The ideal goal for these digital modes is to move the
actual decoding of these signals directly to the DSP.
By doing so you eleiminate the introduction of
distortions by the D to A process, a chain audio
amplification, lenghty (relatively speaking) audio
leads potentially picking up noise, a D to A process
(in the computer) and then finally decoding the
signal. Bottom line is digital modes like PSK31, WSJT,
etc. should be handled natively in the DSP circuitry
of the radio itself. Or equally well feed the D to A
digital stream out of the radio to the computer for
processing. There is no good reason to make all of
those conversions to and from the digital realm
several times. The audio output is really only good
for monitoring purposes of us humans.
Duane
N9DG
--- Ken Hopper - Amateur Radio N-9-V-V
<n9vv@wideopenwest.com> wrote:
> Dear Mark and the group,
> I am confused about this. Can you help me out? I
> thought the strength of
> PSK (and MFSK) was in the DSP filtering done at
> 31.5hz by the SOUND CARD
> and the front end RX didn't really matter. For
> example the PSK-20
> (PSK-80 Warbler, PSK-10) is purposely a BROAD BAND
> receiver and works
> like gangbusters on PSK. I certainly agree that some
> receivers exhibit
> very bad desensitization when in the presence of a
> S9+ PSK signal nearby
> (make that PACTOR signal nearby :-) but programs
> like HamScope 1.5 have
> a NOTCH filter and BANDWIDTH filter that knock out
> the offending sigs.
> PSK-Deluxe shows more than 40 signals at once on my
> display (outstanding
> freeware) and it _relies_ on broad banded RX.
>
> So does the bandwidth of the RX matter on PSK? or is
> it something
> mysterious like Dynamic Range and AGC?
>
> TU,
> de ken n9vv
> http://www.n9vv.com/psk31resources.html
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