Hi At that frequency, the crystal is likely some sort of bar cut rather than an AT. If the transmitter has no oven / heater around the crystal, it will indeed drift quite a bit.
Bob On Jun 21, 2013, at 12:09 AM, Joseph Gray <[email protected]> wrote: > This is not strictly Time Nuts, but it is about a crystal oscillator that > needs some temperature compensation, or something. Please ignore this > posting if you like. In fact, so as not to clutter up the list, it would be > best to email me directly about this. > > I have an old AM transmitter that has three 6AL11 compactrons. The crystal > is a fundamental, cut for 660 KHz. I don't have a schematic for this thing, > but I believe that one half of one 6AL11 is used for the oscillator. > > The problem is, the frequency decreases as the rig warms up. It will > eventually stabilize, but the final frequency is over 200 Hz low. Not as > good as it should be. I think the original specification was well under > half of that. > > I have replaced the electrolytic caps. The others are mostly silver/mica > with a few ceramics. I checked all of the resistors and only found one that > was out of tolerance (I replaced it).Three NOS tubes were installed. There > are no tunable components in the oscillator section. Only the output > section has anything tunable. > > I know that there are many Amateurs on the list and I'm sure many know more > about old tube rigs than I do. Does anyone have a suggestion as to what the > trouble might be? > > Joe Gray > W5JG > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
