I was suspecting my 2m Landwehr was having problems one day, don't know when it really started having problems, but last night I checked it out. Last night when I was listening to AO-7, when I turned the pre-amp on I got about S 7 of noise and the signals from the satellite were buried in the noise, and I couldn't tell that the signals were boosted much, but I could still hear them with difficulty through the noise. Turning the pre-amp off made hearing the signals easier, due to lack of noise. Obviously since I could still hear stations, RF is still going through the device. Checking it out on stronger fm signals, did seem to amplify them more, but I could tell there was still noise.
I don't know much about gaAsFet's but what I guess I'm asking, is when they Fail, could they fail in the noisy position, or when then they fail do they die with no amplification? I guess it could be possible some other component around the gaasfet failed making the device run wild. Maybe dirty relay contacts? The RF sensor still works still works fine.
I won't be able to get my hands on it for a while as there is too much snow on the roof yet, and I don't have weak signal noise generators to try to isolated the problems. Landwehr gives you a schematic but they didn't like to reveal too much. The pre-amp is about 16 years old. My 70cm Landwehr which is the same age and gets much more use is chugging away just fine. The 2m pre-amp is under an eggbeater. I don't need a 2m pre-amp on LEO's with the beam.
Give me some things to check, Thanks, 73 KB7ADL