Most of the so called 'flat-side' or horizontal mobile antennas aren't actually horizontally polarized. And quite frankly, why bother? If a horizontal antenna is mounted as low as almost any mobile antenna, it has no directivity to speak of, and has a radiation pattern not all that much different from a fairly short mobile antenna. I wouldn't count on that "over the horizon" thingy as much as I would a vertical's ability to get 'over the horizon'. What would be the point of using a horizontal antenna as a base antenna is it's only something like 5 - 9 feet off the ground?
An antenna's polarity is a matter of how the thing is physically arranged. If it's mostly up and down it's probably vertically polarized. If it's mostly 'laying down' then it's horizontally polarized (lay that groundplane antenna over on it's side and you just changed polarity). If the 'other side' of that mobile antenna is the vehicle it's mounted on, and if it extends above that vehicle, it's vertically polarized. If you want to make it horizontally polarized then the vehicle isn't part of the antenna at all, or the antenna sticks out away from the front/back or sides of the vehicle (not at 45 degrees, but at about 70 degrees AND less). Draw your own conclusions.
- 'Doc
