[Milsurplus] Crystal Oscillator Vexation/TDQ
Rob Flory
robandpj at earthlink.net
Wed Dec 26 13:26:46 EST 2007
Hi All,
I have never had such a frustrating experience as I am having with my TDQ transmitter. The oscillator was hammed up a bit, so I restored the circuit to its original configuration, but I am not sure of the values of the components.
The oscillator won't drive the first tripler. DC values look good, with 200V on the screen and 250+ on the plate of the 807 oscillator, which runs a 3rd overtone crystal at 16Mc(5.3 crystal frequency). I've tried 50k, 100k, and 150k for crystal load resistance. 20 and 100pF for feedback cap. Looking at the plate circuit with a scope, I can see the 5.3Mc and 10.6Mc overtones but not 16mc. Tuning the oscillator plate tuning results in a plate current peak at 10.6Mc. Nothing at 16. When I put a 7Mc. crystal in, I can get an Ip peak at 14Mc, and no joy at the tripler either.
The grid circuit of the 1st tripler seems alright. I've tried replacing the 807 oscillator and the 829 tripler.
Any suggestions? Schematic available on request.
73, Rob K2WI
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