>The fading on SSB and CW modes can tell you a lot about what the >band is doing.
Yes, but not necessarily what you think. Most of the "in and out" fading we hear on HF is the result of multipath. That is, the signal travels over two paths that differ a bit in time, which puts them out of phase. When they out of phase by some odd multiple of 180 degrees, they cancel, and by an even multiple of 180 degrees, they add. The time interval of the fading depends on the time difference of the arrivals and the wavelength of the signal. We're used to hearing this kind of thing on mobile signals, and also when an aircraft reflects a VHF or UHF signal. Those VHF/UHF wavelengths are short, so the fading has a fast characteristic (an interval often less than a second). Down on 160M, it's common for the fading interval to be tens of seconds or a minute. The DEPTH of fading (that is, the weak part of the fade) depends on perfect cancellation of the signal, which happens when the two arrivals are almost precisely equal in strength. 73, Jim Brown K9YC _______________________________________________ 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
