[Elecraft] DSP Unit and PSK31 and other digital modes

[Bob Nielsen]

On Wed, Apr 07, 2004 at 01:11:14PM -0000, Robert McGwier wrote:
> It would be inappropriate to use the LMS noise canceling in the
> DSP option on PSK31.  I don't have mine yet so I can't tell you if it will
> dial in narrower filters that are straight bandpass (not adaptive)
> filters, but the KDSP2 page seems to imply this.  Unfortunately,
> the KDSP2 pdf file for the manual is no longer available for
> download on that page.  If you can dial in a narrowband FIR filter
> (bandpass) with the DSP unit, this will not likely hurt PSK31 and will
> likely
> help so long as you do not get it too narrow.  200 Hz given what
> I think would be likely filter lengths is the narrowest setting
> I would use on PSK31.  The issue with using narrow audio filters
> is the AGC level before the audio filter sets the level of the
> signal following the filter unless this is compensated for in
> the DSP audio filter.  You would see this is a strong signal inside
> your IF bandwidth, set by the K2 IF filters, resulting in a
> pumping of the level of the signal coming out of the KDSP2 audio
> filter.
> 

Bob, 

I just checked the Elecraft web site and the KDSP2 manual is still
there <http://www.elecraft.com/manuals/KDSP2_A1.pdf>.  The only
adaptive filters provided are for the autonotch and denoiser functions;
FIR filters are used for the bandpass filtering.  Lyle included a brief
discussion of DSP filtering as part of the manual.

73, Bob N7XY
K2 #3273, KDSP2 Field Tester

-- 
Bob Nielsen, N7XY                          n7xy (at) n7xy.net
Bainbridge Island, WA                      http://www.n7xy.net