Topband: Magnetic Variation and Gyrofrequency

[Robert Brown]

Bob,

This has been worked out by a couple of BBC engineers, G.J. Phillips and
P. Knight, and published in Proc. IEE, Vol. 112, No. 1, January 1965.

I applied their results to 160 meter propagation and DXing in an article
that appeared in the Communications Quarterly, Summer 1999 issue, p. 95.

The power coupling question is really an aspect of magneto-ionic
propagation, going back to Appleton.  It is discussed in books by
Ratcliffe (now out of print but in better libraries) and Davies.

In essence, power coupling in and out of the ionosphere depends on the
local geomagnetic field and antenna polarization at each site.  Most
favorable coupling is for vertical antennas at high latitudes, where the
field is nearly vertical.  At equatorial latitudes, E-W propagation is
favored for horizontal polarization while vertical polarization is better
for propagation toward the polar latitudes.

73,

Bob, NM7M



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