I think the thing to remember about rx antennas like small loops is
that, while some of the noise may have a preferred polarization and
small loops may provide some polarization isolation, they mostly reduce
noise because of their directional characteristics. While they have very
low efficiency, that's not a problem for rx purposes. If we assume that
the noise comes equally form all directions because a loop has such
sharp nulls means that the noise in those nulls is heavily attenuated
while the desired signal isn't. If there is a particular noise source
(that's not in the direction of your desired signal) adjusting the loop
to null that source may be even more beneficial.
Kim N5OP
On 9/22/2013 12:46 PM, Spencer wrote:
I almost gave up SWL in metropolitan areas outside
the USA. I made a small multi-turn loop using FLAT
4 conductor telephone wire and resonated with a BCB capacitor. A small
ferrite bead on one of the wires to couple to the radio. Very narrow
band but almost noise free.
Spencer W1GAK
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