I hope everyone has had a chance to work FT5ZM on topband. With respect to circular polarization on our HF bands (3.5 - 28 MHz) and on 6m, theory says both the ordinary and extraordinary waves propagate thru the ionosphere with pretty much equal ionospheric absorption. Thus circularly polarized antennas can provide an advantage. Some of the real-world examples I'm aware of have been documented by G2HCG on 10m (in the old Communications Quarterly), by the original K6CT on 20m (in the RSGB Bulletin) and by WA3WDR on 75m (a web paper). I'm sure there are others out there, too.
On 160m, theory says the extraordinary wave incurs much more ionospheric absorption (more heavily attenuated) due to 1.8 MHz being so close to the electron-gyro frequency. Thus in theory only the ordinary wave is useful on 160m, which says circular polarization wouldn't do any good. Now things happen on 160m in the real-world that we simply don't understand. For example, an ordinary wave can excite an extraordinary wave under certain ionospheric conditions (if you'd like to read more, curl up in a warm place on a cold night with Chapter 3 in Ionospheric Radio by Kenneth Davies). Could this be happening? I don't think we can rule it out. In my opinion based on all the reports on this reflector over the years, it seems to me that having selectable elevation angles is more important than polarization. But I also admit that there hasn't been much work in the polarization field (no pun intended) on 160m (except for N4IS with his horizontal Waller flag - which makes sense with theory for roughly East-West propagation close to the geomagnetic equator). Carl K9LA _________________ Topband Reflector Archives - http://www.contesting.com/_topband
