From hbr@mailman.qth.net  Sat Feb  1 02:32:11 2003
From: hbr@mailman.qth.net (hbr@mailman.qth.net)
Date: Fri, 31 Jan 2003 20:32:11 -0600
Subject: [HBR] HBR-11 AVAILABLE FOR TRADE
Message-ID: <6C07122052CB7749A391B01A4C66D31E0E68AA@ausx2kmps304.aus.amer.dell.com>

Niel-
I have a nice looking HBR-11 that works well with coils for two bands ( 80 &
40) that is available for trade or possibly tade.
If you are intrested, I will take some pictures and get them your way.
Cliff






Niel Wiegand hbr@mailman.qth.net  <mailto:hbr%40mailman.qth.net
<mailto:hbr%40mailman.qth.net> > 
Tue, 24 Dec 2002 11:17:11 -0500 
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I'm looking for a HBR 8 - 16 in most any condx. I like either a parts
source or a HBR rcvr in reasonable shape to do restoration of.

I've got a variety of trade stock from bugs to HRO60s.

Any interest?

73, Niel
w0vlz@arrl.net
http://www.io.com/~nielw/wa5vlz.htm <http://www.io.com/~nielw/wa5vlz.htm> 




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From hbr@mailman.qth.net  Sat Feb  1 02:56:40 2003
From: hbr@mailman.qth.net (Bob)
Date: Fri, 31 Jan 2003 21:56:40 -0500
Subject: [HBR] HBR-11 AVAILABLE FOR TRADE
References: <6C07122052CB7749A391B01A4C66D31E0E68AA@ausx2kmps304.aus.amer.dell.com>
Message-ID: <000701c2c99d$8b7b7e90$0300a8c0@bobspc1>

Cliff;

    What are you interested in trading for?

Bob, W4RLC
----- Original Message -----
From: <Cliff_White@Dell.com>
To: <hbr@mailman.qth.net>
Sent: Friday, January 31, 2003 9:32 PM
Subject: [HBR] HBR-11 AVAILABLE FOR TRADE


> Niel-
> I have a nice looking HBR-11 that works well with coils for two bands ( 80
&
> 40) that is available for trade or possibly tade.
> If you are intrested, I will take some pictures and get them your way.
> Cliff
>
>
>
>
>
>
> Niel Wiegand hbr@mailman.qth.net  <mailto:hbr%40mailman.qth.net
> <mailto:hbr%40mailman.qth.net> >
> Tue, 24 Dec 2002 11:17:11 -0500
> * Previous message: Fw: [HBR] nice hbr on ebay  <000412.html>
> * Next message: [HBR] HBR Tuning Cap, Coil Forms  <000414.html>
> * Messages sorted by: [ date ] <date.html>  [ thread ]
> <thread.html>  [ subject ] <subject.html>  [ author ] <author.html>
>
> I'm looking for a HBR 8 - 16 in most any condx. I like either a parts
> source or a HBR rcvr in reasonable shape to do restoration of.
>
> I've got a variety of trade stock from bugs to HRO60s.
>
> Any interest?
>
> 73, Niel
> w0vlz@arrl.net
> http://www.io.com/~nielw/wa5vlz.htm <http://www.io.com/~nielw/wa5vlz.htm>
>
>
>
>
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> ************************************
> Visit the HBR Receiver Web Site with over 100 pictures of receivers and
> construction notes...... via http://www.qsl.net/k5bcq/
>
> Retrieve reflector archived data via
http://mailman.qth.net/mailman/listinfo/hbr
>
>



From hbr@mailman.qth.net  Sat Feb  1 03:02:36 2003
From: hbr@mailman.qth.net (Sandy and Kees Talen)
Date: Fri, 31 Jan 2003 21:02:36 -0600
Subject: [HBR] HBR-11 AVAILABLE FOR TRADE
Message-ID: <20030131.210239.-285457.1.windy10605@juno.com>

On the previous note, please reply to Cliff directly since
he's not on the reflector (yet). He lives locally but I haven't
talked him into joining yet. This weekend is the WCARC 
swapfest ...should be fun.

I did forward the one from Bob to him.

73  Kees K5BCQ

From hbr@mailman.qth.net  Sat Feb  1 11:13:04 2003
From: hbr@mailman.qth.net (hbr@mailman.qth.net)
Date: Sat, 1 Feb 2003 06:13:04 EST
Subject: [HBR] HBR-11 AVAILABLE FOR TRADE
Message-ID: <179.157b6f83.2b6d05c0@aol.com>

Cliff,
  I am interested. Could you send some pictures and what are you looking for 
for trade or sale??

Steve
N4TKP


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From hbr@mailman.qth.net  Sat Feb  1 18:11:53 2003
From: hbr@mailman.qth.net (hbr@mailman.qth.net)
Date: Sat, 1 Feb 2003 13:11:53 -0500
Subject: [HBR] HBR2K Chapter 12 -- More Details
In-Reply-To: <3E327670.6580.943D67@localhost>
References: <3E2AECCA.21608.1DDFA8D@localhost>
Message-ID: <3E3BC799.24791.3FE548@localhost>

The Miller oscillator failed:  output voltage was higher but apparent 
stray capacitance was enough higher to require lower L and thus cut 
the output on the higher bands so I wound up with a much greater 
variation in output voltage.   I went back to the Pierce.   There's 
plenty of gain in any case.

(The crystal looks inductive in these circuits; with it connected to the 
plate in the Pierce I speculate that it partly cancels out the 
capacitance seen by the plate tank, allowing a larger L for the tank.)

Sensitivity by bands (10 db s/n) after proper alignment and 1st 
oscillator changes:

80 -- 0.5 uV
40 -- 0.28
20 -- 0.38
15 -- 0.5
10 -- 0.6

Good enough for now; I may test a cascode RF stage at a later time. 
Because of the requirement for trapping of strong HF stations on the 
1st IF, a cascode is a bit messier than cathode coupled.   In the next 
few days I'll do the two-tone dynamic range test to see about 
crossmod performance.

As expected there was another bad trimmer on 10 meters; took me 
three tries to get a good one in there.  These are tiny (0.3" diameter) 
disk trimmers with a rotating ceramic plate on a ceramic base.  The 
most common failure is that the solder joint between the rotating 
brass hub breaks loose from the plated-on electrode on the rotor.   

The audio quality was not as good as I thought it should be.  
Revisiting the output transformer roll-off cap I discovered that it was a 
bit large -- fixing that helped the highs.   I went through the audio with 
a scope and found that on SSB, there was some visible distortion in 
the plate detector -- positive peaks were definitely 'squashed' a bit.   I 
reduced the drive from the carrier oscillator (it was pushing the tube 
operating point too far toward cutoff) and fixed that; sure enough the 
audio got better.

But still not really good.   Although a sine wave looked okay all the 
way through, it sounded 'muddy' on music.  I suspected phase 
distortion -- different frequencies shifted in phase by different 
amounts.   Could have put in a square wave and scoped that, but I 
followed a hunch, instead.  

I never liked my audio section design.   I had settled on a 12AX7 in a 
paraphase inverter driving p-p 6AQ5's with feedback from the output 
transformer to the cathode of the 1st stage.   The paraphase circuit, 
however, puts two coupling caps inside the feedback loop and there 
isn't that much surplus gain anyhow, compared to a desired overall 
voltage gain of 20.   Great place for phase distortion.

I tried again.   First time around I had not been able to get a 
conventional phase splitter (equal resistors in plate and cathode of a 
triode) to work with 1/2 12AX7 because with only 140 volts I couldn't 
develop the needed 15 or so volts p-p to drive the 6AQ5s -- the 
12AX7 has too high a plate resistance.   The obvious answer would 
be a 12DW7 = 1/2 12AX7 + 1/2 12AU7 but this tube is much sought 
by hi-fi enthusiasts and sells for $15 up.   

Another lightbulb experience:  The last RCA tube handbooks show a 
series of hi-fi amps using a 7199 triode-pentode.   The pentode does 
the voltage amp job with a gain perhaps around 400; it's direct 
coupled to the triode which is used as a phase splitter.   The 7199 is 
another popular hi-fi tube, but I didn't need extreme low noise and 
hum; could a 6U8 do the job?   The triode is medium-mu; it should 
do better as a phase splitter.

A breadboard hookup showed that It could, and with the RCA circuit 
the audio quality improved dramatically.  On AM, it's now as good as 
you're going to hear from a communications receiver with a 4" 
speaker.   It's better too, on SSB, but still, I think not as good as it 
could be.  I'd characterize the problem as 'slight roughness instead of 
clear as a bell.'

Jim, N2EY said:

> You might consider some sort of buffer to prevent osc pulling. 

You don't see any obvious pulling but with SSB, even a few CPS -- 
maybe 5?  10?  -- occuring on voice peaks would be enough to 
cause audible distortion.   Today's project is to rebuild the VFO with 
a buffer.   I'll probably switch from the 6DZ4 to the more pedestrian 
12AT7 as there does not seem to be a suitable later model dual 
triode.  Not a big job because the tuned circuit parts of the oscillator  
won't change but it requires a new mounting plate for the tube and 
nothing requiring metalwork is trivial.  

The other recent job was the front panel, now drilled and filed into 
shape and temporarily installed.   Big holes and a tougher alloy 
(5052 I think?) than I should have used; I wouldn't want to do that 
every day.  Paint and control markings to come later when the odds 
and ends of mechanical alignment and fitting of various parts are 
done and the set is mostly not being beat around on the bench 
anymore.  The latest picture is at:

http://www.timbreblue.com/HBR2K5.JPG

Not a great panel layout but that's the price of recycling so much FT-
101.   Thought I was being clever using a hard-to-find dual concentric 
control for the RF/AF gain functions but using separate pots with the 
RF gain located midpanel on the right would definitely give a more 
balanced look.

There is a spare tube socket now -- the result of moving the 100 kcs 
calibrator in with the filter driver stage in a 6U8.   The spare will likely 
become a 20 kcs multivibrator locked to the 100 kcs oscillator -- 
wonder if that will work?   I really liked the 25 kcs calibrator steps on 
the FT-101.   Or how 'bout a 6:1 division, giving 16.667 kcs 
calibration points ... Just kidding.   This *has* been a long project, 
hasn't it?

Another FT-101 parts set arrived yesterday.   Sure enough, with a 
modest rearrangement of the chassis it would be possible to use the 
original internal speaker.   Didn't think of that when I did the first 
design but I'll get it in the drawing.

Also in the "well, duh..." department -- the FT-101 doesn't use the 
CW carrier crystal on receive.   The USB crystal (below the 3180 kcs 
2nd IF center because of conversions) is used; you tune in 'the right 
note' of about 800 cps, then switch in the CW filter which has a 
3179.3 kcs center frequency -- i.e. 800 cps above the 3178.5 kcs 
USB crystal.   Guess who wishes he had ever even *listened* to CW 
on an FT-101.   

But I believe there's a patch of slightly less darkness ahead of me in 
the tunnel.   'Nuther month or two.   The documentation is 
progressing.

Walt Hutchens
KJ4KV

From hbr@mailman.qth.net  Sun Feb  9 21:46:47 2003
From: hbr@mailman.qth.net (hbr@mailman.qth.net)
Date: Sun, 9 Feb 2003 16:46:47 -0500
Subject: [HBR] HBR2K -- Chapter 13 -- The VFO Revisited and Futher Work
In-Reply-To: <001501c2d045$66da2b50$8e310cd8@yourus67pi6luv>
Message-ID: <3E4685F7.24027.5F84DF@localhost>

A while back, Jim, N2EY, said:

> You might consider some sort of buffer to prevent osc pulling.

Jim was right.  Replacing the 6DZ4 with a 12AT7 with the second 
triode serving as a cathode follower cleaned up the slight roughness 
in SSB signals.   

I also tweaked the temperature compensation slightly.   Now here's 
no drift at all, after after the first 15 minutes.

The VFO's something of a paradox.   On one hand it's the part of the 
design where there's the greatest payoff for being able to just copy a 
working design.   But on the other hand, it's the part which is the 
hardest to build so that it *can* be duplicated.  If the dial calibration 
is to be accurate the coil has to be exactly right, the 'thermal design' 
is not 100% obvious, temperature compensation is another issue.   I 
have a second FT-101 VFO unit now, so before I finish the 
documentation I'll start from scratch on that one, writing it all down 
from the beginning.

Does anyone have a good source for NPO and neg. temp. coefficient 
ceramic caps?   I have been buying two of every value at fleamarkets 
for twenty years but would like to put a source in the notes.

Picture with the case on:

http://www.timbreblue.com/hbr6.jpg

(The other pictures are at successively lower numbers.)

I did replace the dual concentric control for RF/AF gain with 
independent controls.   Controls now (left to right along the top line):  
STBY, PWR ON, (spare) 100kcs/off/25kcs, tuning, PRESELECTOR, 
RF gain.   Lower line: MODE (LSB/USB/CW/AM2kcs AM4kcs),  AF 
gain, BAND.

It needs paint but that will have to wait for warmer weather.   The 
parts set case is rough; I may sandblast it before painting.

The STANDBY switch is wired, ditto the headphone jack and the 100 
kcs/25 kcs calibrator switch; I haven't done the 25 kcs multivibrator 
yet.   Yeah, it has to be 25 kcs because the 2nd IF (3180 kcs) is a 
multiple of 20 kcs.   

Next is another alignment and then doing the two-tone dynamic 
range measurement.  Also need to check the skirt selectivity -- may 
need a shield across the filters, or ???   I still have to switch the RF 
and 1st oscillator over to +90 regulated HV.   The volume is greater 
on SSB than on AM; I need to look into that.   

I hope someone else will build this thing.   It works fine -- actually, a 
lot better than that -- but there's going to be plenty of room for 
improvements.   Maybe 50% on the notes and schematic.   

Walt Hutchens
KJ4KV

From hbr@mailman.qth.net  Mon Feb 10 01:37:17 2003
From: hbr@mailman.qth.net (hbr@mailman.qth.net)
Date: Sun, 9 Feb 2003 20:37:17 EST
Subject: [HBR] HBR2K -- Chapter 13 -- The VFO Revisited and Futher Work
Message-ID: <1f0.169da13.2b785c4d@aol.com>

In a message dated 2/9/03 4:46:03 PM Eastern Standard Time, 
waltah@earthlink.net writes:

>  Replacing the 6DZ4 with a 12AT7 with the second 
>  triode serving as a cathode follower cleaned up the slight roughness 
>  in SSB signals.   

Glad to hear it!
>  
>  I also tweaked the temperature compensation slightly.   Now here's 
>  no drift at all, after after the first 15 minutes.

COOL!
>  
>  The VFO's something of a paradox.   On one hand it's the part of the 
>  design where there's the greatest payoff for being able to just copy a 
>  working design.   But on the other hand, it's the part which is the 
>  hardest to build so that it *can* be duplicated.  If the dial calibration 
>  is to be accurate the coil has to be exactly right, the 'thermal design' 
>  is not 100% obvious, temperature compensation is another issue.   I 
>  have a second FT-101 VFO unit now, so before I finish the 
>  documentation I'll start from scratch on that one, writing it all down 
>  from the beginning.

In situation where the actual VFO freqs must match a predetermined scale or 
dial, or be linear, the design can be complicated. I use a different method 
for homebrew projects - the old "make the scale/dial match the VFO". The 
trick I use is to  get the VFO working just the way I want it (drift and freq 
coverage), then make up a hand drawn scale out of cardboard using the LM freq 
meter. 

Then I use CAD software to make up a nice dial scale, print it out, and use 
it for the actual dial. 
>  
>  Next is another alignment and then doing the two-tone dynamic 
>  range measurement.  Also need to check the skirt selectivity -- may 
>  need a shield across the filters, or ???  

Good idea, but also check decoupling caps everywhere. Do not be afraid to add 
more bypasses, add chokes, rewire with shielded wire, etc. Sometimes it takes 
a combination of capacitors of different values to get a low Z bypass at all 
important freqs. Do not overlook the heater circuit as a feedback or bypass 
path. 

>  I hope someone else will build this thing.   It works fine -- actually, a 
>  lot better than that -- but there's going to be plenty of room for 
>  improvements.   Maybe 50% on the notes and schematic.   

What is really neat about this project is the concept of recycling an old 
unwanted rig that is not worth restoring into something completely new and 
unique. 

73 de Jim, N2EY

From hbr@mailman.qth.net  Wed Feb 19 16:08:39 2003
From: hbr@mailman.qth.net (hbr@mailman.qth.net)
Date: Wed, 19 Feb 2003 11:08:39 -0500
Subject: [HBR] HBR2K -- Chapter 13 -- The VFO Revisited and Futher Work
In-Reply-To: <1f0.169da13.2b785c4d@aol.com>
Message-ID: <3E5365B7.13634.239ECA@localhost>

Jim comments on my report:

> >  Replacing the 6DZ4 with a 12AT7 with the second 
> >  triode serving as a cathode follower cleaned up the slight roughness 
> >  in SSB signals.   
> 
> Glad to hear it!

The roughness was *very* slight.   Since then I've found that the 
impedance of those filters is actually 500 ohms; I had guessed 1000 
from the FT-101 circuit.   Getting the termination resistors right 
improved quality slightly.

> In situation where the actual VFO freqs must match a predetermined scale or 
> dial, or be linear, the design can be complicated. I use a different method 
> for homebrew projects - the old "make the scale/dial match the VFO". The 
> trick I use is to  get the VFO working just the way I want it (drift and freq 
> coverage), then make up a hand drawn scale out of cardboard using the LM freq 
> meter. 

> Then I use CAD software to make up a nice dial scale, print it out, and use 
> it for the actual dial. 

I have done that on some other projects but I am working here with 
that wonderful FT-101 calibrated-every-1-kc dial -- big payoff for being 
able to track that.   With three adjustments (coil, series and parallel 
trimmer caps) you can get three points exact, then bending plates 
brings it spot on.   The trick is in doing and describing it so that 
someone who has not done it before can duplicate the results.
  
> >  Next is another alignment and then doing the two-tone dynamic 
> >  range measurement.  Also need to check the skirt selectivity -- may 
> >  need a shield across the filters, or ???  
> 
> Good idea, but also check decoupling caps everywhere. Do not be afraid to add 
> more bypasses, add chokes, rewire with shielded wire, etc. Sometimes it takes 
> a combination of capacitors of different values to get a low Z bypass at all 
> important freqs. Do not overlook the heater circuit as a feedback or bypass 
> path. 

Amen, brother!    I'm pretty  encouraged, though, because when 
there are serious problems in these departments there is usually 
enough regeneration to put bumps in the filter passband.   I passed 
the filament circuit to the front end area through a choke and 
feedthrough caps.   I used the same boxed-in area as in the FT-101 
for the front end.   Used lots of bypass caps and lots of decoupling.   

However it takes much less stray coupling to cause degraded skirt 
selectivity than to distort the in-passband response or show up as 
regeneration.   If the output side of a filter just 'sees' the input, that 
can do it.  The filters are built with ground pins between the input and 
output pins and I tried to do the wiring the same way ... but testing is 
the only way to know.   

So far it's looking like a pretty easy radio to build, for 14 tubes.   
There have been none of the kind of problems you're pointing at -- the 
problems have been of the "D'oh!" variety, or pretty simple just-get-
the-darn-design-right issues.   Meaning it should be possible to just 
follow the schematic, chassis layout, and notes and get good 
results.   

> What is really neat about this project is the concept of recycling an old 
> unwanted rig that is not worth restoring into something completely new and 
> unique. 

Yep.   Of three parts rigs, two are clearly ex-CB'er and substantial 
parts of the PA or driver bandswitch area were fried.   Two came with 
no transformer.   And it's pretty cool to be able to say "The receiver 
here is homebrew, OM." 

Walt Hutchens
KJ4KV

From hbr@mailman.qth.net  Sun Feb 23 19:16:39 2003
From: hbr@mailman.qth.net (hbr@mailman.qth.net)
Date: Sun, 23 Feb 2003 14:16:39 -0500
Subject: [HBR] HBR2K -- Chapter 14 -- Large Signal Performance, Part 1
In-Reply-To: <3E4685F7.24027.5F84DF@localhost>
References: <001501c2d045$66da2b50$8e310cd8@yourus67pi6luv>
Message-ID: <3E58D7C7.25827.C6122F@localhost>

Small signal performance (what is the weakest signal you can hear 
when the band isn't crowded) was simple -- around 0.5 uV sensitivity 
for 10 db s/n.   

Large signal performance is generally more important for HF 
receivers because few bands are uncrowded and even when the ham 
band is clear there are many high power SW broadcast stations and 
local sources of interference.   I can measure one SW BC station at 
0.1 volts on my antenna terminals; when I lived near Washington, 
DC, the total antenna voltage was around a volt.  

One measure of strong signal performance is the 'two-tone third order 
dynamic range.' Forgetting the third order part (nobody much 
measures anything else) this is "How strong do two equal signals 
have to be before non-linearity in your receiver produces detectable 
false signals?"   

For example if you put in signals at 7200 kcs and 7220 kcs, you will 
at first hear nothing else.   But as you keep increasing the two 
signals, eventually you'll hear two new signals at 7240 and 7180 kcs. 
For the best typical vintage receivers able to hear an 0.5 uV signal 
you might get spurious signals of detectable strength at around 
5,000 uV -- an 80 db dynamic range.   

How good is 80 db?   S9 is most often 50 uV which is 40 db above 
an 0.5 uV signal.   40 db over S-9 is 80 db above 0.5 uV.    On any 
good night on 80 meters, some of what this typical receiver hears, 
isn't there -- it is spurious signals generated by internal distortion.   
And not only is this receiver hearing signals that aren't there, but the 
signals that *are* there, are distorted -- muddy sounding.   If sigs are 
muddy on your transmitting antenna but clear on a clip lead, your 
receiver doesn't have enough dynamic range for the operating 
conditions and you're experiencing 'intermodulation distortion.'

My HBR2K tested at around 60-70 db -- disappointing and certainly 
not adequate.   Back to the workbench!

Fortunately the set covers 160 meters and I have a 5 Mcs scope so I 
could actually look at the distortion.  The problem can be studied just 
as you would distortion in an audio amp, by injecting a signal and 
seeing where it gets messed up.   You have to use much larger 
signals to see distortion than you do to hear it, but my URM-25 goes 
to 100,000 uV.   WOW -- when you stick that in, the voltage reaching 
the 1st RF grid is 2 volts p-p due to the high Q of the antenna tuned 
circuit!   That's a whole bunch for a low noise RF amplifier and all but 
impossible to handle in a conventional mixer, especially if the RF 
stage jacks it up some more.   

Sure enough, a beautiful 2 volt sine wave in at the RF stage grid gave 
a clipped sine wave between the two sections of the tube and a real 
mess at the cathode of the 1st mixer.   (1st oscillator disabled so the 
waveform would be easy to understand.)   

I switched to a cascode (triode plate drives the cathode of another 
triode) RF amp circuit; that helped some.   Then by increasing the 
cathode resistors on both sections I reduced the gain to just a few 
db.   The situation in the RF stage was much better but the dynamic 
range didn't improve much because the big problem is in the mixer.

I decided that the Pullen mixer isn't a good choice in this situation.   
Although I have an article claiming a two-tone dynamic range 
approaching 120 db with this circuit I can't see how that's possible if 
an RF stage is used and I don't have enough information to figure the 
situation out.   

I changed both mixers to a 'push-push' design favored for large signal 
handling at the expense of lower gain.   That gave a good over-all 
gain distribution -- receiver noise is now dominated by the RF stage, 
as it should be.  But still only a 70 db range.  

The reason is clear enough: the gain of the 1st mixer is low so the 
RF stage gain has to be relatively high.   But that means that the 
signal voltage reaching the mixer is too large for linearity on the input 
signal path -- both the RF stage itself and the mixer are pushed into 
non-linearity at signals of only 1000 uV or so.   

The 1st mixer gain is low partly because of the circuit but also 
because of the low injection voltage from the 1st oscillator.   And 
*that's* low because with the small crystals of the FT-101 my simple 
Pierce oscillator wouldn't deliver more without drift.   

Very interesting design issues here!   There are several ways to go.

D'oh!  Department.    I heard a whistle in the mornings.   It was there 
on more than one band and did not depend on tuning so obviously it 
was a signal coming directly in to the second IF at 3180 kcs.   But 
how?  There are three very good tuned circuits ahead of there.   Then 
I looked at where the antenna connector was mounted.   I had used 
the original FT-101 location but later added a cathode follower to drive 
the 3180 kcs crystal filters, locating the new stage *right by the 
antenna connector*.   Suddenly the problem wasn't that hard to 
understand -- the connector and wiring was radiating directly to the 
filter driver stage, less than an inch away.   I moved the antenna 
connector to the left rear corner of the chassis (shortening the leads 
considerably in the process) and the problem disappeared.

By the way, because the RF stage does really well when there's 
some AGC voltage the receiver works fine in the usual situations.   
Weak signals on a quiet band are okay, strong sigs on a noisy band 
are okay too.   It's the weak signals on a noisy band (that's what 
dynamic range measures) that's a problem.   I still think it ought to 
be possible to build an all-round outstanding receiver along these 
lines and I'm not yet ready to quit trying.

Walt Hutchens
KJ4KV

From hbr@mailman.qth.net  Sun Feb 23 21:00:29 2003
From: hbr@mailman.qth.net (Jeff Noel)
Date: Sun, 23 Feb 2003 16:00:29 -0500
Subject: [HBR] HBR2K -- Chapter 14 -- Large Signal Performance, Part 1
References: <001501c2d045$66da2b50$8e310cd8@yourus67pi6luv> <3E58D7C7.25827.C6122F@localhost>
Message-ID: <000601c2db7e$adb0c2c0$79042c42@hppav>

Well, that explains what is wrong with the Yaesu Mark V,
at least mine. It hears  SWB signals on 40m in the cw band  that do not tune
and are wide and sound muddy, They are not there on the Tentec Omni lV+.



From hbr@mailman.qth.net  Sun Feb 23 21:06:41 2003
From: hbr@mailman.qth.net (hbr@mailman.qth.net)
Date: Sun, 23 Feb 2003 16:06:41 EST
Subject: [HBR] HBR2K -- Chapter 14 -- Large Signal Performance, Part 1
Message-ID: <185.176c8dfa.2b8a91e1@aol.com>

In a message dated 2/23/03 2:16:35 PM Eastern Standard Time, 
waltah@earthlink.net writes:

(lotta good stuff snipped)

> Fortunately the set covers 160 meters and I have a 5 Mcs scope so I 
>  could actually look at the distortion.  The problem can be studied just 
>  as you would distortion in an audio amp, by injecting a signal and 
>  seeing where it gets messed up.   You have to use much larger 
>  signals to see distortion than you do to hear it, but my URM-25 goes 
>  to 100,000 uV.   WOW -- when you stick that in, the voltage reaching 
>  the 1st RF grid is 2 volts p-p due to the high Q of the antenna tuned 
>  circuit!   That's a whole bunch for a low noise RF amplifier and all but 
>  impossible to handle in a conventional mixer, especially if the RF 
>  stage jacks it up some more.   

Ayup.   

>  Sure enough, a beautiful 2 volt sine wave in at the RF stage grid gave 
>  a clipped sine wave between the two sections of the tube and a real 
>  mess at the cathode of the 1st mixer.   (1st oscillator disabled so the 
>  waveform would be easy to understand.)   
>  
>  I switched to a cascode (triode plate drives the cathode of another 
>  triode) RF amp circuit; that helped some.   Then by increasing the 
>  cathode resistors on both sections I reduced the gain to just a few 
>  db.   The situation in the RF stage was much better but the dynamic 
>  range didn't improve much because the big problem is in the mixer.
>  
>  I decided that the Pullen mixer isn't a good choice in this situation.   
>  Although I have an article claiming a two-tone dynamic range 
>  approaching 120 db with this circuit I can't see how that's possible if 
>  an RF stage is used and I don't have enough information to figure the 
>  situation out.   
  
>  I changed both mixers to a 'push-push' design favored for large signal 
>  handling at the expense of lower gain.   That gave a good over-all 
>  gain distribution -- receiver noise is now dominated by the RF stage, 
>  as it should be.  But still only a 70 db range.  
>  
>  The reason is clear enough: the gain of the 1st mixer is low so the 
>  RF stage gain has to be relatively high.   But that means that the 
>  signal voltage reaching the mixer is too large for linearity on the input 
>  signal path -- both the RF stage itself and the mixer are pushed into 
>  non-linearity at signals of only 1000 uV or so.   
  
>  The 1st mixer gain is low partly because of the circuit but also 
>  because of the low injection voltage from the 1st oscillator.   And 
>  *that's* low because with the small crystals of the FT-101 my simple 
>  Pierce oscillator wouldn't deliver more without drift.   

Two words: Buffer stage.
>  
>  Very interesting design issues here!   There are several ways to go.

>  By the way, because the RF stage does really well when there's 
>  some AGC voltage the receiver works fine in the usual situations.   
>  Weak signals on a quiet band are okay, strong sigs on a noisy band 
>  are okay too.   It's the weak signals on a noisy band (that's what 
>  dynamic range measures) that's a problem.   I still think it ought to 
>  be possible to build an all-round outstanding receiver along these 
>  lines and I'm not yet ready to quit trying.

Here's how I handled the same problem in the Southgate Type 7 and all its 
predecessors. Brute force solution learned from W6TC and W2LYH, master 
homebrewers and rx builders. (Anybody know what happened to W2LYH's homebrew 
rig?)

The Type 7 is single conversion, using a 6EH7 RF amp and 7360 mixer. After 
the mixer is an 8 pole 500 Hz xtal filter which I think was originally meant 
for a RACAL receiver. The RF amp has its own manual gain control, which is 
run just high enough to hear band noise. The IF also has its own gain 
control, which is used most of the time. Adequate injection is provided by 
the premixer/buffer setup used to generate the LO signal. 

I don't know the actual dynamic range, but under contest conditions on 40 
meters there is very little I cannot dig out. 

Not a perfect solution but worth considering.>

Also see:
  
Feb 1972 QST, "An Experimental Receiver For 75 Meter DX Work" or something 
like that. By 
W1KLK (SK)
  
- the front end has 4 tuned circuits (2 double tuned and ganged circuits) 
between the antenna and mixer. Very sharp. Slug tuned. Not ganged to the main 
tuning.

- the RF amp is a dual triode grounded grid (both sections parallelled). The 
basing of the 7044 is such that a single shield across the socket will ground 
both grids and shield input from output. Most dual triode pinouts won't allow 
that. The 2C51 and 5687 have similar bases. The RF amp has only enough gain 
to overcome the loss of the 4 tuned circuits - it's not there to boost the 
sensitivity much. 

- the 7360 mixer does not used fixed bias - it uses cathode bias. However, it 
is on the "RF" gain control line (also AGC) along with the IF amps. This 
mixer uses different resistor values than are usually seen, and the B+ is 250 
volts. But it is a single-ended design. 

- there's a choice of xtal or variable BFO

- the audio AGC is considered marginal by the author, but he also says that 
it is not used most of the time anyway.

 The achieved goals were very high sensitivity/selectivity and excellent 
adjacent strong signal elimination.  

6JH8 or 6ME8 are possible subs for the 7360.

73 de Jim, N2EY

From hbr@mailman.qth.net  Mon Feb 24 01:48:17 2003
From: hbr@mailman.qth.net (hbr@mailman.qth.net)
Date: Sun, 23 Feb 2003 20:48:17 -0500
Subject: [HBR] HBR2K -- Chapter 14 -- Large Signal Performance, Part 1
In-Reply-To: <185.176c8dfa.2b8a91e1@aol.com>
Message-ID: <3E593391.30921.22CABBD@localhost>

Jim quotes me

> >  The 1st mixer gain is low partly because of the circuit but also 
> >  because of the low injection voltage from the 1st oscillator.   And
> >  *that's* low because with the small crystals of the FT-101 my simple
> >  Pierce oscillator wouldn't deliver more without drift.   
 
 and adds:

> Two words: Buffer stage.

Maybe.   But it's not a power issue -- 1/2 12AT7 will deliver plenty of 
power.   The first thing I'm trying is a super-Q oscillator coil and after 
that, a transformer.   Only if there isn't another way will I get to a 
buffer stage.   

The overall goal is a bit different than some receiver designs you 
mention.   I'm interested in an outstanding all purpose HF ham 
receiver -- the one designers might have produced in 1970 had there 
been an effort to do it -- rather than a specialized machine with a lot 
of knobs. 

> The Type 7 is single conversion, using a 6EH7 RF amp and 7360 mixer.
> After the mixer is an 8 pole 500 Hz xtal filter which I think was
> originally meant for a RACAL receiver. 

Single conversion is definitely the way to go but it trades internally 
generated spurious signals for the extra mixers taken out of the 
signal path.   And I felt that at my level of experience there was a 
huge advantage to staying with an existing conversion scheme and 
bunch of recycle-able hardware.  You can only answer so many 
questions wrong at the same time and make any progress.   Call 
that Walt's (rusty) razor.

The 6EH7-7360 sounds like a good combination, although I wonder 
at the need for that much gain in front of a 7360.   And beam tubes 
have so many difficult design challenges, from the DC voltages to the 
very high LO drive requirements (and should be push-pull, at that); all 
that means a lot of heat which complicates the stability challenge.

All of which is another way of saying that one day I'd like to try a 
beam tube receiver.   Just not there yet!

> The basing of the 7044 is such that a single shield across the
> socket will ground both grids and shield input from output. Most dual
> triode pinouts won't allow that. The 2C51 and 5687 have similar
> bases. The RF amp has only enough gain to overcome the loss of the 4
> tuned circuits - it's not there to boost the sensitivity much. 

The trade off is peak noise performance for dynamic range, is it not?  
I'm betting that a cascode 6ES8 comes close on the noise (6.5 db in 
a TV tuner) and kicks anatomy dynamically.  1% crossmod at 0.5 
*volts* of signal as you near cutoff -- and not bad at higher gains.   
And since it's impossible for a conventional mixer to equal the large-
signal performance of an amplifier, a key function of an RF stage is 
to have a place to do AGC ahead of the mixer.   

I'm thinking in the direction of a 12AU7 1st mixer.  That would pretty 
well deal with the large signal issues but would require a whole 
bunch of LO drive so we'll see.   Added advantage -- you can put 
some AGC on that tube.

Jeff said:

> ...Yaesu Mark V, at least mine. It hears  SWB signals on 40m in the cw
> band  that do not tune and are wide and sound muddy, They are not
> there on the Tentec Omni lV+. 

While that could be a design flaw, there are also radio and other 
hardware failures that could produce the problem.  I'm not 
experienced enough with modern gear to have an opinion.   Have you 
compared notes with other owners of the same rig?

But it definitely could be a design flaw.  An interesting comment that 
I heard recently: "The basic RF performance of modern ham gear is 
going down steadily, even as computerization gives us more bells 
and whistles." 

In the 60's the ham marketplace accepted SSB sets that drifted a 
few kcs the first hour and a good fraction of that, forever.   Signal 
quality and reception was variable, at best.   By the end of the 
decade Yaesu gave us better performing gear but saved money on 
quality control.   (Anyone out there running an FR-100B/FL-100B 
combo?)   The radios with strong all-round performance cost much 
more and never sold comparable numbers -- Collins is the leading 
example.   Computerization vs. sound basic RF performance is 
another such issue.  

Another quote, possibly more controversial:  "The FT-1000D is 
today's Collins and has a similar future."

Let's face it:  the average ham set today is a transceiver used an 
hour a day for talking to buddies in a 1000 mile radius.    Every set in 
the market, from an eBay FT-101E upwards, will do that job -- at 
least when it isn't out for a few weeks for repair.   

The question of what could have been done in 1970 remains very 
interesting.   Thanks for the discussion and suggestions!

Walt Hutchens
KJ4KV

From hbr@mailman.qth.net  Wed Feb 26 01:07:23 2003
From: hbr@mailman.qth.net (hbr@mailman.qth.net)
Date: Tue, 25 Feb 2003 20:07:23 EST
Subject: [HBR] HBR2K -- Chapter 14 -- Large Signal Performance, Part 1
Message-ID: <140.b88dbef.2b8d6d4b@aol.com>

In a message dated 2/23/03 8:47:48 PM Eastern Standard Time, 
waltah@earthlink.net writes:

> Jim quotes me
>  
>  > >  The 1st mixer gain is low partly because of the circuit but also 
>  > >  because of the low injection voltage from the 1st oscillator.   And
>  > >  *that's* low because with the small crystals of the FT-101 my simple
>  > >  Pierce oscillator wouldn't deliver more without drift.   
>   
>   and adds:
>  
>  > Two words: Buffer stage.
>  
>  Maybe.   But it's not a power issue -- 1/2 12AT7 will deliver plenty of 
>  power.   The first thing I'm trying is a super-Q oscillator coil and after 
>  that, a transformer.   Only if there isn't another way will I get to a 
>  buffer stage.   

OK! My point was that I prefer to have the crystals run easy and build up the 
signal with a buffer. Tubes are easier to find than xtals.
>  
>  The overall goal is a bit different than some receiver designs you 
>  mention.   I'm interested in an outstanding all purpose HF ham 
>  receiver -- the one designers might have produced in 1970 had there 
>  been an effort to do it -- rather than a specialized machine with a lot 
>  of knobs. 

Trouble is, any design involves compromises. The FT-101 conversion schme 
means three stages before the selective knothole of the filter. Two of those 
stages are mixers. 
>  
>  > The Type 7 is single conversion, using a 6EH7 RF amp and 7360 mixer.
>  > After the mixer is an 8 pole 500 Hz xtal filter which I think was
>  > originally meant for a RACAL receiver. 
>  
>  Single conversion is definitely the way to go but it trades internally 
>  generated spurious signals for the extra mixers taken out of the 
>  signal path.  

All depends on the conversion scheme used. The Type 7 scheme is not optimum - 
it evolved around the available filters.

>  And I felt that at my level of experience there was a 
>  huge advantage to staying with an existing conversion scheme and 
>  bunch of recycle-able hardware.  You can only answer so many 
>  questions wrong at the same time and make any progress.   Call 
>  that Walt's (rusty) razor.

Works for me!
>  
>  The 6EH7-7360 sounds like a good combination, although I wonder 
>  at the need for that much gain in front of a 7360.  

The stage normally runs at much less than max gain. Its purposes are:

- to make up the losses in the front end tuned circuits
- to isolate the antenna from the mixer
- to provide a gain control opportunity

>  And beam tubes 
>  have so many difficult design challenges, from the DC voltages to the 
>  very high LO drive requirements (and should be push-pull, at that); all 
>  that means a lot of heat which complicates the stability challenge.

I used th single-ended version shown in the ARRL Handbooks. Drive is only a 
few volts. Maybe a Pullen would do the job better. We'll find out in the 
Southgate Type 8.
>  
>  All of which is another way of saying that one day I'd like to try a 
>  beam tube receiver.   Just not there yet!
> 
Some time back I acquired a pair of 2215 kHz filters as used in the "Miser's 
Dream" receiver. Have been thinking of building a version of same for some 
time, perhaps with a double-tned input circuit rather than an RF Q 
multiplier, and another IF stage for more gain and control. Perhaps a 
premixer type LO chain. 
 
>  > The basing of the 7044 is such that a single shield across the
>  > socket will ground both grids and shield input from output. Most dual
>  > triode pinouts won't allow that. The 2C51 and 5687 have similar
>  > bases. The RF amp has only enough gain to overcome the loss of the 4
>  > tuned circuits - it's not there to boost the sensitivity much. 
>  
>  The trade off is peak noise performance for dynamic range, is it not?  

Not really. The conventional reason for rx RF amps was to make up for noisy 
mixers like the 6L7. But a 7360 is so quiet that the only real reason for an 
RF amp is to make up for tuned circuit losses (the W1KLK circuit has four 
tuned circuits before the mixer!) and perhaps control the gain. 

>  I'm betting that a cascode 6ES8 comes close on the noise (6.5 db in 
>  a TV tuner) and kicks anatomy dynamically.  1% crossmod at 0.5 
>  *volts* of signal as you near cutoff -- and not bad at higher gains.   
>  And since it's impossible for a conventional mixer to equal the large-
>  signal performance of an amplifier, a key function of an RF stage is 
>  to have a place to do AGC ahead of the mixer.   

All true. Also why high performance designs got away from conventional mixers!
>  
>  I'm thinking in the direction of a 12AU7 1st mixer.  That would pretty 
>  well deal with the large signal issues but would require a whole 
>  bunch of LO drive so we'll see.   Added advantage -- you can put 
>  some AGC on that tube.

Interesting!  

>  Jeff said:
>  
>  > ...Yaesu Mark V, at least mine. It hears  SWB signals on 40m in the cw
>  > band  that do not tune and are wide and sound muddy, They are not
>  > there on the Tentec Omni lV+. 
>  
>  While that could be a design flaw, there are also radio and other 
>  hardware failures that could produce the problem.  I'm not 
>  experienced enough with modern gear to have an opinion.   Have you 
>  compared notes with other owners of the same rig?
>  
>  But it definitely could be a design flaw.  An interesting comment that 
>  I heard recently: "The basic RF performance of modern ham gear is 
>  going down steadily, even as computerization gives us more bells 
>  and whistles." 
>  
>  In the 60's the ham marketplace accepted SSB sets that drifted a 
>  few kcs the first hour and a good fraction of that, forever.   Signal 
>  quality and reception was variable, at best.   By the end of the 
>  decade Yaesu gave us better performing gear but saved money on 
>  quality control.   (Anyone out there running an FR-100B/FL-100B 
>  combo?)   The radios with strong all-round performance cost much 
>  more and never sold comparable numbers -- Collins is the leading 
>  example.   Computerization vs. sound basic RF performance is 
>  another such issue.  

Then along comes a rig like the Elecraft K2. Which goes all the way back to 
the single conversion ideal of 1957's "What's Wrong With Our Present 
Receivers". 40 years and back to the fundamentals...
>  
>  Another quote, possibly more controversial:  "The FT-1000D is 
>  today's Collins and has a similar future."
>  
Maybe. One of the things that made S-line popular was that they could be 
worked on by a knowledgeabel ham.

>  Let's face it:  the average ham set today is a transceiver used an 
>  hour a day for talking to buddies in a 1000 mile radius.    Every set in 
>  the market, from an eBay FT-101E upwards, will do that job -- at 
>  least when it isn't out for a few weeks for repair.   

Yep. The top end market is driven by the contesters and the DXers, not the 
ragchewers. 
>  
>  The question of what could have been done in 1970 remains very 
>  interesting.   Thanks for the discussion and suggestions!

Thanks for the great ideas!

Here are some more:

Back in the mid-90s or so, there was a series in "ER" about the R-390A, 
including some front-end mods. Perhaps the circuits and tube lineups used in 
that rx could be adapted to the '101.

The Squires Sanders SS-1R was probably the closest thing to what you seek. 
It's my understanding that the SS-1R had excellent dynamic range and low 
noise. The manual is on BAMA, btw. The main reason it did not achieve 
popularity was the price and the lack of a matching transmitter. Perhaps some 
of its circuitry could be adapted.

The RSGB Handbooks of the mid-60s have some good ideas, too. More info on the 
Pullen mixer, although not identified as such. 

73 es GL de Jim, N2EY


From hbr@mailman.qth.net  Wed Feb 26 05:22:48 2003
From: hbr@mailman.qth.net (Hyotaro HAMANO)
Date: Wed, 26 Feb 2003 14:22:48 +0900
Subject: [HBR] HBR2K -- Chapter 14 -- Large Signal Performance, Part 1
References: <140.b88dbef.2b8d6d4b@aol.com>
Message-ID: <00a901c2dd57$1a0c4460$a50b10ac@setagaya.jqa.or.jp>

Dear all,

Could some one give me an information regarding "Southgate Type7" or
"Type8",
please? I found the name quite often these days and get interested in.


Hyotaro
Tokyo/Japan
-----------------------------------------------------------
:
> > > The Type 7 is single conversion, using a 6EH7 RF amp and 7360 mixer.
> > > After the mixer is an 8 pole 500 Hz xtal filter which I think was
> > > originally meant for a RACAL receiver.
:
> All depends on the conversion scheme used. The Type 7 scheme is not
optimum -
> it evolved around the available filters.
:
> I used th single-ended version shown in the ARRL Handbooks. Drive is only
a
> few volts. Maybe a Pullen would do the job better. We'll find out in the
> Southgate Type 8.
:
 ----- Original Message -----
From: <N2EY@aol.com>
To: <hbr@mailman.qth.net>
Sent: Wednesday, February 26, 2003 10:07 AM
Subject: Re: [HBR] HBR2K -- Chapter 14 -- Large Signal Performance, Part 1



