SG-231 MANUAL
SGC Inc. SGC Building, 13737 S.E. 26th St. Bellevue, WA. 98005 USA
© 11/00 SGC, Inc.
P.O. Box 3526, 98009 Fax: (425) 746-6384 Tel: (425) 746-6310
E-Mail: [email protected] Website: www.sgcworld.com
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installed to communicate at 90 degrees off direction of the first loop antenna. Loop
antennas are low noise antennas. However, because they are used in apartments and
crowded cities, high industrial noise can be expected. Avoid using neon or fluorescent
lights within 50 feet of the loop antenna, as they may completely jam one or several
frequency bands.
Figure 4.6.1 Small loop antenna (3x4 feet)
Pegs or Nails
Smartuner
Cable to Radio
Use 6-8 turns of #16 or larger wire which is
insulated for high voltages. No spacing
between turns. Use a total of 70-90 feet of
wire.
Building wall
Loop antennas of much larger sizes can be used; however, while the low frequency
operation of such antennas may be quite good, the larger antennas may not work well
at very high frequencies when located in a plane parallel to the earth. This is because
large loop antennas generally radiate their maximum lobe (field strength) at right
angles to their plane.
This means that a large loop, say 60 feet on a side, mounted 20 feet above the ground,
would radiate much of its energy upward. While during the day this would work well
for close in communications, longer distances would be achieved with the loop
mounted vertically. The vertical loop antenna of 1/4 wavelength is the basis of the
“quad” type directional antenna.
Loop antennas represent a DC short circuit and for this reason are much less susceptible
to noise than are other kinds of antennas. In certain residential and industrial areas
where high noise levels occur, the loop antenna may provide a substantial
improvement in both receiving and transmitting performance at very little cost.
4.7 Recreational Vehicle (RV) Antennas
RVs or trailers provide an excellent base to install effective low cost antennas, and in
both configurations, end feed or loop antennas can be used.
An end-fed antenna could be effectively used if a metal cabin structure is available.
Loop antennas have the advantage of not requiring a ground system but are highly
directive. The antenna can be mounted simply on short (18” long by .5” diameter)
plastic plumbing pipes. Make the end-fed antenna as long as possible in an “L” shaped
configuration, as illustrated in Figure 4.7.1.