Ultra High Frequency Antenna
The blue struts should be made of wire or tubing. Avoid using coat-hangers
because they are iron and exibit too much ohmic resistance to the Radio
Frequency Energy. Because Radio Frequency Energy only travels in the surface
of a conductor, the wire or tubes should not be subject to corrosion. Corrosion
will destroy the antenna's ability to recieve especially at UHF frequencies.
The material you use should be robust and able to stand the rigors of oudoor
environment. If you use copper or brass tubing, polish them and spray-coat
them with harty outdoor paint to prevent corrosion. Make sure there are
no gaps or missed areas for the coating.
This is a balanced-line 300 ohm design. If you use it with a scanner, try
to match the balun output impedance to the antenna input impedance of the
scanner. This antenna works well with an integrated amplifier but do not
use more than 10 db gain so that the receiver is not swamped.
The 2 foot strut in the rear does not have to be so long or present at all,
if you want to use the antenna in a portable manner, but this will effect
the antenna's directional charateristics. The entire thing can be taped
to a sheet of cardboard or plastic. This make-shift design can come in handy
for that pesky 880 Mhz band. When using the antenna for this purpose it
can be used vertically, taped to a metal umbrella handle or a broom handle.
The metal umbrella handle can substitute for the 2 foot rear reflector strut.
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