5 kcs away (that's a
channel spacing problem -- your receiver can't reject what is actually
within its passband), but whatever you can hear will sound as clean as at
any other time -- not mushy and hard to understand.

One can say "But I don't do weak signal stuff under those conditions."   But
every round table has some stations that are weaker than others, often some
that are MUCH weaker than the others.   A good receiver hears those stations
well if the channel is reasonably clear even if the rest of the band is full
of megastations.   A crummy receiver (one that doesn't handle strong signals
well) makes the weaker stations sound mushy, muffled.

It's also true that intermod distortion makes broadband noise --
thunderstorms are a common example -- worse.   It's 'everywhere' and it is
strong, so in a set with poor intermod performance more of it will be heard
on the channel you're tuned to than would be the case for a better receiver.

'Interference free dynamic range' is a way to give a number to
intermodulation distortion performance.   Take 'a weak signal' as your
standard -- that might be 1 uV or it might be something less; the exact
number doesn't matter.  (A common standard is the signal that gives a 10 dB
S/N ratio.)   Now take two strong signals located 20 kcs and 40 kcs away
from the weak signal:  How much stronger do those two signals (of equal
strength) have to be to produce a spurious signal of the same strength as
the weak signal, on the frequency of that weak signal?

For poor quality receivers -- the early transistorized ham sets were
examples -- the number could be 40-50 dB or so.  Cheap tube ham receivers
like the S-38 and home 'shortwave' sets might be near the lower end of the
range.  I'd guess the HR-10 at 60-70 dB: vacuum tubes are better than
transistors and that crystal filter eliminates problems after the mixer.
Plus using the RF gain as a volume control (as recommended for CW/SSB) will
reduce the RF stage gain and help both it and the mixer.   The R-390 should
hit 80 dB and the SS-1R gets around 90 dB or even higher with a bit more
oscillator injection.

With a receiver having an IFDR over 80 dB you will rarely have a problem
hearing a weak station that's in the clear, regardless of what's on the rest
of the band.   Receivers like the HBRs that have separate gain controls for
the RF stage will also do very well if you back down the RF gain some when
the band is full of strong signals, even if the one you're listening to is
weaker.   

There is no magic about the choice of 20 kcs spacing for the test signals.
It's just a convenient number that's big enough to be clearly
out-of-channel.  Tests are sometimes done with 80 kcs or 100 kcs spacings
and these tell you other things about the set:  While a 20 kcs test result
will only be slightly improved by a high-Q tracking front end (as on the
HBRs), the difference between such a front end and a broadband one (many
modern ham sets) on a 100 kcs test will be dramatic.   (That's why modern
sets all have switchable attenuators ...)

All of that ignores gain and internal noise level.   And that's what one
should (mostly) do when thinking about MF-lower HF receiver designs.   Up to
20M or so front end noise simply isn't an issue but strong signal handling
is very much so.   When using vacuum tubes most designs will be quiet enough
to do well even on 15M and often on 10M as well (IF they have enough LO
injection!) -- but they'll only handle strong signals well enough to be top
performers on 160-80-40 if you design for that.

On the lower HF front end noise only matters in the very worst cases -- like
a 6SA7 mixer with no RF amp -- and gain can be made up anywhere, even in the
audio section.   But once the signal you want to hear is trashed by a
non-linear front end, no later stage of a receiver can fix it.

Walt 
KJ4KV






From waltah at earthlink.net  Tue Nov 29 21:00:02 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Tue, 29 Nov 2011 21:00:02 -0500
Subject: [HBR] A Homebrew design that is rarely mentioned
Message-ID: <CAFAF852.DFC6%waltah@earthlink.net>

Namely, the W5OMX communications receiver, described in QST for January 1968
and in the Single Sideband handbook, 5th edition, 1970.

In concept this could be the best performing of the various home brewable
ham band only sets.   The main features are:

1.  Single conversion using a premixed LO.  The LO tunes 5-5.5 Mcs for all
bands and is mixed with a different crystal for each band -- for example,
7.5 Mcs for the range 3.5-4.0 Mcs.   The IF is 9 Mcs.   The sum of the LO
and band crystal is 9 Mcs above the channel frequency.

2. 7360 beam deflection mixer.

3. Crystal filter in the mixer plate circuit.

4. Bandswitched for 80-40-20-15-11-10M.

5. Pentode RF stage with relatively high-Q (Miniductor) coils.

6. All the other usual HBR features: Product detector for SSB/CW and
infinite impedance detector for AM,

7.  VERY nice panel layout, a Millen two-speed dial, generally good
construction work.   This is a pretty receiver.

Author Dave Curtis (Colonel, USAF) developed the set himself from multiple
sources; he credits W6TC for some of the features.

Except for ease of construction (where the W6TC designs trump all for
home-buildable station receivers) this design should deliver pretty much the
best of all worlds:  The excellent strong signal performance that comes from
having a single mixer ahead of a fixed IF, the stability you get with
running the tunable LO at a lower frequency,  and the low noise of the beam
deflection mixer.  

As built, however, the set has a few faults:

1.  Low mixer gain due to inadequate deflection plate drive.   The author
doesn't say but I'd guess these signals were closer to 1V p-p than the 10V
that would give high gain.

Basically the conversion gain of this tube is directly proportional to the
deflection voltage.   Cut the voltage in half, drop 6 dB of gain.

2.  Due to the low mixer gain he used a fairly high gain RF stage -- and
chose a sharp cutoff pentode for the job.  He also had to boost the IF
stages by adding coupling capacitors across the IFTs.  Doing so makes the
IFTs overcoupled, though at 9 Mcs their contribution to selectivity wouldn't
be important anyway.

He still has a very quiet and sensitive front end and a receiver that is as
stable as the best of them but with these two errors he probably almost
erased the outstanding large signal handling of which the beam mixers are
capable. 

If an RF stage was to be used, it needed to be very low gain -- no more than
slightly above unity -- and use a tube with remote cutoff or even variable
mu characteristics.   The G2DAF set runs the 6ES8 RF stage at LESS than
unity gain -- it is strictly to provide isolation for the two tuned circuits
and allow AGC control of the signal ahead of the mixer.   And the SS-1R uses
no RF stage at all.

3. The chassis is crowded.   The premixed type front end is prone to
'birdies' and thus demands fanatical care in layout and shielding.   That's
hard to do that if you are short of 'real estate.'

4. The single ended crystal/tunable LO setup passed up the opportunity to
use balanced mixing to further reduce birdie troubles.   For example a
single ended tunable LO feeding the control grid of a beam tube premixer
would be rejected in the (balanced) plate circuit that could drive the
signal mixer beam tube.   With decent shielding and bypassing that's one
less signal floating around the set, and the crystal frequencies are in the
tens of Mcs so they're not going to be a big problem.

In addition he fed LO signal to only one deflection plate of the mixer.
That eliminates the balancing of leakage to the control grid where LO
spurious responses are most likely to enter.

The mixer output is taken from just one of the beam tube plates so the mixer
cannot help reject 9 Mcs signals from the antenna side..

Basically what you've got here is a very quiet high gain pentode mixer: the
beam features aren't used at all, except as they contribute to those
characteristics.  

These simplifications made the set a little easier to build but introduced
the second of the two noticeable flaws.   The writer does identify the
birdies as a failing but says that a more felicitous choice of mixing
frequencies might be the solution.   Certainly correct choice of frequencies
is important -- you wouldn't want the premixing image (i.e., xtal freq.
MINUS LO freq. or any simple combination) to be in the corresponding ham
band.   But chucking the chance to attenuate what you do have by 20-30 dB
(through balanced mixer technique) is a self-inflicted wound.

Nonetheless this was a very ambitious project and its goals were largely
realized.   Very few ham receivers of the late 1960's would have come even
close to the performance.  And the glitches could be avoided in a re-do.

I tried to find out more about Colonel Dave Curtis USAF, W5OMX.  I got
nothing from the FCC database: It doesn't even know the call was issued.
There are some 600 Curtis-es currently licensed and without knowing an
initial or anything else, that's it.   There's no info about him either in
the QST article or the SSB Handbook reprint.   There are various on-line
references to a Dave Curtis in the USAF -- an F-80 pilot in 1954-5 and
others -- but nothing that can definitely be tied to W5OMX.

Cold trail, I'm afraid.   That's a shame because it would be nice to give
more meaningful credit where due.

Shame on the ARRL for not picking up this project for the Handbook.  Yes,
it's more challenging than a three or six tube set, yes this one might
require a bit of re-engineering in the ARRL lab to meet their standards,
but it offers superlative performance and isn't at all beyond someone who
has been successful building one of the HBR-series radios.

Once you've done the five or six basic circuits in a receiver, battered them
into proper operation, AND gotten them all to work together, more complex
sets built from established designs are just more drilling and wiring.

Anyhow, this design would be interesting for future work.   So many radio
projects, so little time.

Walt
KJ4KV   



From ianmwilson73 at gmail.com  Wed Nov 30 14:37:57 2011
From: ianmwilson73 at gmail.com (Ian Wilson)
Date: Wed, 30 Nov 2011 11:37:57 -0800
Subject: [HBR] A Homebrew design that is rarely mentioned
In-Reply-To: <CAFAF852.DFC6%waltah@earthlink.net>
References: <CAFAF852.DFC6%waltah@earthlink.net>
Message-ID: <CAEz8jcRSn5+7Pj7=iPHyw1MqCobjYMZcyKTA9viONMD5sb_9Pw@mail.gmail.com>

This is a very interesting read, thank you Walt.

I compared the mixing schemes with the SX-146, which has the following specs
for "in-band tweets": less than 0.25uV equivalent CW except for 1uV at
21.33Mc.

The SX-146 also uses a 5-5.5Mc VFO and 9MHz IF. In contrast to the W5OMX
design, it does no premixing on 80m and 20m. For 15m and 10m the mixing
scheme used by both receivers is the same. For 40m the SX-146 uses a 21.5Mc
xtal while the W5OMX uses an 11Mc xtal.

I haven't worked out the combinations but this means that the SX-146 tunes
some bands backwards and has LSB/USB switched between 80m and 40m.
But that's probably not a bad price to pay if the birdies are minimized as
a result.

Is the tuning drive used any more available than that in the HBR?

73, ian K3IMW

From tshoppa at wmata.com  Wed Nov 30 14:57:06 2011
From: tshoppa at wmata.com (Shoppa, Tim)
Date: Wed, 30 Nov 2011 14:57:06 -0500
Subject: [HBR] A Homebrew design that is rarely mentioned
In-Reply-To: <CAFAF852.DFC6%waltah@earthlink.net>
References: <CAFAF852.DFC6%waltah@earthlink.net>
Message-ID: <B136EDE3DF5EC441B6F08E0A7AB872450F63397CAB@EX2K7-CMS-1.wmata.local>

7360 Mixer beam deflection voltage is limited by simple capacitive coupling from the Hetrodyne mixer. The 10pF series cap has the virtue that it is probably a good and simple way to keep LO level constant as frequency goes up. It's just that the level is always too low by your or my standards :-).

Running enough power through the heterodyne mixer to give 10V at the deflection plates of the 7360 would probably make even more spurs - not made in the 7360 mixer, but from the heterodyne mixer. The heterodyne mixer only has a LC tank to tame the spurs.

Applying HBR-XX style plug in coil per band (would take more than a 5 pin base though) might be a good way to get balance and more drive voltage to the 7360 deflection plates.

In terms of plug in coil sets if we went this hypothetical way... we would get rid of RF amp. Have one plug in coil/cap set (double tuned? I'd aim for that) for front end coupling mixer to antenna; another one for heterodyne oscillator (make it singly balanced to tame spurs even more); a third for coupling heterodyne mixer to 7360. That just might work.

Would certainly be a different approach to all-band coverage, than say Squire-Saunders. That has its elegance too (and optimized the design for the band where you needed the mixer not to crunch - 40M. 40M is tame today compared to how it was when I was a kid! Oh man, SW BC and the woodpecker all over the place.)

Tim N3QE

-----Original Message-----
From: hbr-bounces at mailman.qth.net [mailto:hbr-bounces at mailman.qth.net] On Behalf Of Walt Hutchens
Sent: Tuesday, November 29, 2011 9:00 PM
To: HBR
Subject: [HBR] A Homebrew design that is rarely mentioned

Namely, the W5OMX communications receiver, described in QST for January 1968 and in the Single Sideband handbook, 5th edition, 1970.

In concept this could be the best performing of the various home brewable
ham band only sets.   The main features are:

1.  Single conversion using a premixed LO.  The LO tunes 5-5.5 Mcs for all bands and is mixed with a different crystal for each band -- for example,
7.5 Mcs for the range 3.5-4.0 Mcs.   The IF is 9 Mcs.   The sum of the LO
and band crystal is 9 Mcs above the channel frequency.

2. 7360 beam deflection mixer.

3. Crystal filter in the mixer plate circuit.

4. Bandswitched for 80-40-20-15-11-10M.

5. Pentode RF stage with relatively high-Q (Miniductor) coils.

6. All the other usual HBR features: Product detector for SSB/CW and infinite impedance detector for AM,

7.  VERY nice panel layout, a Millen two-speed dial, generally good
construction work.   This is a pretty receiver.

Author Dave Curtis (Colonel, USAF) developed the set himself from multiple sources; he credits W6TC for some of the features.

Except for ease of construction (where the W6TC designs trump all for home-buildable station receivers) this design should deliver pretty much the best of all worlds:  The excellent strong signal performance that comes from having a single mixer ahead of a fixed IF, the stability you get with running the tunable LO at a lower frequency,  and the low noise of the beam deflection mixer.  

As built, however, the set has a few faults:

1.  Low mixer gain due to inadequate deflection plate drive.   The author
doesn't say but I'd guess these signals were closer to 1V p-p than the 10V that would give high gain.

Basically the conversion gain of this tube is directly proportional to the
deflection voltage.   Cut the voltage in half, drop 6 dB of gain.

2.  Due to the low mixer gain he used a fairly high gain RF stage -- and chose a sharp cutoff pentode for the job.  He also had to boost the IF stages by adding coupling capacitors across the IFTs.  Doing so makes the IFTs overcoupled, though at 9 Mcs their contribution to selectivity wouldn't be important anyway.

He still has a very quiet and sensitive front end and a receiver that is as stable as the best of them but with these two errors he probably almost erased the outstanding large signal handling of which the beam mixers are capable. 

If an RF stage was to be used, it needed to be very low gain -- no more than slightly above unity -- and use a tube with remote cutoff or even variable
mu characteristics.   The G2DAF set runs the 6ES8 RF stage at LESS than
unity gain -- it is strictly to provide isolation for the two tuned circuits
and allow AGC control of the signal ahead of the mixer.   And the SS-1R uses
no RF stage at all.

3. The chassis is crowded.   The premixed type front end is prone to
'birdies' and thus demands fanatical care in layout and shielding.   That's
hard to do that if you are short of 'real estate.'

4. The single ended crystal/tunable LO setup passed up the opportunity to
use balanced mixing to further reduce birdie troubles.   For example a
single ended tunable LO feeding the control grid of a beam tube premixer would be rejected in the (balanced) plate circuit that could drive the
signal mixer beam tube.   With decent shielding and bypassing that's one
less signal floating around the set, and the crystal frequencies are in the tens of Mcs so they're not going to be a big problem.

In addition he fed LO signal to only one deflection plate of the mixer.
That eliminates the balancing of leakage to the control grid where LO spurious responses are most likely to enter.

The mixer output is taken from just one of the beam tube plates so the mixer cannot help reject 9 Mcs signals from the antenna side..

Basically what you've got here is a very quiet high gain pentode mixer: the beam features aren't used at all, except as they contribute to those characteristics.  

These simplifications made the set a little easier to build but introduced
the second of the two noticeable flaws.   The writer does identify the
birdies as a failing but says that a more felicitous choice of mixing
frequencies might be the solution.   Certainly correct choice of frequencies
is important -- you wouldn't want the premixing image (i.e., xtal freq.
MINUS LO freq. or any simple combination) to be in the corresponding ham
band.   But chucking the chance to attenuate what you do have by 20-30 dB
(through balanced mixer technique) is a self-inflicted wound.

Nonetheless this was a very ambitious project and its goals were largely
realized.   Very few ham receivers of the late 1960's would have come even
close to the performance.  And the glitches could be avoided in a re-do.

I tried to find out more about Colonel Dave Curtis USAF, W5OMX.  I got nothing from the FCC database: It doesn't even know the call was issued.
There are some 600 Curtis-es currently licensed and without knowing an
initial or anything else, that's it.   There's no info about him either in
the QST article or the SSB Handbook reprint.   There are various on-line
references to a Dave Curtis in the USAF -- an F-80 pilot in 1954-5 and others -- but nothing that can definitely be tied to W5OMX.

Cold trail, I'm afraid.   That's a shame because it would be nice to give
more meaningful credit where due.

Shame on the ARRL for not picking up this project for the Handbook.  Yes, it's more challenging than a three or six tube set, yes this one might require a bit of re-engineering in the ARRL lab to meet their standards, but it offers superlative performance and isn't at all beyond someone who has been successful building one of the HBR-series radios.

Once you've done the five or six basic circuits in a receiver, battered them into proper operation, AND gotten them all to work together, more complex sets built from established designs are just more drilling and wiring.

Anyhow, this design would be interesting for future work.   So many radio
projects, so little time.

Walt
KJ4KV   


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From waltah at earthlink.net  Wed Nov 30 21:31:48 2011
From: waltah at earthlink.net (Walt Hutchens)
Date: Wed, 30 Nov 2011 21:31:48 -0500
Subject: [HBR] A Homebrew design that is rarely mentioned
In-Reply-To: <CAEz8jcRSn5+7Pj7=iPHyw1MqCobjYMZcyKTA9viONMD5sb_9Pw@mail.gmail.com>
Message-ID: <CAFC5144.E16E%waltah@earthlink.net>

Ian posted:

> I compared the mixing schemes with the SX-146, which has the following specs
> for "in-band tweets": less than 0.25uV equivalent CW except for 1uV at
> 21.33Mc.
> 
> The SX-146 also uses a 5-5.5Mc VFO and 9MHz IF. In contrast to the W5OMX
> design, it does no premixing on 80m and 20m. For 15m and 10m the mixing
> scheme used by both receivers is the same. For 40m the SX-146 uses a 21.5Mc
> xtal while the W5OMX uses an 11Mc xtal.

This is another interesting receiver I didn't know about.   There's also the
predecessor SX-133.   I haven't homed in on a schematic yet.

Most sets that use the 5-5.5 Mcs VFO/9 Mcs IF scheme will tune 80 and 20M
without using a crystal at all.   In this case there shouldn't be detectable
birdies (i.e., they'll be of such high order that the receiver won't hear
them) on these bands.  This is the 80/20 'band imaging' receiver design.

The W5OMX design, OTOH, uses premixing with a crystal on these bands too.
As an example of how that can produce spurious signals, on 80M the crystal
is 7.5 Mcs.   7.5 x 2 - 5.5 x 2 = 4 Mcs.   As it happens, the receiver tunes
4 Mcs with the LO at 5.5 Mcs so that's a very fast moving (reverse direction
from tuning) tweet right at 4 Mcs.  Also, 3 x 5.5 - 7.5 = 9 Mcs; that's a
fast moving SAME direction tweet, also at 4 Mcs.

The more frequencies you generate in a receiver, the more potential for
spurious responses and the more care is needed with mixer design, shielding,
and signal levels.  There's no substitute for a careful study of the numbers
before starting, and thinking how the mixing can best be done to minimize
the problems.

The advantage of multiple conversions (instead of using the same frequencies
by premixing and a single conversion) is that when you add new frequencies
one at a time, there are far fewer products to think about.

> I haven't worked out the combinations but this means that the SX-146 tunes
> some bands backwards and has LSB/USB switched between 80m and 40m.
> But that's probably not a bad price to pay if the birdies are minimized as
> a result.

This depends on your use for the receiver and how much simplification you
get in exchange for the birdies.   In a commercial design, pretty much any
detectable birdie is a no-no.   But I have a homebrew band imaging 80/40 M
receiver with a strong birdie in each band that I consider fully
satisfactory:  It has adequate sensitivity with very good strong signal
handling, very stable, excellent AGC and is VERY simple:  7 tubes including
rectifier, no power transformer ...

Generally as  you raise the complexity/cost of a receiver you want to
improve its performance more or less uniformly across all measures:  The
W5OMX is about the most costly/complex receiver a ham would be likely to
build and should have had few to no birdies.   Indeed, as the author
suspects, the basic design would have allowed fewer.

One very simple improvement would have been the use of a double tuned
circuit (per band) in the plate of the premixer.   Use two separate tuned
circuits located near enough each other to get some coupling, peak them both
near the center of the band, then add capacitive coupling to get a double
peak encompassing the middle half or 2/3 of the band.   This will give both
more uniform drive across the band, and reduced spurs.

This isn't really a design for a beginner to build; that level of
sophistication would  have been okay.

Tim commented:

> 7360 Mixer beam deflection voltage is limited by simple capacitive coupling
> from the Hetrodyne mixer. The 10pF series cap has the virtue that it is
> probably a good and simple way to keep LO level constant as frequency goes up.
> It's just that the level is always too low by your or my standards :-).
> 
> Running enough power through the heterodyne mixer to give 10V at the
> deflection plates of the 7360 would probably make even more spurs - not made
> in the 7360 mixer, but from the heterodyne mixer. The heterodyne mixer only
> has a LC tank to tame the spurs.

All true, however had both the premixing and the signal mixing been done
with balanced circuits that could have been much reduced.   20 dB rejection
can be obtained without any balance adjustment and a one time all band
adjustment ought to get most of another 10 dB.

> Applying HBR-XX style plug in coil per band (would take more than a 5 pin base
> though) might be a good way to get balance and more drive voltage to the 7360
> deflection plates.
> 
> In terms of plug in coil sets if we went this hypothetical way... we would get
> rid of RF amp. Have one plug in coil/cap set (double tuned? I'd aim for that)
> for front end coupling mixer to antenna; another one for heterodyne oscillator
> (make it singly balanced to tame spurs even more); a third for coupling
> heterodyne mixer to 7360. That just might work.

Indeed it might.  If you do go with premixing you also need to swap
crystals.   Another way to do it is to use an LO just as for the HBR-series
but perhaps make it push pull?   Not easy, but not impossible, either.

It's also worth looking at slight tweaks of the numbers when you find spurs
that are on a band edge.  50 kcs one way or the other?   Of course such
adjustments need to be checked for all bands: Sometimes they'll fix problems
on two bands and deliver something really nasty on two others!

Ian again:
 
> Is the tuning drive used any more available than that in the HBR?

The 6:36/1 ball drive was used in a number of medium grade commercial sets
and is accordingly not too hard to find in used condition.   Used ones
generally do have backlash although it seems to me that if the grease is
washed out and new grease worked in, then the 'fingers' squeezed ever so
slightly, it ought to be possible to bring these units back to 'like new'
operation.  

I haven't seen a new one recently but Google and eBay might yield something.

Finally, those who want to really dig into dynamic range testing can hardly
do better than the thoughts of John Thorpe of AOR.   The notes at the link
below aren't pitched for beginners but if you have something like an ARRL
Handbook from 1995 or later to get you over the concepts and terminology
then this will take you on from there.   This testing can be done at home
and it will improve your equipment: You just have to know the pitfalls.

http://www.ab4oj.com/test/ar7030comments.html

Walt 
KJ4KV


