Re: [K3] Attenuator and soundcard digital modes

Posted by Don Wilhelm-4 on Jul 06, 2011; 12:02am
URL: http://elecraft.85.s1.nabble.com/K3-Attenuator-and-soundcard-digital-modes-tp6552276p6552403.html

  Don,

What is your specific problem?  If it is strong signals within the
passband, then more narrow roofing filters are the answer.  Instead of
using the entire 2.7 kHz bandwidth and depending on the software
application to resolve any one signal, use the K3 filtering to zero in
on a specific signal, and you will find the decoding much better, with
or without the presence of noise.

Yes, what I am suggesting is that you first reduce the bandwidth of the
K3, and then the PSK31 software has fewer signals to deal with, and can
decode them better.

I know that most PSK31 operators just use the full SSB bandwidth and let
the software resolve the signals.  While that works when all those
transmitting PSK31 keep their power down to a reasonable level, there
are those few who insist on being "band hogs", and transmit at 100 watts
plus.  PSK31 can be very effective when used at 15 to 25 watts, and many
do keep it at that - but Special Events and contests, I find that some
crank up the power, and decoding for everyone else on the band suffers.

The K3 with its roofing filter selection and DSP filtering can help
greatly, but to take advantage of that, one must reduce the bandwidth of
the K3, and that means not using the full spectrum waterfall display --
use the K3 VFO to move from signal to signal, and your decoding will be
greatly improved.

73,
Don W3FPR

On 7/5/2011 7:39 PM, Don Putnick wrote:

> After having a less than successful time with PSK31 during the 13 Colonies Special Event, I think I need to learn more about noise reduction. I've read the section in KE7X's manual, but I'm looking for guidance specific to the soundcard digital modes.
>
> 1) It appears the K3's attenuator is fixed at -10 dB. Is that the case or is it reprogrammable?
>
> 2) What is the collective wisdom on noise reduction for soundcard digital modes: K3 attenuator, K3 noise reduction, PSK31 software noise reduction, some combination of the three, or none at all?
>
> Thanks and 73,
> Don NA6Z K3 #5495
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