The angle of the beam (for the actual polarization) is determined by the two points on the antenna's characteristics where signal level decreases by 3 dB in comparison with its maximum value.
In the case of terrestrial antennas, lower half-power beam means better directivity, i.e. capability of rejecting reflected signals. In analog TV these signals are superimposed on the main image as "ghosts" - displaced images on the right of primary video information.
Half power beam is inversely correlated with the length of an antenna.
It is not always sensible to use antennas with narrow half-power beam. Sometimes one wants to use single antenna for receiving signals from transmitters situated in different locations - a shorter antenna with a wider angle will be more suitable then.
In the mountains, where usually there is no visibility of the transmitter, there should also be used antennas with wider beam. This solution gives a chance to receive any signal at all, and the reflections are a necessary evil.
In the case of terrestrial antennas, lower half-power beam means better directivity, i.e. capability of rejecting reflected signals. In analog TV these signals are superimposed on the main image as "ghosts" - displaced images on the right of primary video information.
Half power beam is inversely correlated with the length of an antenna.
It is not always sensible to use antennas with narrow half-power beam. Sometimes one wants to use single antenna for receiving signals from transmitters situated in different locations - a shorter antenna with a wider angle will be more suitable then.
In the mountains, where usually there is no visibility of the transmitter, there should also be used antennas with wider beam. This solution gives a chance to receive any signal at all, and the reflections are a necessary evil.
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