Posted by
Guy, K2AV on
Aug 09, 2009; 4:56pm
URL: http://elecraft.85.s1.nabble.com/K3-Filter-Ring-with-Noise-tp3410069p3413249.html
The answer to so-called K3 "ringing" at 50 Hz is called 100 Hz.
Aggressive skirts are what allows me to hear what I want to instead of what
is just a little off my frequency. You're not going to get me to say "yea,
rah" for any lessening of aggressive skirts.
As best as I can tell, the softening of CW signals using IIR at 50 Hz is due
to normal keying artifacts being peeled off by the skirts. Yea, rah to
that. While it's peeling off the artifacts that make CW sound sharp, it's
more so peeling off the interference just a little bit farther away and
significantly increasing my wanted to unwanted signal ratio.
** Please tell me you are not going to throw that away because someone wants
their received CW to sound "broad" even though their selectivity is set to
extreme sharp. **
I would characterize the FIR as 70 and 115 Hz, and the mild increase in
"sharpness" of a CW signal as simply allowing just a bit more of the
make-break artifacts getting through due to what amounts to increased
bandwidth by the choice of shape at the top.
I can make *real* ringing on an old RX with too high a Q in the analog
crystal filter circuit. The kind that takes entire dit lengths to
decay. Those who think the K3 is ringing have obviously never heard that or
it would never occur to them to call hearing only 50 Hz of background as
ringing. Ringing is basically an analog issue unless the digital processing
unwittingly duplicates it. I use the K3's 50 Hz IIR all the time and I don't
think it rings.
If you think that the audio from the 50 Hz width sounds "pinched" then
everything is working, including your ears. 50 Hz is the DEFINITION of
pinched bandwidth.
Some folks do better at deciphering CW with wider bandwidth. That is not a
receiver issue, just a particular ham's personal arrangement of brain cells.
73, Guy.
On Sat, Aug 8, 2009 at 8:24 PM, Lyle Johnson <
[hidden email]> wrote:
> The K3 offers IIR and FIR filters for the narrowest bandwidths (100 Hz
> and 50 Hz).
>
> IIR may have some amount ringing. The disable IIR, go to CONFIG:FLx ON
> (or any other filter menu) and tap "7" on the keypad until you see IIR OFF.
>
> The K3 uses fairly aggressive skirts on its filters. We have talked
> about implementing a "soft slope" which would make heavily filtered
> noise a bit broader, but that has implications on dynamic range and
> other issues that keep it from getting near the top of the list.
>
> 73,
>
> Lyle KK7P
>
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--
73, Guy K2AV
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