Rick,
I deliberately aimed for a slightly high resonant frequency - from
memory it was around 2.2MHz. Then I put a small loading coil at the base
to pull it onto frequency; that coil had a couple of taps on it that
could be relay switched remotely from the shack to give me stepped
coverage of the band that I needed. Finally there was a 9:1 broadband
transformer to bring the impedance up to 50 Ohms.
I don't have the antenna now, but I just noticed the 3 position
switching is still there built into my shack SWR meter! Left switch here:
http://www.karinya.net/g3txq/swr_meter/front.jpg
Hope that's clear,
Steve G3TXQ
On 09/11/2013 14:17, Rick - DJ0IP / NJ0IP wrote:
Steve,
The merits of that design are apparent, but how do you tune it?
Seems it would be awfully difficult to adjust top-hat lengths when they are
connected together.
Sevick did something like that using a real sun umbrella, but he had it
split in the middle and inserted a coil. He could tune by adjusting the
coil.
73
Rick, DJ0IP
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