[Milsurplus] Hey Bob, W9RAN

[Hubert Miller]

I welcome comments on:
1. The single 813 transmitter - is that one that's instant death for post - 1940s crystals ?
2. The "special crystal current limiting device" i.e. pilot lamp bulb, in the Conar single tube novice transmitter ? Effective, or just a warning device ? ( "Oops ! Darn it ! )
3. I think i posted here, long ago, about an item i saw in an old 'Short Wave Craft' magazine, that you could use a fragment of a cracked quartz crystal and still have it work.

I have the QST 'Novice Pair' from the 1950s, with its single tube 6DQ6 transmitter. When i get around to it...i won't need to push the watts thru it; i can tone it down.
-Hue Miller


Sent from my Galaxy



-------- Original message --------
From: sbjohnston--- via Milsurplus <milsurplus at mailman.qth.net>
Date: 1/11/26 10:51 (GMT-08:00)
To: milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] Hey Bob, W9RAN


One-tube power-oscillator transmitters can definitely kill FT-243 crystals.  I know this from sad personal experience.

I think the crystal-controlled power-oscillator designs originated in the 1930s when the crystals in use had a much larger "chunk" of quartz inside. High crystal current did not matter so much in that case.  The designs persisted over the decades but the quartz mass in the contemporary crystals declined greatly.

In my business AF4K Crystals, many of my sales are of vintage crystals re-stuffed with HC-49 crystals.  They are perfectly fine in multi-stage tube equipment, but I do caution users about the one-tube transmitters.

Interestingly quite a few customers report success with the power-oscillators.  The factors involved seem to be (A) limiting crystal current with a series resistor and (B) not trying to get absolute maximum power out of the single stage.   If you are satisfied to consider it a QRP rig you have a much better experience.

I much prefer to build a two-stage MOPA rig.  For example:

https://www.wd8das.net/TTTTT.html

or

https://www.wd8das.net/dream.html

or even splurge on three tubes:

https://www.wd8das.net/Raider/Raider.html


73   Steve  WD8DAS

sbjohnston at aol.com
http://www.wd8das.net/
http://af4k-crystals.com<http://af4k-crystals.com/>/
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