Dittel FSG71 Radio / Squelch Questions

All,

My radio (Dittel FSG 71) Squelch seems to be a bit sensitive (but by design, cannot be adjusted by the pilot). In my case, when flying, the squelch is a bit sensitive and the “white noise” of the radio comes on at times, even when there are no communications received. I can always reset the Squelch by pressing and releasing the PPT button. The radio then goes silent for a while until a real transmission is received, or until the sensitive squelch problem reappears. I cannot reproduce the problem on the ground.

I have noticed that the problem gets worse when I connect my PCAS MRX to the 12V bus of the aircraft. The problem is not as bad when I run the PCAS off AA batteries. I have also a vario+pda connected to the same 12V battery bus.

- Can the Dittel FSG71 squelch be adjusted internally? (it can not be done externally via a knob)
- If my other equipment connected on the 12V creates noise, can I install a capacitor between the power leads going into the radio to reduce the noise?
- What else could be the source of this nuissance?

Thanks,

Bastoune

Note: I have another radio related question but will post it separatly.