Speaking to the narrowness of filters for
CW; I recently had an issue with my K3s
which has the dual Rx and a full
compliment of filters with 200Hz the most
narrow in the main & Sub Rx receivers. I
sent it for repair and used my backup K3
which has been upgraded to essentially a
K3s with the exception of the newest PA
and tuner. The backup K3 has only a 2.8
filter and for the closer filtering, I had
to use the digital filter.
I did very well with the K3 in DX contacts
but in the CW contest & on 160, I had a
different experience. I could hear
everything but the selectivity was nowhere
near as good as with that 200 Crystal
filter in line. I use the Audio Peak
feature with faint CW and that helps
markedly in weak signal conditions.
When I got the K3s back I really
appreciated again having the tightest
filter and using the audio peaking
function, I was able to get narrow enough
reception that I was usually able to pull
a weak DX from under QRM on their Tx
frequency. Add then the diversity mode in
and the K3s and it magnified my hearing
capability but I'm just speaking to the
narrow filter being by far, my choice of
filter for any CW reception. My digital CW
filter is always at 50Hz.
Maybe there's something even better
setting-wise I'm unaware of, but I thought
I'd share my experiences
73,
Gary
KA1J
<Snip>
> But also note that there's a lot of reasons why an operator might not
> want to use a narrow filter for CW.
>
> Especially on the low bands, in the face of lightning crashes, many of
> us prefer to use wider bandwidths. In part this is because
> historically many rigs had narrow filters that rung like the dickens.
> (This was the trap of "shape factors" as a selling point for a few
> decades). But even with modern rigs with more optimal phase response a
> lot of us are more comfortable especially putting in long hours with
> wider rather than narrower filters.
>
> In VHF/UHF and EME weak-signal CW work, a lot of operators also liked
> listening with wider RX filters too, often preferring Gaussian filter
> shapes, and letting their ear pull the signal out of the noise.
>
> The psychoacoustics of listening to narrow bandwidths for extended
> periods leads to a lot of these preferences. There's an "acoustical
> paranoia" that sets in if you listen to noise too long with a narrow
> bandwidth and don't change things up (bandwidth, center frequency,
> something!) at least occasionally. When you find yourself in that
> paranoia it seems like the signal you are trying to hear is exactly
> the same shape and bandwidth of your narrow filter.
>
> And finally: one man's noise is another man's signal. Or even a Nobel
> prize. This is the story of how NBS scientists unintentionally
> discovered radio emissions from Jupiter by tracking down their noise
> source: https://www.nist.gov/news-events/news/2017/08/field-dreams
>
> Tim N3QE
>
>
> >
> >
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