Hi Bill: You stated it correctly. Here's an example.
There are two US stations calling the DX. Me and you both within my 50Hz passband. I send my call once and you send your call twice. You are S9 at my receiver and the DX is S7. When I finish calling I can hear you and I can also hear the DX station. (If there is no pitch difference there are still differences in strength and speed). I may not hear every character he is sending but I might hear him come back immediately after I stop sending and I might hear parts of a number 2 and parts of a letter K in his response. So when I no longer hear him I take a chance and assume he called me and I respond with my info. This all happened while you were still sending your call. This was not an unusual situation this weekend. I had a good signal and was getting most stations in one or two calls so it was not really a big leap for me to respond. But I was only able to do it because I could still hear him through the QRM. Now take the same situation except you were calling 70Hz off of his frequency. My receiver was dead until you stopped sending. Once you stopped I might hear the tail end of his message but I wouldn't know if it was me unless he called me a second time. And of those 20 occurrences that I described earlier, maybe half of those times he was calling me but I had to wait for the re-call. Someone else asked if I had the text decode on and I did not. As for NR, I usually had it on. But I always try to keep the aggressiveness low. And I did experiment and I still had the same problem with NR off. 73, Mike K2MK Bill Tippett Mon, 23 Feb 2009 09:20:14 -0800 Hi Mike, On Mon, Feb 23, 2009 at 11:00 AM, K2MK <k...@comcast.net> wrote: > Here are my CONFIG settings related to the AGC. The only ones I played > with > during the contest were SLP and THR. I always use AGC-F but did > occasionally > try AGC-S. > > AGC-HOLD 000 > AGC-PLS NOR > AGC-SLP 010 > AGC-THR 005 > AGC-F 120 > AGC-S 020 These all look reasonable. I set my AGC-S to the max 040 but I actually never use AGC-S. If I were an AMer or 75m SSB ragchewer, I might. > The differing conditions I described were the situation of everyone > calling > the DX close to his frequency versus one strong station calling 70Hz off > frequency. When even strong stations called the DX right on frequency I > was > able to hear signals through the QRM. When strong stations called 70Hz off > of the DX frequency the receiver went quiet and took about 1/4 to 1/2 > second > to recover after he stopped sending. This is what I'm having problems understanding: "When even strong stations called the DX right on frequency I was able to hear signals through the QRM." 1. If two stations are exactly on frequency, the best ears in the world will not be able to separate them. I can distinguish pitch *differences* (i.e. one after the other) of about 0.4 Hz repeatably (see link below), but there's no way I could copy two simultaneous CW signals dead zero beat, so I don't understand your comment. The human ear's DSP has an effective bandwidth of ~50 Hz, so I could probably distinguish two signals 70 Hz apart if their amplitude was not too different (the human ear has AGC limits also!) http://tonometric.com/adaptivepitch/ (a fun test to take!) 2. The way the K3 and similar front ends (i.e. Orion, FT2000/9000, IC 7700/7800) work, strong signals inside the roofing filter passband will desense *all* signals within the passband...i.e. they will affect zero beat signals just as much as those 70 Hz away (which would be the case even if you were using the 200 Hz filter). So I cannot understand how signals off zero beat would be affected more than those zero beat. Anyhow, I'm clearly not understanding what you're saying. 73, Bill ______________________________________________________________ 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
