50 Mhz Transmit Module.

[pbunn]

I am looking at building a 50Mhz RF deck mostly for fun. Does anyone know the actual crystal frequency that futaba uses in their module. Is it an overtone type on 50 mhz or is it doubled in the RF driver?

Thanks for any help.

[Bruce Abbott]

The crystal must operate in fundamental mode, but I don't know whether it is tripled or quadrupled to get 50MHz. One way to find out would be to obtain a Futaba 50MHz FM TX crystal, put it into a fundamental mode xtal oscillator (eg. this Crystal Test Circuit (http://www.zen22142.zen.co.uk/Circuits/Testgear/crystal.htm)), and measure the frequency.

[pbunn]

My guess is that it is quadrupled as a 17 mhz fundamental crystal is harder to make - but i'll check the one that I have in my module. I have a crystal tester somewhere around here that I built years ago for matching crystals for filters.

BTW - Thanks again for the switch software - It made a great compact opto isolated glow driver with a 12C508 - about the size of a postage stamp - good for near 5 amps. My son used it this weekend.