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 _________________ Topband Reflector Archives - http://www.contesting.com/_topband