>Conventional wisdom has it that the horizontal polarization of >television signals was established to prevent having a "net" on top of >every house that would trap and injure birds.
Here is another theory from: http://www.isp-planet.com/fixed_wireless/technology/2001/horizontal_bol.html "The only reason that TV and FM started with horizontal polarization goes back to the FCC hearings of the 1950s, when the RCA electronic scan system for TV was doing battle against the CBS mechanical disk system. Both systems were horribly sensitive to reflections (ghosts) and every effort was made to reduce ghosting. Since the trials were done in New York City, and since tall buildings tend to act as a vertical grate and pass vertically polarized signals, in order to reduce the number of signals seen by the customer, horizontal polarization was chosen. That's basically why TV and FM use horizontal polarization, and every other terrestrial service uses vertical. When you have a forest of vertical reflectors (buildings, masts, flagpoles, vent pipes, etc), there is a greater chance of getting a vertically polarized reflection than a horizontally polarized reflection. Therefore, where multipath is an issue, horizontal works better than vertical." It turns out that multipath reflections and cancellation is the single biggest problem on our PSK63 2m net, and it sometimes helps to be able to minimize that by rotating a beam. In fact, the broad beamwidth of the skeleton-slot antenna is a disadvantage in reducing multipath (attenuating signals from the side), but has the advantage of wider angle coverage so usually rotation is not needed. 73, Skip KH6TY
