GW0ETF wrote: > > My K3 #145 was used casually in ARRL DX this weekend. One thing that > really impressed me was when an extremely strong carrier appeared on top > of K1TTT just as I was about to call - and stayed there. I turned on the > manual notch and tuned it onto the carrier and lo and behold K1TTT > re-appeared and was worked. Obviously not *exactly* on the same frequency > but near enough to prevent any copy even with the 250Hz roofing filter > in and DSP right down to 50Hz; the notch on the K3 is so sharp it's almost > unbelievable. >
Stewart I haven't found the Manual CW Notch to be very useful. Are you sure the carrier did not actually disappear rather than the notch removing it? Here are some measurements using the XG1 at 50 uV as a source and the K3's internal dBV meter (AGC off for valid measurements). At 100 Hz offset (XFIL, Width, Pitch, Notch all = 500), the interfering signal was approximately -12 dB down. At 100 Hz offset (XFIL=200, Pitch & Notch = 500, DSP settings as shown) the interfering signal was: DSP=200, interfering signal -12 dB down DSP=150, " " -32 dB " DSP=100, " " -54 dB " DSP=050, " " -57 dB " I conclude CW Notch is nowhere near as effective as the DSP settings of 150 and lower. An additional problem is that the Notch is inside the DSP's AGC loop, so the K3 is still desensed by the presence of the carrier, even though it may not be present in the audio. On-frequency the Notch has ~55 dB of rejection which is excellent, but of course that also notches out the desired signal the same amount. I did these measurements hastily and could have made some errors, but they agree with my first impression that the CW Manual Notch is not too useful. It's a little difficult to use since you must guess its tone and the 20 Hz setting granularity is higher than I'm accustomed to. Orion had 10 Hz granularity in setting the tone and also offered a range of notch bandwidths from 10 Hz and up (going from memory since I no longer have it to compare). 73, Bill W4ZV -- View this message in context: http://www.nabble.com/K3-s-in-ARRL-CW-Test--tp15538850p15547072.html Sent from the Elecraft mailing list archive at Nabble.com. _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
