I use the APF in my K3 all the time. The wide base with a sharp
peak are very helpful for CW intelligibility. I would like the peak to
have a little more gain, though. Maybe it could be adjustable in the K4?
73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 16/05/2020 1:11, Wayne Burdick wrote:
CW ops, especially those doing weak-signal DXing and DXpedition work,
will now benefit from a second APF filter bandwidth in the K4. The
original bandwidth is 30 Hz, which is good for code speeds up to
about 30 WPM. The second bandwidth selection is 50 Hz, which allows
copy up to about 50 WPM.
On the air, I'm finding this a great addition to the receiver
toolbox, especially for close-spaced, fast CW contests. Adjacent
signals just seem to disappear.
APF has a narrow bandwidth only for the first several dB from its
peak, then flares wider below that. This can dramatically improve S/N
for weak signals right at the noise floor: it brings up the signal
without "boxing up" band noise into a very narrow bandwidth. That's
what causes ringing with "brick wall" filters.
73, Wayne N6KR
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