[hpsdr] PowerSDR 'ATT on Tx' doesn't work with digital step attenuator selected

[Dick Lichtel]

I've got a problem with a the RX ADC overloading on Tx for 15/10/6M.  
Selecting the 'Attn On TX' with the Hermes digital step attenuator 
selected, does not change the attenuation while transmitting.

If I use the Mercury style attenuation, I see a 20dB attention when 
transmitting, which fixes my problem.

I'm using the latest 2 RX version of PowerSDR.

Dick KD4JP