[Elecraft] DSP impressions

[George, W5YR]

DSP NR is becoming fairly common now, but is still a relatively new tool for
most hams. We are so used to cranking down on the bandwidth when the noise
offends that we haven't yet developed the habit of going the other way when
using NR.

Probably a good operational approach to this is to employ NR with the widest
possible IF bandwidth and then to use an outboard DSP audio filter to gain
some bandwidth reduction for QRM-fighting purposes. This is, of course, the
K2 DSP approach.

Not the best solution since it puts the selectivity outside the AGC loop(s),
but better than losing NR capability altogether in order to get around the
QRM.

I know a lot of guys using true IF DSP radios for the first time that fall
in love with that 100 Hz filter setting because it eliminates so much band
noise. But under really rough conditions, choosing that bandwidth pretty
well cripples the NR if it is needed as well. Especially, if that narrow
filter rings on noise excitation . . .

Hope this helped a little and was interesting to you and others, Vic.

73/72, George
Amateur Radio W5YR -  the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"In the 57th year and it just keeps getting better!"
<mailto:w5yr@att.net>





----- Original Message -----
From: "Vic Rosenthal" <vic@rakefet.com>
To: "George, W5YR" <w5yr@att.net>
Cc: "Wolf-Ruediger Juergens" <WJuergens@t-online.de>; "Elecraft List"
<elecraft@mailman.qth.net>
Sent: Sunday, August 10, 2003 2:56 PM
Subject: Re: [Elecraft] DSP impressions


> George, W5YR wrote:
>
> > Wolf has the right idea: use the widest bandwidth you can tolerate in
order
> > to give the NR the most noisy noise to work with. Don't expect it to do
much
> > when you narrow the bandwidth way down. That is another approach to
> > improving S/N but the two are almost mutually exclusive when one
attempts to
> > use it with NR as well.
>
> VERY interesting.  I have found myself using wider bandwidths since
> getting the DSP, and now I understand why.  Before installing the DSP, I
> was often reducing the bandwidth to improve the s/n ratio and only
> rarely to eliminate QRM.  I guess that for the kind of noise I seem to
> be dealing with, the DSP approach is more effective.  I think I will
> rethink my crystal filter b/w settings in the light of this.
>
> 73
> Vic K2VCO