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Robert11 wrote:
a. Anyone have any idea if a receiving Discone type of antenna is Polarized horiz. or vert. ? It is vertically polarized over its entire frequency range. b. Same question for a Scantenna ? If it is installed as usually illustrated with the elements vertical, then, yes, it too is vertically polarized. c. On VHF and UHF scanner freq's, are the (typically vertical, I believe ?) transmitted polarizations from Fire and PD transmitters usually maintained over distances of, e.g., 10 miles or so ? Or does "bounce", etc., tend to totally de-polarize them ? Land mobile and aircraft radios almost invariably use vertically polarized antennas. That wave polarization is generally maintained under conditions of reflection and refraction over short- and long- distance paths. For polarization rotation to occur during propagation, the medium generally must be birefringent (eg: the ionosphere). This rarely occurs with terrestrial waves. d. If a receiving signal is well polarized in one direction, say vertically, how much loss would one expect if the receiving antenna is oriented such that its preferred polarization is horiz. ? The usual figure one sees bandied about is 20 dB. e.g., for a rubber-duckie scanner antenna ? There's an additional penalty of 20 dB imposed on any antenna that has the word "duckie" in its name. ;-) ;-) ;-) Jim, K7JEB |
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