See the ARRL Handbook. If it isn't a question on the current ham exam, it should be. :)
Each RX has its own antenna, separated by some distance. Most fading is the result of cancellation between a direct wave and a reflected wave. When the two signals are nearly in phase, they add. When they are nearly 180 degrees out of phase, they cancel. These peaks and dips are the result of time differences between the direct and reflected waves, and these differences vary from one point to another. So, when a signal is fading down (cancelling) at one location, it is often fading UP (adding) at another nearby location. If the two RXs are synchronous (same osciallator) and the signal paths have the same phase response, detected audio will be in phase, so adding the output of the two RXs will result in coherent addition on signal (6 dB increase if the signals are equal) but only a 3 dB increase in random noise. Also, there are some nice psychoacoustic things that the brain can do if you put one RX in one ear and the other RX in the other. But this is ONLY true if the RXs are synchronous (running on the same oscillator) and have matched phase responses. THAT's why we care about matching the filters -- the phase response of the filters is additive with the phase response of the rest of the signal path. 73, Jim K9YC On Fri, 4 Jul 2008 14:36:25 -0500, Jim Miller wrote: >OK, I have to ask. WHAT is diversity? _______________________________________________ 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
