Dave G4AON wrote:
Members of the RSGB may wish to sneak a preview of the December
RadCom article on SDR where the authors compare a K3 with a HPSDR
Mercury receiver and explain why the SDR sounds better than the K3
(noise through a crystal filter causing phase changes).
I've read the article and it is really comparing two types of SDR
receiver, rather than SDR and analogue.
The type they are claiming the benefit for is one in which digitisation
is performed at signal frequency. The other type is the design used by
both SoftRock and K3, in which the signal is first mixed down before
being digitised.
The sort of noise they are talking about is impulsive noise,
specifically atmospherics due to global lightening. A filter with
non-constant group delay will turn these from clicks to chirps.
It is possible the SoftRock will do better in this respect, because
typical sound cards have a constant group delay anti-aliasing filter.
http://www.rsgb.org/membersonly/radcom/techfeatures/sdr_1208.pdf
</div>
--
David Woolley
"The Elecraft list is a forum for the discussion of topics related to
Elecraft products and more general topics related ham radio"
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