Aspects for Antenna height considerations depend on the wave range and economic reasons.
Video Antenna height considerations
Low wavelength/frequency antenna
In VLF, LF and MF, the pole or radio tower is often used directly as an antenna. The altitude determines the vertical radiation pattern. Poles and towers with a height of about a quarter wave or shorter, radiate considerable force into the sky. This allows only a small reception area that is free of fade at night, since the distance at which ground waves and sky waves have comparable and interdependent forces is very limited (about 40 kilometers to 200 kilometers from the transmission site, depending on the frequency and soil conductivity ).
For high-power transmitters, poles with a height of about half the wavelength emitted are preferred because they concentrate power radiated to the horizon. This increases the distance where the selective fading occurs. However, poles with a height of about half wavelength are much more expensive than shorter ones and are often too expensive for lower-middle-wave stations.
For long wave transmitters, the construction of a semi-wave pole is not feasible in most cases, either for economic reasons or due to problems with aviation safety. The only radio pole for long waves with half-wave height built up today is the Polish Radio pole (which does not survive). For frequencies lower than the longwave range, the pole must be electrically enlarged by the base load coil or upper structure, since the height required for the poles even a quarter wavelength is too large to be realized physically.
Usage is usually not made of poles higher than five-eight (5/8) of wavelength, since such poles (except for some special constructions for high power medium wave broadcasting) exhibit poor vertical radiation patterns. The height of the pole for the medium wave transmitter usually does not exceed 300 meters (1000 feet).
Sometimes a cage antenna or longwire antenna is used for the transmission of LF and MF. In this case the tower height may be larger than usual. Because towers or poles used for cages or long wire antennas are grounded at the base, they are well suited to supporting antennas for UHF or VHF broadcasting.
Maps Antenna height considerations
Short-wave/high-frequency antenna
For transmissions in shortwave range, the pole height has no effect on efficiency. The poles are generally used to support the antenna. The shortest pole has a height of less than 100 meters.
Antenna for point-to-point radio service
In most applications, line-of-sight is required between transmitter and receiver antennas for point-to-point service, and antennas may have to be installed at a certain height of ground. For microwave radio systems, it is not always possible to use long transmission lines between transmitters and antennas, so towers with equipment or closet space close to the antenna height may be required.
Source of the article : Wikipedia
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