I have a problem with my 83650L synth. It seems to be ok up to 20.000 GHz but from 20.001 GHz and up the output power is unleveled and drops down significantly. At 20.001 GHz max output power is about -14 dBm and it goes down to below -100 dBm at 40GHz. The built-in selftest says that everything is working properly, but obviously this is not the case. I have access to the trouble shooting guide and the service guide for the 8360 sweeper series but i would appreciate any good ideas where to start looking for this failure. My initial guess after having a look at the block diagram is that it could be one of the amp/multiplier modules on the RF DECK, but this is so far just a guess. I have not measured anything yet. I hope the very abrupt power drop above exactly 20.000 GHz could be a hint what the problem might be for some person experienced with repairing 8360 sweepers.
83650L has different frequency bands that switch to different YIG oscillator harmonics to get the higher frequencies... 20 GHz to <26.5 GHz switches to the YIG 4th harmonic; RF out should be +10 dBm 26.5 to <38 GHz it switches to the 6th YIG harmonic; RF out should be +5 dBm 38 to 50 GHz it switches to the 8th YIG harmonic; RF out should be +2.5 dBm