I'm really having a really hard time identifying with any of the AGC & NB complaints.
I used the second-to-last alpha test firmware (not latest) installed to my K3 in the recent ARRL DX CW on 40m from NY4A and was simply delighted. I can nearly or effectively remove key clicks with certain choices of *digital only* NB coupled with same bandwidth narrow roofing and DSP. The K3 front end plus these settings turned the usual 40m incoming cr*p into a zone where not copying a QRP signal was the exception as long as there wasn't a stronger station calling. At most there were a dozen or two signals all weekend calling that were not pulled out. It was, frankly, astounding. And *very* beneficial to score (1700 Q's on 40m). I did not experience AGC pileup distortion of any kind. With the key click nullification I was able to work 3/4 of the contest USING SLOW AGC, albeit set to its fastest decay. No theory here, just what happened. The most exceptional reduction was one period, about two hours, where a 20+ over clicky EU station was right below me, and was so close I had to use 350 width for running. With NB off had S6-8 key clicks, NB on had S1 S2 S3 band bottom. I used slow AGC during this time and worked QRP stations and weak Russians through it. Slow AGC was easiest to listen to (no idea how to express technically what I mean). There used to be that "next unworkable layer", stations you could hear were there, but just could never pull out. The unworkable layer was workable this contest. The end of workability occurred with the station dropping into absorbtion, as I now know is a very clean and transparent transition that doesn't sound like anything else on HF. You could hear it happen. I suspect it sounds like a vhf beacon signal dropping into solar noise though that is a very old memory for me. We worked Russians on 40m at 1130Z when it was 1:30 or 2:30 in the afternoon their time, which were only a whisper above a remarkably constant and unjunky noise level. More specifics on click removal: The clicky station must be well down on the skirts of the roofing filter for the trick to work and the best results seem with DSP width set at the TRUE bandwidth of roofer. Both my "250" 8 poles measure out ~ 330. 350/300 DSP width was best. Narrowing DSP below Roofer width seems to mildly worsen results. I presume getting the clicky station well down the roofer skirt makes sure that within the DSP IF the click appears as a detached click rather than a clickish aspect of discrete signal that is inside the DSP IF. There is one necessary artifact to nullifying key clicks, and that is a discernable notch on a very weak signal, that with a little help from fast deep QSB can break a dash into two dots, or turn a dash into a dot. I figured that out very early and made upward tweaks on my callsign correctness paranoia to compensate. I will take that mild mental adjustment with a smile anyday over frequencies rendered useless for weak signal work by key clicks. I cannot comment on use of 5 poles for this. For running bandwidth reasons I use 400/"250" 8 pole roofers in both RX, set to kick in at 450/350 Hz width settings. I did not use IF NB, or use NR at any point in the contest. I do not find NR at all useful on CW, confirming Lyle's statement that he did not see how it would be useful, everything else optimal. Be careful that in messing with the AGC for these complaints I don't understand, you don't UNDO what I used last weekend. 73, and thanks for a real edge in the contest past. Guy, K2AV P.S. Puhleeze, 10 Hz step for shift and width on CW. ----- Original Message ----- From: "ni0c" <[email protected]> To: <[email protected]> Sent: Friday, February 27, 2009 5:24 AM Subject: [Elecraft] K3 Cw pileup problem: effects of Noise blanker? > I've been thinking about the recently reported "cw pileup" problem, > wondering why this apparently wasn't noticed before-- particularly by > the VP6DX operators. > My guess is that the VP6DX operators probably never needed the noise > blanker in their (presumably) quiet QTH. > > It may be that the solution to this problem may be different for those > using > a single receiver K3 versus the dual receiver. It may be that the > solution could be as simple as disabling the NB when switching from VFO A > to VFO B. > ______________________________________________________________ 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
