Hello, I am using a 1,2m offset dish and a POTY feed. Never had that problem before with different amplifers from low power up to 70W. But now I have built an new amplifier using a Doherty transistor pallet module. I am getting increasing noise on the RX (MiniTioune Scan & Tune), if I increase the transmitting power. I don't have this with the diver stage alone, which is also good for 20W DATV. I do have a very sharp band filter (-70 dB) just before the final amplifier. And I cannot see any spurious signal up to 2,9 GHz on the HP spectrum analyser. Shoulders at 75 W output are at 30 dBc. The signal on the WebRX is very clean and I can produce a 16APSK signal at 15 dB without shoulders. I don't have an increase of noise on my nearby 85 cm dish, while I am transmitting with the bigger dish.
So, what can it be? I don't have oscillations, I don't have a spurious emission on 2,6 GHz. The only difference to the other amplifiers is, that this one is a Doherty type. The operating point of the transistors are correct according to the data sheet and changed only a little bit to increased linearity, but without any change to this noise problem.
Has anyone had this problem before or has some idea what I could check?
73 de Gerhard OE3GBB