[hpsdr] Dither on Mercury-EU

[Walter Schellenberg]

Dear Alfred,

My measurements of the effect of Dither (and also of Random) in 2009 on a
TAPR-Mercury show an increase of the noise floor of about 4dB, see
http://openhpsdr.org/wiki/index.php?title=Mercury_-_intermodulation_(IMD)_te
sts .

Best 73 de Walter HB9AJG 

 

Alfred wrote:

> 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

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