Hi Guy
Your folded counterpoise idea sounds excellent. About 12 years ago, I built
a miniature quad antenna for 7MHz that used folded capacitive loading to
make two elements, each with sides around 20', using techniques pioneered by
G3FPQ.
During the course of this experimentation, I learnt that it was possible to
make relatively low-loss capacitive loading using folded wires (bent back on
themselves) if a minimum spacing was observed. The miniature 40m quad
antenna, mounted at 20 metres high, was a very effective antenna.
At 7MHz, this minimum spacing transcribed to about 0.005 of a wavelength, or
about 9 inches (23 cm). Scaling this up to 1.8MHz, this gave a spacing of
about one metre between the folded wires and I built my late father Ossie
G0TYJ a very effective folded 160m antenna and counterpoise that fitted into
a very small space, using this technique.
I would be very interested - as am sure other users of this reflector would
be - on what spacing you use between the folded wires on your counterpoise
system. If you have found you can use a spacing of less than a metre
between the wires, this would be good news to myself and others! One metre
spacing was rather cumbersome.
Vy 73
Steve, VK6VZ (ex-G3ZZD)
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Guy, K2AV wrote:
SNIP
>Remember that the current entering the FCP is set by the radiating
wire because the apparent series resistance in the FCP is so low
relative to the radiation resistance of the vertical radiator. The
FCP's beginning current would be the same amplitude as the beginning
current on the two radials. Set our imaginary power drive to get one
ampere at the base of the antenna in both cases.
Counting FCP segments 1 through 5. 33 feet per segment. Directions
used are for illustration only.
1: center to 33 feet east
2: 33 feet east back to center
3: center to 33 feet west
4: 33 feet west back to center
5: center to 33 feet east and end insulator.
Segments 2 through 5 carry the typical cosine current curve of a 0 to
90 degrees quarter wavelength. This is enforced working backward from
the end insulator. Segment 1 has the cosine of -22.5 degrees to 0
degrees. The current max is at the connection between segments 1 and
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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