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Old May 24th 05, 07:01 PM
Chuck Olson
 
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Default Off-Center-Fed horizontal wire with capacitive loading

I want to put up the best antenna within the constraints of my lot size and
building locations. I would also like it to work on 80 to 10 meters,
including the WARC and 60 meter frequencies. I can put up a north/south leg
57 ft long and an east/west leg 63 ft long from a 28 ft steel TV mast at the
southeast corner of my lot. I visualize tuning it through a 20 ft ladder
line feeder using an ATU such as the SG-239 and perhaps a 4:1 current balun.

One objective is to locate all high-current sections of the antenna in the
clear (contrast that to the G5RV which, for example, at 3.5 MHz folds the
center 32 ft of high current wire of the 80 meter version into the feed
line - - am I wrong?) To that end, I propose locating capacitive disks - -
just a few 3 ft radials and a circumferential ring, mounted on Delrin
standoffs from PVC masts at each end of the antenna to move the high current
regions out away from the feed point on each leg.

I thought of using a couple of relays to modify the feed to selectively
drive just the end of each leg or off-center feed both, as a form of
transmission diversity, but that would require I add some hardware-cloth
ground-cover under each leg for a counterpoise.

My questions: A) is there any undesirable effect of using capacitive loading
on a horizontal wire? I Googled for similar ideas and couldn't find any use
of capacitive loading on horizontal wire - - just capacitive hats on
vertical antennas. B) What directivity can I expect from the 90 degree angle
between legs?

Thanks,

Chuck W6PKP


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