The DSP is behind the roofing filters. I set my 400 Hz filter to cut in at 450 Hz width. If I set width to 500, the K3 uses the 1.8 kHz roofing filter. The information diversity of the noise vs CW signal as a ratio is much larger there and the algorithm seems to take advantage of that. To my ears there is a lot more "bite" by the NR when the roofing is wide. This wide roofing won't do for contests, but it's quite nice for listening and regular QSO's.
In your case I would compare NR with width at 550 and 500 for CW in uncrowded non-contest situations. That should tell you a lot. In any event, at some level of signal going down past merely weak, NR no longer "digs into" the noise and IMHO begins to obfuscate the signal. At this point only narrowing bandwidth helps. I <never> use the NR in contests for this reason. NR seems to kill about a couple dB range where I can dig it out with the dB between the ears if the NR is off. In a contest, those are the very contacts that if made will put distance between one and the competition. And lest anyone think that a dig on the K3, I have exactly the same observation/experience on the Orions. 73, Guy On Tue, Dec 29, 2009 at 12:53 PM, John Lawrence <j...@hughes.net> wrote: > Over the past two months I've been enjoying weak signal low band DXing on > good antennas with my K3 using roofing filters for CW (500Hz) and SSB (2.1 > KHz) . My K3 has the latest DSP board and the firmware is up to date with the > thirty-two(?) NR choices. What I'm finding is that the NR Firmware likes to > see a wide bandwidth from which the weakest signals can be dug out of the in > the noise on SSB or CW. If I narrow up the bandwidth with the optional > filters I can't copy the signals as well. i.e. with NR enabled together a 2.1 > or 500 Hz filter. I hear best with NR together with the 2.7 KHz filter. > Interesting! > > This means that QRM must be considered as a secondary matter within the > bandpass if the NR feature is to work at its best for me. I find different NR > settings depending on band conditions and the ultimate setting varies with > incoming signals. I've been working lots of JAs on 80 meters where the NR > truly helps. The narrow CW/SSB filters are great but I don't use NR with > them. Weak signal reception comes down to using the narrow roofing filters > without NR. OR, just the 2.7 KHz wide filter with NR enabled. Yes, over and > over, the 2.7 KHz bandwidth together with NR brings them out from the depths > of ESP level to readable signals. > > So, why have the optional filters? I use them to get signals so I can copy > them through QRM when the band is busy. > . > Happy Holidays > > 73, > > John, W1QS > ______________________________________________________________ > 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 > ______________________________________________________________ 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
