Subject: GLOWBUGS digest 414

From: [email-masked]
Date: Tue, 14 Jan 1997 10:41:27 -0600 (CST)

GLOWBUGS Digest 414

Topics covered in this issue include:

  1) Re: 45 tube
	by John Michael <[email-masked]>
  2) Re: Push-Pull Oscillator/Transmitter
	by [email-masked]
  3) Re: Images of my homebrew CW TX.
	by "Robert M. Bratcher Jr." <[email-masked]>
  4) Re: 45 tube
	by "Robert M. Bratcher Jr." <[email-masked]>
  5) Traders Nets???
	by "Brian Carling" <[email-masked]>
  6) Re: Need 3.3957mHz Crystal
	by "Brian Carling" <[email-masked]>
  7) ER article
	by "Brian Carling" <[email-masked]>
  8) SB-101 VFO - what freq?
	by Dave <[email-masked]>
  9) Son of Reluctant Regen
	by Art Winterbauer <[email-masked]>
 10) Re: Son of Reluctant Regen
	by "Joseph L. Hartmann, Jr." <[email-masked]>
 11) Military Surplus
	by "Brian Carling" <[email-masked]>
 12) 6DQ6 -A or -B?
	by [email-masked] (John Heck)
 13) Quote of the Month!
	by "Claton Cadmus" <[email-masked]>
 14) Re: VFO question
RE: VFO QUESTION
	by [email-masked] (Larry Szendrei, ARS NE1S)

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

Date: Mon, 13 Jan 1997 12:38:20 -0500
From: John Michael <[email-masked]>
To: [email-masked]
Subject: Re: 45 tube
Message-ID: <[email-masked]>

>I have a friend in need of a number 45 tube.  Where can one find one at a
>reasonable price?  Are there any substitutes?

The 45 is a filimentary power triode, used singly and in push-pull in
lots of 30's-era home radios like the Philco cathedrals and consoles.
For some reason the golden-ears crowd took a fancy to them and have
driven the prices out of sight--last I looked, in excess of $50 for a
new one.  Don't know of any substitutes that aren't just as scarce.

John Michael      [email-masked]

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

Date: Mon, 13 Jan 1997 15:33:52 -0500 (EST)
From: [email-masked]
To: [email-masked]
Cc: [email-masked] (), [email-masked]
Subject: Re: Push-Pull Oscillator/Transmitter
Message-ID: <[email-masked]>

> 
> New year greetings to my fellow lovers of fire bottles and radios that glow
> in the dark.
> 
> Over the holiday I finally had a chance to work on my next project; a push
> pull oscillator/transmitter for 40 meters.  At this time I feel I am a bit to
> inexperienced to attempt a TPTG style transmitter and so I have chose a
> design that uses a crystal for the grid circuit.  I built up a push pull
> crystal oscillator circuit using two 6C5s and it seems to oscillate quite
> nicely near the crystal frequency.  Before I try to put this this beast on
> the air, I have a few questions I would like to ask the group:

Hey, sounds like a great lil glowebugge ye gots there, matey!

> 1.  What would be the best way to couple a push-pull stage into a low
> impeadance load (50 ohm coax feeding a wire dipole)?  I was thinking that I
> should link couple the push pull tank to a second tuned circuit that is end
> linked.

Well, there are numerous ways to couple out of it, but the use of a two
turn link around the center of the plate coil will be the starting point
for most simple ways.  Ground the link and wrap 2 turns around the tank,
fairly closely coupled.  I used old coax and strip the braid off to make
a nice high voltage wire for winding links with the plastic as spacer.

Then, almost any simple tuner would work to feed the coax from there.

For a coax feed, it would be entirely appropriate to use a pi-net tuner
to feed the coax to the dipole.  Make sure the input and output caps
are at or very near maximum capacitance, then adjust the coil for maximum
output on a field strength meter with the output capacitor fully meshed
and use what coil is required.  Then adjust the output capacitor slightly
to peak, and then the input capacitor to peak (or if the tuner has an swr
bridge [what the heck is swr to a glowebugge, but mostly mythology, anyway]
you can use the swr bridge to tune for the swr null).  A pair of 365pf
broadcast variables with a coil of maybe 40 turns 2-2.5 inches in diameter
should do nicely.  If you have a piece of miniductor stock of anything
close to that size and number of turns, it should work well, since you
need to adjust the turns to suit.

Alternatively, you can use merely a series coil and capacitor to feed
a low impedance antenna of any sort, hooked up to the link.  Try a
coil about 2-2.5 inches in diameter with 40 turns of bell wire and
a series capacitor to the coax of about 150 pf or so.  Merely tune for
maximum output on a field strength meter and you are matched.  This
is what I use for almost all of my rigs.  It has worked great, since
the spark era.

My expectation is that you should get about 2 watts output from a pair
of 6C5's.  More than that may be pushing, slightly.  If you want more,
try a larger triode, maybe, or possibly paired 6N7's or 6SN7's.  Then you
should be able to get 10 watts output comfortably.

> 2.  I have noticed that if the tank is tuned below the frequency of the
> crystal, oscillation stops.  As a result, it is difficult to tell optimum
> tuning of the tank.  When tuning from minimum capacitance, I can see the the
> plate current go up when the circuit starts oscillating and can see the
> current start to decrease as the tank approaches the crystal frequency;
> However, once I pass the crystal frequency, the oscillations stop before the
> plate current goes up again.  Should there be a dip in plate current before
> the dip or is this simply the way these oscillators work?

On an oscillator you will not see a dip, only on an amplifier.  The plate
current on the oscillator will increase as the tank nears resonance.
As it goes below resonance, it will reach a point where IT controls the
circuit and the xtal will stop oscillating and it becomes a TPTG sort of
rig.  It will then oscillate anywhere the tank happens to tune (bad bad).
If the thing does not oscillate as a tptg rig then, it will just sit there
and draw enough current to possibly exceed plate dissipation ratings of the
tubes.  The usual practice is to find the point at where the xtal stops
oscillating or pulls badly, and then tune up from that sufficiently to
give a stable signal.  The sufficient uptuning will usually be only 2-3
divisions on an oscillator dial (relatively critical).  As you couple
out the oscillator the tuning will be slightly affected, so it may require
some slight retuning for most stable signal.  It is sort of a two-fisted
operation, but once you get the hang of it, it goes smoothly, thereafter.

Your mileage may vary, but that should get you in the ballpark.

You might consult some of the classic practicum on the subject to get
a bit more understanding of what to expect.  See the following.....

1.  Cody, W.G., Proc. I.R.E. April, 1922.22.

2.  Pierce, George W., Proc. Am. Acad. Arts Sci., October, 1923.

3.  Shaw, H.S., QST, July, 1924.

Also, it was covered fairly well in any of the late 20's and early 30's
handbooks, if you can find them in the local library.  The first editions
of the Radio Handbook seem to cover it pretty well.

> 73, 
> Eric, WD6DGX

Good Luck!  Glowebugges ferever!

73/ZUT DE NA4G/Bob UP

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

Date: Mon, 13 Jan 1997 12:56:19 -0600
From: "Robert M. Bratcher Jr." <[email-masked]>
To: [email-masked]
Cc: Multiple recipients of list <[email-masked]>
Subject: Re: Images of my homebrew CW TX.
Message-ID: <[email-masked]>

At 04:30 AM 1/13/97 +0000, Chris Broadbent wrote:
>Hello all,
>
>I have finally put together a couple of web pages displaying images of my
>homebrew 6LR8 based TX, along with what I believe are useful comments on
>construction and composition of said device.  The URL is:
>
>	http://www.bga.com/~cfb/
>
>If your web browser does not like this, try dropping the rightmost / (after
>~cfb).  If you still have problems or you don't have a browser, drop me a
>message and I'll put the images into an ftp site or mail them to you.
>
>I look forward to your comments.  I am proud of this first tube effort, but
>please don't be shy to criticise as I have much to learn.
>
>I really look forward to meeting anyone from this group on the air using
>the device (if you're on the 80M novice band at any time - currently 3695
>and 3710 KHz given my current crystals).
>
>-- 
>
>Cheers,
>
>Chris F. Broadbent ( KC5VQL )
>

Looks very nice! Now how bout the schematic? How much power does it put out?

Robert M. Bratcher Jr.
E-mail to:
[email-masked]
Record collector, 8mm, super 8, 16 and 35mm Film collector.
I like old radio's too.
Collins, Hallicrafters, National & Hammurland are my Favorites!

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

Date: Mon, 13 Jan 1997 13:14:30 -0600
From: "Robert M. Bratcher Jr." <[email-masked]>
To: [email-masked]
Subject: Re: 45 tube
Message-ID: <[email-masked]>

At 05:45 PM 1/13/97 +0000, you wrote:
>>I have a friend in need of a number 45 tube.  Where can one find one at a
>>reasonable price?  Are there any substitutes?
>
>The 45 is a filimentary power triode, used singly and in push-pull in
>lots of 30's-era home radios like the Philco cathedrals and consoles.
>For some reason the golden-ears crowd took a fancy to them and have
>driven the prices out of sight--last I looked, in excess of $50 for a
>new one.  Don't know of any substitutes that aren't just as scarce.
>
>John Michael      [email-masked]
>

A.E.S should have them. My local antique radio club (Houston Vintage Radio
Association)is having a 2 day mega auction this Friday & Saturday. If a box
of tubes has one or more 45's I'll buy it & pass the 45 tubes along at a
fair price. Since these would be used the price would be much cheaper than
A.E.S charges. How much, I don't know yet. If I get one or more 45's in a
box then I'll post here to the group. If I don't report a "found" 45 by
monday then there wasn't one at the club action. Thats the best I can do...

Robert M. Bratcher Jr.
E-mail to:
[email-masked]
Record collector, 8mm, super 8, 16 and 35mm Film collector.
I like old radio's too.
Collins, Hallicrafters, National & Hammurland are my Favorites!

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

Date: Mon, 13 Jan 1997 14:12:12 +0000
From: "Brian Carling" <[email-masked]>
To: [email-masked]
Subject: Traders Nets???
Message-ID: <[email-masked]>

Does any one know about any Traders Nets on HF or VHF?

If you can tell me the UTC TIME and FREQUENCY
that these nets meet on I would really appreciate it.

I keep alist here for anyone that would like to see what I already 
have:

It's in the ham radio resources area at the URL below. 
Under HAM FILES/ SWAP NETS.

Let me know what you can guys. Thanks
********************************************************
*** 73 from Radio AF4K / G3XLQ in Gaithersburg, MD USA *
**  E-mail to:  [email-masked]                         *
*** See the great ham radio resources at:              *
**  http://www.mnsinc.com/bry/                         *
********************************************************

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

Date: Mon, 13 Jan 1997 16:28:32 +0000
From: "Brian Carling" <[email-masked]>
To: [email-masked] (Adam J McLaughlin), [email-masked]
Subject: Re: Need 3.3957mHz Crystal
Message-ID: <[email-masked]>

Adam I have a huge list of XTAL suppliers and sources at:
http://www.mnsinc.com/bry/
in the ham radio resources section

Enjoy! AF4K, Bry

On 11 Jan 97 at 15:58, Adam J McLaughlin chatted merrily:

> Hello Fellow Glowbuggers!
> 
> I need a rock for 3.3957 mHz as fast as I can get it. Does anyone
> know of any sources where I can get this rock? I need it for a
> heterodyne rig. 
> 
> Thanks in Advance,
> 
> Adam Mclaughlin KD6POC
> [email-masked]
> kd6poc@kd6kwm.#nocal.ca.usa.noam
> 
********************************************************
*** 73 from Radio AF4K / G3XLQ in Gaithersburg, MD USA *
**  E-mail to:  [email-masked]                         *
*** See the great ham radio resources at:              *
**  http://www.mnsinc.com/bry/                         *
********************************************************

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

Date: Mon, 13 Jan 1997 17:15:49 +0000
From: "Brian Carling" <[email-masked]>
To: [email-masked]
Subject: ER article
Message-ID: <[email-masked]>

Anyone see the nice little "Cakepan 6AQ5" XMTR design in the December 
issue of  Electric Radio?

I think it look spretty nifty, even theough the kit seemed like it 
was a little steeply priced! But heck WHERE are you going to find any 
OTHER Glowbug kits these days? There just aren't many!
********************************************************
*** 73 from Radio AF4K / G3XLQ in Gaithersburg, MD USA *
**  E-mail to:  [email-masked]                         *
*** See the great ham radio resources at:              *
**  http://www.mnsinc.com/bry/                         *
********************************************************

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

Date: Mon, 13 Jan 1997 19:10:38 -0800
From: Dave <[email-masked]>
To: [email-masked]
Subject: SB-101 VFO - what freq?
Message-ID: <[email-masked]>

Hi gang,

I have just acquired, through the generousity of Jon Mitchel (possibly
a member of the group) a 'fried' SB-101.  The PTO seems ok, though.

I was wondering - can I use this in a standalone mode?  What frequency
does it cover?  If it covers the standard 5 - 5.5 MHZ, it would make
a perfect VFO for a 30 meter mono-bander (one of my plans).  Or maybe
I could alter the frequency range.  Does anyone have a schematic?

Any info regarding this VFO unit would be very much appreciated.  I don't
feel guilty about gutting a dead SB-101 instead of my old ARC-5
receivers I wrote about last week!!

I'd like to find a glowbug home for this in one of my ongoing projects.

Thanks,

Dave  WB7AWK

"I want to die peacefully in my sleep, like my Grandfather.  Not screaming
and in terror like his passengers"

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

Date: Mon, 13 Jan 1997 21:42:19 -0700 (MST)
From: Art Winterbauer <[email-masked]>
To: glowbugs <[email-masked]>
Subject: Son of Reluctant Regen
Message-ID: <Pine.SUN.3.95.970113213416.19288A-100000@spike>

Well, after spending a good 30 hours or so playing with tickler/grid
coils, the beastie still won't regenerate.  So, I'll be a bit more
specific about the circuit.

'Tis the one described in the Feb 1990 CQ, p. 74, by the venerable
Ingram.  I'd like to get this two-tuber going, and I wonder if anyone
else has gotten this particular circuit to work.  To repeat, I can
copy my old Jackson R.F. signal generator on the specified
frequencies, using the windings described and reproduced exactly.  But
no regen.  I've taken the tickler coils from 60% down to 1% (well, one
turn) with varying degrees of spacing between the two sets of coils.
I've used all different kinds of wire, from #30 to #20 enameled wire.  

Is the circuit pictured just so off-the-wall that the chances of it
working are very slim?  

Most of my homebrew circuits don't work.  But I thought I'd stand a
chance with this one...it has so few parts! 

--Art WA5OES

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

Date: Tue, 14 Jan 1997 03:11:09 -0500 (EST)
From: "Joseph L. Hartmann, Jr." <[email-masked]>
To: Art Winterbauer <[email-masked]>
Subject: Re: Son of Reluctant Regen
Message-ID: <Pine.BSD/[email-masked]>

Heck -- at 2:26 AM do you expect to get any sense out of me?  Art, in 
1952 I tried to build the one-tuber in the handbook. I never got it to 
work.  What a bummer.  Now that a lot of water has gone down the sewer 
pipe:  
1. Is it an "amplifier".  If you have a GDO you should verify that the 
tuned circuits are tuning!  Once you have that established.  Use the GDO 
as a signal generator -- figure out some way to measure the output -- you 
won't have a tone till you regenerate -- but don't even worry about 
regenerating at first.  Read the manual on the GDO -- there should be 
some way you can measure the Q of the tuned circuit.  Even if it's only 
approximate.  If it doesn't have a fairly high Q I don't think you will 
ever get it to regen, or even to amplify.  Once you can get some kind of 
measurement going so you you can say "Yes it is receiving the GDO 
signal", then you can experiment with the regen.  You need Positive 
feedback to get the regen effect -- and if you have positive regen, you 
will get a progressively more sensitive receiver as you increase the 
regen.  You have to be able to measure the approximate gain so you can 
see if your amplifier is actually getting positive feedback from your 
regen circuit.  A hf scope and sig gen would probably be the best 
approach, but I think you could use a GDO.  If you have a sig gen and 
scope, by all means use them.  The key is measurement: you must know when 
you are getting a higher gain Rcvr by doing your regen tricks.  Maybe 
something is backwards and you are inducing negative feedback around the 
amp.  Coil winding orientation problems.  Things like that.  You are 
making me re-live my own regen frustration now from the vantage point of 
spending a lot of time learning different things.  Don't give up.  But 
MEASURE!  It's the only sure way you are going to get that
thing to work.

Good luck.

Best Regards,
 
Joe Hartmann      Tel: (603) 863 6073     
K2AJV -issued     email: [email-masked]   
    1951          home-page: http://www.sugar-river.net/~joeh 
-------------------------------------------------------------
First Student at the:

      Linux Academy in the Sunshine Town of Newport, NH

Thanks to RMS, Linus, and other contributors of free software!
------------- I grant this to the public domain -------------

On Mon, 13 Jan 1997, Art Winterbauer wrote:

> 
> Well, after spending a good 30 hours or so playing with tickler/grid
> coils, the beastie still won't regenerate.  So, I'll be a bit more
> specific about the circuit.
> 
> 'Tis the one described in the Feb 1990 CQ, p. 74, by the venerable
> Ingram.  I'd like to get this two-tuber going, and I wonder if anyone
> else has gotten this particular circuit to work.  To repeat, I can
> copy my old Jackson R.F. signal generator on the specified
> frequencies, using the windings described and reproduced exactly.  But
> no regen.  I've taken the tickler coils from 60% down to 1% (well, one
> turn) with varying degrees of spacing between the two sets of coils.
> I've used all different kinds of wire, from #30 to #20 enameled wire.  
> 
> Is the circuit pictured just so off-the-wall that the chances of it
> working are very slim?  
> 
> Most of my homebrew circuits don't work.  But I thought I'd stand a
> chance with this one...it has so few parts! 
> 
> --Art WA5OES
> 
> 

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

Date: Tue, 14 Jan 1997 03:46:24 +0000
From: "Brian Carling" <[email-masked]>
To: [email-masked]
Subject: Military Surplus
Message-ID: <[email-masked]>

There used to be a GREAT listing and description of MANY models of 
military surplus equipment available on the web at:

http://linux.cec.army.mil/hamradio/equipment/mi.html

It no longer works! Does anyone have any idea where it has been moved 
to or has it just disappeared?

ANY help would be appreciated!

Thanks! Bry, AF4K
********************************************************
*** 73 from Radio AF4K / G3XLQ in Gaithersburg, MD USA *
**  E-mail to:  [email-masked]                         *
*** See the great ham radio resources at:              *
**  http://www.mnsinc.com/bry/                         *
********************************************************

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

Date: Tue, 14 Jan 97 08:37:54 EST
From: [email-masked] (John Heck)
To: [email-masked]
Subject: 6DQ6 -A or -B?
Message-ID: <[email-masked]>

Folks,
Can anyone tell me what is the difference between a 6DQ6-A and a 6DQ6-B?
Especially with respect to its use as a class C amplifier?
Thanks,
Regards,
John Heck, KC8ETS
1009 Donson Drive
Dayton, Ohio 45429
(513)865-7036(work)
[email-masked]

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

Date: Tue, 14 Jan 1997 07:38:48 -0600
From: "Claton Cadmus" <[email-masked]>
To: "Multiple recipients of list" <[email-masked]>
Subject: Quote of the Month!
Message-ID: <[email-masked]>

My apologies to Art but this has got to be the quote of the month!

"Most of my homebrew circuits don't work.  But I thought I'd stand a
chance with this one...it has so few parts!" --Art WA5OES

73 de KA0GKC Claton Cadmus
Ph.  (612)926-8886  Fax  (612)926-8545
E-mail  [email-masked]
TCP/IP  [email-masked]
Packet  ka0gkc@wb0gdb.#stp.mn.us
ARRL, QRP-ARCI, NorCal, ARCC, MNQRP Society

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

Date: Tue, 14 Jan 1997 09:22:33 -0500
From: [email-masked] (Larry Szendrei, ARS NE1S)
To: [email-masked], [email-masked]
Subject: Re: VFO question
RE: VFO QUESTION
Message-ID: <[email-masked]>

Greetings, Ray...

On 01/10/97 to wrote to GLOWBUGS:

>The easiest way to get the first doubling is to feed the 
>output of the oscillator through a full wave center tap transformer 
>with 2 signal diodes.  This is a very efficient doubler.  Just put in 
>a switch to select the doubled or straight through signals.  All bands 
>above 160M will require at least one 2X so that is an easy way to get 
>it.  This would allow the second 5763 to be 1X, 2X, or 3X depending on 
>the band selected.  The diodes will give a fairly constant load to the 
>oscillator as well.  As an even better solution,  change the diodes to 
>a 6AL5.  This will allow a higher grid signal voltage to the second 
>5763.

My situation is thus: 

I have a Knight VFO (model # unknown) which uses a 6AU6 (or 6BA6?) 160M 
(Colpitts?) osc. and a 6AK5 doubler to 80M. Although the dial is calibrated for 
80M, 40M, 20M, 15M, and 10M, there is good and bad news. The good news is that 
despite the lack of calibration and doubling stage there is still enough output 
on the fundamental (160M) to use this VFO on 160M with my otherwise homegrown 3-
stage 160M-10M low power AM/CW transmitter. The bad news is that this 
transmitter wants to see an input from the VFO on 40M for the 15M and 10M bands. 
The plate tank of the doubler stage in the VFO is a slug-tuned coil, which 
resonates on 80M with the parallel circuit capacitances (coax to transmitter, 
transmitter grid circuit, etc.). I tried winding another inductance to resonate 
on 40M but this requires the multiplier stage in the VFO to quadruple, which 
doesn't provide sufficent drive for the subsequent multiplier stage in the 
homebrew XMTR. I get similar results by taking the 80M output and attempting to 
quadruple to 20M (for ultimate 10M operation after doubling in the driver) in 
the subsequent multiplier stage --> insufficient grid drive to the final. 

Your posting has perhaps provided a solution. Please tell me if there are any 
caveats to the following proposal. Lets say I center-tap the 80M tank coil in 
the plate circuit of the doubler in the VFO, and hook this to the plate supply 
(instead of one end going to the plate supply as presently configured). The ends 
of the coil would then hook to the 2 signal diodes in the "full wave" connection 
to provide doubling to 40M. The 80M output would be at either end of the tank 
coil, and the 40M output would be at the junction of the diodes cathodes (or 
anodes - since we don't care if the DC bias at this point is (+) or (-)). Of 
course the output at this point would be blocked for DC with a cap., as it is 
for the 80M output already. On one hand it would seem that this should work, on 
the other hand I feel like I'm breaking a basic law that says "you don't get 
something for nothing." I realize that this approach might reduce my output on 
160M and 80M, but I seem to have surplus drive on these bands. What I am trying 
to avoid like the plague is building an additional (active) multiplier stage in 
order to make the transmitter function with the VFO for 15M and 10M operation. 

Or do you have any other ideas to propose??

Thanks,
Larry, NE1S
[email-masked]

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

End of GLOWBUGS Digest 414
**************************