I want to end-feed a half wave vertical so I can get a nice low angle of
radiation. The base of the antenna would be about 0.05 to 0.10
wavelengths above ground. It looks like the antenna impedance will be
around 4,000 ohms. I would prefer not to use tuned circuits or stubs as
I would like the device to work over a 2:1 frequency range. (No, I'm
not expecting the antenna to be a half wave over a 2:1 frequency range!!
I would have 2 different antennas to choose from.) Power level is 200W.
I was thinking that an auto-transformer with a 9:1 turns ratio would do
the job and provide a reasonably low SWR for 50 ohm coax. I figure on
making the primary winding reactance about 500 Ohms at the lowest
frequency of interest and adding 8 times as many turns for the
secondary, presumably all on a suitable toroid. The wire insulation
would have to be suitable to withstand several hundred volts.
The auto-transformer would also nicely solve the static drain problem.
Am I nuts or is this actually feasible?
If it isn't, my next step would be to look into stubs.
73 de Jim Smith VE7FO
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See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
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