I suspect that when the K3 APF was first engineered, the Yaesu FT-1000D APF (original hi-Q version) was used as the model because many prominent dx'ers/topbanders always raved about it.
73, Barry N1EU On Fri, Feb 5, 2016 at 12:37 PM, Scott via Elecraft < [email protected]> wrote: > > In the last month of listening to really weak signals here in 9 land I've > found it helpful but not radical. > > Just for fun I tried tuning some of the same VP8SGI signals on a Drake > 2B/2BQ and found adding the 2BQ in the mix more user friendly and making a > bigger difference, but hey, the 2B was starting from a worse spot. > > Still it would be nice if the APF was user adjustable like the 2BQ or the > old outbaord audio filters, peak magnitude, and maybe even frequency, > within > a selected passband. > > Not sure why Wayne picked only 3 db - I'd like it to be user adustable to > try a bit more peak if conditions permit. > > If APF is user adjustable in that way and I missed it somebody please > point out the page number....or if the experiment's been done and it's not > workable would like to know that too. > > 73 Scott ka9p > > > > In a message dated 2/5/2016 11:08:53 A.M. Central Standard Time, > [email protected] writes: > > > > one must also discover the > > artful use of the RF Gain control as well > > Adjustment of the RF gain control is not mentioned in Wayne's note on > using APF. > > When I tried it here, the RF gain might have made some small > difference but it still did not allow un-copyable signals to be > copied. When testing APF I have made all adjustments the I thought > might affect signal quality. IIRC correctly I also tinkered with the > AGC parameters. But the APF never produced results any better than > simply narrowing the filters. Usually the regular narrow filters > worked better. I know I had not switched APF on for months. I did > switch it on to recheck before sending my note. But the noise is not > currently high enough to give it a good test. > > I have found, in general, that careful adjustment of the RF gain > control can be useful. This applies to all receivers I have tried it on. > > I'm wondering if the difference is in the type of noise. I have mostly > tried APF at times of high lightning activity. I think we in the SE > get more of that than other parts of the country. The higher noise > level means more weak signals. You need all the help you can get. But > that noise differs from the usual band noise. > > And it may depend on each individual's hearing. > > I have always puzzled over why some rave about how great APF is while > for myself, and obviously others, it is of no help at all. > > 73 de dave > ab9ca/4 > > > > On 2/5/16 10:13 AM, Bob McGraw K4TAX wrote: > > While I find the APF works really nice, one must also discover the > > artful use of the RF Gain control as well. Most hams seem to use > > excessive RF Gain which will force noise through the filter and all of > > those undesirable artifacts will be heard. If in doubt, reduce the RF > > Gain. > > > > Using this technique, I can tune the band with the APF engaged, > > adjusting the RF Gain a bit, and actually hear signals with this > > configuration which without the APC no signal could be heard. I view > > this gives one the ability to actually "dig signals out of the noise". > > > > 73 > > Bob, K4TAX > > > > On 2/5/2016 9:56 AM, dave wrote: > >> > >> 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] . > >>> > >> ______________________________________________________________ > >> 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] > > > ______________________________________________________________ > 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] > ______________________________________________________________ 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]
