Subject: GLOWBUGS digest 338

From: [email-masked]
Date: Fri, 1 Nov 1996 09:38:47 -0600 (CST)

GLOWBUGS Digest 338

Topics covered in this issue include:

  1) Solving the copyright problem
	by [email-masked] (Jeff Duntemann)
  2) 4CX250 Input for VHF
	by "Barry L. Ornitz" <[email-masked]>
  3) Obtaining use permission from QST
	by [email-masked]
  4) Pictures of homebrew tube stuff
	by [email-masked] (Jeff Duntemann)
  5) Re: Obtaining use permission from QST
	by [email-masked] (John Heck)
  6) Request permission to use serveral old QST articles
	by [email-masked]
  7) Well, I opened Pandora's box.....(:+\\.....
	by [email-masked]
  8) 6AE8 tubes
	by [email-masked]
  9) Re: regen audio amplifier funzies
	by [email-masked] (michael silva)
 10) WTB: 1950's ARRL Hw To Become a Radio Amateur
	by [email-masked] (Richard H. Arland)
 11) 3A4 Regen RX in Sep 1995 CQ
	by [email-masked] (Richard H. Arland)
 12) Re: Request permission to use serveral old QST articles
	by Jeffrey Herman <[email-masked]>
 13) Re: Regens & Things that go "SSsssssst" in the night
	by [email-masked] (Michael Herr)
 14) BA net
	by Richard Wilkerson <[email-masked]>
 15) Amplifier help!
	by Tony Gallagher <[email-masked]>
 16) Re: Tube Reactivation Info Sheet - 1927 ARRL Handbook
	by [email-masked]
 17) SP600 Parts Needed
	by [email-masked]
 18) Re: regen audio amplifier funzies
	by [email-masked]

----------------------------------------------------------------------

Date: Thu, 31 Oct 1996 09:09:33 -0700
From: [email-masked] (Jeff Duntemann)
To: [email-masked]
Subject: Solving the copyright problem
Message-ID: <[email-masked]>

Hi gang--

Followed the thread on copyright law with some interest.  I know something
there, since I have been in publishing for 11 years now, have written seven
books and portions of a dozen others, (plus more magazine articles than I
remember) and now co-own a significant publishing company that employs 34
people and puts out sixty books a year.

The sad truth is that in copyright law (like in most areas of law today)
*nothing* is really clear anymore.  This is deliberate on the part of the
trial lawyers' bloc: The idea is to make it impossible to do anything
without incurring some liability somewhere.  And since judges are just
promoted lawyers, well...but we don't need to discuss that here.

The point is that the law itself means very little these days.  Fair use is
only fair use until somebody with money challenges you in court.  Intel
tried to trademark the small letter "e" some years ago.  A few years later
Lexis sued Lexus because, obviously, people were mistaking a car for a
lawyers' online service...and it gets nuttier and nuttier.  Vote AGAINST the
lawyers' bloc if you value the rule of law.  When the rule of law vanishes
in a sea of mud, freedom is next in line.

Some things are quite plain: Posting scanned copies of old QST articles is a
copyright violation.  I doubt ARRL would go after anybody too hard; most
likely they would say, Stop that and expect us to stop it.  Handing copies
of old articles to friends is technically a violation, but it's a small
enough thing that I doubt there's much potential for litigation in it.  The
legal guideline of "lost sales" does apply as a mitigating factor; if the
material being copied cannot be obtained for a fee there are limits on the
sorts of redress a copyright holder can demand.  It's still an ethical
question, but as the copied material is in fact being used for educational
purposes (that is, no one is going to start a production line to sell 6L6
transmitters, nor gathering circuits into a book to be sold, nor
distributing it in any organized fashion) legality is in fact the darkest of
all dark grays.

Probably the high road would be for one of us to approach ARRL about
licensing some selected articles (probably the ten or fifteen best glowbug
circuits of the last sixty years) for distribution at no cost to interested
parties.  ARRL is always asking for money, and I've sent it from time to
time; perhaps a couple hundred bucks in return for written permission would
be a good thing to do.  For them it would be "free money" and it would keep
us reliably out of trouble.

On the other hand, is that really necessary?  How many of us slavishly
reproduce the circuits in the old articles *precisely* as given?  In fact,
given the current parts situation, a published article from 1955 is nearly
always a point of departure.  You gather the parts you can and you build the
radio that works.  This is almost never the same radio you see in the magazine.

My suggestion is that people who are actually building radios redraw the
circuits they actually build, *including all the changes they made.*  It
can't hurt, in fact, to "mutate" the design a little, in the process--and
then post the mutated circuit with a whole new written description.

A lawyer might object that such a circuit is a "derivative work" and to a
degree this is true.  However, a combination of factors puts this strategy,
in my view and experience, clearly outside the realm of actionable copyright
violation:

1. The circuits we are fussing with here are *very* simple.  The design of a
Hartley oscillator is governed by physical laws (that is, it's not a mystery
novel) and there are only so many ways one can go together.  One cannot
copyright things like that, although in their time (which was long ago,
thank you Major Armstrong!) they could be patented.

2. We are in fact engaged in nonprofit educational activities.  We are not
an organized school, but that is not a criterion.  We are the radio school
in the marketplace.  We teach.

3. This is the way things have always been done.  In many of the articles in
my files, the author will say something like, "This circuit is based on one
by old Elmer Sparkbanger published in Radio Age in the Forties..." and if
you go back to the original it looks *mighty* similar.  Hams have always
been seat-of-the-pants technologists.  We look in a catalog of standard
circuits and we string them together.  Or we take a published circuit and
beat on it until it does what we want.

4. This is what ham radio is *for*.  I cannot imagine that ARRL or other
holders of copyright on material forty, fifty, or sixty years old would be
so petty as to grumble about derivative work in our efforts to keep a "lost
technology" alive through new and original research.  If they are, then it's
time to rethink our loyalties in this hobby--or maybe the hobby itself.

I did something interesting last night.  I gathered all the 6AG7-6L6
transmitter circuits I had on file together on the desk, and I created a new
one by taking a little bit here, a little bit there, doing some math, adding
some features, and drawing it all neatly in one piece.  I tried to minimize
the "unobtainium" factor. This circuit was among the most common "novice"
designs ever conceived.  Dozens of them have been published, many have been
manufactured. (The cute little Micamold novice rig is one of the best.) The
one I drew is not precisely like any of them, though it depends to a degree
on all of them.  I would lay money that the circuit would work as I drew it,
though I won't know until somebody builds at, at which time the circuit will
change yet again.

I propose we do something like this: Take the commonest glowbug designs, the
ones we want to play with, and re-create them as I did last night.  Get the
"secret masters" on line to look over the circuits, suggest improvements,
and then build a couple.  When we get a circuit that works well, we place
the design in the public domain and post it all over the place.

I'll start with two circuits: My "KickAss regen" which I have built and does
work (though I'm sure it could be improved) and the 6L6 transmitter I drew
last night.  Neither is a dead-on copy of any published design.  I drew them
in Visio, and if you'll give me a weekend to clean them up I'll post them on
my FTP site in TIF format.  Let's talk about them, improve them, prove them
out, and then put them in the public domain.  I can draw other circuits in
Visio as well given a clear sketch; it produces a *very*
professional-looking diagram.  (I'm a good draftsman and fast, too.)

Those who don't have FTP capability can send me an SASE for a paper copy.

This seems to me the best way to go.  Any interest?

--73--

--Jeff Duntemann KG7JF
  Scottsdale, Arizona

------------------------------

Date: Thu, 31 Oct 1996 12:13:24 -0500 (EST)
From: "Barry L. Ornitz" <[email-masked]>
To: [email-masked]
Cc: Rossi Giuseppe <[email-masked]>
Subject: 4CX250 Input for VHF
Message-ID: <[email-masked]>

On Thu, 31 Oct 1996, Giuseppe Rossi wrote:

> I'm trying to build a linear tube amlifier with a couple of 4cx250 for
> 2 meter band.  The tubes, feeded on the grid, are coupled in parallel,
> and I have a question about the input tuning circut: 

On two meters, it might be much simpler to use the two tubes in push-pull.
This places the input and output capacitances in series rather than
parallel. Since the tubes already have significant capacitances, a
conventional Pi output network is not possible unless an extremely high
value of circuit Q is used.  Push-pull operation, with the output
capacitances in series, allows a more reasonable output tank circuit. 

Parallel operation is possible however if the right kind of matching
networks are used.  My discussion below is for parallel operation.  Many
designs for push-pull may be found in older ARRL handbooks and VHF
manuals. Many use copper water pipe as the tuned circuits (known to U.S.
hams as plumber's delight construction). 

> I 've seen a project in which the author tunes the input circuit by a
> lambda/2 long "microstrip", directly connected at the tube side on the
> grid, while at the front end side there is a shunt cap. 

This is not really a microstrip transmission line in the normal sense.  It
is, however, a 1/2 wavelength resonator inside a shielded box.  The tube
capacitance shunts one end while the shunt capacitor shunts the other. The
result is 1/2 wavelength electrical resonance even though the physical
length is much less than 1/2 wavelength. 

> The question is: since the metal strip has a noticeable physical length
> more than 40 cm (exactly 44cm) and i wish to avoid that strip (otherwise
> the aplifier is too cumbersome).
>
> Can anyone explain to me why to use a lambda/2 line? A lambda/2 line
> doesn't transform the input impedance, so why to use it?  What about of
> using a line with a dielectric ( e.g. teflon )? 

A 1/2 wavelength line is often easier to tune that a 1/4 wavelength line.
If you study the circuit a little more, you will likely see that the
coupling loop for the drive signal is located near the middle of the line.
In this case, the line really is an impedance step-up "transformer" since
the drive is applied at the middle (RF grounded) and the tube grids, which
are high impedance, are 1/4 wavelength away.  This should give you a hint
on what you might consider... 

A 1/4 wavelength line, grounded to the chassis on one end, with the "hot" 
end tied to the grids through DC blocking capacitors, is exactly half of
the input circuit you describe.  The input coupling loop will still be on
the grounded end.  As a starting point, take the existing dimension and
divide it by 2 giving 22 cm.  Now this is only about 42% of a free-space
1/4 wavelength which means that the line is inductive.  The input
capacitance of the tubes, however, brings the line back into resonance. 

This is certainly one approach to try, but you will find that getting
low-loss DC blocking capacitors is a problem and that the DC bias on the
tubes will require RF chokes and some thought since the grids are at a
high impedance point.  With the 1/2 wavelength line, the entire line can
be isolated for DC and the grid bias introduced in the center where it is
a low impedance point.  This greatly reduces the requirements on the RF
choke.  However connecting the grids together like this eliminates the
possibility of separately adjusting the grid bias on each tube.  This
means that matched tubes will be needed. 

As to your question about using a dielectric to shorten the line, this
will certainly work.  You will need an extremely low loss dielectric like
polytetrafluorethylene (PTFE, Teflon).  I would tend to avoid this
approach however. 

Another possibility is to add a little extra capacitance to each end of
the line to shorten it a few additional centimeters.  Be sure and do this
symmetrically to keep everything balanced.  Another possibility is
"folding" the line a little to keep the same total surface length but fit
it in your slightly shorter box. 

To read a little more about these design issues, I would suggest some of
the later editions of the ARRL handbook, or better still the RSGB VHF/UHF
manual.  I have not seen a recent edition of this but my older RSGB
Handbook and VHF/UHF books give lots of information.  [Note to all
Glowbugs readers:  the RSGB books are much more practical than the
comparible ARRL books, yet the theory is there too.  They are great for
any amateur considering homebrewing his own radio equipment. RSGB is the
Radio Society of Great Britain.]

One final reminder too, Guiseppe...  Be sure and use the proper sockets 
for the 4CX250's.  This means you will definately need the ones with 
built-in screen bypass capacitors.  You can get away with external bypass 
capacitors on HF but at two meters you will certainly need them.

> thank you
> iw1clx, Giuseppe Rossi

Thank you for participating here and for asking a good technical question.
Good luck with the amplifier; please let us know how it turns out. 

		73, Barry L. Ornitz  WA4VZQ  [email-masked]

------------------------------

Date: Thu, 31 Oct 1996 13:21:10 -0500 (EST)
From: [email-masked]
To: [email-masked]
Cc: [email-masked] ()
Subject: Obtaining use permission from QST
Message-ID: <[email-masked]>

Whilst we are hot on the copyright issue, and because I think there is a
simple way to approach the problem, with complete satisfaction, allow me
to approach the ARRL, on behalf of myself (and maybe on behalf of the
glowbugs list, if desired) to officially obtain permission to use certain
QST articles as reprints, in our scholarly pursuit of the art and craft
of early radio.

I did just this several years back, and received an open ended permission
to use what articles I desired, provided the following credit line was
affixed to each article, ``Reprinted courtesy [issue date] QST.''
That was all that was required.  That is how we are able to use the
Grammer Hartley oscillator article and the Barracks Bag VFO article
in my archives.  That is how I am able to use QST articles in the
regen and hartley manuscripts that I have been working on for too many
moons.

I would appreciate feedback from those interested, directly to
[email-masked], and those that have minor/professional
publishing capability that could be adapted to this effort for making
commonly available on-line reprints possible, for our scholarly purposes.

I have primitive publishing capability, here, via my TeX/LaTeX and
troff typesetters, that output postscript with graphics, in the manner
of many of the scientific publishing houses, and in a close repro of
what the original QST articles were set into type like, although  my
time is most often in short supply.  I have boilerplates already up
for such articles.  It is mostly a matter of rekeying the texts, adding
notes and scanning or redrawing schematics and photographic images,
and proofing.

As long as we don't abuse our potential, in this area, I think there
should be no real problems, pursuing our scholarly learning and wisdom
in ancient technologies.  After all, it is history, right, .......but,
what fun history and what fun wisdom, with proper citation and permission.

73/ZUT DE NA4G/Bob UP

------------------------------

Date: Thu, 31 Oct 1996 11:01:25 -0700
From: [email-masked] (Jeff Duntemann)
To: [email-masked]
Subject: Pictures of homebrew tube stuff
Message-ID: <[email-masked]>

Hi gang--

My Junkbox Radio Web site isn't done yet, but I scanned a bunch of pictures
for it and thought some of you might want to see them early, as they may
cast light on some things I've mentioned recently on this list.  So I snuck
a ZIP file full of JPG images up on our FTP site for you to grab if you want
a look:

ftp://ftp.coriolis.com/pub/Shareware/junkbox.zip

Note well: This URL *IS* case-sensitive.  "Shareware" must be capitalized or
the machine will shrug at you.

The file is hefty (1.2MB) because I haven't space-optimized the scans yet.
It contains:

1. Three views of the chassis work on my superhet project, which I described
here a couple days ago.
2. Inside and outside views of the first transmitter I ever made back in
1973, the transformerless wonder I called The Ol' Shockbox for obvious
reasons.  It was an Electronics Illustrated project originally named the
Mini-Mitter, from 1965 or so.
3. Several pictures of tube breadboard lashups I've made, one a complete
regen with a 12AX7 detector and 6T9 audio, and the other part of a superhet
I put together to tinker with mixer circuits and RF amp tracking.
4. A shot of some regen coils I've made, one on a commercial form, two on
vitamin bottles, and one on a piece of spindle from an ancient mainframe
line printer.

The photography isn't super terrific.  I've been hinted at that I'm getting
a better camera for Christmas.  That should help.

I can't leave the file up there forever, but it should be there for a week
or two.  Once the Web site is finished they'll be permanently available
(with associated text) and not quite so big.

--73--

--Jeff Duntemann KG7JF
  Scottsdale, Arizona

------------------------------

Date: Thu, 31 Oct 96 13:39:02 EST
From: [email-masked] (John Heck)
To: [email-masked]
Subject: Re: Obtaining use permission from QST
Message-ID: <[email-masked]>

Folks,
I highly support Bob's efforts to persue this idea. I, for one, don't intend to
stop making copies for friends and myself, but it would be nice to make it possible
to have a database of articles. As you see, probably most publishers are willing to
allow us to share their intellectual property as long as proper credit is given.
Regards,
John Heck, KC8ETS
1009 Donson Drive
Dayton, Ohio 45429
(513)865-7036(work)
[email-masked]

> Whilst we are hot on the copyright issue, and because I think there is a
> simple way to approach the problem, with complete satisfaction, allow me
> to approach the ARRL, on behalf of myself (and maybe on behalf of the
> glowbugs list, if desired) to officially obtain permission to use certain
> QST articles as reprints, in our scholarly pursuit of the art and craft
> of early radio.
>

------------------------------

Date: Thu, 31 Oct 1996 15:22:33 -0500 (EST)
From: [email-masked]
To: [email-masked]
Cc: [email-masked] (), [email-masked],
Subject: Request permission to use serveral old QST articles
Message-ID: <[email-masked]>

Lori Weinberg,                                  31 October, 1996
Mark Wilson, Publications Manager
American Radio Relay League,
225 Main Street,
Newington, CT 06111-1494.

Dear Lori and Mark:

Back in 1993, I requested and was granted permission to use several
early QST articles in a historical radio work that I was writing for
use by interested local hams in our club's Homebrew SIG.  That went
well, and was well received.  Thank you for your permission to use
those articles.

Lately, there has been some interest, amongst a group of radio history
buffs and constructors, known as the Glowbugs, a group interested in
learning about the history and development and practical application
of vacuum tube electronics in amateur radio, in using some of these
articles as a basis for building/testing/learning about early receivers
and transmitters.  This group meets via the internet as a mailing list
of about 200 individuals.  Out of these 200, perhaps some 25 or so are
interested in actually building and testing such early equipment.
It would be of benefit to me or them/us, collectively, to be able to use
about half a dozen or so of the historically more important articles
that have appeared in QST, for our building/testing/discussions on the
topic.  Of particular interest would be classic articles such as the
John Reinartz regen receiver article in 1922, the 1928/29 articles on
receivers and transmitters (the ``1929'' style amateur station series
put together by the ARRL Technical Department under the able direction
of the well known Ross Hull), several of the articles made famous by
the other well known Technical Department staffer, George Grammer,
in the 30's, and then one or two after the war when the last general
use of such equipment was made, and the transition to the classic
novice style single tuber rig began.  These are basically the articles
that you granted me permission to use, previously, plus one or two other
selections that seem appropriate.

My/our(the Glowbugs) use of these articles should fall under the
scholarly use category, as I interpret such matters.  But, I feel
that it is appropriate to obtain express permission, and credit/cite
``Reprinted, [issue date], courtesy QST'', as I had done earlier in
previous works.

To this end, I would like to formally request permission from the ARRL
to make a few copies of selected early QST articles, as covered above,
for my/our(the Glowbugs) use in our discussions/building/learning about
early radio.

Thank you for your consideration in this matter.
 
Sincerely,
Robert D. Keys/NA4G
[email-masked]

p.s.  Two other things that might be of interest to other amateur radio
      operators.....  1) a short note in QST about the Glowbugs, and
      how interested members of the amateur community may join in on
      our discussions and on-the-air nets, and 2) the articles that I
      put together back in 1993 are in electronic PostScript format which
      might be worth archiving in the ARRL's on-line archives somewhere,
      if interested (I would be happy to forward copies via email if
      so interested)(perhaps other such historical reprints could be
      put there, too).

  cc C.F. Murray/WS4S [email-masked]
                      (listowner of [email-masked])
  cc Glowbugs mailing list ([email-masked])

Note:  The Glowbugs mailing list information can be obtained from
       the listowner, C.F. Murray/WS4S, [email-masked],
       via email.

------------------------------

Date: Thu, 31 Oct 1996 15:26:10 -0500 (EST)
From: [email-masked]
To: [email-masked]
Cc: [email-masked] ()
Subject: Well, I opened Pandora's box.....(:+\\.....
Message-ID: <[email-masked]>

In a prior mailing, you all should have received a copy of a letter I
just sent to ARRL, requesting permission to use some of the QST articles.
Keep your fingers crossed, and maybe we will get our OK permission.

Please DO NOT let your mailers reply to the ARRL or the listowner's
mailbox.  Make all replies specifically to ME.

Thanks, and keep yer glowbottles warm and do an incantantion over them,
tonight.....

73/ZUT DE NA4G/Bob UP

------------------------------

Date: Thu, 31 Oct 1996 15:36:20 -0800
From: [email-masked]
To: [email-masked]
Subject: 6AE8 tubes
Message-ID: <[email-masked]>

Well I am surprised some of you tube gurus out there could not identify the 
6AE8. I have one clue and that is it is a triode heptode but has a different 
pinout to the 6EA8. Probably of British origin with no known US equivalent. 
Presumably used as a frequency converter???
If anyone has a use for them I have 12 NIB here.
Nice collectors item as they were made in Australia by the Amalgamated 
Wireless Valve Company (AWV).
73 de Dave KI6QE/7

------------------------------

Date: Thu, 31 Oct 1996 17:43:36 -0800
From: [email-masked] (michael silva)
To: [email-masked]
Subject: Re: regen audio amplifier funzies
Message-ID: <[email-masked]>

Hi gang,

Was out of town for a few days and was glad to see so much activity on 
the list when I got back.  Now to the particulars...

Bob wrote: 

>Output - a 1 inch cube size 5 h choke

>Tube - common 6J5 with no biasing

>Voltage gain - 40 (did not measure plate current, probably 1 ma or 
so).

Just so happens I've been musing on the low calculated gain of triodes 
when driving the "standard" 2000 ohm headset.  With a gm of 2000 and a 
load of 2000 the gain works out to only 4 (assuming the plate 
resistance is well over 2000 ohms).  With such a low load it seems that 
transconductance is everything.  Makes me wonder how a 2-tube rig would 
work with 6AG7s...

Now, about this gain of 40.  My first reaction is "no, can't get more 
then the amplification factor" (20 for a 6J5, and fairly constant at 
different operating points for any tube, since it's based on geometric 
considerations).  But then there's that matter of an inductive load.  
So, is it possible to "cheat" and get more gain than the amplification 
factor by using a reactive load?  Since the "bucking effect" of the 
output voltage on the plate current is not in phase, I wonder?  I'll 
have to think about it, but it sounds too much like a free lunch.  
OTOH, that's what reactance is anyway, right?

Well, time to dress the kids up and go haunt the neighborhood.

73,
Mike, KK6GM

------------------------------

Date: Thu, 31 Oct 1996 23:18:36 PST
From: [email-masked] (Richard H. Arland)
To: [email-masked]
Cc: [email-masked]
Subject: WTB: 1950's ARRL Hw To Become a Radio Amateur
Message-ID: <[email-masked]>

Gang:

Does anyone have a copy of an early-to-mid '50s ARRL pub titled: How to
Become a Radio Amateur that they would like to sell?

If so pls send private e-mail.

73 es tnx.

rich K7YHA

------------------------------

Date: Thu, 31 Oct 1996 23:58:57 PST
From: [email-masked] (Richard H. Arland)
To: [email-masked]
Subject: 3A4 Regen RX in Sep 1995 CQ
Message-ID: <[email-masked]>

Gang:

I originally built this little project as a gag last winter. I teach
vocational electronics and wanted to show the class a "real" Armstrong
regen set as part of the course. Normally I show "The Men Who Made
Radio" video from PBS in my course, and I thought that this little
project would be a good "show and tell" so the class could actually
experience using a primitive set. 

Unfortunately, the little set never did work the way Ingram's article
said it was supposed to (nothing surprising there....seldom do
"U-Build-It" articles in magazines EVER work the way they are
portrayed).

One of the things I noted was that my set would not go into regen
smoothly...it "popped" into regen and had several degrees of
oscillation. Another disturbing problem was extremely low volume in the
2K ohm headphones. Finally, sensitivity was REALLY bad. 

Yesterday I pulled the little rig out of the equipment cabinet and got
the article out to check out what might be the problem (OK, I was
bored....no BAs to play with). 

I also had a 1959 copy of the ARRL HB that had a similar regen receiver
described on pg 118.

Ingram calls for using only 18 VDC on the plate of the 3A4. In my
experimentation this is way too low....but I digress.

FIrst order of business was to check the coil and reposition the wires. I
came up with a 23 microhenry value for the main coil as checked on our
General Instruments RLC bridge. This, coupled with the 10-120 picofarad
tuning cap would tune 80 and 40 meters no problem. My coil was built on
a 1 inch OD pill bottle (just like the article) but I only used
23 turns of #26 wire, close wound near the top, for the coil. The
tickler was only 4 turns placed about one quarter inch below the main
winding (Ingram specifies 7 turns which is way to much, as witnessed by
my rig's erratic regenning....besides, the HB says that you are to use
only enough turns to insure the rig "gens" over the tuning
range....hence, I removed several turns and found that my receiver
regened just fine, with no popping and erratic behavior).

Rewinding the main coil and tickler coil really made a difference in the
way the rig worked.

On to plate voltage: Ingram's article says you can use as little as 18
VDC on the plate of the 3A4. He might be able to, but I can't. My tube
performs miserably with only 18 VDC on the  plate. Upping the voltage to
27 VDC and performance improves dramatically. I kept on increasing the
plate supply voltage and taking MDS measurements via a HP 600D RF
generator. Once past 27 volts, regenning was consistent and smooth.
Under 27VDC and the tube behaved erratically with almost no gain. 

I ended up at 90 VDC on the plate with a MDS of  -87 dBm. Not good, but
not totally deaf, either. MDS between 36 and 72 VDC was pretty
consistent at -80 dBm. Morale of the story: get the plate voltage up
around 36 to 45 volts MINIMUM in order to start seeing some performance
from the tube. 

I am NOT satisfied with the overall sensitivity and lack of audio gain.
Ingram, in his article, states that this is a "red hot"
performer....can't prove that by me. In comparing the schematics between
the CQ article and the HB, I noticed that the rig in the HB had the antenna coupled to the main tuning tank circuit via a capacitor and an
air-would link turn. This may be something to look at. Certainly, I am
going to include a small triode as an AF amplifier. Unless you are in a
VERY quite room with the headphones clamped on real tight, you just don't hear much.

One other comment about the regen control: I find that the 1K ohm pot
used to provide regen is EXTREMELY sensitive and is very critical in
adjustment. A slight, and I MEAN tiny, movement of the regen control and
the receiver either drops out or de-senses. You MUST make the regen
adjustment very precisely. My Heath GR-81 super-regen SW set is not that
critical at all. I am wondering if replacing that 1K pot with a more
conventional regen control might not prove to be a good move?

One final comment: The tuning is really NON-linear. 80 meters is fairly
easy to tune but 40 meters is quite tightly packed near the high end of the tuning range of the cap. I think what I will end up doing is re-designing the tank circuit to cover just 80 meters with a lot more bandspread
using a smaller cap along with a bandspread cap. I really don't know how
anyone can actually use this rig on 40 meters the way it performs built
according to the article. 80 meters might be OK but 40 is really pushing
the envelope of reality.

Anyway, for all who have e-mailed me, there it is: my findings regarding
the Ingram glowbugs article in Sept 1995 CQ. I am not faulting Ingram in
any way.....having written columns for magazines for 9 years, it is not surprising to find things like this creeping in. I usually dreaded any
kind of construction article, cuz I knowed that someone was gonna blow
holes in it, regardless of how much debugging I did.

Comments?

73 rich K7YHA

------------------------------

Date: 	Thu, 31 Oct 1996 17:49:45 -1000
From: Jeffrey Herman <[email-masked]>
To: [email-masked]
Subject: Re: Request permission to use serveral old QST articles
Message-ID: <[email-masked]>

Bravo, Bob! Very well written.
73 from Hawaii,
Jeff KH2PZ / KH6

------------------------------

Date: Fri, 1 Nov 1996 00:10:19 -0800
From: [email-masked] (Michael Herr)
To: [email-masked]
Subject: Re: Regens & Things that go "SSsssssst" in the night
Message-ID: <v01530500ae9f1d73e707@[199.120.150.178]>

>Gang:
>
>OK shoot me! Go ahead. I've been bad. Very, VERY bad. I haven't been
>saving the postings about regens. Now I decided (today) to take the old
>3A4 >My little regen does not have a smooth regen action. Volume is very
>low
>and tuning range is limited. Somewhere I thought I saw a post about this
>circuit and the author said that Ingram's coil data was all
>wrong...especially the tickler....it should only be 3 or 4 turns. Just
>enuff to get the thing to go into regeneration.
>
>(Boatanchor Bob, where are you?!?!?)
>73 rich K7YHA

Rich,
     The 3A4 tube rig is very similar to the one out of the old Boy Scout
Radio Merit badge book. I built one as a kid and had a ball. On that one
the volume isn't all that loud but acceptable (hey, it's only one tube!) It
used a variable condenser for regen control rather than a pot. The B+ used
was 22 volts. I have the coil info somewhere for the Boy Scout version,
I'll look for it this weekend.
73
Mike WA6ARA

------------------------------

Date: Fri, 01 Nov 1996 03:27:20 +0000
From: Richard Wilkerson <[email-masked]>
To: [email-masked]
Subject: BA net
Message-ID: <[email-masked]>

Could someone please tell me the frequency of the Net and the time?
I thought it was 7050kc. but dont really remember.
thanks, rich, wd6fdd

------------------------------

Date: Fri, 1 Nov 1996 12:57:28 GMT
From: Tony Gallagher <[email-masked]>
To: [email-masked]
Subject: Amplifier help!
Message-ID: <[email-masked]>

Does anyboduy have any scematics that they could JPEG, FAX or Snail-Mail me?
I'm trying to build a 88-108Mhz linear amplifier, built around a 4CX250.

Any help would be appriciated!

Thanks a million!

73's 88's!

CHECK OUT OUR NEW LIMERICK 95 HOMEPAGE!!!!

                                     ,,,              
                                    (o o)
--------------------------------oOO--(_)--OOo-------------------------------
*CHECK OUT OUR WWW SITE!!**FIND US AT: www.iol.ie/limerick95/ **************
*RADIO LIMERICK 95Mhz FM **BROADCASTING TO LIMERICK, IRELAND AND TO EUROPE *
*100 O'CONNELL STREET *****VIA THE ASTRA SATELITE ON THE VH1 TRANSPONDER 22*
*LIMERICK *****************AUDIO SUBCARRIER 7.92Mhz ************************
* IRELAND ****************|* www.iol.ie/limerick95/***| TONY- [email-masked]  *
****************************************************************************
***** VISIT OUR RADIO STATIONS PAGE AND ENTER GREAT WEEKLY COMPETITIONS!! **
****************************************************************************

------------------------------

Date: Fri, 1 Nov 1996 09:39:38 -0500
From: [email-masked]
To: [email-masked]
Subject: Re: Tube Reactivation Info Sheet - 1927 ARRL Handbook
Message-ID: <[email-masked]>

In a message dated 96-10-30 18:39:50 EST, NA4/G quotes an article saying in
part:

<<   The  old  types  of
           tungsten-filament  (bright)  tubes  have a more limited emission
           remaining constant until burn-out of the filament.   >>

This reminded me of something I've wondered about for some time, but have
never had the chance to try.  

Suppose you have a thoriated tungsten filament tube and the rejuvination
process doesn't work.  (It eventually will not work when no more thorium is
available to be boiled to the surface).  In that case how about just using it
as a tungsten filament tube, that is, jack the filament voltage up until the
tube glows good and bright and puts out plenty of electrons.  Seems to me
that you have nothing to loose at that point, since the tube is no good in
its present condition anyway, so if you could get enough emission just as a
tungsten filament to do the job at hand you could get some more hours out of
the tube.  Inconvenient perhaps to supply an adjustable filament voltage just
for that tube, but desperate men are driven to desperate measures!

Your thoughts please gang

Bob [email-masked] 

------------------------------

Date: Fri, 1 Nov 1996 09:39:42 -0500
From: [email-masked]
To: [email-masked]
Subject: SP600 Parts Needed
Message-ID: <[email-masked]>

Hello gang

I am looking for the rf coil turret assembly from a SP600, plus the tuning
capacitor assembly.  If necessary would buy the complete rf. front end
assembly, or a parts radio with these parts intact.

Thanks

Bob [email-masked]

------------------------------

Date: Fri, 1 Nov 1996 10:59:00 -0500 (EST)
From: [email-masked]
To: [email-masked]
Cc: [email-masked] (), [email-masked]
Subject: Re: regen audio amplifier funzies
Message-ID: <[email-masked]>

> Makes me wonder how a 2-tube rig would with 6AG7's...

Well, I had good luck one time using a pair of 6V6's at 12-24 vdc on the
plates.  It was loud enough to hurt on strong signals with 2 K ohm fones.
It was choke coupled in the audio with an old tv tube choke of a few
henries to the audio stage and to the tin cans.  0.68uf coupling caps
were used.

> Now, about this gain of 40.  My first reaction is "no, can't get more 
> then the amplification factor" (20 for a 6J5, and fairly constant at 
> different operating points for any tube, since it's based on geometric 
> considerations).  But then there's that matter of an inductive load.  
> So, is it possible to "cheat" and get more gain than the amplification 
> factor by using a reactive load?  Since the "bucking effect" of the 
> output voltage on the plate current is not in phase, I wonder?  I'll 
> have to think about it, but it sounds too much like a free lunch.  
> OTOH, that's what reactance is anyway, right?

Well, I measured the input voltage at 0.1vac on the grid with a 600 ohm
line to voice coil transformer as the grid inductance, and about 4.4 vac
on the plate, across the 5h choke.  I was not taking power from the plate
circuit, so that would have some effect.  Plate voltage was 12vdc.  I will
try to set it up again on the bench this weekend and see how it does into
a tin can load.  I dunno why it amplified so well.  AC meters are not
accurate at low voltages.  My meter moved about 2 needle widths on the
input reading (I maybe should use a scope to measure it next time).
It is possible that that reading was anywhere from 0 to 0.22 vac, but 
2 needlewidths on the meter was closer to 0.05 vac than 0.20 vac.
I rounded the measured value up to 0.10 vac because of the inaccuracies.
That is what I get for measuring on a 10vac scale.  When a 600 ohm load
was coupled to the output (another ls-144 speaker), the voltage dropped
down to a little over 1.5 vac across the 600 ohm load.  The tone frequency
was about 440 hz.  I did not try other tone frequencies.  So, the plate
load did affect the output voltage.

73/ZUT DE NA4G/Bob UP

------------------------------

End of GLOWBUGS Digest 338
**************************