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I am very very proud that I hung a 80-Meter dipole about 100 feet
above my QTH last week. But I also had a hankering to cover 40 Meters with it too (although I already had a 40 Meter dipole). So the section in the antenna book about fan dipoles came to mind. I looked in the ARRL antenna book, it told me that the seperation of wires was not all that important. So I sort-of duplicated one of the sketches in the book, and hung the 40 meter wire from an tiny little egg insulator on the 80 meter wire. Result: DID NOT WORK AT ALL. No indication of any kind of antenna resonance anywere from 5 to 9 MHz. Sky-high SWR over the whole range. It didn't mess up 80-meter operation, though. Looked at W4RNL's "My Top 5 Backyard Multi-Band Antennas". The fan dipole is in there, but not in the way it looked in the ARRL book. He says you need a big spacer at the end of the line, like 10 feet, to get consistent results. He has some other notes about modeling Fan dipoles at http://www.antennex.com/w4rnl/col0507/amod111.html I give it a shot, and holy moly, it looks like this should work. Maybe some bigger spacing would result in a bit more bandwidth but I'm mostly working at the bottom of the CW band. So I'm going to find some skinny 10-foot fiberglass poles and try re- rigging this weekend. Tim N3QE |
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