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Full-wave loops are very popular antennas. They are especially
useful on 80 and 40 meters where they perform well at modest heights.
These are closed loops that are one full wavelength long. Horizontal
loops may be fed at any convenient spot. For best performance, make
your horizontal loop into a square, especially if it is to be used on
several bands.
The Vertical Loop is a good DX antenna. The shape can be a circle,
square, rectangle or a triangle. The larger the area of the loop the
better it will work. Feed square and rectangular loops at a corner.
For best results, triangular loops should be supported apex-down. This
puts less of the antenna parallel with the ground and increased the
effective height. Feed triangular loops either at a corner or in the
case of apex-down loop, at the apex.
Use ladder line and a wideband transmatch (a naturally balanced
tuner, like a Johnson Matchbox) for multiband operation. The
RemoteBalun 4 is recommended if you will have problem getting ladder
line to the operation position. Multiband operation is possible when
feeding the loop with coax. The losses will be slightly higher, but
the convenience of the coax may be worth the slight signal loss.
The design frequency, the feedpoint impedance, will be between 80
and 150 ohms. Coax fed loops will usually have an SWR between 2:1 and
3:1. You may feed this antenna with a 4:1 balun. If the loop is in the
shape of square or large rectangle, the SWR can be below 2:1, but will
not get much below 1.5:1.
If you decide to feed your loop with coax, I'd suggest using RG-8X
or RG-213 and a high power, high performance 1:1 or 4:1 Current-type
balun. Experiment with full-wave loops. You may find them to be
excellent multiband antennas.
Antenna wire can be #14 hard-drawn antenna wire. Use #12 wire for
large loops on 160 or 80 meters. |
