[Amps] 10dB and propagation

[TexasRF at aol.com]

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