The K3 APF has a very sharp peak (about 30 Hz @ 3 dB) but broader
shoulders (about 300 Hz wide). It is not in the AGC loop, so any signals
inside the bandwidth set by the bandwidth control may activate the AGC.
Therefore, if you have nearby strong signals, you should reduce the
bandwidth to keep them from affecting the signal you are peaking with
the APF.
But if you reduce the bandwidth below 300 Hz, then you will cut into the
shoulders. This starts to have a negative effect on CW intelligibility.
For some biological reason that I don't understand, the "context"
provided by the shoulders helps overcome the ringing effect of the very
narrow peak.
High noise levels also negatively impact the usefulness of the sharp
peak, because of the ringing.
73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 25/08/2020 23:49, Fred Jensen wrote:
Kevin:
1) For a K3, APF seems to be very dependent on current AGC action. If
there are very strong signals close in and the AGC is doing its thing,
APF doesn't seem to work. You can adjust the AGC parameters, however my
experience is that I use APF infrequently enough that it's better to
adjust the AGC to non-APF situations.
2) The APF will ring, it is very narrow. With APF on, using a wider
DSP BW [400 or 500 Hz] will help some. Tuning just off the peak, if
possible, can also help although even at 1 Hz tuning, sometimes that's
hard.
73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
On 8/24/2020 7:33 PM, kevinr wrote:
I have used APF a number of times. Sometimes it worked, but often the
ringing makes it hard to hear anything intelligible.
I have a two families of questions to hopefully remedy my problem.
1) What are the best band conditions to try APF? Does it work under
medium QSB against medium to high noise levels? Is it better on 80,
40, or 20 meters?
2) What are the procedures to use APF on your K3, KX2, KX3, etc.? How
should I set the bandwidth of the filter I'm already using? How do I
peak the APF performance? Does the set up change on a per band basis
or does one setting fit all cases?
As I mentioned, I have gotten it to work well a few times, but usually
the signal sounds buried in a hard walled well. Then I get emails
telling me how well it worked during ECN. My interest is renewed,
hence my questions.
Help?
Kevin. KD5ONS
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com
