K3 Filter Ring with Noise?

Posted by Edwin Johnson on Aug 08, 2009; 7:34pm
URL: http://elecraft.85.s1.nabble.com/K3-Filter-Ring-with-Noise-tp3410069.html

I've had my K3, which I assembled, about a month, outfitted with 13kHz, 6kHz,
2.8kHz, and 400Hz filters. Thus far I've been exceptionally pleased with all
aspects of the rig. I've read with interest the audio discussions of this
group. There is one area in which I'm not totally satisfied, but this may be
due, partially, with my expectations of the rig.

When using CW on noisy bands, meaning the sort of atmospheric noise we often
are having now (NOT static crashes from storms), there appears to be an audio
product as the bandwidth is narrowed which is annoying to my ears, which
occurs both in speakers and phones. This is basically like a ringing of the
filters and especially evident as the passband is narrowed to 50-150Hz. This
phenomenon is not a problem in quiet conditions nor if the station is
especially strong, but can overpower a very weak station. (I'm using a pitch
of 600Hz for CW.)

(I've tried eliminating the 400Hz filter to make certain there isn't a
problem there, and all is well with that filter, apparently.)

I've been reducing RF gain and sometimes widening the passband to help
aleviate the problem, as well as using the NR. I've also modified the RX
equalizer from flat to settings of: #1=0, #2=3, #3=3, #4=-1, #5=-4, #6=-5,
#7=-8, #8=-10. Admittedly, part of these settings accomodate SSB to give,
what I hear, as a very pleasant sound for that mode. The primary ranges of
this noise are affected mostly by filters #4 and #5.

If the RX equalizer settings remain flat, hence 0, the sound is even more
annoying. But remember this is really only in noisy conditions, so my
hypothesis is that the chaotic sounds in the noise are mixing to produce
what sounds like a ringing of the filters. (So not necessarily the filters
actually ringing, as we think of it.) But this makes working very weak
signals very difficult without widening the passband quite a bit.

So, guess I would like to hear comments regarding this, as well as settings
and techniques people use to combat this phenomenon.

73 ...Edwin, KD5ZLB
____________________________________________________________
"Once you have flown, you will walk the earth with your eyes
turned skyward, for there you have been, there you long to
return."-da Vinci http://bellsouthpwp2.net/e/d/edwinljohnson
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