----- Original Message -----
From: "John Pfeifer" <jpfeifer@gci.net>
To: <tentec@contesting.com>
Sent: Tuesday, December 02, 2003 15:36
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.
Sounds like your not tuned to the filter center i.e. you tuned to the wrong
pitch.
You cans how that with the 6.3 MHz PBT filters. If you tune a signal with
the 1.8 KHz
filter and then select 500 or 250 and the signal drops, turn the PBT control
and see if the
signal increases as you get it into the center of the filter.
> 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?
Not very much. Attenuation is present only if there was a hardware problem
or you were
not tuned properly.
>
> 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.
AH! Really have to make sure you are tuned on freq.
Sounds ike your problem may be as a rersult of your
desire to deliberately tune to a higher pitch which is the
same as saying tuning OFF frequency.
>
> Thanks,
>
> John Pfeifer - KL0WN
> Kodiak, Alaska
>
>
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