I've only just now noticed that the "oscillation" when NR is enabled that I hear when tuning through an S9 carrier in USB/LSB happens only when VOX is enabled. In fact, I just now noticed that the red TX indicator is illuminated when this happens - although there is no indication of power out on either the K3 or the outboard power meter.
So with AGC SLP=5, THR=5, NR enabled, VOX enabled, tuning through S9 carrier triggers this on USB/LSB, but not CW. Very strange. Bob NW8L On Sat, Apr 25, 2009 at 3:20 PM, Bob Cunnings <[email protected]> wrote: > Apparently NR *is* upstream of AGC, since a while back NR was > disallowed unless AGC was enabled [1] in order, according to K2VCO, to > prevent instability [2]. > > By the way, I can observe this instability (a "wup-wup" oscillation) > in LSB/USB modes with an S9 carrier, and AGC settings on the "light" > side (high threshold, low slope, with THR=8 and SLP=0 being the > extreme). I ran into this tuning through shortwave BC stations with NR > enabled with THR and SLP set to 5. I'm using firmware version 3.11. > > What seems odd to me is that although I can reproduce the audio level > increase cases observed by others when NR is enabled, the S-meter > indication doesn't change - I suppose that the S-meter pickoff point > is upstream of NR? > > On the flip side you mention, if notch filtering was before AGC as you > wish, would you expect the S-meter indication to change when the notch > filter is active? > > Bob NW8L > > [1] http://www.mail-archive.com/[email protected]/msg58245.html > [2] http://www.mail-archive.com/[email protected]/msg60930.html > > On Sat, Apr 25, 2009 at 12:55 PM, Joe Subich, W4TV <[email protected]> wrote: >> >> It's not working as it should ... there should be no volume >> change when engaging NR. Noise reduction should work on the >> audio AFTER AGC. If anything, the test results below should >> show a very slight drop with NR due to the removal of the >> unwanted (broadband) components but the peak level should >> not change. >> >> This NR problem is the flip side of the issue with the notch >> filter ... Notch is working AFTER the AGC where it should >> work before AGC while NR is working before the AGC where it >> should work AFTER the AGC. >> >> 73, >> >> ... Joe, W4TV >> > ______________________________________________________________ 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
