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Height above average terrain (HAAT) (or less popularly, EHAAT, Effective Height Above Average Terrain) is used extensively in FM
Frequency modulation

In telecommunications, frequency modulation conveys information over a carrier wave by varying its frequency . In analog signal applications, the instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal....
 radio
Radio

Radio is the transmission of signals, by modulation of electromagnetic radiation with frequency below those of visible light.Electromagnetic radiation radio propagation by means of oscillating electromagnetic fields that pass through the air and the vacuum of space....
 and television
Television

Television is a widely used telecommunication mass-media for transmitting and receiving moving , either monochrome or color, usually accompanied by 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 non-International System of Units unit Decibel, 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 a range of Electromagnetic radiation waves with frequency between 300 megahertz and 3 gigahertz . Also known as the decimetre band or decimetre wave as the wavelengths range from ten to one decimetres....
 in particular, as they are line of sight
Line-of-sight propagation

Line-of-sight propagation refers to electro-magnetic radiation including light emissions traveling in a straight line. The rays or waves are diffracted, refracted, reflected, or absorbed by atmosphere and obstructions with material and generally cannot travel over the horizon or behind obstacles....
 transmissions). For international
International

International or internationally most often describes interaction between nations, or encompassing two or more nations, constituting a group or association having members in two or more nations, or generally reaching 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 agencies of the United States government, created, directed, and empowered by United States Congress statute , and with the majority of its commissioners appointed by the current President of the United States....
 in the United States
United States

The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
, as Canada
Canada

Canada is a country occupying most of northern North America, extending 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 federalism constitutionalism 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 Mexico....
 (both of which use metric) have extensive border zones where international stations can be received on either side of the international boundaries.






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Height above average terrain (HAAT) (or less popularly, EHAAT, Effective Height Above Average Terrain) is used extensively in FM
Frequency modulation

In telecommunications, frequency modulation conveys information over a carrier wave by varying its frequency . In analog signal applications, the instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal....
 radio
Radio

Radio is the transmission of signals, by modulation of electromagnetic radiation with frequency below those of visible light.Electromagnetic radiation radio propagation by means of oscillating electromagnetic fields that pass through the air and the vacuum of space....
 and television
Television

Television is a widely used telecommunication mass-media for transmitting and receiving moving , either monochrome or color, usually accompanied by 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 non-International System of Units unit Decibel, 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 a range of Electromagnetic radiation waves with frequency between 300 megahertz and 3 gigahertz . Also known as the decimetre band or decimetre wave as the wavelengths range from ten to one decimetres....
 in particular, as they are line of sight
Line-of-sight propagation

Line-of-sight propagation refers to electro-magnetic radiation including light emissions traveling in a straight line. The rays or waves are diffracted, refracted, reflected, or absorbed by atmosphere and obstructions with material and generally cannot travel over the horizon or behind obstacles....
 transmissions). For international
International

International or internationally most often describes interaction between nations, or encompassing two or more nations, constituting a group or association having members in two or more nations, or generally reaching 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 agencies of the United States government, created, directed, and empowered by United States Congress statute , and with the majority of its commissioners appointed by the current President of the United States....
 in the United States
United States

The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
, as Canada
Canada

Canada is a country occupying most of northern North America, extending 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 federalism constitutionalism 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 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
List of broadcast station classes

This is a list of broadcast station classes applicable in much of North America under international agreements between the United States, Canada and Mexico....
 for more information on this).

Before metrification
Metric system

The metric system is an international decimalised systems of measurement, founded by France in 1791, that is the common system of Unit of measurement used by most of the world....
 at the FCC
Federal Communications Commission

The Federal Communications Commission is an Independent agencies of the United States government, created, directed, and empowered by United States Congress statute , and with the majority of its commissioners appointed by the current President of the United States....
, the procedure to figure HAAT was relatively simple: from the proposed or actual antenna site, either 12 or 16 radials
Radial (radio)

In radio, evenly-spaced points along evenly-spaced radials or lines through a common point on a map, are used to determine average elevation above mean sea level within a radio station's coverage area ....
 were drawn, and points at 2, 4, 6, 8, and 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 mountain
Mountain

A mountain is a landform that stretches above the surrounding land in a limited area usually in the form of a peak. A mountain is generally steeper than a hill....
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 is a Depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge....
, 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; three examples are listed here....
.

Us Fm Broadcast Zones
The FCC regulations for ERP and HAAT are listed under Title 47, Part 73 of the Code of Federal Regulations
Code of Federal Regulations

File:Codeoffederalregulations.jpgThe 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....
 (CFR).

FM


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).


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


Maximum HAAT

  • Zone I: 305 meters (1000 ft)
  • Zones II and III: 610 meters (2000 ft)


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: Connecticut
Connecticut

Connecticut is a U.S. state located in the New England region of the northeastern United States. The state borders New York to the west and south , Massachusetts to the north, and Rhode Island to the east....
, Delaware
Delaware

Delaware is a U.S. state located on the East Coast of the United States in the Mid-Atlantic States region of the United States. The state takes its name from Thomas West, 3rd Baron De La Warr, a British nobleman and Virginia's first colonial governor, after whom Cape Henlopen was originally named....
, Illinois
Illinois

The State of Illinois is a U.S. state of the United States, the 21st to be admitted to the United States. Illinois is the most populous and demographically diverse Midwestern United States state and the fifth most populous state in the nation....
, Indiana
Indiana

The State of Indiana was the 19th U.S. state admitted into the union. It is located in the Midwestern United States of the United States of America....
, Maryland
Maryland

Maryland is a U.S. state located in the Mid Atlantic States of the United States, bordering Virginia, West Virginia and the Washington, D.C. to the south and west, Pennsylvania to the north, and Delaware to the east....
, Massachusetts
Massachusetts

The Commonwealth of Massachusetts is a U.S. state located in the New England region of the Northeastern United States United States. It borders Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north....
, New Jersey
New Jersey

New Jersey is a state in the Mid-Atlantic States and Northeastern United States regions of the United States. It is bordered on the north by New York, on the east by the Hudson River and the Atlantic Ocean, on the southwest by Delaware, and on the west by Pennsylvania....
, Ohio
Ohio

Ohio is a Midwestern United States U.S. state of the United States. As part of the Great Lakes region , Ohio has long been a cultural and geographical crossroads in North America....
, Pennsylvania
Pennsylvania

The Commonwealth of Pennsylvania , often colloquially referred to as PA by natives and Northeasterners, is a U.S. state located in the Northeastern United States and Mid-Atlantic States regions of the United States....
, Rhode Island
Rhode Island

Rhode Island and Providence Plantations, more commonly referred to as Rhode Island , is a U.S. state in the New England region of the United States....
, and West Virginia
West Virginia

West Virginia is a U.S. state in the Appalachian, Upland South, and Mid-Atlantic States regions of the United States, bordered by Virginia on the southeast, Kentucky on the southwest, Ohio on the northwest, and Pennsylvania and Maryland on the northeast....
; in addition to the southern and eastern portions of Virginia
Virginia

The Commonwealth of Virginia is an United States U.S. state on the East Coast of the United States of the Southern United States. The state is known as the "Old Dominion" and sometimes as "Mother of Presidents", because it is the birthplace of Lists of United States Presidents by place of birth#By state....
; the areas of Michigan
Michigan

Michigan is a Midwestern United States U.S. state of the United States of America. It was named after Lake Michigan, whose name is a French adaptation of the Anishinaabe language term mishigama, meaning "large water" or "large lake"....
 and southeastern Wisconsin
Wisconsin

Wisconsin is one of the fifty U.S. state in the United States of America, located in the north central part of the United States. It borders two of the five Great Lakes and four U.S....
 south of 43° 30' north latitude; the coastal strip of Maine
Maine

The State of Maine is a U.S. state in the New England region of the northeastern United States of America, bordering the Atlantic Ocean to the southeast, New Hampshire to the southwest, the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast....
; the areas of New Hampshire
New Hampshire

New Hampshire is a U.S. state in the New England region of the Northeastern United States United States of America. The state was named after the southern English Counties of England of Hampshire....
 and Vermont
Vermont

Vermont is a U.S. state in the New England region of the Northeastern United States United States. The state ranks 43rd by land area, , and 45th by total area....
 south of 45° north latitude; and the areas of western New York
New York

The State of New York is a U.S. state in the Mid-Atlantic States and Northeastern United States regions of the United States and is the nation's List of U.S....
 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 U.S. state on the West Coast of the United States of the United States, along the Pacific Ocean. It is bordered by Oregon to the north, Nevada to the east, Arizona to the southeast, and to the south the Mexico state of Baja California....
 south of 40° north latitude, Puerto Rico
Puerto Rico

Puerto Rico , officially the Commonwealth of Puerto Rico , is a Autonomy Territories of the United States of the United States located in the northeastern Caribbean, east of the Dominican Republic and west of the Virgin Islands....
 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

A grandfather clause is an exception that allows an old rule to continue to apply to some existing situations, when a new rule will apply to all future situations....
 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. As of the United States 2000 Census, the city population was 197,800. It is the county seat of Kent County, Michigan, 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
Florida

Florida is a U.S. state located in the Southeastern United States of the United States, bordering Alabama to the northwest and Georgia to the northeast....
 and the areas of Alabama
Alabama

Alabama is a state located in the Southern United States of the United States of America. 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....
, Georgia
Georgia (U.S. state)

Georgia is a U.S. state in the United States and was one of the original Thirteen Colonies that revolted against United Kingdom rule in the American Revolution....
, Louisiana
Louisiana

The State of Louisiana is a U.S. state located in the U.S. Southern States of the United States of America. Its capital is Baton Rouge and largest city is New Orleans....
, Mississippi
Mississippi

Mississippi is a U.S. state located in the Deep South of the United States. Jackson, Mississippi is the state capital and largest city. The state's name comes from the Mississippi River, which flows along its western boundary, and takes its name from the Anishinaabe language word misi-ziibi ....
, and Texas
Texas

Texas is a U.S. state located in the South Central United States, nicknamed the Lone Star State. Texas is the second largest U.S. state in both area and population, spanning , and with a growing population of 24.3 million residents....
 within approximately 241.4 kilometers (150 miles) of the Gulf of Mexico
Gulf of Mexico

The Gulf of Mexico is the ninth largest body of water in the world. Considered a smaller part of the Atlantic Ocean, it is an oceanic basin largely surrounded by the North American continent and the island of Cuba....
.

Zone II is all the rest of the Continental United States, Alaska
Alaska

Alaska is the largest U.S. state of 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

File:Pahoehoe and Aa flows at Hawaii.jpgThe State of Hawaii is a U.S. state in the United States, located on an archipelago in the central Pacific Ocean southwest of the continental United States, southeast of Japan, and northeast of Australia....
.

See also

  • Above mean sea level
    Above mean sea level

    The 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 level
    Above ground level

    In aviation and atmospheric sciences, an altitude is said to be above ground level when it is measured with respect to the underlying earth's surface....
     (AGL)
  • Canadian Radio-television and Telecommunications Commission (CRTC)
  • List of broadcast station classes
    List of broadcast station classes

    This is a list of broadcast station classes applicable in much of North America under international agreements between the United States, Canada and Mexico....
  • United States
    United States

    The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
     Federal Communications Commission
    Federal Communications Commission

    The Federal Communications Commission is an Independent agencies of the United States government, created, directed, and empowered by United States Congress statute , and with the majority of its commissioners appointed by the current President of the United States....
     (FCC)


External links