[hpsdr] Pennywhistle bias control failure

[Chris Smith]

Hi

I've just had my first component failure with any HPSDR board. Q3 on Pennywhistle has died in a strange mode. Without the gate grounded the gate & drain are at approx +8V. With the gate grounded the drain is at approx +9V. The result is that bias is always applied to the PA FETs and subsequently PW 's heatsink gets quite hot.

I guess that unless there is some stray  RF getting into the input of PW this won't have a detrimental effect - just waste power.

Another problem I'm having is RF getting back into the mic input on 20M and above. I made a (grounded) metal plate with sockets for phones, keyer & mic/PTT so that I could locate all these conveniently away from Pandora. Despite using screened lead for the mic I can't prevent RF getting into the mic input. Strangely this doesn't appear on the phones when I select MON on PowerSDR. I'm thinking of going back to a direct mic connection to Penny and bypassing my plate. Anyone got any ideas?

BTW is there an optimum impedance for the mic? I had been using a cheap headset with electret boom mic and this worked OK on all bands. Since relocating all sockets to my plate and rejumpering Penny to remove electret bias, I'm using a moving coil mic with 200 ohm impedance.

Cheers & 73

Chris G4NUX