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message</a></small>)</i></span></div></td></tr></tbody></table> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">"EHAAT" redirects here. For the air ambulance service, see <a href="/wiki/Essex_%26_Herts_Air_Ambulance" title="Essex & Herts Air Ambulance">Essex & Herts Air Ambulance</a>.</div> <p><b>Height above average terrain</b> (<b>HAAT</b>), or (less popularly) <b>effective height above average terrain</b> (<b>EHAAT</b>), is the <a href="/wiki/Vertical_position" title="Vertical position">vertical position</a> of an <a href="/wiki/Antenna_(radio)" title="Antenna (radio)">antenna</a> site above the surrounding landscape. HAAT is used extensively in <a href="/wiki/FM_radio" class="mw-redirect" title="FM radio">FM radio</a> and <a href="/wiki/Television" title="Television">television</a>, as it is more important than <a href="/wiki/Effective_radiated_power" title="Effective radiated power">effective radiated power</a> (ERP) in determining the range of broadcasts (<a href="/wiki/Very_high_frequency" title="Very high frequency">VHF</a> and <a href="/wiki/Ultra_high_frequency" title="Ultra high frequency">UHF</a> in particular, as they are <a href="/wiki/Line-of-sight_propagation" title="Line-of-sight propagation">line of sight</a> transmissions). For international coordination, it is officially measured in meters, even by the <a href="/wiki/Federal_Communications_Commission" title="Federal Communications Commission">Federal Communications Commission</a> in the <a href="/wiki/United_States" title="United States">United States</a>, as <a href="/wiki/Canada" title="Canada">Canada</a> and <a href="/wiki/Mexico" title="Mexico">Mexico</a> have extensive border zones where 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 <a href="/wiki/List_of_North_American_broadcast_station_classes" title="List of North American broadcast station classes">List of North American broadcast station classes</a> for more information on this). </p><p>The <a href="/wiki/Federal_Communications_Commission" title="Federal Communications Commission">FCC</a> procedure to calculate HAAT is: from the proposed or actual antenna site, either 12 or 16 <a href="/wiki/Radial_(radio)" title="Radial (radio)">radials</a> were drawn, and points at 2, 4, 6, 8, and 10 miles (16 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, is the HAAT. This can create some unusual cases, particularly in <a href="/wiki/Mountain" title="Mountain">mountainous</a> regions—it is possible to have a negative number for HAAT (the transmitter would not be located underground, but rather in a <a href="/wiki/Valley" title="Valley">valley</a>, with hills on both sides taller than the transmitter itself, for example). </p><p>The FCC has divided the <a href="/wiki/Contiguous_United_States" title="Contiguous United States">Contiguous United States</a> 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 <a href="/wiki/Co-channel_interference" title="Co-channel interference">co-channel interference</a>. </p> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:US_FM_broadcast_zones.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/9a/US_FM_broadcast_zones.png/300px-US_FM_broadcast_zones.png" decoding="async" width="300" height="194" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/9/9a/US_FM_broadcast_zones.png 1.5x" data-file-width="398" data-file-height="258" /></a><figcaption>FM broadcast zones in the U.S.</figcaption></figure> <p>The FCC regulations for ERP and HAAT are listed under Title 47, Part 73 of the <a href="/wiki/Code_of_Federal_Regulations" title="Code of Federal Regulations">Code of Federal Regulations</a> (CFR). </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="FM">FM</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Height_above_average_terrain&action=edit&section=1" title="Edit section: FM"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Zones_I_and_I-A">Zones I and I-A</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Height_above_average_terrain&action=edit&section=2" title="Edit section: Zones I and I-A"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>Maximum HAAT: 150 metres (492 ft 2 in)</li> <li>Maximum ERP: 50 kilowatts (47<a href="/wiki/DBW" class="mw-redirect" title="DBW">dBW</a>)</li> <li>Minimum co-channel separation: 241 km (150 mi)</li></ul> <div class="mw-heading mw-heading3"><h3 id="Zones_II_and_III">Zones II and III</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Height_above_average_terrain&action=edit&section=3" title="Edit section: Zones II and III"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>Maximum HAAT: 600 metres (1,968 ft 6 in)</li> <li>Maximum ERP: 100 kilowatts (50dBW)</li> <li>Minimum co-channel separation: 290 km (180 mi).</li></ul> <div class="mw-heading mw-heading2"><h2 id="TV">TV</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Height_above_average_terrain&action=edit&section=4" title="Edit section: TV"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In all zones, maximum ERP for analog TV transmitters is as follows: </p> <ul><li>VHF 2-6: 100 kilowatts (50dBW) (analog); 45 kilowatts (46.5dBW) (digital)</li> <li>VHF 7-13: 316 kilowatts (55dBW) (analog); 160 kilowatts (52dBW) (digital)</li> <li>UHF: 5,000 kilowatts (67dBW) (analog); 1,000 kilowatts (60dBW) (digital)</li></ul> <div class="mw-heading mw-heading3"><h3 id="Maximum_HAAT">Maximum HAAT</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Height_above_average_terrain&action=edit&section=5" title="Edit section: Maximum HAAT"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>Zone I: 305 metres (1,000 ft 8 in)</li> <li>Zones II and III: 610 metres (2,001 ft 4 in)</li></ul> <div class="mw-heading mw-heading3"><h3 id="Minimum_co-channel_separation">Minimum co-channel separation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Height_above_average_terrain&action=edit&section=6" title="Edit section: Minimum co-channel separation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <table> <tbody><tr> <th>Band </th> <th>Zone I </th> <th>Zone II </th> <th>Zone III </th></tr> <tr> <td>VHF </td> <td>272.7 km<br />(169.5 miles) </td> <td>304.9 km<br />(189.5 miles) </td> <td>353.2 km<br />(219.5 miles) </td></tr> <tr> <td>UHF </td> <td>248.6 km<br />(154.5 miles) </td> <td>280.8 km<br />(174.5 miles) </td> <td>329.0 km<br />(204.5 miles) </td></tr></tbody></table> <div class="mw-heading mw-heading2"><h2 id="Zone_layouts">Zone layouts</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Height_above_average_terrain&action=edit&section=7" title="Edit section: Zone layouts"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Zone I (the most densely populated zone) consists of the entire land masses of the following states: <a href="/wiki/Connecticut" title="Connecticut">Connecticut</a>, <a href="/wiki/Delaware" title="Delaware">Delaware</a>, <a href="/wiki/Illinois" title="Illinois">Illinois</a>, <a href="/wiki/Indiana" title="Indiana">Indiana</a>, <a href="/wiki/Maryland" title="Maryland">Maryland</a>, <a href="/wiki/Massachusetts" title="Massachusetts">Massachusetts</a>, <a href="/wiki/New_Jersey" title="New Jersey">New Jersey</a>, <a href="/wiki/Ohio" title="Ohio">Ohio</a>, <a href="/wiki/Pennsylvania" title="Pennsylvania">Pennsylvania</a>, <a href="/wiki/Rhode_Island" title="Rhode Island">Rhode Island</a>, and <a href="/wiki/West_Virginia" title="West Virginia">West Virginia</a>; in addition to the northern and eastern portions of <a href="/wiki/Virginia" title="Virginia">Virginia</a>; the areas of <a href="/wiki/Michigan" title="Michigan">Michigan</a> and southeastern <a href="/wiki/Wisconsin" title="Wisconsin">Wisconsin</a> south of 43° 30' north latitude; the coastal strip of <a href="/wiki/Maine" title="Maine">Maine</a>; the areas of <a href="/wiki/New_Hampshire" title="New Hampshire">New Hampshire</a> and <a href="/wiki/Vermont" title="Vermont">Vermont</a> south of 45° north latitude; and the areas of western <a href="/wiki/New_York_(state)" title="New York (state)">New York</a> 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 <a href="/wiki/California" title="California">California</a> south of 40° north latitude, <a href="/wiki/Puerto_Rico" title="Puerto Rico">Puerto Rico</a> and the <a href="/wiki/United_States_Virgin_Islands" title="United States Virgin Islands">U.S. Virgin Islands</a> (If the dividing line between Zones I and II runs through a city, that city is considered to be in Zone I.). </p><p>Zones I and I-A have the most <a href="/wiki/Grandfather_clause" title="Grandfather clause">"grandfathered"</a> 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 <a href="/wiki/WBCT" title="WBCT">WBCT</a> in <a href="/wiki/Grand_Rapids,_Michigan" title="Grand Rapids, Michigan">Grand Rapids, Michigan</a>, which operates at 320,000 watts and 238 meters (781 ft) HAAT. </p><p>Zone III (the zone with the flattest terrain) consists of all of <a href="/wiki/Florida" title="Florida">Florida</a> and the areas of <a href="/wiki/Alabama" title="Alabama">Alabama</a>, <a href="/wiki/Georgia_(U.S._state)" title="Georgia (U.S. state)">Georgia</a>, <a href="/wiki/Louisiana" title="Louisiana">Louisiana</a>, <a href="/wiki/Mississippi" title="Mississippi">Mississippi</a>, and <a href="/wiki/Texas" title="Texas">Texas</a> within approximately 241.4 kilometers (150.0 mi) of the <a href="/wiki/Gulf_of_Mexico" title="Gulf of Mexico">Gulf of Mexico</a>. </p><p>Zone II is all the rest of the Continental United States, <a href="/wiki/Alaska" title="Alaska">Alaska</a> and <a href="/wiki/Hawaii" title="Hawaii">Hawaii</a>. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Height_above_average_terrain&action=edit&section=8" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Above_mean_sea_level" class="mw-redirect" title="Above mean sea level">Above mean sea level</a> (AMSL)</li> <li><a href="/wiki/Above_ground_level" class="mw-redirect" title="Above ground level">Above ground level</a> (AGL)</li> <li><a href="/wiki/Canadian_Radio-television_and_Telecommunications_Commission" title="Canadian Radio-television and Telecommunications Commission">Canadian Radio-television and Telecommunications Commission</a> (CRTC)</li> <li><a href="/wiki/List_of_broadcast_station_classes" class="mw-redirect" title="List of broadcast station classes">List of broadcast station classes</a></li> <li><a href="/wiki/Topographic_prominence" title="Topographic prominence">Topographic prominence</a> – a similar measurement for mountains</li></ul> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Height_above_average_terrain&action=edit&section=9" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="http://www.access.gpo.gov/nara/cfr/waisidx_05/47cfr73_05.html">47 CFR Part 73 Index (2005)</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110717025218/http://www.access.gpo.gov/nara/cfr/waisidx_05/47cfr73_05.html">Archived</a> 2011-07-17 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20050117155245/http://ftp.fcc.gov/oet/info/maps/mmb/">FCC: Mass Media Calculated Contours</a></li> <li><a rel="nofollow" class="external text" href="https://www.fcc.gov/media/radio/haat-calculator">FCC: HAAT Calculator</a></li> <li><a rel="nofollow" class="external text" href="http://www.w9wi.com/articles/superfm.html">"Superpower" Grandfathered FM stations</a></li></ul>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; 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