[Amps] Low pass filter in transmitter audio in

[tzikas tzik]

Hi i have a transmittre. I would like to put a low pass filter with Fc about
100khz or lower in transmitter's audio input to cut off the R.F witch is
collected from 20meters audio coaxial cable and it is causes problems to my
pll. any schematic? I can not design a filter for this use because the input
and output are not 50ohm.

callsign: sv1bln
Athens