DIYbanter - View Single Post - RC transmitter transmits on first harmonic

[email protected]

wrote:

I've got a JR 72 MHz transmitter module that was transmitting a very
weak signal on the correct frequency. I replaced the power transistor
and the module worked for a few minutes, but now it transmits a very
strong signal on 144 MHz. There is no signal being transmitted on 72
any more. I imagine I've got to get the crystal back into its
fundamental mode but I could use some hints. Does anyone have a service
manual or schematic for the module?

A 2m RC system would be really neat but I don't think it'll be easy to
find a receiver.

2nd harmonic, 1st is the base frequency! IIRC 144 is ambulance service
band, here at least, so maybe not so neat. Need to show us the
oscillator circuit, otherwise can only say the osc cct needs to be
tweaked so it prefers the lower frequency. Can probably be done with a
little capacitance added to reduce closed loop gain at 144.

NT