[hpsdr] TAPR Hermes - Noise on Audio Out

[Ron Nelson]

Hi,

I have my TAPR Hermes working using PowerSDR, however, there is loud 
noise on the audio output independent of the RX input. The noise 
consists of  sharp spikes, 2 V p-p with a period of about 2.8 ms.  I do 
hear stations with an antenna connected, but the noise level is 
comparable to audio from strong stations.

I think I have ruled out external local sources:

Tried DC power from a switching power supply, a regulated lab bench 
supply and a battery.

Connected Ethernet to PC directly and via a Linksys router.

Tested with and without antennas. Always used 50 Ohm dummy load on Tx out.

Tried two locations and turned off all other PCs and devices nearby.

Put in the Anan case and grounded it. None of the above made any change 
to the noise.

Suggestions please?

73
Ron NR5ON