[Milsurplus] Just had to comment - chirp
sbjohnston at aol.com
sbjohnston at aol.com
Tue Aug 20 20:59:38 EDT 2024
The formatting seems to have gone awry on this message. I'll try again...
I've noticed some possible confusion of the CW transmitter descriptions "Power Oscillator" and "MOPA". I use these terms in this way:
"Power Oscillator" = one tube, one stage, oscillator feeds antenna directly. Can destroy FT-243 and later crystals, especially if optimized for maximum power output. Also can be challenging to get a good signal. Examples:
http://www.radioboatanchorblog.com/blog/homebrew-cw-6l6-vacuum-tube-transmitter-build
https://www.frostburg.edu/personal/latta/ee/6cl6xmtr/6cl6schematic.html
https://onetuberadio.com/2017/03/25/1967-one-tube-cw-transmitter/
https://www.frostburg.edu/personal/latta/ee/6cl6xmtr/6cl6schematic.html
"MOPA" = two tubes, two stages, oscillator followed by an amplifier. Master Oscillator and a Power Amplifier. Easier to get a good signal. Examples:
http://www.wd8das.net/TTTTT.html
http://www.wd8das.net/dream.html
https://www.qsl.net/wd4nka/TEXTS/MOPAf.HTM
https://www.qsl.net/k5dh/6ag7_6l6.html
https://www.qsl.net/k5dh/6ag7_807.html
Examples of good, simple rigs with with three stages (addition of buffer/multiplier between oscillator and power amplifier):
http://www.wd8das.net/Raider/Raider.html
https://www.wd8das.net/HW-16_transmitter.jpg
Speaking very generally, I find the ease of achieving a good signal improves with more stages.
Steve WD8DAS
sbjohnston at aol.com
http://www.wd8das.net/
http://af4k-crystals.com/
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On Tuesday, August 20, 2024 at 02:46:41 PM HST, milsurplus-request at mailman.qth.net <milsurplus-request at mailman.qth.net> wrote:
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Today's Topics:
1. Re: Just had to comment - chirp (Hubert Miller)
2. 813's (CL in NC)
3. Re: Article on crystal oscillators (Ken Gordon)
4. Re: Just had to comment - chirp (mstangelo at comcast.net)
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Message: 1
Date: Tue, 20 Aug 2024 23:26:59 +0000
From: Hubert Miller <Kargo_cult at msn.com>
To: "milsurplus at mailman.qth.net" <milsurplus at mailman.qth.net>
Subject: Re: [Milsurplus] Just had to comment - chirp
Message-ID:
<SN1PR20MB2029AB3C663DDF8815800E86E48D2 at SN1PR20MB2029.namprd20.prod.outlook.com>
Content-Type: text/plain; charset="us-ascii"
MOPA = master oscillator, power amplifier, right ?
This isn't difficult. It goes back to the early 1920s.
-Hue
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Message: 2
Date: Tue, 20 Aug 2024 23:34:33 +0000 (UTC)
From: CL in NC <mjcal77 at yahoo.com>
To: Milsurplus <milsurplus at mailman.qth.net>
Subject: [Milsurplus] 813's
Message-ID: <1170686325.5434467.1724196873040 at mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8
Many moons ago, I heard that the seals around the pins of 813's would eventually allow air in and if you fired the tubes up now and then, this would preserve their longevity. I have been searching for my 4 NOS 813's I have around here somewhere, but I may have to activate plan B, buy a new one. Antique Radio has NOS US made 813's, and an email inquiry about issues reported back they have had none, tubes as good as the day they were made. I am a bit skeptical of those on Epay, and the Chinese copies at places like Tubedepot are out of stock. So, is that an old wives tale about firing up you spare 813's that are sitting on a shelf? I found 3 pulls I had, 2 have not been lit in 50 years, and I know one has not been on in over 60 because I remember the day an Elmer gave me one telling me to one day build an amp around it. I tried them each in turn in my ART13 and all seemed to be fine, but wanted to try a new one to see if I get any more power out. In my search I did fi
nd 2 brand new US made VT4C/211's, and for what they go for on epay wanted by audiophiles, that's a small fortune. But I use a BC375 so holding on to those. Never did build that amp around that 813, but did with a pair of 811's and later 4-125's, guess that 813 I got handed when I was 11, was destined for the ART13 sometime in the future.
Charlie, W4MEC in NC
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Message: 3
Date: Tue, 20 Aug 2024 17:10:44 -0700
From: "Ken Gordon" <kgordon2006 at frontier.com>
To: "milsurplus at mailman.qth.net" <milsurplus at mailman.qth.net>,
"sbjohnston at aol.com" <sbjohnston at aol.com>
Subject: Re: [Milsurplus] Article on crystal oscillators
Message-ID: <66C53084.8488.20BA6051 at kgordon2006.frontier.com>
Content-Type: text/plain; charset=US-ASCII
On 20 Aug 2024 at 20:03, sbjohnston--- via Milsurplus wrote:
>
> Interesting article on crystal oscillators from March 1950 QST
>
> https://www.wd8das.net/CrystalOscillators.pdf
I have had that exact article posted on my website, www.w7ekb.com/glowbugs, for at least
the past 20 years, here:
http://www.w7ekb.com/glowbugs/projects/index.html
Down near the bottom of the page under Crystal Control.
Ken W7EKB
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This email has been checked for viruses by Avast antivirus software.
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Message: 4
Date: Tue, 20 Aug 2024 20:45:49 -0400 (EDT)
From: mstangelo at comcast.net
To: "milsurplus at mailman.qth.net" <milsurplus at mailman.qth.net>
Subject: Re: [Milsurplus] Just had to comment - chirp
Message-ID: <1333823707.751459.1724201149791 at connect.xfinity.com>
Content-Type: text/plain; charset=UTF-8
I stand corrected. I meant to say it was a MOPA transmitter.
Mike N2MS
> On 08/20/2024 7:08 PM EDT hwhall at aol.com <hwhall at compuserve.com> wrote:
>
>
>
>
> > The Philmore NT-200 is a two stage transmitter so I do not consider it a MOPA transmitter.
>
>
> I'm not sure I understand that. I assumed that if the oscillator is a different tube than the final amplifier, then that was the meaning of a MOPA.
>
> Wayne
> WB4OGM
>
> On Tuesday, August 20, 2024 at 07:51:00 AM MDT, mstangelo--- via Milsurplus <milsurplus at mailman.qth.net> wrote:
>
>
> Thanks to all about the information about the Bruce Kelly and Philmore transmitters. The Philmore NT-200 is a two stage transmitter so I do not consider it a MOPA transmitter.
>
> Does anyone remember the W5LET had single tube transmitters in Electronics Illustrated?
>
> I built one using the 6AQ5A tube and it exhibited less chirp than my AC-1. It specified and coil only available from Allied Industrial division and had a long time delivery so I substituted a 4.5MHz television IF coil and it worked like a charm.
>
> A copy of the article starts on page 100:
>
> <https://www.worldradiohistory.com/Archive-Electronics-Illustrated/Electronics-Illustrated-1967-03.pdf>
>
> Mike N2MS
>
>
>
> > On 08/19/2024 10:16 PM EDT Robert Nickels <ranickels at gmail.com> wrote:
> >
> >
> > On 8/19/2024 7:59 PM, Hubert Miller wrote:
> >
> > > Philmore had a one tube Novice type transmitter, but not many sold, quite rare.
> > Hue,
> > The Philmore NT-200 is a MOPA with 6V6 oscillator and 6L6 amplifier. It keys nicely - you can get the entire pictorial manual from BAMA.
> >
> > Did they make another ?
> > 73, Bob W9RAN
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