Tree wrote:
http://www.kkn.net/~tree/160/3b7cQSO.mp3
MP3 is probably not a good choice for critical evaluation of the audio
of a DSP based system, as it involves heavy additional DSP to produce
it. In particular, MP3 works by limiting close in dynamic range
(because the ear cannot hear weaker sounds close to a strong one), so
weak signals which are close to strong ones will be reproduced with
worse resolution, or lost. (It's a bit more complex than that as it is
done on frequency blocks.)
It's also a block based encoder and, although I'm not sure, it is
possible that it loses phase information and fakes wideband noise. (I
presume it must retain low frequency phase information, for stereo to
work, but I don't know if it encodes I and Q in all frequency bands or
whether it falls back to just power at the higher ones.)
Even if it retains phase, I wouldn't expect it to reproduce multi-tone
or, in particular, noise like digital modes well, and if you can hear
subtle DSP artefacts in the K3 you can probably hear those resulting
from MP3 encoding.
Unfortunately, doing an extra A to D / D to A pair is inevitable, given
there is no digital output, but it needs to be done at a carefully
chosen sample rate.
--
David Woolley
Emails are not formal business letters, whatever businesses may want.
RFC1855 says there should be an address here, but, in a world of spam,
that is no longer good advice, as archive address hiding may not work.
_______________________________________________
Elecraft mailing list
Post to: Elecraft@mailman.qth.net
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
