On Mon, 26 Mar 2012 19:57:32 -0700 "Robin" <[email protected]> wrote: > Maybe this is a good time to share the techniques we >individually find successful for > hearing through the giant sparks. > Here are my experiences from TX3A (and other low-band DXpeditions). On TX3A, for 30 nights in a row, 8 hours each, I had the challenge of copying weak signals through strong, incessant lightning crashes (especially from sunset until about 10:30 local time). With the following set up, this is what I found to work best:
Local Set-Up and Conditions: Receiver K3, ANT DHDL (-36 dBi Gain), No local RF noise, Bose noise cancelling headphones (strong local acoustic noise from birds): I set the AGC to Fast, mostly used the RF gain to control levels, and set the IF Filter to 600 Hz. This last one may sound counterintuitive, but I have found that: a) setting the filter too narrow results in ringing which stretches out the effects of a lightening crash, masking more of the signal, b) setting the K3's DSP filter narrower changes the shape of the CW pulses and makes them stand-out less, and, c) somehow the narrower filter settings degrade the "understandability" of weak signals. (This last one was also confirmed by my DXpedition partner, Tomi, HA7RY, who has better ears and can copy CW great.) One more thing, with the above settings and with weak signals, it was absolutely essential to be able to totally concentrate during the crucial seconds when copying a call. I found that allowing any thoughts to intrude would wipe a call. Usually, with strong signals, you don't need total concentration to work without errors. You can think of other things, such as: should I change the RX settings?, should I try the other antenna?, shift in the chair as my butt is getting sore, etc. But with really weak signals, any intruding thought would create internal "noise" that could cause me to miss a call. I believe that learning to concentrate, and to be able to switch off all thoughts for a few crucial moments, is as important as any DSP filter or or other signal processing "hardware". I hope this helps, George, AA7JV _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
