The receiver has to be tuned precisely to the signal in question for APF to work.
73, Barry N1EU On Fri, Feb 5, 2016 at 9:53 AM, David Kuechenmeister <n...@bellsouth.net> 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 <n...@elecraft.com> > 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: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 n...@bellsouth.net > > > > ______________________________________________________________ > 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 n1eu.ba...@gmail.com > ______________________________________________________________ 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
