It really does make a difference on some signals, even on the K3 and KX3, especially when there's a lot of band noise.
73, Wayne N6KR On Jun 26, 2012, at 12:17 PM, Andrew Faber wrote: > Wayne, > I was pleased to see the APF added to the K3, though I think it is > not as useful on radios with such good basic filtering, as compared > to older radios. OTOH: it's a favorite feature of my old FT1000D! > 73, andy ae6y > > -----Original Message----- From: Wayne Burdick > Sent: Tuesday, June 26, 2012 11:19 AM > To: [email protected] > Cc: Elecraft Reflector > Subject: [Elecraft] K3/KX3 Operating Tip: APF (audio peaking filter) > forweak-signal CW work > > Both the K3 and KX3 have an APF control (audio peaking filter). APF > can be extremely effective when you're trying to copy weak CW signals > buried in noise. > > Most DSP filters have very steep skirts; they're often referred to as > "brick-wall" filters for this reason. This is the type of filtering > associated with the WIDTH control (K3) or PBT control (KX3). > > In contrast, the APF is a filter with a very narrow peak (about 30 Hz > at the -3 dB points) and very broad skirts. The narrow peak brings up > the signal amplitude slightly, while the broad skirts prevent noise > from being amplified and delayed in such a way as to dominate the > signal. The APF function used in the K3 and KX3 is a modern DSP > reinterpretation of the hardware APF circuit found on some legacy > transceivers, which was very effective. > > On the KX3, the APF switch is labeled "APF" (tap), while on the K3, > it's labeled "DUAL PB" (hold). The K3 actually provides two different > special filter functions; use the DUAL PB menu entry to set up the > switch for APF. > > When you turn on APF, the DSP graphic changes to remind you of the > nature of APF, with its narrow peak and broad skirts. > > I suggest setting the passband width to about 250-300 Hz when using > APF. The DSP graphic still shows an approximate representation of the > width even with APF turned on. > > 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 ______________________________________________________________ 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
