Topband: Non-reciprocity of path and checking polarization

[Tom W8JI]

Here's some things to think about when we think we know polarization or 
polarization tilt, or non-reciprocal propagation or paths:

1.) When receiving, antenna response to the desired signal compared to 
antenna response to noise determines copy, NOT the gain or absolute signal 
level. An antenna with the best signal level is not often the antenna with 
the best signal level, so we cannot use readability as a determinant.

2.) Most simple vertically polarized antennas have good low angle response, 
and are vertically polarized in all directions. The exception is a small 
loop antenna, which is only perfectly vertical along the horizon off the 
radial direction of the loop. At all other angles it is a mix of 
polarization.

3.) Most horizontal antennas are mixed polarization, and are only perfectly 
horizontal off the broadside. The exception is properly built and installed 
small horizontally-polarized loop.

4.) When we mix antennas or compare antennas to determine polarization, each 
reference antenna has to be normalized to the same response level at the 
angle and direction of the arriving signal. If response (sensitivity) is 
different and we have no idea how different, then we have no idea of 
polarization tilt or rotation.

5.) When we compare signals to make a claim or study if a path is 
non-reciprocal, we have to precisely know the difference in signal field 
strength levels on two paths. We can't tell anything for certain if we are 
listening only to S/N (readability) or the antennas are optimal for 
polarization and wave angle.

I don't think there is much chance of resolving this into useful 
information, because Hams really don't even want to bother with simple field 
strength measurements of antenna changes. We live mostly by feelings, and 
don't generally want to be bothered with facts or science. :-)

Unless we know what to measure and how to measure it, and actually measure 
or compare something, we are just guessing.

73 Tom