Friends in Radio Land -
Recently, the reflector carried some remarks about reciprocal
propagation. Unfortunately, they did not convey the idea that
low-band propagation is magneto-ionic in nature, i.e., because the
operating frequency is comparable to the electron gyro-frequency.
Thus, the propagation mode is important, depending on the wave
direction relative to magnetic field lines.
To carry out a test for reciprocity, one should look for sites
with comparable magnetic environments - connected by a magnetic
meridian, with almost equal local field strengths (i.e., electron
gyro-frequencies) and equal magnetic dip angles, leaning toward the
low latitudes (i.e., essentially at equal distances from the dip
equator).
Signal propagation modes betweeen the sites should bethe same,
either by the quasi-transverse or quasi-longitudinal
propagation. And the reciprocity test should be conducted in
evening hours when the solar declination would put the sub-solar
point on the dip equator at local noon; that would assure a night-
time ionosphere that remains after a symmetrical illumination
during the day.
On reviewing the distribution of land masses, a possible pair
of sites for a reciprocity test are in the VK6 and JA8/UA0 areas.
The physical parameters in those regions are within about +/-5% of
each other and propagation would be by the quasi-transverse mode.
The test could be in the first week of September to equalize solar
illuimination above and below the dip equator. Perhaps there are
other sites; any suggestions or comments?
73,
Bob, NM7M
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