Thank you to everyone for your kind suggestions. After doing some extensive testing with my spectrum analyzer and o'scope I've determined the T-21 transmitter is stable. The issue is the tuned circuit I'm transmitting into is changing impedance and pulling the oscillator off frequency. I have a design change to make today and will report the results here after further testing.

Thank you again to everyone!
73,

Mack
W4AX
https://www.qrz.com/db/w4ax


On Tue, Nov 8, 2022 at 12:16 PM <milsurplus-request@mailman.qth.net> wrote:
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Today's Topics:

   1. Advice Please: Frequency stabilizing a 80M ARC-5  transmitter
      (Mack McCormick)
   2. Re: Lawrenceville GA hamfest photos (Joe Connor)
   3. Re: Advice Please: Frequency stabilizing a 80M ARC-5
      transmitter (Mark Foltarz)



---------- Forwarded message ----------
From: Mack McCormick <w4ax.mack@gmail.com>
To: milsurplus@mailman.qth.net
Cc: 
Bcc: 
Date: Tue, 8 Nov 2022 10:41:25 -0500
Subject: [Milsurplus] Advice Please: Frequency stabilizing a 80M ARC-5 transmitter
I have an ARC-5 transmitter that I am using as a VFO for the BC-375 to prevent FMing from the BC-375 MOPA oscillator/PA. 

The ARC-5 exciter is working great except for frequency stability. The peak carrier frequency starts about 1 kc low and after about 1 minute is about 1 kc high. Not really a big deal except it drives the SDR folks crazy when I'm on an AM net. 

The 1626 oscillator is exceptionally well regulated using a FET in the external power supply. It is rock solid. 

Do you have other ideas on how I might further improve frequency stability? I built a crystal oscillator but it does not have enough drive using a 12A6 vacuum tube to drive the 1625's above about 5 watts. I'm still troubleshooting this circuit. 

I need about 20 watts out of the 1625s. 




---------- Forwarded message ----------
From: Joe Connor <joeconnor53@yahoo.com>
To: "milsurplus@mailman.qth.net" <milsurplus@mailman.qth.net>, Hubert Miller <kargo_cult@msn.com>
Cc: 
Bcc: 
Date: Tue, 8 Nov 2022 16:50:49 +0000 (UTC)
Subject: Re: [Milsurplus] Lawrenceville GA hamfest photos
A belated thank you for the hamfest photos, Nick. As always, they're a blast to scroll through. I say this as I continue cleaning the drool off my keyboard!

                          Joe Connor

On Sunday, November 6, 2022 at 01:58:40 PM EST, Hubert Miller <kargo_cult@msn.com> wrote:


Yes, really great photos, it's the real thing, a fully qualified hamfair. I see plenty of items that at one time, would have really tempted me.  A Drake TR-7, R-392, BC-683, even a GE table radio X-371, 2 photos. I saw one recently on Ebay sold   for 
around $500. I had for years wanted one but...i looked at Ebay closeups of the semicircular tuning scale and realized that the bands toward the center of the scale, closer to the axis, have sparer room for markings. Hence the low band on the X-371, the MW broadcast band, has really miserable frequency markings. Oh, good, i wised up and can delete that thing from my "list". Sliderule dials rule!
Hue Miller


Sent from my Verizon, Samsung Galaxy smartphone
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---------- Forwarded message ----------
From: Mark Foltarz <Foltarz@rocketmail.com>
To: "milsurplus@mailman.qth.net" <milsurplus@mailman.qth.net>, Mack McCormick <w4ax.mack@gmail.com>
Cc: 
Bcc: 
Date: Tue, 8 Nov 2022 17:15:52 +0000 (UTC)
Subject: Re: [Milsurplus] Advice Please: Frequency stabilizing a 80M ARC-5       transmitter
Tell the SDR folks where they can go.
Of course having a freq counter to show you where you're at is probably the cheapest and easiest.
Otherwise, you may try something like the following : http://www.hanssummers.com/images/stories/library/afc.pdf

73
de WA4AM
Mark

On Tuesday, November 8, 2022 at 10:41:48 AM EST, Mack McCormick <w4ax.mack@gmail.com> wrote:


I have an ARC-5 transmitter that I am using as a VFO for the BC-375 to prevent FMing from the BC-375 MOPA oscillator/PA. 

The ARC-5 exciter is working great except for frequency stability. The peak carrier frequency starts about 1 kc low and after about 1 minute is about 1 kc high. Not really a big deal except it drives the SDR folks crazy when I'm on an AM net. 

The 1626 oscillator is exceptionally well regulated using a FET in the external power supply. It is rock solid. 

Do you have other ideas on how I might further improve frequency stability? I built a crystal oscillator but it does not have enough drive using a 12A6 vacuum tube to drive the 1625's above about 5 watts. I'm still troubleshooting this circuit. 

I need about 20 watts out of the 1625s. 

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