[Elecraft] K3 Filter Ring with Noise?

[Steve Ellington]

Edwin
You did a wonderful job explaining exactly what I've noticed. To me, it 
seems as if the noise mixes or blends with the cw and at times blips out cw 
characters. This only happens when signals are weak and the band is noisy. I 
recently came across an older TenTec Jupiter which has very wide skirts and 
virtually no roofing filter (15kHz). The same noise has no effect on it. I 
have done dozens of A/B test and the Jupiter always comes out the winner 
until someone with an S9+30 signal gets within the roofing filter's 
bandpass, like 6kHz away, and pumps the hardware AGC violently. Then it's 
all over and I either switch back to the K3 and suffer poor copy or just 
QRT.
I've tried all the EQ settings, NR (which helps) and AGC settings to no 
avail. I don't consider this "ringing" since that's not what I'm hearing.

Steve
N4LQ
N4LQ at carolina.rr.com
----- Original Message ----- 
From: "Edwin Johnson" <kd5zlb at gmail.com>
To: <elecraft at mailman.qth.net>
Sent: Saturday, August 08, 2009 3:34 PM
Subject: [Elecraft] K3 Filter Ring with Noise?


> 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
> ____________________________________________________________
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