[Moon-net] Disabling/Protecting a preamp

[Koellner, Guenter (NSN - DE/Muenich)]

Hello all,

with interest I followed Trevor's problem about the destroyed preamp. For luck, I do not have the same problem, but I probably will run into a compareable situation...

For 9cm, I want to use a former C-Band LNB as feed. It already has 62mm diameter, well matching to become equipped with a septum plate for circular polarisation. As far as I know, the 2 stage preamp consists of an NE32584 (marked "D") and another device marked with "K". Assuming that my power will be about 50W and the cross talk about 25dB (worse case), there might be somewhat 100mW at the other port. As for every LNB, there is no protection relay.

In the past we have learned to leave power applied to the preamp for better protection, now
I am asking if it would be sufficient just driving the gate as far as possible to negative, say about -2V, in order to protect the preamp?

73, Günter (dl4mea)