I don't recall any mention of polarization changes in this discussion. Being
an EME operator I am keenly aware of the faraday rotation problem at VHF. As
the frequency is lowered the rotation speed increases dramatically. The
lowest frequency that I have personal experience with is 50 MHz and the
rotation
there is typically about one fourth degree per second. At times of disturbed
(by the sun) conditions the rotation speed can be much faster.
I have not seen any data for 40 or 20 meters but if it scales like VHF could
be on the order of 3 or 4 degrees or more per second. A time interval of
several seconds could make quite a difference if the polarity of the antenna is
not adjusted. The difference in signal strength at VHF and UHF between matched
and mismatched polarity can approach 20 dB. Interestingly, for some unknown
reason there are periods that the polarity smears enough that the problem
disappears. We know this because quite a few 432 MHz EME operators have
polarity
rotators on their antennas and can receive at any polarization angle.
73,
Gerald/K5GW
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