I'd agree. My experience with APF is that it will indeed pop a signal that is already copyable, if a bit weak, out of the noise. Makes for easier copy. However the ringing is so bad on a really weak signal that it is of no help. I guess it depends on what you view as 'weak' and your noise level. I was hoping it would make previously un-copyable signals copyable, but that does not happen. Instead it improves the copyability of weak but already copyable signals.
I find that simply narrowing the filters to 50, 100, or 150 Hz will give essentially identical results as using the APF and is much easier to do.
As for the super critical tuning, I do not find it to be all that critical. The signal can be improved somewhat by going to the 'fine' tuning, but it makes only a small difference. 10 Hz steps are OK and much quicker. The APF has a BW of about 30 Hz so tuning cannot be all that critical. +/- 5 Hz out of 30 is not that big of a deal.
This has been one of my biggest disappointments with the K3. After reading all the hype about APF I was hoping for a real improvement. But does not happen. OTOH, the narrow filters of the K3 are outstanding.
73 de dave ab9ca/4 On 2/5/16 8:53 AM, David Kuechenmeister wrote:
I tried this the other day with no success. That is, the weak signal that was barely detectable, became so buried in ringing that I couldn't detect it at all. I think I followed the procedure outlined in Wayne's email below... Noise was around S5 on 40m and the K3 was configured with APF active. I had my 500 Hz filter selected and varied the DSP WIDTH from 500 to 300 without substantial improvement. FINE tuning selected. What am I forgetting? vy 73,Dave N4KD On Tuesday, February 2, 2016 9:36 AM, Wayne Burdick <[email protected]> wrote: Hi all, This morning I was hearing lots of very weak signals in the 40-meter CW band, right at today's noise floor of about S-5. (Among others, I copied BG4GOV in Shanghai.) Many of the signals were not copyable until I turned on APF (audio peaking filter). This filter's center peak is very narrow (around 30 Hz), but the response broadens out quickly below the 3-dB points in the curve. This brings up the desired signal without allowing noise to cause ringing--something often heard with narrow filters of the "brick-wall" variety. On a noisy band, the effect is just short of magic. APF is very narrow, so you'll need to tune in 1-Hz increments when it is turned on. Also, APF works best when used with a DSP/crystal filter WIDTH setting of 300-500 Hz. Use of APF differs for the three transceivers. KX3: 1-Hz tuning is selected automatically on the when the APF switch is pressed. K3/K3S: APF is accessed via a hold of the XFIL switch. This function is labeled "APF" on a K3S, or "DUAL PB" on the K3). Use CONFIG:DUAL PB to make sure the selected filter function is APF. See the K3/K3S owner's manual for a description of the alternate setting. 1-Hz tuning can be selected by tapping FINE. You might want to give APF a try if you haven't already. 73, Wayne N6KR ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] .
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