On Mon, 2008-06-30 at 07:32, Stephen W. Kercel wrote: > >FD is about how to put several transmitters in a 1000 foot circle > >and making it all work. I've never been to a 22A, but I bet that is > >interesting on HF. > > ********************* > How do they do that? > *********************
1. Transceivers with low phase noise and broadband transmit noise. 2. Narrow-band filters between transceivers and antennas. 3. Antennas placed as far apart as possible. 4. Antennas oriented for minimum coupling. Murphys' Maurauders used to (still does?) run that kind of operation. One "secret weapon" they had was a set of helical resonators for the HF bands. As I recall, the 20 meter version was about a foot in diameter. They were narrow-band enough to allow simultaneous CW and phone operation on the same band while maintaining reasonably low insertion loss. The problem is that, even if one transceiver is "perfect" (for example, a K3 :=), if the other transceiver has excessive phase noise, then BOTH stations will experience interference. The only cure is to use a narrow-band filter on the "dirty" transceiver. For FD stations located near the east or west coast, one effective technique is to locate all CW antennas on the north end of the site and all phone on the south end (or vice versa). Since the main interference problem is between phone and CW stations on the same band, that gets the antennas as far apart as possible and orients them so the interference is off the side of the antenna, where most antennas have minimum pickup. Al N1AL _______________________________________________ Elecraft mailing list Post to: [email protected] 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
