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Old March 31st 10, 08:15 PM posted to rec.radio.amateur.antenna
Jim Lux Jim Lux is offline
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First recorded activity by RadioBanter: Mar 2007
Posts: 801
Default Radiation patterns and loss of antennas operated well below resonance

Joel Koltner wrote:
"Richard Clark" wrote in message
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So, in commemoration of that sort of criteria, what do you mean by
...don't take up a lot of space.


I'm liking panel-type antennas that are on the order of, oh, say,
0.2\lambda by 0.2\lamba by perhaps .05\lambda or less. So electrically
small, but not super-electrically small. :-)


Considering a dipole is 0.5 lambda by 0.01 lambda, getting a factor of
2.5 smaller is easy. (that is, you want 40cm by 40cm or so)

A simple short dipole with capacity hats and inductive loading will get
you there quite nicely.

Imagine a "I" with the feedpoint at the middle, on a piece of FR-4 or
G-10 (epsilon about 2). make it, say, 30x30 cm. You could also make the
dipole diagonal across the square, and have the "capacity hats" be along
the edge.

You could fool with NEC for a bit and get pretty close.

Or, do what I'd do.. get yourself a piece of suitable insulating
substrate (a plastic cutting board or piece of acrylic window pane) and
some copper foil tape. Lay it down, measure it with an antenna analyzer
or similar, and start adjusting.

I've built more than one antenna like this using copper foil tape on
paper or plastic sheets.