From waltah at ntelos.net  Sun Oct  1 12:46:46 2006
From: waltah at ntelos.net (Walt Hutchens)
Date: Sun Oct  1 12:51:40 2006
Subject: [HBR] That General Coverage HBR Project -- 2
In-Reply-To: <451DE2CA.2080801@ntelos.net>
References: <4512F9A0.5080300@ntelos.net> <451DE2CA.2080801@ntelos.net>
Message-ID: <451FF0F6.90300@ntelos.net>

I've got a temporary substitute for the choke and with that and a few
more hours work yesterday, the mechanical stuff is done for now.  Still
gotta make the bandswitch out of an FT-101 unit but it will be months
before that needs to be installed.  Not only will I work from the audio
backward but the bandswitch somewhat restricts access to the tube socket
level of wiring in the front end so I won't install it until that's done.

Metric hardware on the bandswitch -- I got the M3x0.5 die for the switch 
rods from Tower Hobby.  Does anyone have a favorite online hardware 
store with better prices?   $13 with shipping for a 1" die seems a bit 
steep.

I took some photos of the radio and should have them up somewhere tonight.

This is basically the circuit of the R8040A band imaging design with a
simpleminded crystal synthesized converter front ending it. I will 
improve the R8040A design with a 6BN6 product detector and a 12AU7 p-p 
audio output stage.  115 bands of 250 kcs from 1.75 Mcs to 30.75 Mcs. 
That's not using the first five crystals of the BC-1335 set; if they ARE 
used then you pick up the top of the broadcast band but with a 
substantial birdie where the band crystal(those would be 5675-5775 kcs 
inclusive) falls within the 1st IF, 5550-5800 kcs. It's 14 tubes, series 
string filaments so no filament or plate transformer.

I think the main risk areas are getting the synthesizer to work properly 
and building a ladder filter broad enough for SSB at 4.096 Mcs -- that's 
lower than generally recommended.

The R8040A used a 150 mA string but with the higher tube count this one
requires 300 mA.

Having seen the chassis corner gussets in the HBR-16 that just sold on
eBay, I thought I'd try them in the GC-HBR.  WOW, does that stiffen your
chassis -- the thing is almost like a brick.  Definitely worth the
trouble for any design where rigidity/stability is important.

One of the kinds of knowledge I have most regularly picked up is this
kind of "obvious once you see it."  No idea why I so rarely figure it
out ahead of time.

Walt
KJ4KV



From amargosaent at iscweb.com  Sun Oct  1 16:29:33 2006
From: amargosaent at iscweb.com (Amargosa Enterprises)
Date: Sun Oct  1 16:29:00 2006
Subject: [HBR] Locked-up (almost) Eddystone 898 Dial Assembly
Message-ID: <USER_ANONYMOUS$69.85.158.115$.001701c6e598$4f568de0$739e5545@vucppqlj>

My HBR 20 Eddystone 898 dial, which has been getting progressively harder to turn lately, has finally tightened up where it is now approaching a "frozen" condition.  I have partially dis-assembled the dial in place on the panel to be sure it is the dial and not the tuning capacitor; for better or worse, it is the dial.  Partial dis-assembly in my case still does not allow access to the dial main shaft bearing - I must disconnect and remove everything else off the panel so I can pull it (and the dial) straight up and out for final removal and dial dis-assembly.  Obviously, 40 years ago I did not do the panel/dial layout with sufficient thought to dial gearing maintenance.

I suspect there is nothing wrong with the gearing itself, but that the original lubricant (whatever that might be) is fast drying out and in that process has begun to lock the gearing.

Can anyone tell me - 

   1.  How best to remove the dried-up lube (assuming that is the problem), and if solvent is the answer, what to use and what to avoid ?

   2.  Should application of heat to the dial shaft (for the purpose of loosening any hardened lube) be attempted or avoided ?

   3.  What type of lube works best as a replacement in this application ? 

Any thoughts from some having experience or knowledge of resolving this problem would be most appreciated before I go dive in.

Tnx  W6HHT/Jay

 
From windy10605 at juno.com  Sun Oct  1 16:50:34 2006
From: windy10605 at juno.com (windy10605@juno.com)
Date: Sun Oct  1 17:13:51 2006
Subject: [HBR] Locked-up (almost) Eddystone 898 Dial Assembly
Message-ID: <20061001.160723.2500.0.windy10605@juno.com>

Hi Jay,
 
Applying heat with a soldering iron has worked for me in remelting the
grease. Automotive chassis grease works fine for relubrication (wheel
bearing grease is too thick). Some really good lube is the stuff they use
on camshafts/lifters during engine rebuilding.
 
73 Kees K5BCQ.
From daileyservices at qwest.net  Sun Oct  1 19:36:08 2006
From: daileyservices at qwest.net (TC Dailey)
Date: Sun Oct  1 19:46:23 2006
Subject: [HBR] Eddystone 898 Dial Assembly
References: <USER_ANONYMOUS$69.85.158.115$.001701c6e598$4f568de0$739e5545@vucppqlj>
Message-ID: <009201c6e5b2$5f2a87c0$6502a8c0@dailey>

I've had GREAT SUCCESS with the application of a couple of drops of "TriFlo"
on the shaft-to-bearing interface.  It's a teflon compound with the
consistency of WD-40 (black can with orange and yellow markings).  It will
break loose the most stubborn of these problems, and after you've broken it
loose, you can use some of the light PETROLEUM or SILICONE type greases
(Never Lithum based) to make it shine.  Some years ago, there was "silicone
oil" produced for the retarder pistons of turntables (vinyl records), and
it's splendid stuff - never hardens, never flows out due to heat - just
works.

Tom - W?EAJ

From windy10605 at juno.com  Sun Oct  1 22:29:01 2006
From: windy10605 at juno.com (windy10605@juno.com)
Date: Sun Oct  1 22:33:16 2006
Subject: [HBR] Fw: [BOATANCHORS-TEMPE] HBR parts, unbuilt kits
Message-ID: <20061001.212901.1584.4.windy10605@juno.com>

Doc, there is still an active HBR Website .....just search on "HBR
Receiver" and it will bring it up. I have also taken the liberty of
sending your note to the HBR reflector and you can expect some contacts
from the group, since several people are looking for parts.

73 Kees K5BCQ

--------- Forwarded message ----------
From: Lewis c Emerson <lemerson@JUNO.COM>
To: BOATANCHORS@LISTSERV.TEMPE.GOV
Date: Sun, 1 Oct 2006 22:18:38 -0400
Subject: [BOATANCHORS-TEMPE] HBR parts, unbuilt kits
Message-ID: <20061001.221844.-276319.18.lemerson@juno.com>
 
Guys and gals,
 
I've posted here before about my aborted plans to build Ted Crosby's HBR
receiver, but have just not followed through.  I've been sorting through
many boxes and am still finding things.  Now, it's pretty dern certain
that I'll never get around to building it - although I'd still dearly
like to (the XYL would have a fit).  Building stuff, and then getting it
to work was a big time passion for me for many years.  (I'm a retired
research physicist)
 
Here's the problem - while I did collect parts for the HBR, and have most
of them still, I've somehow or other misplaced the schematic and the
associated parts list, so I don't know what I may be missing.  I can't
put up the list on e-Bay or anywhere else until I can give a complete
listing of what I have that's needed to build the HBR.  I, unfortunately,
sold off about 200 vacuum tubes, but may still have a few that are needed
for there HBR, but need to see the parts list.  The tubes should be still
available from a reseller (mine went to Radio Daze - he advertises in
QST)  I'm most sorry that I let these go, but may still have a few among
the 100 or so that are still here.  I think I have most of the rest of
the parts, i.e. the Eddystone 898 dial, all the J.W. Miller coils, the
clear  Amphenol coil forms (even the winding wire), the Hammerlund air
padder capacitors, the parts for the power supply - power Xformer,
chokes, etc.  While I probably have the electrolitics it might be best to
use new ones - mine are 20/30 years old.  I've got tons of resistors and
caps, but have not sorted them.
 
Can someone of you helpful folks point me to a website that has the
schematic/parts list?  And also where I should post my list.  At one time
there was a website devoted to HBR stuff.
 
Finally, is there a place where I can advertise unbuilt kits?  I still
have a few.
 
73 - Doc, W4ITJ
 
-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
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Subscription control -
http://www.tempe.gov/lists/control.asp?list=BOATANCHORS
To post - BOATANCHORS@LISTSERV.TEMPE.GOV
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From waltah at ntelos.net  Tue Oct  3 21:59:23 2006
From: waltah at ntelos.net (Walt Hutchens)
Date: Tue Oct  3 22:04:28 2006
Subject: [HBR] That General Coverage HBR Project -- 3
In-Reply-To: <451FF0F6.90300@ntelos.net>
References: <4512F9A0.5080300@ntelos.net> <451DE2CA.2080801@ntelos.net>
	<451FF0F6.90300@ntelos.net>
Message-ID: <4523157B.6010008@ntelos.net>

There are some pictures of the chassis with parts mounted at:

http://timbreblue.com/radio/hbr1006.html

Looking at the under chassis view, the upper left compartment is the 1st
mixer (no RF stage) and crystal calibrator.  The extra socket hole is in
case I wind up using two tubes for the calibrator -- I want 50 kcs from
a 100 kc crystal, so ... don't know.  The center compartment is the 2nd
mixer and 1454-1704 kcs local oscillator.  Upper right quarter is the
simpleminded synthesizer that supplies the mixing signal to the 1st mixer.

The signal leaves the 2nd mixer box through a 4096 kcs ladder filter
that will be mounted on top of the chassis.  You can just see the 1/4" 
holes for that below the coil form in the compartment and above the IFT
directly below, outside the compartment.  Two stages of IF run off to
the left from there.  The two tubes all the way to the left are the
BFO/AM  (plate) detector and a 6BN6 product detector.  Coming back to
the right are the 1st audio/phase splitter, and p-p 12AU7 2nd audio.

The variable cap at the lower left corner tunes a VXO BFO.   The two
tubes sitting by themselves at center left are 12X4 rectifiers for the
160V HV -- all four sections in parallel.  Bias needed for the AGC and 
standby circuits is rectified by a diode-connected triode section of the 
triode-pentode 1st IF stage.

The top rear view shows the two mixer subassemblies -- they can be
removed/replaced without major destruction.  The three dual crystal
sockets contain the band crystals for 250-kcs segments of the six 'real'
ham bands.  The two black dots toward the upper left are the holes for
the crystal filter assembly.  The speaker is stolen from a military
LS-166.   I checked the response with an audio oscillator -- it is 
indeed 'communications,' with almost no low end and little above 3500 cps.

The front view shows the usual suspects.  The crystal is the 'external'
crystal that can be used to add any desired additional 250 kcs band
within the range of coverage.  The dial's a Miller MD-4 with a two-speed
drive and replacement (LARGE) knob.  The dial and drive are actually
made by Jackson Brothers, though labeled 'Miller.'

The knob at the lower left corner and the top one just left of the dial
have 5:1 J-B drives; these are the front end and synthesizer tuning,
respectively.  The pointers are made from aluminum and will be painted
white to match the fixed pointers on the other knobs.

The empty hole at the lower left of the dial is for the bandswitch.

Walt
KJ4KV

From shoppa_hbr at trailing-edge.com  Sat Oct  7 09:40:06 2006
From: shoppa_hbr at trailing-edge.com (shoppa_hbr@trailing-edge.com)
Date: Sat Oct  7 09:44:54 2006
Subject: [HBR] That General Coverage HBR Project -- 2
In-Reply-To: <451FF0F6.90300@ntelos.net>
References: <4512F9A0.5080300@ntelos.net> <451DE2CA.2080801@ntelos.net>
	<451FF0F6.90300@ntelos.net>
Message-ID: <20061007134006.A06FCBA415B@mini-me.trailing-edge.com>

Walt Hutchens <waltah@ntelos.net> wrote:
> Metric hardware on the bandswitch -- I got the M3x0.5 die for the switch 
> rods from Tower Hobby.  Does anyone have a favorite online hardware 
> store with better prices?

http://www.mcmaster.com/

Their printed catalog is humongous (and the object of great desire
and longing). Their online catalog is pure heaven.

Remember that internally threaded M3x0.5 spacers and male/female M3x0.5
threaded spacers are standard stock items from several sources
(not only mcmaster-carr, but also digikey and mouser). M3 is kind
of the metric equivalent of #6 hardware and seems to be the standard
for a lot of PC-clone hardware/spacers/screws/etc.

>   $13 with shipping for a 1" die seems a bit steep.

And McMaster-Carr is very reasonable on shipping. Almost everything I order
arrives overnight via UPS ground, with a shipping cost of $4, no hassles
about minimum orders.

Tim.
From bob at atl.org  Sat Oct  7 10:22:02 2006
From: bob at atl.org (Bob AH7I)
Date: Sat Oct  7 10:27:30 2006
Subject: [HBR] That General Coverage HBR Project -- 2
In-Reply-To: <20061007134006.A06FCBA415B@mini-me.trailing-edge.com>
References: <4512F9A0.5080300@ntelos.net> <451DE2CA.2080801@ntelos.net>
	<451FF0F6.90300@ntelos.net>
	<20061007134006.A06FCBA415B@mini-me.trailing-edge.com>
Message-ID: <Pine.LNX.4.58.0610071020270.32507@arthur.atl.org>


metric HW?
mdmetric.com
From waltah at ntelos.net  Sat Oct  7 19:56:02 2006
From: waltah at ntelos.net (Walt Hutchens)
Date: Sat Oct  7 21:47:11 2006
Subject: [HBR] That General Coverage HBR Project -- 2
In-Reply-To: <20061007134006.A06FCBA415B@mini-me.trailing-edge.com>
References: <4512F9A0.5080300@ntelos.net>
	<451DE2CA.2080801@ntelos.net>	<451FF0F6.90300@ntelos.net>
	<20061007134006.A06FCBA415B@mini-me.trailing-edge.com>
Message-ID: <45283E92.7040804@ntelos.net>

Tim said:
> http://www.mcmaster.com/
> 
> Their printed catalog is humongous (and the object of great desire
> and longing). Their online catalog is pure heaven.
> 
> Remember that internally threaded M3x0.5 spacers and male/female M3x0.5
> threaded spacers are standard stock items from several sources
> (not only mcmaster-carr, but also digikey and mouser). M3 is kind
> of the metric equivalent of #6 hardware and seems to be the standard
> for a lot of PC-clone hardware/spacers/screws/etc.

Thanks -- I didn't know about McMaster-Carr.

I suspect that's like Homer Simpson admitting he doesn't know about beer 
... DOH!

The current switch is assembled with rods, threaded M3x0.5 at the ends. 
  It didn't occur to me (though it should have) that I could probably 
buy threaded rods like that and cut them to the desired length.

McMaster-Carr is filed for the future.  Thanks!

Right now the stupid project is tripping the GFCI receptical every time 
I turn it on.  SOMEWHERE in the dozen or two bypass caps on the series 
filament line I suspect there is one that has gone a bit leaky.  In 
theory this is easy to find ... Pulling the hottest tube stops it but 
not the one at the very end so I should just go down the line pulling 
tubes in turn ... right?

Walt
KJ4KV


From Hopperdhh at aol.com  Sun Oct  8 09:31:50 2006
From: Hopperdhh at aol.com (Hopperdhh@aol.com)
Date: Sun Oct  8 09:36:39 2006
Subject: [HBR] That General Coverage HBR Project -- 2
Message-ID: <4ac.5e1c1e3.325a57c6@aol.com>

 
In a message dated 10/7/2006 9:42:57 P.M. Eastern Daylight Time,  
waltah@ntelos.net writes:

Right  now the stupid project is tripping the GFCI receptical every time 
I turn  it on.  SOMEWHERE in the dozen or two bypass caps on the series  
filament line I suspect there is one that has gone a bit leaky.  In  
theory this is easy to find ... Pulling the hottest tube stops it but  
not the one at the very end so I should just go down the line pulling  
tubes in turn ...  right?

Walt
KJ4KV




Walt,
 
Maybe just the capacitance is tripping the GFI.  You could try  capacitors 
from hot the ground on the GFI without the radio to see how much  capacitance it 
will tolerate.  Just a thought.
Dan K9WEK
 
From Hopperdhh at aol.com  Sun Oct  8 09:48:38 2006
From: Hopperdhh at aol.com (Hopperdhh@aol.com)
Date: Sun Oct  8 09:53:24 2006
Subject: [HBR] That General Coverage HBR Project -- 2
Message-ID: <c50.4da75fd.325a5bb6@aol.com>

 
In a message dated 10/8/2006 9:32:07 A.M. Eastern Daylight Time,  
Hopperdhh@aol.com writes:

Walt,

Maybe just the capacitance is tripping the GFI.  You  could try  capacitors 
from hot the ground on the GFI without the  radio to see how much  
capacitance it 
will tolerate.  Just a  thought.
Dan K9WEK




Maybe hot to ground is not the right thing to try.  Maybe try neutral  to 
ground.  You get the idea! Dan K9WEK
 
From N2EY at aol.com  Sun Oct  8 10:28:40 2006
From: N2EY at aol.com (N2EY@aol.com)
Date: Sun Oct  8 10:33:28 2006
Subject: [HBR] That General Coverage HBR Project -- 2
Message-ID: <563.779dae3.325a6518@aol.com>

In a message dated 10/8/06 9:48:53 AM Eastern Daylight Time, 
Hopperdhh@aol.com writes:


> Maybe just the capacitance is tripping the GFI. 

Hmmm....let's do the math...

IIRC, a 120 volt GFI is supposed to trip at 20 mA or less. Say Walt's got one 
that trips at 10 mA.

120 volts divided by .010 amp is 12,000 ohms. So a capacitance of 12,000 ohms 
at 60 Hz is needed.

Xc = 1/(6.28 x f x C)

Rearrange to 

C = 1/(6.28 x f x Xc)

For 60 Hz and 12,000 ohms

C = 1/(6.28 x 60 x 12,000)

C = .00000022 F or 0.22 uF

If there's a dozen or more bypass caps of .01 each, plus some other leakage - 
SNAP!!


Of course there's also the C of all the wiring and any other sources of 
leakage to ground. 


73 de Jim, N2EY
From waltah at ntelos.net  Sun Oct  8 14:13:14 2006
From: waltah at ntelos.net (Walt Hutchens)
Date: Sun Oct  8 14:57:05 2006
Subject: [HBR] That General Coverage HBR Project -- 2
In-Reply-To: <563.779dae3.325a6518@aol.com>
References: <563.779dae3.325a6518@aol.com>
Message-ID: <45293FBA.2050001@ntelos.net>

Jim said:
> C = .00000022 F or 0.22 uF
> 
> If there's a dozen or more bypass caps of .01 each, plus some other
> leakage - SNAP!!

You guys are terrific!  Don't ask me why, but it never occured to me to
try to calculate that.

As it turned out, the problem was a bad (cracked) feedthrough cap on the
filament line going into the 2nd mixer assembly.  Starting at the hot
end I went down the filament line pulling tubes in turn until it
switched from 'problem goes away' to 'problem is still there' meaning
that whatever component was the source, now had voltage on it.  Sure
enough, when I looked closely at the feedthrough going into that box, I 
could see a hairline crack.  Swapping it made the problem go away.

I really hate using those things -- they break at a careless look, or if 
you even wave a small wrench past them while still in the packaging. 
Mine are all salvage so I have several chances to break them -- 
attrition runs around 25%.  Then there's the risk of soldering ...

Anyway, now I know how to think about bypassing in the set.  The
filaments aren't quite so bad as they seem because the voltage declines
as you go along -- only the first tube has the full 120 VAC on its
filament bypass.  Other bypasses are on lines that are nominally DC-only
-- the currents would be just stray signals, probably mostly in the
microampere range.  The HV filter caps are huge and carry high currents
but they go hot line to neutral line -- there shouldn't be any current
in the ground wire.

I have, however, had trouble in the past with a bypass from the neutral
line to ground.  One factor is that there can be a significant voltage
between neutral and ground; I just measured 4 mV in this receiver with
the switch off and 0.75 VAC with it on.  Since that represents a current
flow of 0.3A (filament current), there's a roughly 2.5 ohm resistance in
the neutral line between the point where the pole pig is grounded and
the entrance to the set where I made the measurement.

There is considerable trash on the neutral line -- I have looked at it 
with a scope in the past and there's all manner of stuff.  Plenty of 
reason for heavy bypassing -- but you have to be careful.  If you use 
solid state rectifiers for HV supply then unless there's a series 
impedance you get very large current spikes in the neutral and if you 
observe that those VOLTAGE spikes (remember the 2.5 ohms) are a source 
of a buzz in your audio, then you might like to put a really big cap -- 
say 1 mfd or more -- from the neutral to ground.

You can help the buzz that way, but you are likely to get GFI problems
-- been there, done that, on previous sets.  It's better to add some
impedance in series with your rectifiers.  Either resistance -- using
vacuum rectifiers as in this set gives you that automatically -- or a 
suitable inductance.  The latter would be better for a transmitter or 
other high-current supply and I guess you'd want a reactance in the
ballpark of a hundred ohms at 60 or 120 cps, depending on the rectifier
circuit.  That would considerably flatten the current peaks and greatly
reduce the resulting noise pulses on the neutral line.

Not too many people build 'transformerless' transmitters these days, but
it can be done reasonably easily and with advantages similar to those
for receivers at modest power levels.  The killer at higher levels is 
the need for a voltage multiplier to get the necessary HV; at the 
currents typical of a transmitter the power supply filter (and series) 
caps begin to compare to a plate transformer in size.  I build an AM 
transmitter that ran around 40 watts output and worked okay, but I 
wouldn't want to try to go much higher.  I think that one was parallel 
22JF6's modulated by P-P 22JF6's with two or three more tubes as crystal 
oscillator and audio.  0.45A filaments.

The Rx audio stages are working okay for now and I'm trying to get the 
VXO BFO working correctly.  None of the circuits I have are exactly 
right and as usual I don't know exactly how to think about the theory ...

All things in good time.  It won't be possible to finish the VXO until 
the frequency range of the ladder filter is known.

Bob said:

> metric HW?
> mdmetric.com

Thanks -- bookmarked!

Walt
KJ4KV


From gswynar at durham.net  Sun Oct  8 15:10:06 2006
From: gswynar at durham.net (Ed Swynar)
Date: Sun Oct  8 15:15:01 2006
Subject: [HBR] That General Coverage HBR Project -- 2
References: <563.779dae3.325a6518@aol.com> <45293FBA.2050001@ntelos.net>
Message-ID: <005301c6eb0d$616d19c0$45305a45@CompaqS5000>

Hi Walt et al,

Just a minor point of interest here, but one well worth noting in the future
re. working with those oh-so-fragile feedthrough capacitors...

Before installing them, "beef up" the body of the capacitor right at its
fragile point of exit for the one lead with a good, evenly distributed
build-up of slow cure epoxy glue. Let it dry at least a day, & then go head
& install it (you still have to be careful, of course, but not all THAT
careful, if you know what I mean).

I got this seemingly long forgotten idea out of a tip in "Hints & Kinks"
eons ago. It works like a charm, & I have yet to bust up any feedthough
capacitor since invoking the epoxy rule here at VE3CUI - VE3XZ!

~73~ Eddy VE3CUI - VE3XZ




----- Original Message -----
From: "Walt Hutchens" <waltah@ntelos.net>
To: "HBR Receiver List" <hbr@mailman.qth.net>
Sent: Sunday, October 08, 2006 1:13 PM
Subject: Re: [HBR] That General Coverage HBR Project -- 2


> Jim said:
> > C = .00000022 F or 0.22 uF
> >
> > If there's a dozen or more bypass caps of .01 each, plus some other
> > leakage - SNAP!!
>
> You guys are terrific!  Don't ask me why, but it never occured to me to
> try to calculate that.
>
> As it turned out, the problem was a bad (cracked) feedthrough cap on the
> filament line going into the 2nd mixer assembly.  Starting at the hot
> end I went down the filament line pulling tubes in turn until it
> switched from 'problem goes away' to 'problem is still there' meaning
> that whatever component was the source, now had voltage on it.  Sure
> enough, when I looked closely at the feedthrough going into that box, I
> could see a hairline crack.  Swapping it made the problem go away.
>
> I really hate using those things -- they break at a careless look, or if
> you even wave a small wrench past them while still in the packaging.
> Mine are all salvage so I have several chances to break them --
> attrition runs around 25%.  Then there's the risk of soldering ...
>
> Anyway, now I know how to think about bypassing in the set.  The
> filaments aren't quite so bad as they seem because the voltage declines
> as you go along -- only the first tube has the full 120 VAC on its
> filament bypass.  Other bypasses are on lines that are nominally DC-only
> -- the currents would be just stray signals, probably mostly in the
> microampere range.  The HV filter caps are huge and carry high currents
> but they go hot line to neutral line -- there shouldn't be any current
> in the ground wire.
>
> I have, however, had trouble in the past with a bypass from the neutral
> line to ground.  One factor is that there can be a significant voltage
> between neutral and ground; I just measured 4 mV in this receiver with
> the switch off and 0.75 VAC with it on.  Since that represents a current
> flow of 0.3A (filament current), there's a roughly 2.5 ohm resistance in
> the neutral line between the point where the pole pig is grounded and
> the entrance to the set where I made the measurement.
>
> There is considerable trash on the neutral line -- I have looked at it
> with a scope in the past and there's all manner of stuff.  Plenty of
> reason for heavy bypassing -- but you have to be careful.  If you use
> solid state rectifiers for HV supply then unless there's a series
> impedance you get very large current spikes in the neutral and if you
> observe that those VOLTAGE spikes (remember the 2.5 ohms) are a source
> of a buzz in your audio, then you might like to put a really big cap --
> say 1 mfd or more -- from the neutral to ground.
>
> You can help the buzz that way, but you are likely to get GFI problems
> -- been there, done that, on previous sets.  It's better to add some
> impedance in series with your rectifiers.  Either resistance -- using
> vacuum rectifiers as in this set gives you that automatically -- or a
> suitable inductance.  The latter would be better for a transmitter or
> other high-current supply and I guess you'd want a reactance in the
> ballpark of a hundred ohms at 60 or 120 cps, depending on the rectifier
> circuit.  That would considerably flatten the current peaks and greatly
> reduce the resulting noise pulses on the neutral line.
>
> Not too many people build 'transformerless' transmitters these days, but
> it can be done reasonably easily and with advantages similar to those
> for receivers at modest power levels.  The killer at higher levels is
> the need for a voltage multiplier to get the necessary HV; at the
> currents typical of a transmitter the power supply filter (and series)
> caps begin to compare to a plate transformer in size.  I build an AM
> transmitter that ran around 40 watts output and worked okay, but I
> wouldn't want to try to go much higher.  I think that one was parallel
> 22JF6's modulated by P-P 22JF6's with two or three more tubes as crystal
> oscillator and audio.  0.45A filaments.
>
> The Rx audio stages are working okay for now and I'm trying to get the
> VXO BFO working correctly.  None of the circuits I have are exactly
> right and as usual I don't know exactly how to think about the theory ...
>
> All things in good time.  It won't be possible to finish the VXO until
> the frequency range of the ladder filter is known.
>
> Bob said:
>
> > metric HW?
> > mdmetric.com
>
> Thanks -- bookmarked!
>
> Walt
> KJ4KV
>
>
> ************************************
> Visit the HBR Receiver Web Site with over 100 pictures of receivers and
> construction notes...... via http://www.qsl.net/k5bcq/
> there is also a mirror (faster response)at http://k5bcq.edebris.com/
>
>
> Retrieve reflector archived data via
http://mailman.qth.net/mailman/listinfo/hbr


From Ejparagi at aol.com  Sun Oct  8 22:55:58 2006
From: Ejparagi at aol.com (Ejparagi@aol.com)
Date: Sun Oct  8 23:00:49 2006
Subject: [HBR] That General Coverage HBR Project -- 2
Message-ID: <262.11b99a08.325b143e@aol.com>

Hello,

A 120 VAC GFI device is supposed to trip at 5 mA.  A current of 20 mA through 
the body is enought to cause more than a mild tingle for some people.

Ed
WB9RMA
From Ejparagi at aol.com  Tue Oct 10 22:24:41 2006
From: Ejparagi at aol.com (Ejparagi@aol.com)
Date: Tue Oct 10 22:29:48 2006
Subject: [HBR] Coil Forms
Message-ID: <c2a.2b67b7a.325dafe9@aol.com>

In a message dated 9/16/2006 6:47:29 AM US Eastern Standard Time, 
johnmb@nc.rr.com writes:


> If you're interested in NOS Meissner coils (which can be stripped of the 
> wire and rewound) made of black bakelite, I have some for sale. Price is $3 
> ea plus actual cost of shipping.
> 
> I have 4, 5 and 6 pin versions available.
> 
> Shameless plug....I apologize...!
> 
> John K5MO
> 
John,

I have been meaning to write to you about the Meissner coil forms since you 
first advertised them.  I would like to buy 6 of the 6 pin forms, if you have 
that many left.   If not, I will consider half a dozen of the 5 pin style.  My 
zip code is 46774 (New Haven, IN).  What method of shipping do you prefer?  Is 
a personal check okay?

73,
Ed
WB9RMA

From bcromwell at michonline.net  Fri Oct 13 14:09:46 2006
From: bcromwell at michonline.net (Bill Cromwell)
Date: Fri Oct 13 14:20:13 2006
Subject: [HBR] That General Coverage HBR Project -- 2
In-Reply-To: 451DE2CA.2080801@ntelos.net
Message-ID: <1160762986.10055.13.camel@localhost.localdomain>

Hi Walt,

I just found this reflector so I might be asking a question that is
obvious to everybody else. You mention a 'simple minded synthesizer'
that sounds like a "crystalpexer" scheme. You referenced R8040A. Where
can more information and maybe some block and schematic diagrams.
Searches for R4080 have turned up empty.

73,

Bill  KU8H

From waltah at ntelos.net  Sat Oct 14 09:34:59 2006
From: waltah at ntelos.net (Walt Hutchens)
Date: Sat Oct 14 09:41:22 2006
Subject: [HBR] That General Coverage HBR Project -- 2
In-Reply-To: <1160762986.10055.13.camel@localhost.localdomain>
References: <1160762986.10055.13.camel@localhost.localdomain>
Message-ID: <4530E783.3080305@ntelos.net>

Bill wondered:
> You mention a 'simple minded synthesizer' that sounds like a
> "crystalpexer" scheme.

Welcome to the list, Bill!

"Crystalplexer" is a term I haven't heard but the scheme in the GC-HBR
is to use the tenth harmonic of the 120 crystals of the WW-II surplus
BC-1335 FM set.  They run 5675-8650 kcs I think, by 25 kcs steps so that
gives you 56.75 -86.5 Mcs.  Subtract from that 49.2 Mcs yielding
7.55-37.3 Mcs.  Use that as the crystal mixing frequency to get to a 1st
(tunable) IF of 5.550-5.80 Mcs with coverage of 0.75-30.5 Mcs.  (Front
end probably won't tune the bottom end -- I don't need the BC band and 
the first few crystals show up in the tunable IF so they'll give large 
birdies.)  The 2nd (fixed) IF is 4.096 Mcs (clock crystals are 
available) and LO tunes 1.454-1.704 Mcs.

That's all from memory so if it doesn't quite add up ...

The modern cheap clock crystals are amazing.  Out of 20, I got two 
groups of five matched within a total of 7 CPS each -- that's perfect 
matching for an SSB filter at 4096 Kcs.  The BFO will be a VXO and must 
tune completely across the filter range; that's what I'm working on 
right now.  Fallback is two BFO crystals but I don't want to have to 
switch them.

Anyway there's one crystal multiplier and one mixing to get the 1st 
mixer injection frequency = 'simpleminded.'

> You referenced R8040A. Where can more information and maybe some
> block and schematic diagrams. Searches for R4080 have turned up
> empty.

R8040 was a band imaging design 80 & 40 meters, five tubes, series 
filaments, that I did in the mid 90's -- it worked pretty well and was 
documented in an article in Electric Radio at the time.  A search of 
their on-line index should locate it.

Last year I revisited the design, changing just about everything. 
R8040A (which I am listening to as I write) turned out to be an 
excellent performer for 7 tubes+rectifier.  And easier to build than the 
forerunner.   It's not written up anywhere at this point, though I have 
most of the circuit diagram and -- since most is being recycled in the 
current project -- I'll obviously be finishing that up.

12AT7 push-pull mixer.  This has a single toroid push-pull tuned circuit 
in the grid and is on the AGC buss.  There is slight leakage of 40M 
signals onto 80M when using the set with a large antenna that's resonant 
on both bands -- I use a 160M FW loop for everything but it hasn't ever 
been a problem.  An antenna tuner or separate antenna for each band 
would eliminate this if necessary.

A push-pull triode mixer with no RF stage is 'strong' enough that a 
single tuned circuit of high-Q preceding it is adequate.

12AU7 push-pull LO.  Decoupling is enough that there's no pulling at 
all, even with the AGC controlled mixer.  IF is 5400 kcs (I think) and 
LO tunes 1400-1900, giving coverage 3500-4000 kcs and 6800-7300 kcs.

There's a two-crystal half-lattice filter in the plate of the mixer, two 
stages of 7GH8 IF.  The triode in the 1st IF is used as a diode 
rectifier for -160 VDC bias line needed for the AGC; the triode in the 
2nd IF is an AGC plate detector (cathode biased negative so the plate 
runs negative from 0 VDC for AGC).  No problems with attack speed -- 
clicks at the start of a sentence or such -- and it works the same on 
SSB and AM.

Half of a 12AU7 is used as a plate detector on AM, with BFO injection it 
becomes an adequate product detector.  The other half of the 12AU7 is 
the 2nd audio -- it's enough power for a 3" speaker.   The pentode half 
of a third 7GH8 is the 1st audio stage, the triode is the BFO, crystal 
controlled on the high side of the IF.

The conversion scheme renders LSB as LSB in the IF for both bands so 
there's no need to tune the BFO.  The only control is ON-OFF.

A 35W4 delivers plate voltage.  You could use a diode rectifier and a 
35C5 audio output stage, but there's really plenty of audio for anything 
you'd want to use a relatively simple receiver for.  The S-meter runs 
from the 1st IF cathode/screen using the common bridge circuit.  7 tubes 
total.

Every receiver is a compromise.  This one is compact, stable, has 
excellent selectivity, doesn't use much power (little warm-up drift) has 
great AGC (3 controlled stages), few controls, has very good overall 
audio quality, and isn't too hard to build.  The negatives are 
non-excellent audio because a triode isn't a perfect product detector, 
the 40M breakthrough, AM signals are a bit distorted unless received 
with the BFO on because the crystal filter is optimized for SSB and 
isn't quite wide enough to pass both the carrier and sideband.

For the GC-HBR I'll use the R8040A design as a tunable IF with the 
obvious tweaking of the tuning range.  Other changes are a 12AU7 with 
the sections in push-pull for audio output, a 6BN6 product detector, and 
  the VX0 BFO as mentioned.  Most of the tube types have to change to 
get a 300 mA filament string instead of 150 mA.  It's conceptually not 
much more complicated but there are quite a few pieces to make.

Today I hope to put together the ladder filter, then I can go back and 
finish the VXO with exact knowledge of the tuning range I need.

Loosely a VXO will tune from the series resonance of the crystal up to 
the parallel resonance but this space can vary considerably -- from say 
1 kc to 5-6 kcs at 4 Mcs, depending on the crystal parameters.  And it's 
common to put an inductor in series with the crystal in order to lower 
the series resonant frequency.  If the inductor is too big you can lose 
stability or even oscillation.  The usual VXO tuning cap has a 
substantial minimum so you don't get too near the parallel resonant 
frequency either.  You could put an inductance across it but man, this 
thing is starting to get complicated!  The oscillator output varies 
considerably over the tuning range -- that's a problem for the product 
detector ... and so on.

Walt Hutchens
KJ4KV

From waltah at ntelos.net  Sun Oct 15 18:55:23 2006
From: waltah at ntelos.net (Walt Hutchens)
Date: Sun Oct 15 19:01:49 2006
Subject: [HBR] That General Coverage HBR Project -- 4
In-Reply-To: <4523157B.6010008@ntelos.net>
References: <4512F9A0.5080300@ntelos.net>
	<451DE2CA.2080801@ntelos.net>	<451FF0F6.90300@ntelos.net>
	<4523157B.6010008@ntelos.net>
Message-ID: <4532BC5B.9030206@ntelos.net>

The crystal filter is finished for now.  It's a ladder design, with five 
crystals at 4096 kcs.

A ladder is just a few crystals of the same frequency in series, 
capacitors couple from each end to the input and output load resistors 
and from each junction between crystals to ground.  All six caps in this 
one are 22 mmf.

I bought 20 crystals of the same frequency (about $10 worth) and got two 
sets of 5 that were within a range of 7 cps of the same.  The caps are 
within about 1/2 mmf, matched with a capacitance meter.

There's a picture at:

http://www.timbreblue.com/radio/crystal_filter.html

The colors aren't quite right and the reflections on the back wall make 
it a bit confusing but I think you can see the ladder circuit diagram. 
It's 2" long, 7/8" height and depth, made from tin can stock.  The end 
flaps bend up and I'll cover the top and front with another tin can 
stock section when the receiver is done.

I drilled holes in the back wall and soldered the cases of the five 
HC-49US (short HC-49/U) crystals in the holes, then bent the leads 
together in a zigzag pattern and soldered the caps from each to ground. 
  The two bluegreen feed throughs on the ends are threaded and will be 
used to mount the unit.

The best explanation of experimental design of ladder filters that I 
found is the QST article by Wes Hayward, July 1987.   He gives all the 
info you need to tinker one of these into existence: more crystals = 
steeper sides and fewer bumps, smaller caps = wider bandwidth and higher 
impedance, higher terminating resistors = smoother passband but less 
steep sides.

Use of equal caps makes this a Cohn filter -- minimum loss, a compromise 
on bumps in the bandpass.  Other articles discuss other designs with 
minimum bumps or steepest sides.

I did a crude check with another receiver: it does pass a signal and 
with 4.7k termination resistors the passband is pretty smooth but using 
a grid dip meter as a signal source that's about all I can tell. I'll 
probably add shields inside the filter housing at each end so the input 
and output connectors can't 'see' each other -- at 60-80 db down, even 
small amounts of coupling matter.  There's no problem under the chassis 
because the filter input is in the 2nd mixer compartment and the output 
is outside it.

I'm sure the terminating resistors will need to be changed once it's in 
the set.  But it's good enough to proceed with the BFO and other work!

Walt
KJ4KV
From bcromwell at michonline.net  Sun Oct 15 19:43:11 2006
From: bcromwell at michonline.net (Bill Cromwell)
Date: Sun Oct 15 19:54:06 2006
Subject: [HBR] Re: That General Coverage HBR Project -- 2 (Walt Hutchens)
In-Reply-To: <20061015080109.E7583859D17@mailman.qth.net>
References: <20061015080109.E7583859D17@mailman.qth.net>
Message-ID: <1160955791.14728.1.camel@localhost.localdomain>

Thanks Walt,

I'll see where I can take this info.

73,

Bill   KU8H

From waltah at ntelos.net  Tue Oct 17 17:57:39 2006
From: waltah at ntelos.net (Walt Hutchens)
Date: Tue Oct 17 18:04:18 2006
Subject: [HBR] Good GRIEF -- Talk about a homebrew general coverage receiver!
In-Reply-To: <1160955791.14728.1.camel@localhost.localdomain>
References: <20061015080109.E7583859D17@mailman.qth.net>
	<1160955791.14728.1.camel@localhost.localdomain>
Message-ID: <453551D3.1050002@ntelos.net>

This is probably one that some of us already know about but it was new
to me when I happened to see it in the November 1970 issue of QST.  One
John E. Pitts Jr., W6BD, built what must be close to the ultimate vacuum
tube general coverage receiver in his 24 tube GCR-100A.

The receiver is triple conversion starting with a 7360 mixer.  It covers
  3.5-30 Mcs in 500 kcs bands.  The 1st conversion oscillator is crystal
controlled using 31 separate crystals.  Since 51 crystal converted bands
would be needed, it sounds like 2nd harmonics are used where possible.

The IFs are 4-3.5 Mcs (so on 80, the receiver tunes backwards and the
1st mixer is straight through), 2215 kcs (LO tunes 5715-6215 kcs), and
455 kcs.  The final conversion was done to eliminate problems with BFO
feedthrough in the IF.  There are three crystal filters in the 2215 kcs
IF, a Lamb noise silencer in the 1st (broadband) IF, a Q-multiplier in
the front end, and a Select-O-Ject circuit in the audio.

The IF tubes are 6GM6's -- the runner up to the 6EH7 as an IF stage.

The mechanical work is elaborate to say the least: The VFO is built of
milled 1/4" aluminum stock, the Eddystone 898 is geared down slightly so
the full dial range rotates the Miller 2101 LO tuning cap only 154
degrees, thus eliminating end effects, and he linearized the oscillator
so the dial reads approximately directly in kcs.  Everything is done as
subassemblies, mounted on a 13x17" chassis and connected by RG-58 as needed.

Sensitivity is claimed to be 0.1 uV for 10 dB S/N, he doesn't give
numbers for crossmodulation performance but gives anecdotal evidence
that it's extremely good.  Long term drift is 30 CPS/hour; the LO runs
continuously whether the switch is on or off.

It's hard to find any fault with this, but when did that ever stop me?
30 cps/hour drift isn't remarkably good for a very solidly-built
oscillator that runs continuously.  He used a 7587 Nuvistor pentode in a
Colpitts circuit.  I think a push-pull oscillator would have done
somewhat better -- more gain makes possible less coupling between tube
and tank.  Use of back-biased diodes (1N64's) to shift a VFO for
calibration and sideband switching and an RF choke in the cathode of the
tube are significant compromises with stability -- these components are
never stable enough for such use.

The cathode of a stable oscillator should be at the same RF potential as
the filaments because the filament-cathode interface is basically a
crummy diode shunted by a small capacitor of unstable characteristics.
The 7587 is probably better than larger tubes but the filament wires
tend to squirm inside the cathode sleeve so this cannot be an
electrically stable component.  You can somewhat 'fudge' this by biasing
the cathode negative with respect to the filament to take the diode out
of the circuit (that gets rid of the hum modulation you pick up from
having AC on a diode that carries part of the oscillator RF) but you've
still got that capacitor.

A good check on a local oscillator is to listen to a harmonic -- say
something like the 5th or so.  If you can hear line frequency FM, it
needs more work because even if you CAN'T hear anything on the
fundamental, there'll be enough phase shift to cause audible distortion
when receiving SSB signals.

The same test should be applied to the BFO and any crystal oscillators
that are involved in the conversion scheme.

However those comments are just quibbles.  This is an outstanding job of
building a fairly straightforward but elaborate design.  I wouldn't call
any of the design 'inspired' -- it was all taken from other receivers of 
the day -- but the selection of the circuits and overall execution is 
outstanding.  This is basically an exceptionally skilled home 
constructor's answer to the R-390A.

W6BD appears to have been reassigned as a vanity call.  Google finds a
John E. Pitts, Jr. but he was an Air Force General who passed away in
'77 and does not appear to ever have been stationed in California -- the
address given in the QST article.  Nor did Brig. Gen. Pitts have the
kind of career suggesting this level of electronic skill -- he was a
fighter pilot's fighter pilot from 1946 until his retirement, 30 years
later.

W6BD had plenty of radio design and construction experience, he had
machine shop access, and either plenty of money or a source of crystals
-- 30-some custom HC-6/U crystals at the time would have cost more than
week's pay for an engineer, would they not?

I guess that starting with the 80 meter band as the 1st IF it would have
been possible to use at least some crystals from the R-390 or -392
receivers.  That's a possibility I didn't think of when doing the GC-HBR
design.  In fact, by switching the 1st IF so it covered a whole Mc, you
might do most of it with those crystals.

The project took Mr. Pitts about four years -- 1965-69.  He concludes:
"Deep appreciation is given to the XYL for her patience during the
construction of the receiver.  She had only one request after it was
finished -- 'Please don't build anything else for a long time.'"  Sharyn
got a good laugh out of that!

Walt Hutchens
KJ4KV


From bcromwell at michonline.net  Wed Oct 18 10:41:04 2006
From: bcromwell at michonline.net (Bill Cromwell)
Date: Wed Oct 18 10:52:40 2006
Subject: [HBR] That General Coverage HBR Project -- 2
In-Reply-To: 1160762986.10055.13.camel@localhost.localdomain
Message-ID: <1161182464.20210.22.camel@localhost.localdomain>

Walt KJ4KV said, among other things:

"Crystalplexer" is a term I haven't heard but the scheme in the GC-HBR
is to use the tenth harmonic of the 120 crystals of the WW-II surplus
BC-1335 FM set.  They run 5675-8650 kcs I think, by 25 kcs steps so that
gives you 56.75 -86.5 Mcs.  Subtract from that 49.2 Mcs yielding
7.55-37.3 Mcs.  Use that as the crystal mixing frequency to get to a 1st
(tunable) IF of 5.550-5.80 Mcs with coverage of 0.75-30.5 Mcs.  (Front
end probably won't tune the bottom end -- I don't need the BC band and 
the first few crystals show up in the tunable IF so they'll give large 
birdies.)  The 2nd (fixed) IF is 4.096 Mcs (clock crystals are 
available) and LO tunes 1.454-1.704 Mcs.

That's all from memory so if it doesn't quite add up ...

Hi Walt,

....and everybody.

It does add up Walt. I am revisiting the "crystalplexer" as used in 23
channel CB radios before the switch to PLL frequency control. That block
of crystals you describe at 25 kHz times ten gives you 250kHz "steps".
If that block only used four crystals at 25kHz spacing you would get an
output (at 10x) that covers one MHz with 250kHz steps. Then revisit that
49.2 MHz oscillator and add crystals at one MHz steps. The one Mhz steps
could be selected for ham band only use (or CB channel selection). Even
with a "zero to 30 MHz" frequency coverage the number of crystals is
dramatically reduced to something like 34 from 120. Add a vfo with a
250kHz range.... Other combinations are possible.

I am playing with a spread sheet to look for combinations that might
avoid landmines like large birdies, etc. It just happens that I have a
coffee can full of those 25kHz spaced crystals....and several old 23
channel crystalplexed CB radios. I suppose I would be excommunicated if
I used this info to build a solid state radio. So I will use the info to
build a vacuum tube based radio instead.

73,

Bill  KU8H

From waltah at ntelos.net  Wed Oct 18 12:39:37 2006
From: waltah at ntelos.net (Walt Hutchens)
Date: Wed Oct 18 18:59:39 2006
Subject: [HBR] That General Coverage HBR Project -- 2
In-Reply-To: <1161182464.20210.22.camel@localhost.localdomain>
References: <1161182464.20210.22.camel@localhost.localdomain>
Message-ID: <453658C9.5050202@ntelos.net>

Bill said:
> I am revisiting the "crystalplexer" as used in 23 channel CB radios 
> before the switch to PLL frequency control. That block of crystals 
> you describe at 25 kHz times ten gives you 250kHz "steps". If that 
> block only used four crystals at 25kHz spacing you would get an 
> output (at 10x) that covers one MHz with 250kHz steps. Then revisit 
> that 49.2 MHz oscillator and add crystals at one MHz steps. The one 
> Mhz steps could be selected for ham band only use (or CB channel 
> selection). Even with a "zero to 30 MHz" frequency coverage the 
> number of crystals is dramatically reduced to something like 34 from 
> 120. Add a vfo with a 250kHz range.... Other combinations are 
> possible.

Ah, yes -- that all makes sense.  I just hadn't heard the term.  I 
decided not to go down that path because it seemed to me that the
switching and tuning would get very complicated very quickly.
> 
> I am playing with a spread sheet to look for combinations that might
>  avoid landmines like large birdies, etc.

It could be that I just didn't 'work smart' enough. Hopefully you'll 
come up with something better.

I did feel when I was doing the spreadsheet thing that each additional
mixing created a whole new minefield and that (since I had all the
crystals) there was much to recommend brute force -- the use of just two
crystal frequencies in the front end.

> It just happens that I have a coffee can full of those 25kHz spaced 
> crystals....and several old 23 channel crystalplexed CB radios.

Let me know if you come up missing a few -- I have enough to fill
several coffee cans and could certainly spare a handful or two for just
postage.  No spare 7025's -- the CW boys seem to have eaten all of those
-- but plenty of most others.

These crystals were used (in the BC-1335) in a triode connected 3Q4 
(power pentode) Pierce circuit with the 90 volt plate voltage 
shamelessly applied to the crystal so they are very easy to adapt to ham 
use.

Another idea that might be tossed into the mix would be the use of a 
VXO.  Working on (struggling with ...) the GC-HBR BFO, I did quite a bit 
of reading on the topic and there's more to it than I thought.  The QRP 
boys have come up with several ideas I had never seen.  Of course they 
are all solid state so they require translation.

> I suppose I would be excommunicated if I used this info to build a
> solid state radio. So I will use the info to build a vacuum tube
> based radio instead.

It would be great to hear about more projects here.  I'm still 
recovering from reading about the W6BD receiver.  Wonder where that one 
went?  Boy, what a find THAT would be.

Walt
KJ4KV

From waltah at ntelos.net  Fri Oct 20 07:04:28 2006
From: waltah at ntelos.net (Walt Hutchens)
Date: Fri Oct 20 07:11:20 2006
Subject: [HBR] That General Coverage HBR Project -- 2
In-Reply-To: <1161284996.12687.23.camel@localhost.localdomain>
References: <1161182464.20210.22.camel@localhost.localdomain>	
	<453658C9.5050202@ntelos.net>
	<1161284996.12687.23.camel@localhost.localdomain>
Message-ID: <4538AD3C.2020707@ntelos.net>

Bill said:
> I have some things I want to try that will take advantage of VXO
> methods, too, related to my observations during maintenance of crystal
> controlled radios. Right now I just have a pipe dream. If I get a good
> result I will surely share. If it turns out to be something too silly to
> mention...I will just keep quiet <grin>. Unless somebody else asks "what
> about...." Then I would spill those beans.

But Bill, if you do something that turns out too silly to mention and 
you keep quiet, that means I have to do it too!  I have my very own 
silly ideas!

One of the most interesting things about this list is hearing what other 
people are doing, building, restoring, and what all. Learning what 
doesn't work well is probably the most useful part of that.  I've been 
writing some further adventures with the VXO thing that I'll probably 
post today, but the short story is, doing it again from scratch this 
isn't where I'd start for a BFO that must tune a frequency range as 
large as ~0.1%.

Walt
KJ4KV
From daileyservices at qwest.net  Fri Oct 20 10:59:43 2006
From: daileyservices at qwest.net (TC Dailey)
Date: Fri Oct 20 11:12:35 2006
Subject: [HBR] That General Coverage HBR Project -- 2
References: <1161182464.20210.22.camel@localhost.localdomain>	<453658C9.5050202@ntelos.net><1161284996.12687.23.camel@localhost.localdomain>
	<4538AD3C.2020707@ntelos.net>
Message-ID: <003001c6f458$60ad3020$6502a8c0@dailey>

Hey Mates

I'm heading over the Pond to the UK this evening, so is there a way to hold
my HBR traffic until the 30th?

I have limited space in the cache, thus the request.

Thanx - Tom  W?EAJ

From bcromwell at michonline.net  Fri Oct 20 12:10:12 2006
From: bcromwell at michonline.net (Bill Cromwell)
Date: Fri Oct 20 12:22:21 2006
Subject: [HBR] That General Coverage HBR Project -- 2
In-Reply-To: 1161284996.12687.23.camel@localhost.localdomain
Message-ID: <1161360612.31819.18.camel@localhost.localdomain>

Walt KJ4KV said:

But Bill, if you do something that turns out too silly to mention and 
you keep quiet, that means I have to do it too!  I have my very own 
silly ideas!

One of the most interesting things about this list is hearing what other 
people are doing, building, restoring, and what all. Learning what 
doesn't work well is probably the most useful part of that.  I've been 
writing some further adventures with the VXO thing that I'll probably 
post today, but the short story is, doing it again from scratch this 
isn't where I'd start for a BFO that must tune a frequency range as 
large as ~0.1%.

Walt
KJ4KV

OK Walt,

Maybe somebody else has been down the street I'm looking at and bumped
into a dead end. VXOs are recommended for stability (among other things)
in portable equipment. The drawback with a VXO is the limited tuning
range. A VXO might be built in the mid to high HF range with a few small
kHz of tuning range and the output multiplied into the vhf or uhf area.
The tuning range gets multiplied, too, along with any instabilities.
Another crystal controlled oscillator can be multiplied to a nearby
frequency and mixed with the multiplied output from the VXO. If we are
really lucky, or maybe if we plan it that way, the difference frequency
can be the range needed for operation as our local oscillator in the HF
band. Maybe we can increase the tuning range 3 kHz to 50 or 100 kHz.
Maybe this approach will work for your BFO. Of course the complexity
increases.

We might also start with an overtone crystal oscillator or two. I have
observed a fairly large "tweaking" range on those at the output
frequency and the initial oscillator frequency is already higher than
our HF bands. That will help reduce the number of mines in the
'minefield'. Again with the birdies and other spurious pitfalls. 

73,

Bill  KU8H

From waltah at ntelos.net  Fri Oct 20 13:49:53 2006
From: waltah at ntelos.net (Walt Hutchens)
Date: Fri Oct 20 13:58:39 2006
Subject: [HBR] That General Coverage HBR Project -- 5
Message-ID: <45390C41.7070904@ntelos.net>

Call this 'fun with a VXO' -- variable frequency crystal oscillator.  Or
"how I learned more than I wanted to know about this subject."  Or --
still closer to the truth -- "What happens when you suddenly think
you've made a big design mistake."

Quartz crystals are equivalent to a tuned circuit consisting of an
inductor, a capacitor, and a resistor all in series, with the lot
shunted by a small capacitor.  What's remarkable is that the inductor in
this equivalent circuit can be in the ballpark of 0.1 to a quarter of a
henry at frequencies of a few Mcs, giving typical Q's well in the tens
of thousands.  For modern crystals with plated electrodes, Q = 100,000
is common; the older pressure mounts (FT-243 ...) are not so good.  You
can often see where a pressure-mount crystal that has been driven hard
has rubbed some metal off on the corners of the plate itself showing
that friction does occur.

Crystals have two resonant frequencies.  They appear as capacitors over
most of the spectrum, however, over a narrow range of frequencies
between the series and parallel resonances, they look inductive.  Nearly
all oscillators work within this range.

The series resonant frequency is the lower of the two; at this point the
crystal appears to be a resistance that's usually in the ballpark of
10-1000 ohms.  Conceptually the oscillators that use the series
resonance are those like the Butler (crystal between cathodes of two
triodes) in which you could think of replacing the crystal with a small
resistor.

A fraction of a percent higher in frequency, the crystal appears to be a
parallel resonant circuit.  However what we usually think of as parallel
resonant crystal oscillators (Pierce -- crystal from plate to grid,
Miller -- crystal from grid to ground, many others) actually operate
more or less on the inductive side of resonance -- that is, between the
series and parallel resonant points but nearer the parallel resonance.

Typical spacings between the two resonant points for crystals I've
fooled with in the last few days are 1 to 4 kcs at 4 Mcs.  The spacing
goes up roughly proportionately with frequency.  Crystals are made and
calibrated to operate either at series resonance or at parallel
resonance with a specified parallel load capacitance -- a convenient way
of saying how close they're supposed to be to the parallel resonant
point.  Common load cap specifications for modern crystals are 20 mmf
and 32 mmf; some of the large pre-WW II ones were operated with much
more, I believe.

Either series or parallel resonant crystal circuits can be adjusted in
frequency by varying the reactance in the external circuit.  For series
resonant circuits the practical range of variation is fairly small
because of the awkward component requirements (either a variable
inductor or a capacitor that, if of reasonable size, will give only a
modest range of tuning) and accordingly these oscillators are usually
made adjustable only for trimming purposes -- series resonant 100 kcs
crystals for calibrator service are an example.

On the inductive side of parallel resonance, however, the crystal
oscillation frequency can be shifted considerably with a fairly small
shunt capacitor.  In the Pierce VXO circuit, stable oscillations can be
had over most of the range from the parallel resonance (with minimum
shunt capacitance) down to the series resonance.

A commonly used trick is to add an inductor in series with the crystal.
If you think of the inductive reactance of the crystal dropping from
infinite to zero at the frequency goes from the parallel to the series
resonance you can see that the added inductor moves the apparent series
resonance down but has very little effect on the parallel resonance.
The VXO can now be tuned over a wider range.

However, if you keep adding inductance, the inductance of the crystal
forms a smaller and smaller part of the circuit.  Since it's the
variation of the crystal's inductive reactance that allows it to control
the frequency, you may lose crystal control.  VXOs with too-large series
inductors may suddenly hop from a crystal controlled frequency to a
nearby frequency that is only slightly affected by the crystal as they
are tuned downward.  Reducing the Q of the coil with a resistor reduces
the effect but gives you an overall reduction of Q (meaning less stable
frequency) in exchange ... now why were we using a crystal?

A typical value for the series inductor at a few Mcs is 10-50 uH.  I'm
using 44 uH right now and getting a tuning range of about 4.5 kcs at
4096 kcs.  It's very stable, even at the low end, and I'll probably go a
bit higher on the coil.

Tuning of a VXO tends to be non-linear: the first few mmf in parallel
with the crystal change the frequency rapidly but as you continue to add
capacitance, each successive mmf has less and less effect.  Broadcast or
similar type non-linear capacitors help.  Typical maximum values at a
few Mcs are 100-350 mmf.

This suggests that the range can be increased by decreasing stray shunt
capacitance and it can.  However the oscillator tube sets a lower limit
and the instability of the tube capacitance becomes proportionately
greater at the same time that it has a greater effect on frequency per
mmf of change.  A push-pull oscillator (crystal between the grids,
fixed-tuned plate tank circuit) might work well.

An additional issue is that as shunt capacitance is increased the tank
reactance falls, meaning reduced voltage output.  At some point, adding
more capacitance causes the circuit to go out of oscillation.

I suspect that the common Pierce VXO is not the best possible circuit --
as in other areas, tubes went out of favor before an optimum was
developed. But it's probably not worth chewing on this just now.

There are two very interesting techniques for further increasing VXO
tuning range.  One is the use of two (or even more) nominally identical
crystals in parallel -- called the 'super VXO.'  This effectively
parallels the two inductances so the effect of the minimum (stray)
capacitance becomes smaller and by using a slightly larger tuning cap,
the tuning range is increased.  Very simple and with the better crystals
it works well.

The second technique is the use of two crystals of different frequencies
feeding a mixer which delivers the difference.  For example, a VXO at 5
mcs could be implimented with crystals of 12 and 17 Mcs.  Some builders
tune the two in opposite directions: with (17-12) = 5 you'd get ~six
times the tuning range of a 5 Mcs VXO while somewhat correcting the
tuning non-linearity and output voltage variation.  You would, however,
need a differential tuning capacitor.  I have seen one version of this
circuit in which a single bipolar transistor was used, simultaneously
running one crystal in series mode (fixed tuned), the other in shunt
mode (tuned) and providing output to a tuned circuit in the collector
that was tuned to the difference.  The same probably could be done with
a vacuum tube.

As with most things, the circuits that do the most to lift the inherent
limitations are also those that most complicate a circuit that's of
value mainly for its simplicity.

My day of wondering if I had seriously goofed came from discovering that
the clock crystals I used for the filter had series-parallel spacings of
only around 1 kc.  Nor did these crystals take well to use of a series
inductor. However, after some digging I found an FT-243 at 3990
kcs with a 4 kcs spacing and ground it to the desired range.  I had not
tried this exercise in about 20 years and I don't think I ever moved an
80-meter rock by 100+ kcs successfully, but it worked this time.  Hint:
a piece of quartz .016 x 3/8" x 3/8" is easily mislaid if a dog runs
between your legs while you're handling it.  Part of the reason for the
success was undoubtedly that I did most of it between 2-6 AM on two
nights.

It looks like I'll end up about where I had hoped, with a Pierce circuit
covering 4095.5-4099.5 kcs.  I'll probably wind an adjustable coil to
replace the two 22-uH chokes I've been testing with and then install a
socket for the crystal.

With the 'broadcast' type capacitor I'm using, the non-linearity isn't
too bad.  The tuning range is 4.7 kcs and the midpoint of the knob swing
is about 2 kcs from the lower end.  However cleaning up the wiring is
likely to add another kc or so at the high end making the linearity that
much worse.  It wouldn't be too difficult to improve that by grinding
the capacitor plates some on the high frequency end, give or take the
possiblity of trashing the cap.

There are still a couple of serious issues.  The plate waveform is
dreadful at the high frequency end -- a square wave with trash.  That
means lots of harmonics that might (will ...) be picked up by the front
end of the receiver.

Furthermore, there's a tenfold variation of output voltage across the
tuning range.  That's not going to work, driving a 6BN6 product detector
directly.  Fortunately I don't actually need much output -- just a
couple of volts p-p, I think, for the second grid on the 6BN6. I will
try a pentode ECO circuit (screen of pentode acts as plate for the
oscillator); I suspect that the tube current is a lot more consistent 
across the range and that the variation in the plate circuit will be 
correspondingly more reasonable. I had noticed that Pierce ECOs are 
common as VXO's; maybe I now know why.

A tuned circuit in the pentode plate will reduce the waveform problems 
too, although there'll still be radiation from other components that 
carry the trashy square wave.  With only a tuning range of 0.1%, this 
circuit can be fix-tuned.

A minor additional factor is that crystals that are ground (rather than
etched) tend to 'age' upward in frequency as fragments break off the
sides of the scratches caused by grinding; this effect can be hundreds
of CPS.  So I'm not going to be in a hurry to move the crystal the last
kc or so.

Doing this again I would reconsider use of separate crystals for upper
and lower sidebands.  In this design it was necessary to put the
oscillator at the rear of the chassis; I thought that using a VXO with a
long shaft for the capacitor was a good solution to that problem while
offering a measure of IF shift operation.  However the relatively low IF
is making that a challenge.

I think there's room to add another tube and a second crystal socket if 
that should be necessary.  It's always interesting, the way the various 
design choices interact.

Walt
KJ4KV



From N2EY at aol.com  Fri Oct 20 18:05:49 2006
From: N2EY at aol.com (N2EY@aol.com)
Date: Fri Oct 20 18:11:54 2006
Subject: [HBR] That General Coverage HBR Project -- 2
Message-ID: <cd8.b7f7a5.326aa23d@aol.com>

In a message dated 10/20/06 7:05:29 AM Eastern Daylight Time, 
waltah@ntelos.net writes:


> Bill said:
> > I have some things I want to try that will take advantage of VXO
> > methods, too, related to my observations during maintenance of crystal
> > controlled radios. Right now I just have a pipe dream. If I get a good
> > result I will surely share. If it turns out to be something too silly to
> > mention...I will just keep quiet <grin>. Unless somebody else asks "what
> > about...." Then I would spill those beans.
> 
> But Bill, if you do something that turns out too silly to mention and 
> you keep quiet, that means I have to do it too!  I have my very own 
> silly ideas!

Me too!

One of the most important functions of engineering is figuring out what 
*won't* work before committing lots of resources to it. 


> 
> One of the most interesting things about this list is hearing what other 
> people are doing, building, restoring, and what all. Learning what 
> doesn't work well is probably the most useful part of that.  I've been 
> writing some further adventures with the VXO thing that I'll probably 
> post today, but the short story is, doing it again from scratch this 
> isn't where I'd start for a BFO that must tune a frequency range as 
> large as ~0.1%.
> 

Did you try the Elecraft trick (two identical xtals in parallel in a VXO)?  
(Actually it's just one of their ingenious tricks).

73 de Jim, N2EY
From waltah at ntelos.net  Fri Oct 20 19:07:56 2006
From: waltah at ntelos.net (Walt Hutchens)
Date: Fri Oct 20 19:14:47 2006
Subject: [HBR] That General Coverage HBR Project -- 2
In-Reply-To: <cd8.b7f7a5.326aa23d@aol.com>
References: <cd8.b7f7a5.326aa23d@aol.com>
Message-ID: <453956CC.3040909@ntelos.net>

Jim said:
> One of the most important functions of engineering is figuring out what 
> *won't* work before committing lots of resources to it.

Oh shoot -- BEFORE committing lots of resources?  I KNEW I had one of 
the details wrong ...

Walt
KJ4KV
From amargosaent at iscweb.com  Thu Oct 26 13:55:28 2006
From: amargosaent at iscweb.com (Amargosa Enterprises)
Date: Thu Oct 26 13:59:53 2006
Subject: [HBR] Re original/present HBR values
Message-ID: <USER_ANONYMOUS$69.85.136.41$.005001c6f928$626a9cc0$29885545@vucppqlj>

Re my post 28 Sept in reply to N2EY's query on HBR-16 original/present values. 

For those who missed it, CQ Magazine for Oct 2006 page 18 has some interesting data on calculating radio equipment "present" values from "original" costs based on consumer price index models.  The article gives a URL for two different on-line calculators, both based on the Bureau of Labor Statistics model for Consumer Price Index.  It also provides some original/present value conversions for various receivers popular in the 1940/1970 era.  

Per my Sept post, a 1967 HBR20 at an original hard-money parts-only cost of $225 gives a calculated 2006 "present" value of $1367, and using an original soft-money parts-only cost of $325 gives a present value of $1670.

Using N2EY's posted HBR 16 cost estimates of $70 to $150 (and assuming construction in 1967) the calculator gives us $425 to $911 respectively as present values.

Keep in mind all these numeric gyrations provide no allowance for labor to construct; the gyrations assume those of us who built these beauties were either worthless or priceless !! 

The HBR20 uses substantially more parts than does the HBR16, so the difference in present costs appears rational.

If we simply average the high/low values, a case can be made that one of the more complex Crosby HBR designs (HBR16/HBR18/HBR20) has a probable present value (based solely on CPI manipulation) falling in a range of $668 to $1518, and a mid-point present value of $1093.

Seems to me this tracks pretty well with the present e-Bay sell values in the $500/$600 range.  The CPI projection is based on economic theory, while the e-Bay bid price is based on present market perception.

Jay W6HHT   

