[TenTec] Crystal vs. DSP Filtering

[Carl Moreschi]

John,

What you describe is in fact not normal.  When you go to a tighter filter,
the background noise gets less and results in a better signal to noise
ratio.  You should be able to hear weaker signals with tighter filters.  But
you need to tune them in much more carefully.  Also, if you can hear high
pitched signals better, you can move PBT and go to a narrower filter to get
the center of the filter to be higher pitched.

73,

Carl Moreschi N4PY
Franklinton, NC
----- Original Message -----
From: "John Pfeifer" <jpfeifer at gci.net>
To: <tentec at contesting.com>
Sent: Tuesday, December 02, 2003 3:36 PM
Subject: [TenTec] Crystal vs. DSP Filtering


> Hello all,
>
> I've been playing around with my Omni V.9 in some QRP contests lately
where I am trying to pick out one weak signal from a bunch of  weak signals.
Everybody's running QRP and nobody is above S5.  When I crank in any
filtering below 1.8 kHz, however, all of the signals are attenuated to the
point that I can't hear anything.  I've noticed the same phenomena with my
Elecraft K1 as well.  It seems like narrow filtering only works for signals
that are S6 and above.
>
> Is this simply a function of crystal filtering?  Is there always some
attenuation occuring inside the passband?
>
> If so, do rigs with DSP filtering like the Argo V and Pegasus/Jupiter do
better with weak signals when narrow filters are used?
>
> BTW, I also notice that when I'm not using filters, it seems easier to
pick out weak CW signals when you are tuned further off frequency and the
resulting tone is higher.
>
> Thanks,
>
> John Pfeifer - KL0WN
> Kodiak, Alaska
>
>
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