Another possibility for a receiving loop on Topband is to use an untuned
loop--very simple to make using 1? hardline mounted on a frame of PVC pipe.
The shield of the hardline is used as the antenna, balance being preserved
by isolating the antenna from the coax feedline using a simple binocular
core choke balun (see W8JI?s site for details). With a loop between 8 and
12 feet diameter there is adequate sensitivity. Some transceivers may
require an external preamplifier; at my city lot using an Orion the internal
preamplifier is sufficient. I have no idea what the pattern of this type of
antenna is on higher bands, but they are very useful to me, many times
providing copy on signals I can?t hear using the transmitting antenna for
receiving.
My experience is that loops, tuned or untuned, made from hardline with its
solid shield and greater diameter, have always greatly outperformed those
made from RG-58 or RG-59. If for some reason one wants a rectangular loop,
¾? or 1? copper pipe should work fine.
73 Paul W5DM
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