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, ho13d...@gmail.com 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 >>> <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 >>> ho13d...@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 rmcg...@blomand.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 ho13d...@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 k...@aol.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
