Topband: 160m polarization and elevation angles

[Carl Luetzelschwab]

Mark,

> I learned that polarization is not predictable after the first
ionospheric bounce.

Theoretically, polarization is well-defined as an electromagnetic wave
progresses thru the ionosphere. What's important is the "limiting"
polarization at the entry and exit points of the ionosphere, and our job is
to best match our antennas to the limiting polarization to couple the most
energy into the ordinary wave or the extraordinary and couple the most
down-coming energy into our receive antenna. On 3.5 MHz and higher, the
limiting polarization is essentially circular, so your antenna's
polarization is not real important as both waves propagate with similar
absorption and refraction. But on 160m, because of being close to the
electron gyro-frequency, the extraordinary wave suffers significantly more
absorption. Thus you better make sure you couple the most energy to the
ordinary wave on 160m - which is vertical for those at mid to high
latitudes.

It would have been great to have had the OH8X 160m Yagi up for a long time
so RBN could have been used to compare it to nearby vertical antennas. It
would have shown how much of this theory is applicable in the real world.

Of course the limiting polarization will vary as the ionosphere varies
diurnally and day-to-day. But still, in general, most of us at mid to high
latitudes should use vertical polarization on 160m. For those near the
equator (like the W4s), when they work 160m long path to the southeast thru
southwest, their entry and exit points are near the equator, where
horizontal polarization should be optimum. Those stations down south using
HWFs (horizontal Waller flags) for receive seem to hear long path very
well. It would be interesting to see what happens if they used horizontal
antennas for transmit.

Carl K9LA