Encyclopedia > Antenna height above average terrain
In telecommunication, antenna height above average terrain is the antenna height above the average terrain elevations from 3.2 to 16 kilometers (2 to 10 miles) from the antenna for the eight directions spaced evenly for each 45° of azimuth starting with true north.
Note: In general, a different antenna height above average terrain will be determined in each direction from the antenna. The average of these eight heights is the antenna height above average terrain. In some cases, such as seashore, fewer than eight directions may be used.
This may be obtained by averaging a large number of equally spaced points, by using a planimeter, or by obtaining the median elevation (that exceeded for 50% of the distance) in sectors and averaging those values.
The heightaboveaverageterrain of the 3 to 10 kilometer portion of the 90[deg] radial is 105 meters.
In directions where the terrain is such that antennaheights less than 30 meters for the 3 to 16 kilometer sector are obtained, an assumed height of 30 meters must be used for the prediction of coverage.
H is the height in meters of the transmitting antenna radiation center aboveaverageterrain of the 3.2-16.1 kilometers (2-10 miles) sector of the pertinent radial.
In directions where the terrain is such that negative antennaheights or heights below 30.5 meters (100 feet) for the 3.2 to 16.1 kilometers (2 to 10 mile) sector are obtained, an assumed height of 30.5 meters (100 feet) shall be used for the prediction of coverage.
Where mechanical beam tilt is intended, the amount of tilt in degrees of the antenna vertical axis and the orientation of the downward tilt with respect to true North must be specified, and the horizontal plane pattern must reflect the use of mechanical beam tilt.
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