From windy10605 at juno.com  Mon Jul  5 14:02:48 2004
From: windy10605 at juno.com (windy10605@juno.com)
Date: Mon Jul  5 14:14:42 2004
Subject: [HBR] Receiver debug/improvement
Message-ID: <20040705.130248.1664.3.windy10605@juno.com>

To many of you, this is probably old news, but sometimes you/I can hear
things discussed, even participate in the discussions, but it just does
not sink in or you don't realize the application until you see it
demonstrated and focus a little. Many times we are in conversations, hear
a few key words, and the brain either clicks "in" or "out". That just
happened to me, except this time I clicked "in". I know Spectrum
Analyzers are expensive and the computer software/ hardware most people
have is not sufficient for a Mhz/Ghz SA. However, here is one that does
work, is easy to use, provides great results, and is free. All you need
is a computer with the typical sound card. I'm a great advocate for
tools, especially cost effective tools.

It's very useful to be able to analyze signal bandwidths for each
section/element of a receiver and that will require a Spectrum Analyzer
(or a lot of time on a scope), but what if we look at the total receiver
as ONE section/element ? What you really want to analyze on a given
receiver is the end result, the audio you hear. That audio is simple for
a sound card to digitize and for other software to massage into a visual
display. What you will "see" is the audio from 0 to xxKhz coming through
the receiver passband.....1) the signal you are receiving  2) the noise,
3) adjacent signals, 4) the effect of filters, 5) DSP effect, 6) notch
filter effect, 7) Q-Multiplier results, 8) audio stage design, 9) etc,
etc. The particular program I'm using is called Spectrogram (freeware)
and you connect the receiver "audio out" to the computer "microphone in".
The resolution is adequate to see the shape of the filters (peak or
notch) as you tune across the signals and any design changes you make.
You don't have to be attached at the filter, running at the RF/IF
frequency, etc. You are monitoring the RESULTS of whatever
selectivity/sensitivity components are installed (tuned RFs, IFs,
filters, DSPs, etc) in the total receiver passband at the audio out end,
the human interface end.

Cool !

73 Kees K5BCQ
From waltah at earthlink.net  Wed Jul  7 11:43:56 2004
From: waltah at earthlink.net (waltah@earthlink.net)
Date: Wed Jul  7 11:48:43 2004
Subject: [HBR] Another Receiver Project
In-Reply-To: <20040705.130248.1664.3.windy10605@juno.com>
Message-ID: <40EBE1FC.14311.13D081B@localhost>

The list has been fairly quiet the last couple of months ... summer 
and growing grass, I suppose.  

I decided that the recent general coverage receiver project was 
simply too many tubes for current conditions in the KJ4KV 
household -- growing grass and various other things.   That project 
has been set aside and I've started on something a lot simpler, 
namely an attempt at a better ham-band only set under the name 
'HBR-4' for 2004.   That series of names will be good until it starts 
overlapping Ted Crosby's numbers and six years is a long time.

I wanted a single-conversion premixed design along the lines of the 
W1OMX set and the Tempo One transceiver.   That eliminated the 
3.18 Mcs IF of the FT-101 because the VFO frequency comes out 
too low when that conversion scheme is switched to single 
conversion.  The Tempo One used a 9 mcs IF with crystals 14 Mcs 
above the upper end of each band and a VFO tuning 5 - 5.5 Mcs 
and subtracting the VFO from the crystal frequency and I had a 
couple of parts sets, including an intact VFO, crystal filters, and 
more.  

I wanted either the push-pull front end of the G2DAF receiver or a 
beam tube front end, probably without an RF stage, along the lines 
of the JMD and others.   I settled on the beam tube because of the 
difficulty of tuning and bandswitching three sets of balanced coils 
and because I wanted to try a beam mixer.  

I'm using a 6JH8 beam tube -- much cheaper *and* later than the 
7360.  Plus one of the SSB For The Radio Amateur books gives a 
few design numbers and some discussion of that tube.

Only the SS-1R of all the sets I found used a beam tube correctly --
that is, with push-pull excitation of the deflection plates and push-
pull output to the IF.   But that was a double conversion design, 
with beam tubes for both first and second mixers, leaving me to 
work out a scheme for doing the premixing that would have 
balanced output.

I settled on a pair of 6J6's, each tube operating as a push-push 
mixer, #1 grids excited in parallel from the VFO and #2 grids push-
pull from the crystal oscillator, probably through a suitable 
transformer.   (No push-pull oscillator circuits that I know of for 
series-mode crystals.)  The plates of each 6J6 are in parallel and 
the two tubes operated push-pull to drive the beam tube deflection 
plates.  

That arrangement is balanced against the VFO which is the only 
oscillator below the signal frequency.   W1OMX had some trouble 
with birdies (1 per band except 6 on 15M); I'm hoping to at least 
keep the amplitudes down.

The VFO will be a 6KT6 pentode.  

Three IF's because there's no RF stage for AGC.   There's space 
for a multivibrator for 25 Kcs marks.   The T-1 IFs are basically 
unusable because they were intended for PC board mounting; I'll 
wind my own using toroids.

I used an FT-101 chassis and planned the compartment layout to 
further reduce spurious signal propagation.   The oscillators are in 
one compartment, the front end coils (planned with no RF stage) in 
another with no other wiring except the crystal calibrator.  The 
mixer is located at the partition between the compartments.   

The mixer output goes through a 9 Mcs crystal filter which hops 
over the partition separating the front end area from the rest of the 
set.   Everything coming into the front end goes through feed 
through caps; the IF/mixer filament supply is daisy-chained through 
chokes and is on one leg of the 6-0-6 VAC filament transformer 
with the oscillators on the other.   

I'm sure I've missed something but it's the best layout I've done.  

The Tempo One VFO parts mix and match pretty well with the FT-
101 and what I've got is the best of both -- the T-1's excellent 
planetary ball final drive and VFO box with the FT-101's dial plate 
which is correct for my conversion scheme which tunes in the 
same direction on all bands.   (The T-1 uses no crystals for 80 and 
20 so its dial is calibrated 0-500 and 500-0 with nothing that's really 
right for 80.)  A few adjustments are requred to shaft lengths to 
make everything fit.

The alternative would have been to use the FT-101 VFO as a  
foundation but that one tunes 8.7-9.2 Mcs so I'd have had to 
replace the coil and start at square one getting dial tracking.   

The tank circuit parts are all in the VFO box; I used glass-metal 
feed throughs to get the two connections to the tube socket so as 
to sink the heat coming up the wires.   

There are a few other novel points but I'll wait until they work (or 
fail!) to describe them.   

After about a month I have the chassis -- new top plate on FT-101 
frame -- and panel done.   Most parts are mounted and wiring of the 
power supply and audio is done; starting on the second detectors 
and AGC stages.   

Hoping to get over 100 db dynamic range with decent sensitivity 
with this scheme but -- we'll see.   

Walt Hutchens
KJ4KV

From windy10605 at juno.com  Wed Jul  7 14:20:57 2004
From: windy10605 at juno.com (windy10605@juno.com)
Date: Wed Jul  7 14:24:07 2004
Subject: [HBR] Another Receiver Project
Message-ID: <20040707.132057.340.2.windy10605@juno.com>

Keep up the good work, Walt.

I took a retro spin and built a replica of my first receiver kit, the Air
Champ AC-100 regen. It's on my web site.
http://www.qsl.net/k5bcq/    Quite a shift from these concepts
....plywood, fanestock clips, batteries, etc. 

73 Kees K5BCQ



 
From waltah at earthlink.net  Wed Jul  7 19:26:37 2004
From: waltah at earthlink.net (waltah@earthlink.net)
Date: Wed Jul  7 19:31:19 2004
Subject: [HBR] Another Receiver Project
In-Reply-To: <20040707.132057.340.2.windy10605@juno.com>
Message-ID: <40EC4E6D.19854.2E4B0B1@localhost>

Kees said:

> I took a retro spin and built a replica of my first receiver kit,
> the Air Champ AC-100 regen. It's on my web site.
> http://www.qsl.net/k5bcq/    Quite a shift from these concepts
> ....plywood, fanestock clips, batteries, etc. 

And quite a nice job, too.  The 3Q4 is an interesting choice for a 
tube.  

Regenerative receivers are a whole 'nuther ball game; it's too bad 
that there's not time to do everything.   I thought I was going to 
have more time in retirement but as best I can recall this is worse 
than when I was working.

Walt
KJ4KV


From windy10605 at juno.com  Wed Jul  7 20:36:03 2004
From: windy10605 at juno.com (windy10605@juno.com)
Date: Wed Jul  7 20:42:47 2004
Subject: Fw: Re: [HBR] Another Receiver Project
Message-ID: <20040707.193851.1844.8.windy10605@juno.com>

I know what you mean about the time available, Walt.

Since that AC-100 result, although working, didn't perform quite as well
as I had wanted (and my ears were better back then), I'm going to try a
more "serious" regen pass, then go back to something else. Here are some
exchanges, any other input is welcome.


--------------------------------------------------------------------
Sounds great!
Would suggest two stages audio, and an audio filter as in the 2JJ rx.
1.4V octal tubes not hard to find down here, if supply is a problem.
Experience down here is that output tetrodes like 1Q5 do well as low B
voltage regen dets.
73
Barry
 
end
Barry Kirkwood PhD ZL1DD
Signal Hill Homestay
66 Cory Road
Palm Beach
Waiheke Island 1240
NEW ZEALAND
ph/fax 64-9-372-5161
www.waiheke.co.nz/signal.htm
----- Original Message ----- 
From: <windy10605@juno.com>
To: <glowbugs@piobaire.mines.uidaho.edu>
Sent: Wednesday, July 07, 2004 9:53 PM
Subject: Fw: Re: GB> Looking for Regen suggestions
 
 
> Thanks for the input, but I was thinking more along the lines of what
> "Boatanchor Bob" discussed several years ago for a tube regen using the
> classic Jones design as a start ....with a 365pf throttle cap, 1-3pf
> antenna coupler, 200pf tuning cap, BC-221 tuning drive, large ceramic
> high Q coil with taps, pluggable mica caps if needed, maybe a 1U4
(regen)
> and 1U5 (AF) combination (uses 100ma of 1.5V and <10ma of 18-27V),
> ceramic 1U4 socket, ceramic standoffs, all on a breadboard, small 8ohm
> output transformer to the headphones,  ???
>
> 73 Kees K5BCQ
From waltah at earthlink.net  Fri Jul 16 17:36:49 2004
From: waltah at earthlink.net (waltah@earthlink.net)
Date: Fri Jul 16 17:41:40 2004
Subject: [HBR] Another Receiver Project
In-Reply-To: <40EBE1FC.14311.13D081B@localhost>
References: <20040705.130248.1664.3.windy10605@juno.com>
Message-ID: <40F81231.5156.176EA4B@localhost>

I'm going to use a KVG XF-9 (no letters after) crystal filter in this 
project; I have a guesstimate of the impedance from the circuit in 
the donor set but I wonder if anyone has a spec sheet or long 
memory?  

All the (later) letter models seem to be 500 ohm but this is from a 
vaccum tube set and I'm guessing 50k input and output.   Anyone 
know for sure?  

Thanks!

Walt
KJ4KV
From waltah at earthlink.net  Tue Jul 20 14:27:27 2004
From: waltah at earthlink.net (waltah@earthlink.net)
Date: Tue Jul 20 14:33:02 2004
Subject: [HBR] Another Receiver Project -- HBR-4, Part 2
In-Reply-To: <40EBE1FC.14311.13D081B@localhost>
References: <20040705.130248.1664.3.windy10605@juno.com>
Message-ID: <40FD2BCF.8044.B7ADB6@localhost>

Gee, just *sailing along* -- considering that I only have a couple of 
hours a day to work on it. 

The three IF stages are wired and test okay -- only modest 
problems with instablity.   The plate detector for AM is fine, ditto a 
6BN6 beam discriminator tube as a product detector.   And the 
audio amp -- 6U8 driving a 6J6 -- is okay.   The function switch -- 
LSB-USB-CW-AM is working.   Probably will add an audio tuned 
circuit for CW selectivity at a later time.   

With the S-meter at half scale the audio amp overloads at about 
1/3 of full volume.   Have to use a scope to look at what's 
overloading; I probably have to reduce the overall audio gain by 
increasing the feedback.  This is the RCA tube handbook 15-watt 
hi-fi amp, adjusted to a 6U8 and 6J6, with overall voltage gain set to 
10.   

Or the problem could be too-high output from the IF stages -- 
around 100 mV is right.   If that's it I need to increase ratio of the 
AGC voltage to detector signal -- most easily done with a voltage 
divider at the last IFT output.

The output of the AM plate detector is about 2x the voltage of the 
product detector for the same input.   Adjustment of the plate load 
should take care of that.  

The 6BN6 circuit is excellent; not even close to the complexity of a 
beam tube product detector, conversion voltage gain of about 50 -- 
it's a much better match to a plate detector (for AM) than the usual 
triode or diode product detector.   The authors I followed 
(W9BIY/W9IHT, 'Some Ideas in a Ham-Band Receiver; SSB for The 
Radio Amateur, 4th edition, 1965) claim 40 db rejection of AM, 
meaning really great detection linearity.  Plus the tube limits 
sharply at not too much more than usual signal levels, meaning 
you get something of a free noise limiter.

That article is one of the best I've seen for discussing how-to with 
technical details, rather than just telling you the radio is great, be 
sure to leave plenty of room in the chassis, use small wire ... The 
receiver's not bad either -- plug in coils a la Crosby and a pretty 
straightforward *single conversion* (4500 kcs IF with a lattice filter) 
design.   Replace the AM detector (diode) with a plate detector, get 
rid of the hang AGC circuit, and substitute better tubes (6AK5 RF 
stage ...) and you'd have a most worthy HBR project with about 12 
tubes.   

Well, it needs a calibrated dial.   The writers used a NPW-0 dial as 
on the HROs.   

Anyhow, this stuff's fun when it goes well.  Maybe I'm not making 
so many mistakes as on previous projects.   (So far only one tube 
filament wired wrong ...)   Or maybe something in the front end will 
prove to be impossible?   Should know in a couple of weeks!

Walt 
KJ4KV

From windy10605 at juno.com  Tue Jul 20 18:50:43 2004
From: windy10605 at juno.com (windy10605@juno.com)
Date: Tue Jul 20 19:31:18 2004
Subject: [HBR] Another Receiver Project -- HBR-4, Part 2
Message-ID: <20040720.182620.228.8.windy10605@juno.com>

I really enjoy reading all your material, Walt. I have a book of e-mails
and put it on the CD

73 Kees K5BCQ
From future212 at comcast.net  Thu Jul 22 13:20:51 2004
From: future212 at comcast.net (DW Holtman)
Date: Thu Jul 22 13:23:58 2004
Subject: [HBR] Another Receiver Project -- HBR-4, Part 2
References: <20040720.182620.228.8.windy10605@juno.com>
Message-ID: <000b01c47010$3d8cc5c0$6401a8c0@dw2q2am1a08eq5>

Windy,

I say your post here a while back about a 40 page document on home
construction ideas that was posted in PDF format. Do you have a link where I
might down load it. Thank you for your tome and trouble.

Best,
DW Holtman

----- Original Message ----- 
From: <windy10605@juno.com>
To: <hbr@mailman.qth.net>
Sent: Tuesday, July 20, 2004 4:50 PM
Subject: Re: [HBR] Another Receiver Project -- HBR-4, Part 2


> I really enjoy reading all your material, Walt. I have a book of e-mails
> and put it on the CD
>
> 73 Kees K5BCQ
> ************************************
> 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 windy10605 at juno.com  Thu Jul 22 14:02:34 2004
From: windy10605 at juno.com (windy10605@juno.com)
Date: Thu Jul 22 14:07:03 2004
Subject: Fw: Re: [HBR] Another Receiver Project -- HBR-4, Part 2
Message-ID: <20040722.130234.784.14.windy10605@juno.com>

I don't have that RSGB manual in PDF format yet since I don't have PDF
capability (haven't gotten with the local guy who does that). I DO have
hard copies available for $5 including shipping, to cover my cost. It is
a most usefull book.

73 Kees K5BCQ


--------- Forwarded message ----------
From: "DW Holtman" <future212@comcast.net>
To: "HBR Receiver List" <hbr@mailman.qth.net>
Date: Thu, 22 Jul 2004 11:20:51 -0600
Subject: Re: [HBR] Another Receiver Project -- HBR-4, Part 2
Message-ID: <000b01c47010$3d8cc5c0$6401a8c0@dw2q2am1a08eq5>
References: <20040720.182620.228.8.windy10605@juno.com>

Windy,

I say your post here a while back about a 40 page document on home
construction ideas that was posted in PDF format. Do you have a link
where I
might down load it. Thank you for your tome and trouble.

Best,
DW Holtman

----- Original Message ----- 
From: <windy10605@juno.com>
To: <hbr@mailman.qth.net>
Sent: Tuesday, July 20, 2004 4:50 PM
Subject: Re: [HBR] Another Receiver Project -- HBR-4, Part 2


> I really enjoy reading all your material, Walt. I have a book of
e-mails
> and put it on the CD
>
> 73 Kees K5BCQ
> ************************************
> 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
>


************************************
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 k4oah at mindspring.com  Thu Jul 22 14:42:22 2004
From: k4oah at mindspring.com (Garey Barrell)
Date: Thu Jul 22 14:45:08 2004
Subject: Fw: Re: [HBR] Another Receiver Project -- HBR-4, Part 2
In-Reply-To: <20040722.130234.784.14.windy10605@juno.com>
References: <20040722.130234.784.14.windy10605@juno.com>
Message-ID: <41000A8E.10206@mindspring.com>

Kees -

Have you tried PDF995 for PDF conversion?  It's free if you don't mind 
it "phoning home" and opening an ad with each conversion, or for $9.95 
you can get a "key" that turns that stuff off.

73, Garey - K4OAH
Atlanta


windy10605@juno.com wrote:

>I don't have that RSGB manual in PDF format yet since I don't have PDF
>capability (haven't gotten with the local guy who does that). I DO have
>hard copies available for $5 including shipping, to cover my cost. It is
>a most usefull book.
>
>73 Kees K5BCQ
>
>
>--------- Forwarded message ----------
>From: "DW Holtman" <future212@comcast.net>
>To: "HBR Receiver List" <hbr@mailman.qth.net>
>Date: Thu, 22 Jul 2004 11:20:51 -0600
>Subject: Re: [HBR] Another Receiver Project -- HBR-4, Part 2
>Message-ID: <000b01c47010$3d8cc5c0$6401a8c0@dw2q2am1a08eq5>
>References: <20040720.182620.228.8.windy10605@juno.com>
>
>Windy,
>
>I say your post here a while back about a 40 page document on home
>construction ideas that was posted in PDF format. Do you have a link
>where I
>might down load it. Thank you for your tome and trouble.
>
>Best,
>DW Holtman
>
>----- Original Message ----- 
>From: <windy10605@juno.com>
>To: <hbr@mailman.qth.net>
>Sent: Tuesday, July 20, 2004 4:50 PM
>Subject: Re: [HBR] Another Receiver Project -- HBR-4, Part 2
>
>
>  
>
>>I really enjoy reading all your material, Walt. I have a book of
>>    
>>
>e-mails
>  
>
>>and put it on the CD
>>
>>73 Kees K5BCQ
>>************************************
>>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
>  
>
>
>
>************************************
>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
>************************************
>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 waltah at earthlink.net  Fri Jul 23 18:33:36 2004
From: waltah at earthlink.net (waltah@earthlink.net)
Date: Fri Jul 23 18:39:54 2004
Subject: [HBR] Another Receiver Project -- HBR-4, Part 3
In-Reply-To: <40FD2BCF.8044.B7ADB6@localhost>
References: <40EBE1FC.14311.13D081B@localhost>
Message-ID: <41015A00.282.22291A9@localhost>

Someth'n is gonna go wrong -- it has been too easy so far.

Both the product detector for SSB/CW and the plate detector for 
AM seem to be working fine, plus all the IFs, the AGC, the S-meter 
and audio stages.  There's way too much audio gain, so that needs 
to be adjusted.   I think the gain of the SSB detector is high 
compared to the AM detector but that's best adjusted by listening 
to actual signals.  

Doing a product detector with a 6BN6 was ... interesting.   The 
tube description is 'gated beam discriminator' but when you dig into 
what that means, things get complicated.

Like the 7360 (etc.) electrons leaving the cathode are focused into 
a narrow beam.   However there is just one plate and no deflection 
arrangement.   Instead, there are two control grids, both with very 
sharp cutoff characteristics -- plate current goes from off to 
saturated over just three volts or so.  When supplied with a signal 
large enough to put the tube in limiting mode (as normal for an FM 
discriminator circuit) the plate current flows in rectangular pulses at 
the signal frequency.  

In discriminator use, G1 is the signal input, G3 (called the 
'quadrature grid') is connected to a tuned circuit adjusted to the IF 
center frequency.   G3 picks up some current from the beam and 
because 'beam on' corresponds to the maximum excitation current 
to the tuned circuit, the tuned circuit (and G3 voltage) *lags* the G1 
signal by 90% on average.  In this situation the beam is gated on 
and off by the combined action of two signals 90 degrees apart.   
The tuned circuit/G3 signal does not instantly follow changes of 
phase by the beam current so phase shifts of the input signal lead 
to pulse width modulation of the beam.   A capacitor in the plate 
circuit integrates the pulses to recover the modulation of the input 
signal.

When used as a product detector, G3 is excited with a BFO signal 
of 5 volts p-p or so.   A CW signal at a slightly different frequency 
(a phase difference changing at a constant rate) leads to sine wave 
modulation of the beam pulse width, recovered as a sine wave at 
the difference frequency in the plate circuit.   

For SSB detection, G1 must be operated in the linear range.   In 
this case the beam is *both* PWM and amplitude modulated and 
the modulation is again recovered at the plate integrating capacitor.

The serious CW man could push G1 into limiting mode and recover 
a pure CW note, stripped of nearly all background noise.  The 
advantage over audio limiting (sometimes so used) is that doing it 
at the IF avoids audio harmonics -- of course some CW ops like 
the complex sound of a near-square wave output. 

As an SSB detector the tube has a conversion gain of about 50 
and begins to limit at around 2 V p-p input.   Furthermore, to obtain 
proper (linear) operation you cannot change the gain or limiting 
range.   Plate and cathode resistors must be set according to the 
directions, the focusing electrode voltage must be as specified, or 
you will get distortion.   When properly adjusted, it produces the 
nicest sine waves I've seen from a detector, but it is not very 
flexible -- to get good results you have to feed it what it wants.   

The audio gain is way too high, the plate detector doesn't seem to 
have as much gain as the product detector -- it's a little hard to be 
sure because the percentage of modulation on AM affects results 
and I don't have a high percentage source handy.   With that stuff 
fixed it will be time to start on the oscillators.   A Butler crystal 
oscillator and a Colpitts VFO ... how hard can it be?   

We'll see!

Does everyone know about Frank's tube data sheet archive?   Over 
20,000 tube data sheets -- stuff you can't imagine! -- is available at:

http://home.wxs.nl/~frank.philipse/frank/frank.html

I was reading RCA tube handbooks about the time I finished with 
Dick and Jane -- RC-15, with the 12AT7 and 50C5 among 'recently 
added types' listed in the rear of the book.   But Franks' site is  
*wonderful* -- you get full manufacturer's data on tubes that are 
barely or even completely unmentioned in the little handbooks.   
Understanding the 6BN6 would have been impossible without those 
sheets, the transfer characteristics for the 12AT7 were very handy 
for checking the design of the plate detector.  

Walt 
KJ4KV


From waltah at earthlink.net  Sun Jul 25 20:57:28 2004
From: waltah at earthlink.net (waltah@earthlink.net)
Date: Sun Jul 25 21:04:18 2004
Subject: [HBR] Another Receiver Project -- HBR-4, Part 4
In-Reply-To: <41015A00.282.22291A9@localhost>
References: <40FD2BCF.8044.B7ADB6@localhost>
Message-ID: <41041EB8.18353.2A3C72F@localhost>

The detectors and audio section seem to be okay.   By bypassing 
most of the plate load for the product detector (SSB) and plate 
detector (AM) with a 10 mf cap I cut their gain way down, but the 
product detector more that the plate detector because the 6BN6 
has a much higher plate resistance.   That brought the audio to the 
volume control to the right range while roughly equalizing SSB and 
AM output.   Reducing the gain of the audio stages to 2 (vol. 
control to loudspeaker) ended overloading in the audio stages.   

A single 6J6 seems to make a perfectly adequate audio output 
stage at this low plate voltage (160) and for ordinary shack volume 
levels.   Considering the low gain requirement it might have been 
possible to skip the 1st audio and phase splitter entirely and drive 
the 6J6 directly from the volume control, allowing it to self-invert via 
the unbypassed common cathode resistor.  

The VFO seems to be working fine.   Second to the usual 
requirements for warm up and mechanical stability the goal there 
was to change the tank circuit as little as possible so as to not 
have to spend a day getting the tracking right.

I had intended a 6KT6 high gain pentode oscillator but had 
forgotten that pentodes aren't a good bet unless you need buffering 
or frequency multiplication from an ECO circuit.   So I settled on a 
6GK5 VHF RF amp triode.  With a transconductance of 15,000 
umhos it needs only about 1/3 the coupling to the tank that a 
12AT7 or similar tube would require, meaning better stability.   

The original circuit was a grounded base bypolar transisitor 
oscillator; the tank circuit portion mapped directly to a Colpitts 
circuit with the tube cathode bypassed with a 470 mmf cap and the 
grid bypassed to the cathode with 250 mmf.   Those values proved 
too large to allow oscillation; I got it working by changing them to 
270 and 180, respectively.   Plate voltage 50V, current 2 mA, 
output 1V p-p on the cathode.   

With the trimmer adjusted at the high end of the range (tunes 5 - 
5.5 Mcs) it tracks within about 1 kcs from end to end which is 
plenty good enough for now.   It drifts upward -- no surprise there 
because the tube shunt caps had been silver micas and I replaced 
them with NP0 ceramics.  This VFO assembly has adjustable 
temp compensation via a differential trimmer so it shouldn't be hard 
to get it close to spot on.  

Next -- the crystal oscillator.   Butler circuit, one crystal for each 
band, 14 Mcs above the high end of the band.   Must deliver output 
push-pull to the premixer stage.

Walt
KJ4KV
From waltah at earthlink.net  Mon Jul 26 12:45:51 2004
From: waltah at earthlink.net (waltah@earthlink.net)
Date: Mon Jul 26 12:52:52 2004
Subject: [HBR] Another Receiver Project -- HBR-4, Part 5
In-Reply-To: <41041EB8.18353.2A3C72F@localhost>
References: <41015A00.282.22291A9@localhost>
Message-ID: <4104FCFF.8401.1462B69@localhost>

I have only one of the crystals I need because Yaesu jiggered the 
conversion scheme for lowest cost and eliminated the crystals for 
80 and 20, changed the scheme to use a crystal that's no good for 
me on 40, and my parts set was owned by a CB'er who changed 
the 10 meter crystals for his band.   So all I've got is 15 meters.   
But that's enough to get the oscillator working. 

I have ordered the rest of the crystals for it -- five HC-49/U, ranging 
18 Mcs-42.5 Mcs for now, with space for a total of 11 bands -- FT-
101 bandswitch.  

I contacted ICM where I have in the past bought crystals for such 
projects.   Unfortunately the website is a lot more cumbersome for 
ordering than it was the last time round and they seem indisposed 
to fix that.  Basically you must simply email them with a list of 
what you want.  

Does anyone know a reliable supplier of '1 each' quantities of 
crystals who has an up-to-date ordering process?   Guess I'm kind 
of spoiled by places like AES and online metals.

Lessons relearned while working on the transplanted TEMPO One 
(Yaesu FT-200) VFO:  

1.  Even small 'jumpiness' of frequency -- like stable at one 
frequency for 10 seconds, then a jump of 30 cps, and stable there 
for 15 seconds, then a hop back -- means a bad part breaking 
down.  

Voltages in a vacuum tube VFO will be higher than those in a 
bypolar transistor one, even if there isn't any plate voltage on the 
tank circuit, because the circuit Q is higher.   (Losses in the 
biasing circuits for the transistor and in the transistor itself are 
higher than in a vacuum tube circuit.)   Never trust those small 
silver mica caps that Yaesu uses so freely.    It's best to replace all 
the SMs in the VFO box with the best NP0 ceramics you can find.  

(Four other frequent causes of 'jumpiness' -- (1) VHF or UHF 
oscillation -- all tubes worthy of VFO use will do this and one 
should start with a 100 ohm resistor connected at the grid with a 
1/8" lead.   (2) Inadequately filtered B+.    (3)  Tube with an internal 
short or loose internal structure -- very light tapping of the tube will 
expose this.  It is best to have at least three VFO tubes on hand 
for initial testing.   (4) For Hartley or Colpitts circuits, heater to 
cathode leakage -- the biggest disadvantage of these circuits.)

2.  Yaesu's scheme was to build a good VFO, populate it with 
inexpensive caps, then reduce the drift with temp compensating 
caps.  As a result, replacing Yaesu's silver micas with NP0 
ceramics will give you a VFO with way too much temperature 
compensation.   The original basic non-adjustable TC capacitor (7 
mmf, N750!) should be replaced with an NP0 at the same time the 
silvered micas are done.

They'd have been money ahead if they had started with good caps 
and used a fixed temperature compensating cap, value chosen at 
the end of the design process, rather than cheap caps, two TC 
caps, and an air-variable differential cap to allow adjustment.   
Especially since the differential cap was always set to mid position.

Walt 
KJ4KV
From djmerz at 3-cities.com  Mon Jul 26 18:15:49 2004
From: djmerz at 3-cities.com (Dan Merz)
Date: Mon Jul 26 18:19:36 2004
Subject: [HBR] Another Receiver Project -- HBR-4, Part 5
References: <41015A00.282.22291A9@localhost> <4104FCFF.8401.1462B69@localhost>
Message-ID: <001a01c4735e$2028a070$2322fecf@DansDell>

Hi Walt,  I don't know if my experience was any better than yours as far as
ordering crystals but I was happy with what I got.  I ordered from MH
Electronics,  one each of replacement crystals for a Mackay 3010 receiver in
range of 50  to 60 Mhz,  at $15 each.  For my need,  I sent them an example
crystal since I wasn't sure what spec to use.  They have an online request
for quote form,  again essentially an email request form.    I didn't do any
price comparisons with IMC but I seem to recall looking at their site - I
seem to recall someone on the 390 reflector recommended MH,  good luck ,
Dan
----- Original Message ----- 
From: <waltah@earthlink.net>
To: "HBR Receiver List" <hbr@mailman.qth.net>
Sent: Monday, July 26, 2004 9:45 AM
Subject: Re: [HBR] Another Receiver Project -- HBR-4, Part 5


> I have only one of the crystals I need because Yaesu jiggered the
> conversion scheme for lowest cost and eliminated the crystals for
> 80 and 20, changed the scheme to use a crystal that's no good for
> me on 40, and my parts set was owned by a CB'er who changed
> the 10 meter crystals for his band.   So all I've got is 15 meters.
> But that's enough to get the oscillator working.
>
> I have ordered the rest of the crystals for it -- five HC-49/U, ranging
> 18 Mcs-42.5 Mcs for now, with space for a total of 11 bands -- FT-
> 101 bandswitch.
>
> I contacted ICM where I have in the past bought crystals for such
> projects.   Unfortunately the website is a lot more cumbersome for
> ordering than it was the last time round and they seem indisposed
> to fix that.  Basically you must simply email them with a list of
> what you want.
>
> Does anyone know a reliable supplier of '1 each' quantities of
> crystals who has an up-to-date ordering process?   Guess I'm kind
> of spoiled by places like AES and online metals.
>
> Lessons relearned while working on the transplanted TEMPO One
> (Yaesu FT-200) VFO:
>
> 1.  Even small 'jumpiness' of frequency -- like stable at one
> frequency for 10 seconds, then a jump of 30 cps, and stable there
> for 15 seconds, then a hop back -- means a bad part breaking
> down.
>
> Voltages in a vacuum tube VFO will be higher than those in a
> bypolar transistor one, even if there isn't any plate voltage on the
> tank circuit, because the circuit Q is higher.   (Losses in the
> biasing circuits for the transistor and in the transistor itself are
> higher than in a vacuum tube circuit.)   Never trust those small
> silver mica caps that Yaesu uses so freely.    It's best to replace all
> the SMs in the VFO box with the best NP0 ceramics you can find.
>
> (Four other frequent causes of 'jumpiness' -- (1) VHF or UHF
> oscillation -- all tubes worthy of VFO use will do this and one
> should start with a 100 ohm resistor connected at the grid with a
> 1/8" lead.   (2) Inadequately filtered B+.    (3)  Tube with an internal
> short or loose internal structure -- very light tapping of the tube will
> expose this.  It is best to have at least three VFO tubes on hand
> for initial testing.   (4) For Hartley or Colpitts circuits, heater to
> cathode leakage -- the biggest disadvantage of these circuits.)
>
> 2.  Yaesu's scheme was to build a good VFO, populate it with
> inexpensive caps, then reduce the drift with temp compensating
> caps.  As a result, replacing Yaesu's silver micas with NP0
> ceramics will give you a VFO with way too much temperature
> compensation.   The original basic non-adjustable TC capacitor (7
> mmf, N750!) should be replaced with an NP0 at the same time the
> silvered micas are done.
>
> They'd have been money ahead if they had started with good caps
> and used a fixed temperature compensating cap, value chosen at
> the end of the design process, rather than cheap caps, two TC
> caps, and an air-variable differential cap to allow adjustment.
> Especially since the differential cap was always set to mid position.
>
> Walt
> KJ4KV
> ************************************
> 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 waltah at earthlink.net  Mon Jul 26 21:42:41 2004
From: waltah at earthlink.net (waltah@earthlink.net)
Date: Mon Jul 26 21:49:47 2004
Subject: [HBR] Another Receiver Project -- HBR-4, Part 5
In-Reply-To: <001a01c4735e$2028a070$2322fecf@DansDell>
Message-ID: <41057AD1.2982.331B9DA@localhost>

Dan Merz wrote:
> I ordered from MH Electronics,  one each of replacement crystals
> for a Mackay 3010 receiver in range of 50  to 60 Mhz,  at $15 each. 

Thanks Dan -- I found their web site and bookmarked it.   I did get 
an email back from ICM quoting $15.95/each and two weeks 
delivery so we'll see how that goes.   

At the rate I'm going two weeks won't be any problem at all.  And I 
found a couple of 18 Mcs HC-6 units that can be used if necessary 
to get 80 meters working until the real thing shows up.   CR-18's, 
intended to operate on the parallel resonant frequency but they'll do.

Poking around looking for manufacturer web sites I discovered the 
interesting fact that the quartz stock from which crystals are now 
made is produced by disolving sand in water at 400 degrees C and 
1000 psi (I think those are the numbers ...)   Amazing -- to think 
that at the outset of WW II there was serious doubt about 
converting to crystal control because of the vast quantities of 
natural quartz needed and doubts that we'd be able to import it 
under wartime conditions.  

A very interesting recounting of the influence of hams on the early 
history of crystal control may be found at:

http://www.bliley.net/XTAL/Industry-Hams.html

Something I didn't realize:  The ham market for crystals was many 
times the size of the commercial station market in the immediate 
prewar years.  Many of the companies whose names will be found 
in any under-the-hamfest-table box of junk military crystals were 
already in operation in the late 30's, selling to us.   Bliley, Valpey, 
James Knights, Scientific Radio Products -- and more.  It's hard to 
imagine how the war might have been different had it not been for 
this little-known ham resource, for crystal control down to the 
tactical level was critical to operating the vast numbers of channels 
required by our forces.  

Walt 
KJ4KV

From Bill at LizCurtisHiggs.com  Tue Jul 27 10:25:54 2004
From: Bill at LizCurtisHiggs.com (Bill Higgs)
Date: Tue Jul 27 10:29:38 2004
Subject: [HBR] Source for crystals
Message-ID: <000e01c473e5$a037c110$6500a8c0@BILLDESKTOP>

Walt and the group,

I feel your pain! I used to buy odd frequency crystals from ICM or from JAN in Florida, now they are $30-50 each if you can find them.

I have purchased replacement Yaesu BFO crystals from an outfit in Michigan called Ken's Electronics. He is primarily a CB shop, but does have a good selection of crystals at fair prices. The website (probably out of date) shows several Yaesu and Kenwood frequencies in stock. He claims to be able to do a custom order if you need it; my guess is that he saves up several orders to make a minimum and goes through ICM or another crystal house. Anyway, here is the URL:

http://www.kenselectronics.com/lists/cbxtal.htm

Hope this is useful to somebody.

Bill Higgs, NT4C
From bcarling at cfl.rr.com  Tue Jul 27 22:29:56 2004
From: bcarling at cfl.rr.com (Brian Carling)
Date: Tue Jul 27 22:33:57 2004
Subject: [HBR] Source for crystals
In-Reply-To: <000e01c473e5$a037c110$6500a8c0@BILLDESKTOP>
Message-ID: <4106D764.24217.5CEC9F@localhost>

Bill and Co.

I have crystals for $9.00 each
FT243 primarily.
I can also supply them in wire lead HC-49 holders
These are for all bands from 160m to 10m and even 
6m and 2m with multipliers.

See: http://www.af4k.com/crystals.htm

I hope it's helpful.

Brian, AF4K

On 27 Jul 2004 at 10:25, Bill Higgs wrote:

> Walt and the group,
> 
> I feel your pain! I used to buy odd frequency crystals from ICM or
> from JAN in Florida, now they are $30-50 each if you can find them.
> 
> I have purchased replacement Yaesu BFO crystals from an outfit in
> Michigan called Ken's Electronics. He is primarily a CB shop, but does
> have a good selection of crystals at fair prices. The website
> (probably out of date) shows several Yaesu and Kenwood frequencies in
> stock. He claims to be able to do a custom order if you need it; my
> guess is that he saves up several orders to make a minimum and goes
> through ICM or another crystal house. Anyway, here is the URL:
> 
> http://www.kenselectronics.com/lists/cbxtal.htm
> 
> Hope this is useful to somebody.
> 
> Bill Higgs, NT4C
> ************************************
> 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 Bill at LizCurtisHiggs.com  Thu Jul 29 20:36:58 2004
From: Bill at LizCurtisHiggs.com (Bill Higgs)
Date: Thu Jul 29 20:41:00 2004
Subject: [HBR] HBR-?? Progress at NT4C
Message-ID: <004601c475cd$529f17c0$6500a8c0@BILLDESKTOP>

Fellow listers,

Work has been continuing on the HBR-??, although slowly. Several days out of town, plus a five-DAY power outage can put a cramp in one's homebrew.

I've posted a page with the current state of the project at
http://www.lizcurtishiggs.com/images/special/hbrpix2.htm

I'm still getting the hang of this digital camera, so some of the images are not as sharp as they could be if I knew what I was doing. The original page, covering the power supply as well as the roughing in of the chassis unit is still up:

Bill Higgs, NT4C
From Bill at LizCurtisHiggs.com  Thu Jul 29 20:42:33 2004
From: Bill at LizCurtisHiggs.com (Bill Higgs)
Date: Thu Jul 29 20:46:34 2004
Subject: [HBR] HBR-?? progress at NT4C
Message-ID: <005901c475ce$1a795ad0$6500a8c0@BILLDESKTOP>

Fellow listers,

Work has been continuing on the HBR-??, although slowly. Several days out of town, plus a five-DAY power outage can put a cramp in one's homebrew style.

I've posted a page with the current state of the project at:

http://www.lizcurtishiggs.com/images/special/hbrpix2.htm

I'm still getting the hang of this digital camera, so some of the images are not as sharp as they could be if I knew what I was doing. The original page, covering the power supply as well as the roughing in of the chassis unit is still up:

http://www.lizcurtishiggs.com/images/special/hbrpix.htm

On both pages, a click on the pic will bring up a larger image. If anyone wants a REALLY big image with more detail, ask and I'll put it up.

Progress could be a bit slow for a time, as I came home from trip #1 to two inches of water in my shop due to heavy rains and flooding. As the foundation to the little building has been undermined, I may have to rebuild or majorly renovate . . .

73 to all,

Bill Higgs, NT4C
From waltah at earthlink.net  Thu Jul 29 21:52:07 2004
From: waltah at earthlink.net (waltah@earthlink.net)
Date: Thu Jul 29 21:59:35 2004
Subject: [HBR] HBR-?? progress at NT4C
In-Reply-To: <005901c475ce$1a795ad0$6500a8c0@BILLDESKTOP>
Message-ID: <41097187.8442.2BBA4CA@localhost>

Wow, *nice* work!   And I thought I was the only one on the list 
with time for homebrewing this summer.   

Band imaging gives you a whole lot of receiver for not too much 
complexity and is much to be recommended if you don't want to do 
bandswitching.  

Band imaging can either be done with the local oscillator halfway 
between the bands and the IF equal to half the difference or put the 
IF in between and have the VFO around half the difference.   One of 
those frequencies will be ballpark 1600 kcs, the other 5550kcs.   
I've done both a band imaging receiver and an 8-watt transceiver on 
the second scheme.  

With either of these schemes you can tune the front end with a 
single sweep of a pretty large capacitor -- 80 tunes near maximum 
capacitance and 40 is close to minimum.   

Another combination that was popular in the early days of SSB 
was a 9 Mcs IF and a LO tuning 5 to 5.5 Mcs, band imaging 80 
and 20 meters.   There were a lot of 9 Mcs filters made at one 
time, Miller made IFTs ...  

Going the other way -- VFO tunes 8.75 to 9.25, IF is 5.25 Mcs -- 
has the advantage that if you do the IF for USB then the conversion 
scheme automatically puts you on LSB for 3.5-4 Mcs.   I believe 
the NCX-3 and some other sets used that one.   I don't care for the 
job of building VFOs at 9 Mcs, though.   

These schemes need a bandswitched front end; you can't cover 3.5 
to 14.35 Mcs with any practical variable capacitor and if you did the 
LC ratios would be terrible.   

I probably have a socket for that calibrator crystal; tell me the 
spacing and pin diameter/type and I'll check stock.  

The cover over the dial is something I hadn't thought of as a way to 
handle the command set type of dial.   Maybe you'll have a light in 
there?   

I don't consider using silicon diodes as violating the rules of 
vacuum tube home brew; everybody knows that you can replace 
them with 6AL5's.  Time, space, and filament power, that's all.  
Now building a decent local oscillator with a vacuum tube, *that* 
tests your manhood.  

Walt
KJ4KV


From windy10605 at juno.com  Thu Jul 29 22:15:35 2004
From: windy10605 at juno.com (windy10605@juno.com)
Date: Thu Jul 29 22:19:55 2004
Subject: [HBR] HBR-?? progress at NT4C
Message-ID: <20040729.211536.2236.14.windy10605@juno.com>

Bill,

I like the looks of your design. The design for mechanical rigidity with
braces, triangles, and ribs is great. It's also good to see use of the 
excellent old ARC/5 components and ceramic for coil forms and frontend
sockets ...anything related to the frontend. That's the way to build
radios. It will be interesting to watch/read your progress. Keep up the
good work.

How about some of you other guys, are Bill and Walt the only ones right
now  ?

73 Kees K5BCQ  
From waltah at earthlink.net  Thu Jul 29 23:17:28 2004
From: waltah at earthlink.net (waltah@earthlink.net)
Date: Thu Jul 29 23:24:56 2004
Subject: [HBR] Another Receiver Project -- HBR-4, Part 6
In-Reply-To: <4104FCFF.8401.1462B69@localhost>
References: <41041EB8.18353.2A3C72F@localhost>
Message-ID: <41098588.10948.309CC8C@localhost>

The VFO was surprisingly easy and at constant room temperature 
drifts less than 50 cps/hour after just a couple of minutes of warm 
up.   Chalk one up to using a really high gain tube (6GK5, 
transconductance 15,000) and coupling very loosely to the tank 
circuit.  

Speaking of tubes, looking for an oscillator tube in the RCA manual 
I ran across the 6FS5, a beam hexode for VHF RF amp service in 
TV sets.   Beam hexode????   Does anyone know anything about 
this tube?    Seems like anything that odd ought to be good for 
something!

The 12AT7 Butler oscillator supplied the usual quota of new 
challenges.  Surprisingly enough it perked right away with the 35.5 
Mcs  (15 meter) crystal, but using my junkbox 18 Mcs HC-6 it 
wouldn't seem to go.   

There was grid current though, and after about two hours and 50 
minutes more than it should have taken, I realized that that had to 
be a VHF oscillation, switched my Heath IM 2410 counter to the 
high band, and there it was, running right along at 165 Mcs.  That 
had to be the resonance of the leads to the trimmer cap; a 100 
ohm resistor at the grid pin killed it and after that, things started to 
fall into place.

The trick with the plate coil is to get it the right size so it will tune 
the highest frequency (43.5 Mcs for the last 500 kcs of 10); too 
much inductance and the stray capacitance won't let you go that 
high.   But it must also go down to 16 Mcs for 160M while still 
having high enough impedence that the circuit will oscillate.  
Needless to say I had to cut it three times and rewind once to get 
it right.   

I'm using most of the larger trimmer board from an FT-101 -- 11 itty-
bitty 50 mmf trimmers on about a 2-square inch piece of fiberglas 
epoxy circuit board.   Saves tons of space but boy do those things 
tune sharply on the higher bands -- just like on the FT-101.  I 
believe the E and F used smaller trimmers for the highest bands.   I 
found it was best to set the frequency with a dip meter before 
turning on the power; that way it would usually show grid current 
and I could peak it.

That circuit can't be completed until the crystals arrive in about 
another ten days but it's fine at 18 Mcs, 35.5 Mcs, and (thanks to 
our CB friends) 41.5 Mcs.

The plate coil is a toroid; the secondary is bifilar wound with a 
grounded center tap; each half drives one grid of each of two 6J6s 
connected in balanced (pre) mixer circuit.   (The input to the other 
grid on both tubes is the 5 to 5.5 Mcs VFO.)  The plates of the 
premixer tubes drive the deflection plates of the 6JH8 signal mixer 
which feeds the 9 Mcs IF -- already wired and tested except for the 
crystal filter.

In other words, I'm getting near the part where the rubber meets the 
road.   I think the pieces will all work but the *system* can still be 
a flop in various ways.  With luck I'll get a read on that, this 
weekend.   

There is the usual amount of cleanup work -- there's too much 
audio low end, for example, I don't have the calibrator wired yet ... 

Walt 
KJ4KV
