Height above average terrain
Height above average terrain (HAAT) (or less popularly, EHAAT, Effective Height Above Average Terrain) is used extensively in FM
radioand television, as it is actually much more important than effective radiated power(ERP) in determining the range of broadcasts ( VHFand UHF in particular, as they are line of sight transmissions). For internationalcoordination, it is officially measured in meters, even by the Federal Communications Commissionin the United States, as Canadaand Mexico(both of which use metric) have extensive border zones where international stations can be heard on either side of the international boundaries. Stations that want to increase above a certain HAAT must reduce their power accordingly, based on the maximum distance their station class is allowed to cover (see list of broadcast station classesfor more information on this).
Before metrification at the FCC, the procedure to figure HAAT was relatively simple: from the proposed or actual antenna site, either 12 or 16 radials were drawn, and points at 2, 4, 6, 8, and convert|10|mi|km radius along each radial were used. The entire radial graph could be rotated to achieve the best effect for the station. The average altitude of all the specified points, minus the altitude of the antenna site, was the HAAT. This can create some unusual cases, particularly in
mountainous regions—it is possible to have a negative number for HAAT (the transmitter would not be located underground, but rather in a valley, with hills on both sides taller than the transmitter itself, for example).
The FCC has divided the
Continental United Statesinto three zones for the determination of spacing between FM and TV stations using the same frequencies. FM and TV stations are assigned maximum ERP and HAAT values, depending on their assigned zones, to prevent Co-channel interference.
The FCC regulations for ERP and HAAT are listed under Title 47, Part 73 of the
Code of Federal Regulations(CFR).
Zones I and I-A
*Maximum HAAT: 150 meters (492 ft)
*Maximum ERP: 50 kW
*Minimum co-channel separation: 241 km (150 miles)
Zones II and III
*Maximum HAAT: 600 meters (1968 ft)
*Maximum ERP: 100 kW
*Minimum co-channel separation: 290 km (180 miles).
In all zones, maximum ERP for analog TV transmitters is as follows:
*VHF 2-6: 100 kW
*VHF 7-13: 316 kW
*UHF: 5,000 kW
*Zone I: 305 meters (1000 ft)
*Zones II and III: 610 meters (2000 ft)
Minimum co-channel separation
Zone I (the most densely populated zone) consists of the entire land masses of the following states:
Connecticut, Delaware, Illinois, Indiana, Maryland, Massachusetts, New Jersey, Ohio, Pennsylvania, Rhode Island, and West Virginia; in addition to the southern and eastern portions of Virginia; the areas of Michiganand southeastern Wisconsinsouth of 43° 30' north latitude; the coastal strip of Maine; the areas of New Hampshireand Vermontsouth of 45° north latitude; and the areas of western New Yorksouth of 43° 30' north latitude and eastern New York south of 45° north latitude. In addition, Zone I-A (FM only) consists of all of Californiasouth of 40° north latitude, Puerto Ricoand the U.S. Virgin Islands. (If the dividing line between Zones I and II runs through a city, that city is considered to be in Zone I.)
Zones I and I-A have the most "grandfathered" overpowered stations, which are allowed the same extended coverage areas that they had before the zones were established. One of the most powerful of these stations is WBCT in
Grand Rapids, Michigan, which operates at 320,000 watts and 238 meters (781 ft) HAAT.
Zone III (the zone with the flattest terrain) consists of all of
Floridaand the areas of Alabama, Georgia, Louisiana, Mississippi, and Texaswithin approximately 241.4 kilometers (150 miles) of the Gulf of Mexico.
Zone II is all the rest of the Continental United States,
Above mean sea level(AMSL)
Above ground level(AGL)
Canadian Radio-television and Telecommunications Commission(CRTC)
List of broadcast station classes
United States Federal Communications Commission(FCC)
* [http://www.access.gpo.gov/nara/cfr/waisidx_05/47cfr73_05.html 47 CFR Part 73 Index (2005)]
* [http://ftp.fcc.gov/oet/info/maps/mmb/ FCC: Mass Media Calculated Contours]
Wikimedia Foundation. 2010.
Look at other dictionaries:
Height above average terrain — Die Effektive Antennenhöhe (kurz: Effektive Höhe, englisch: Effective Antenna Height) ist die Höhe des Antennenmittelpunktes über dem mittleren Geländeniveau zwischen 3 km und 15 km Entfernung in die zur Berechnung der Wellenausbreitung… … Deutsch Wikipedia
height above average terrain — noun the height of a radio transmitter, including the antenna, as compared to the average terrain height in the surrounding area between three and sixteen kilometers from the antenna site … Wiktionary
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… … Wikipedia
antenna height above average terrain — vidutinis antenos aukštis statusas T sritis radioelektronika atitikmenys: angl. antenna height above average terrain vok. mittlere Antennenhöhe, f rus. средняя высота антенны, f pranc. altitude moyenne de l antenne, f … Radioelektronikos terminų žodynas
Height — ist der Familienname folgender Personen: Dorothy Height (1912–2010), US amerikanische Politikerin, Bürgerrechtlerin und Sozialarbeiterin Siehe auch: Heightmap, siehe Höhenfelder, zweidimensionale skalare Felder, die ein Höhenrelief beschreiben… … Deutsch Wikipedia
Above ground level — In aviation and atmospheric sciences, an altitude is said to be above ground level (AGL) when it is measured with respect to the underlying ground surface. This is as opposed to above mean sea level (AMSL), or in broadcast engineering, height… … Wikipedia
Above mean sea level — The term above mean sea level (AMSL) refers to the elevation (on the ground) or altitude (in the air) of any object, relative to the average sea level datum. AMSL is used extensively in radio (both in broadcasting and other telecommunications… … Wikipedia
above ground level — The height of an aircraft above ground level. Also known as absolute altitude. It is measured by a radio, radar, or laser altimeter. When an aircraft is required to fly at a certain height above ground level, the AGL refers to its average height… … Aviation dictionary
List of mountains on Mars by height — This is a list of mountains on Mars by elevation. The listed elevations are relative to the Martian datum (the elevation defined as zero by average martian atmospheric pressure and planet radius). Elevation is NOT the height above the surrounding … Wikipedia
Broadcast range — A broadcast range (also listening range for radio, or viewing range for TV) is the service area that a broadcast station or other transmission covers via radio waves (or possibly infrared light, which is closely related). It is generally the area … Wikipedia