[hpsdr] Hermes Intermittent Problem

[John Ackermann N8UR]

(Resend as first try was too large to get through)

I am suddenly having intermittent problems with my Hermes.  It has 
firmware 3.1, and I am using PowerSDR 3.2.24 (recently upgraded from 
3.2.21).  I've reset the database multiple times, and that doesn't seem 
to have any effect.

I am experiencing intermittent distortion where it sounds almost like 
listening to CW or SSB with an AM receiver -- CW loses its beat note, 
and SSB sounds very distorted and raspy.

When this happens, the spectrum display changes to show a 
higher-than-normal noise floor, with a series of sharp nulls across the 
displayed spectrum.  I've uploaded two screenshots showing the display 
when this happens to http://www.febo.com/pages/hpsdr/hermes/

I can't figure out what causes it to occur; sometimes it's there when I 
power on, other times it happens after several minutes.  I don't believe 
it's heat related, but I can't definitely rule that out.

I've been using this radio for a couple of years with no previous 
problems, so this has me stumped.  I've removed all external connections 
other than antenna and headphones to track down ground loops, and that 
hasn't made any difference.  I'm using the internal frequency reference.

Any suggestions would be appreciated!

Thanks and 73,
John