Height above average terrain
Encyclopedia
Height above average terrain (HAAT) (or less popularly, EHAAT, Effective Height Above Average Terrain) is used extensively in FM
radio
and television
, as it is actually much more important than effective radiated power
(ERP) in determining the range of broadcasts (VHF and UHF
in particular, as they are line of sight
transmissions). For international
coordination, it is officially measured in meters, even by the Federal Communications Commission
in the United States
, as Canada
and Mexico
(both of which use metric) have extensive border zones where international stations can be received 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 classes for 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 10 miles (16.1 km) radius along each radial were used. The entire radial graph could be rotated to achieve the best effect for the station. The altitude of the antenna site, minus the average altitude of all the specified points, was the HAAT. This can create some unusual cases, particularly in mountain
ous 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 States into 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).
, 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 Michigan
and southeastern Wisconsin
south of 43° 30' north latitude; the coastal strip of Maine
; the areas of New Hampshire
and Vermont
south of 45° north latitude; and the areas of western New York
south 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 California
south of 40° north latitude, Puerto Rico
and 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 Florida
and the areas of Alabama
, Georgia
, Louisiana
, Mississippi
, and Texas
within approximately 241.4 kilometres (150 mi) of the Gulf of Mexico
.
Zone II is all the rest of the Continental United States, Alaska
and Hawaii
.
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
and television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
, as it is actually much more important than effective radiated power
Effective radiated power
In radio telecommunications, effective radiated power or equivalent radiated power is a standardized theoretical measurement of radio frequency energy using the SI unit watts, and is determined by subtracting system losses and adding system gains...
(ERP) in determining the range of broadcasts (VHF and UHF
Ultra high frequency
Ultra-High Frequency designates the ITU Radio frequency range of electromagnetic waves between 300 MHz and 3 GHz , also known as the decimetre band or decimetre wave as the wavelengths range from one to ten decimetres...
in particular, as they are line of sight
Line-of-sight propagation
Line-of-sight propagation refers to electro-magnetic radiation or acoustic wave propagation. Electromagnetic transmission includes light emissions traveling in a straight line...
transmissions). For international
International
----International mostly means something that involves more than one country. The term international as a word means involvement of, interaction between or encompassing more than one nation, or generally beyond national boundaries...
coordination, it is officially measured in meters, even by the Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, as Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
and Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
(both of which use metric) have extensive border zones where international stations can be received 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 classes for more information on this).
Before metrification
Metric system
The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...
at the FCC
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
, the procedure to figure HAAT was relatively simple: from the proposed or actual antenna site, either 12 or 16 radials
Radial (radio)
In RF engineering, radial has two different meanings, both referring to lines which radiate from a radio antenna.-Planning:...
were drawn, and points at 2, 4, 6, 8, and 10 miles (16.1 km) radius along each radial were used. The entire radial graph could be rotated to achieve the best effect for the station. The altitude of the antenna site, minus the average altitude of all the specified points, was the HAAT. This can create some unusual cases, particularly in mountain
Mountain
Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...
ous regions—it is possible to have a negative number for HAAT (the transmitter would not be located underground, but rather in a valley
Valley
In geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...
, with hills on both sides taller than the transmitter itself, for example).
The FCC has divided the Continental United States into 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
Co-channel interference
Co-channel interference or CCI is crosstalk from two different radio transmitters using the same frequency. There can be several causes of co-channel radio interference; four examples are listed here....
.
Code of Federal Regulations
The Code of Federal Regulations is the codification of the general and permanent rules and regulations published in the Federal Register by the executive departments and agencies of the Federal Government of the United States.The CFR is published by the Office of the Federal Register, an agency...
(CFR).
Zones I and I-A
- Maximum HAAT: 150 meters (492 ft)
- Maximum ERP: 50 kW
- Minimum co-channel separation: 241 km (149.8 mi)
Zones II and III
- Maximum HAAT: 600 meters (1968 ft)
- Maximum ERP: 100 kW
- Minimum co-channel separation: 290 km (180.2 mi).
TV
In all zones, maximum ERP for analog TV transmitters is as follows:- VHF 2-6: 300 kW
- VHF 7-13: 316 kW
- UHF: 5,000 kW
Minimum co-channel separation
| Band | Zone I | Zone II | Zone III |
|---|---|---|---|
| VHF | 272.7 km (169.5 miles) |
304.9 km (189.5 miles) |
353.2 km (219.5 miles) |
| UHF | 248.6 km (154.5 miles) |
280.8 km (174.5 miles) |
329.0 km (204.5 miles) |
Zone layouts
Zone I (the most densely populated zone) consists of the entire land masses of the following states: ConnecticutConnecticut
Connecticut is a state in the New England region of the northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, and the state of New York to the west and the south .Connecticut is named for the Connecticut River, the major U.S. river that approximately...
, Delaware
Delaware
Delaware is a U.S. state located on the Atlantic Coast in the Mid-Atlantic region of the United States. It is bordered to the south and west by Maryland, and to the north by Pennsylvania...
, Illinois
Illinois
Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...
, Indiana
Indiana
Indiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...
, Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...
, Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
, New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
, Ohio
Ohio
Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...
, Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...
, Rhode Island
Rhode Island
The state of Rhode Island and Providence Plantations, more commonly referred to as Rhode Island , is a state in the New England region of the United States. It is the smallest U.S. state by area...
, and West Virginia
West Virginia
West Virginia is a state in the Appalachian and Southeastern regions of the United States, bordered by Virginia to the southeast, Kentucky to the southwest, Ohio to the northwest, Pennsylvania to the northeast and Maryland to the east...
; in addition to the southern and eastern portions of Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
; the areas of Michigan
Michigan
Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....
and southeastern Wisconsin
Wisconsin
Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...
south of 43° 30' north latitude; the coastal strip of Maine
Maine
Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost...
; the areas of New Hampshire
New Hampshire
New Hampshire is a state in the New England region of the northeastern United States of America. The state was named after the southern English county of Hampshire. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Atlantic Ocean to the east, and the Canadian...
and Vermont
Vermont
Vermont is a state in the New England region of the northeastern United States of America. The state ranks 43rd in land area, , and 45th in total area. Its population according to the 2010 census, 630,337, is the second smallest in the country, larger only than Wyoming. It is the only New England...
south of 45° north latitude; and the areas of western New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
south 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 California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
south of 40° north latitude, Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
and 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"
Grandfather clause
Grandfather clause is a legal term used to describe a situation in which an old rule continues to apply to some existing situations, while a new rule will apply to all future situations. It is often used as a verb: to grandfather means to grant such an exemption...
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
Grand Rapids, Michigan
Grand Rapids is a city in the U.S. state of Michigan. The city is located on the Grand River about 40 miles east of Lake Michigan. As of the 2010 census, the city population was 188,040. In 2010, the Grand Rapids metropolitan area had a population of 774,160 and a combined statistical area, Grand...
, which operates at 320,000 watts and 238 meters (781 ft) HAAT.
Zone III (the zone with the flattest terrain) consists of all of Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
and the areas of Alabama
Alabama
Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...
, Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
, Louisiana
Louisiana
Louisiana is a state located in the southern region of the United States of America. Its capital is Baton Rouge and largest city is New Orleans. Louisiana is the only state in the U.S. with political subdivisions termed parishes, which are local governments equivalent to counties...
, Mississippi
Mississippi
Mississippi is a U.S. state located in the Southern United States. Jackson is the state capital and largest city. The name of the state derives from the Mississippi River, which flows along its western boundary, whose name comes from the Ojibwe word misi-ziibi...
, and Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
within approximately 241.4 kilometres (150 mi) of the Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
.
Zone II is all the rest of the Continental United States, Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
and Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
.
See also
- Above mean sea levelAbove mean sea levelThe term above mean sea level refers to the elevation or altitude of any object, relative to the average sea level datum. AMSL is used extensively in radio by engineers to determine the coverage area a station will be able to reach...
(AMSL) - Above ground levelAbove ground levelIn aviation and atmospheric sciences, an altitude is said to be above ground level when it is measured with respect to the underlying ground surface. This is as opposed to above mean sea level , or in broadcast engineering, height above average terrain...
(AGL) - Canadian Radio-television and Telecommunications Commission (CRTC)
- List of broadcast station classes
- United StatesUnited StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
Federal Communications CommissionFederal Communications CommissionThe Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
(FCC)