by mvs sarma » Mon Jun 20, 2011 5:53 pm
Please indicate which make display, did you use. Replace the potentiometer used for contrast, by a single diode 1N4148, cathode facing Gnd and anode connected to pin3.
perhaps the sample level of frequency fed into FLLs too high, please reduce it.
Use always a screened cable to connect the signal to FLL circuit, after attenuation inside the Rx or Tx osc unit.
Ensure that the 12V DC used is pure and not having high Carrier level.
the best is to use a choke in series with +12V line as you know. You may place one 0.1 cap across pin1 and 2 of the LCD display module.
the above precautions should work well
Regards
Sarma