[hpsdr] Dither on Mercury-EU

[wully]

Hi all

First, I would like to add my congratulations for Phil Harman for this 
award!

I have noticed a strange behavior of Mercury-EU, which might indicate an 
individual board failure:

Antenna input with 50 Ohms terminated, no antenna. When switching on 
Dither I notice an increase in background noise level of between 7 and 
11 dB depending on the band! Typical noise value without dither is 
around -130dBm (slightly better than tapr-mercury).

Doing the same experiment on my two Tapr-Mercuries, the increase of 
noise is hardly noticable with a value of 1 dB.

Since I don't have two Mercury-EU, I can not compare.
Normally, I am running the HPSDR with Dither off, so this is only a 
"theoretical" problem, but it is interesting anyway.

Any suggestions are much appreciated.

73, Alfred, HB9EPU