[hpsdr] Noise in digital RX modes?

[John]

It has been seven months or so since I operated JT65, but recent 
encounters as a beginner with FLdigi revealed what could be a problem 
in the software.  ***However, it could be something else I have changed.***

I am running the latest firmware and OpenHPSDR software with 
Hermes/Alex/Penny Whistle.  Operating system is Windows 7 Pro 64 and 
VAC is used to connect audio to Hermes.  Observing the JT65HF 
waterfall and in DIGU I notice quite a bit of noise on the JT65HF 
waterfall  centered about 600 Hz below the reference zero.  The band 
of noise does not increase in width if I use Var 1 or Var 2 controls 
to increase the bandwidth.   The display is the same in DIGL.  There 
is no matching indication of noise on the Hermes panoramic display.

In FLdigi this same band of noise is centered about +700 HZ.

This band of noise is present with no signal shown on Hermes 
panoramic display.  When I disconnect the antenna the displayed 
intensity of the band of noise as shown on FLdigi is much less.

I never had a problem like this with JT65HF before.  The band of 
noise seems to act like it is just the bandpass of  Hermes.  It does 
not change as the VFO frequency is varied.  What is different is when 
I try to vary the bandwidth the width of the noise (as displayed on 
JT65HF or FLdigi) does not change.  Using FLdigi, it does go away 
with the 1.0 kHz filter (or narrower) in DIGU.  In DIGL it is present 
with the 3.0 kHz filter but goes away with the narrower filters.  I 
can also make the band of noise go away with the shift slider.  When 
I do that there is some indication the pass band has moved, but it 
doesn't seem as though much is getting through.

Has anybody noticed a problem like this?  I have made a number of 
changes to my station in the last few months, but I am at a loss to 
explain what I see.  Therefore, I'm wondering if recent changes have 
affected the selectivity in DIGu and DIGL modes.


Best regards,

John,  WoGN