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The relationship between broadcasting power and signal range is a function of many things, such as the Frequency band it uses e.g, SW or FM , the Topography of the country in which it operates (lots of mountains or flat), atmospheric conditions, and finally the amount of radio frequency energy it transmits. As a general rule, the more energy it transmits, the further the signal goes. LPFM, '''LPAM''', and '''LPTV''' are in various levels of use across the world, varying widely based on the Law s and their Enforcement . UNITED STATES FM radio In the U.S. , the FCC partially re-legalized LPFM licenses, after the NAB , CPB , and NPR convinced them to stop issuing the FM Class D license in 1978 . The new LPFM licenses in the United States may only be issued to nonprofit educational organizations and state and local governments. Also, the one and so far only "window" for applications closed in 2003 , and at present, the FCC is not entertaining any new broadcast license applications, instead conducting auctions of frequencies for full power uses only. LPFM classes in the United States
Officially, class D is still assigned to Broadcast Translator s, though the rules are actually much looser (up to 250 watts ERP) than for true LPFM stations, though they may not broadcast their own programming. This is due to the influence of NPR and Religious Broadcasting companies, which often rely on translators. Since true class D stations can bump translators, they therefore have less competition in getting or keeping their own translators on the air with new class D stations kept off the air. New classes L1 and L2 are still considered class D for international purposes, but are considered to be equal in status to translators, and subordinate to full class D stations still operating. Part 15 rules are quite strict for FM, making it nearly impossible to operate a legally-unlicensed station that can be heard more than a few yards away. The rule is a Signal Strength of 250 µV/m at 3 meters from the Antenna , set forth in 47 CFR § 15.239. Criticisms of LPFM Many of the proponents of the new LPFM classes have been critical of the actual service. Their complaints include:
AM radio LPAM is generally not licensed in the U.S., but is allowed on the Campus of any School , so long as the normal Part 15 rules are adhered to when measured at the edge of the campus. Most College Radio stations started out this way. Stations may have freestanding Radio Antenna s, or may use Carrier Current methods to ride on Power Line s. These signals cannot pass through Transformer s, however, and are prone to the Electromagnetic Interference of the Alternating Current . The exception is Travelers' Information Stations (TIS), sometimes also called '''highway advisory radio''' ('''HAR'''). These are licensed LPAM stations set up by local Transport departments to provide bulletins to motorists and other travelers regarding Traffic and other delays. These are often near Highway s and Airport s, and occasionally other Tourism attractions such as National Park s. Only governments may have licenses for TIS/HAR stations, and Music is disallowed. Television LPTV is common in the U.S., Canada and most of the Americas where stations are free to either originate their own programming, or to relay a main TV Station as a Broadcast Translator . Some LPTV stations which broadcast their own programming were allowed a slight Upgrade to a new " Class A " status. Unlike FM and AM, unlicensed use of TV bands is prohibited for broadcasting. The Amateur Television channels do allow for some very limited non-entertainment broadcasting however, with some Repeater s airing NASA TV during Space Shuttle Mission s when they are not in local use. UNITED KINGDOM Temporary low-power stations are allowed at times via a Restricted Service Licence . Since 2001 longterm LPFM licences have been available in remote areas of the country. These are currently used for many establishments including Military Base s, Universities and Hospital s with fixed boundaries. NEW ZEALAND In New Zealand you are allowed to broadcast licence free at 0.5 Watts EIRP in the FM guardbands from 88.1 to 88.7 (or 88.1 to 88.4 within 120 km of the Sky Tower in Auckland ) and from 106.7 - 107.7 MHz under a General User Radio License (GURL) issued by Radio Spectrum Management . Broadcasters on these frequencies are required to cease operations if they interfere with other, licensed broadcasters and have no protection from interference from other licensed or unlicensed broadcasters. There are efforts on self-regulation of the broadcasters themselves, see List Of LPFM Stations In New Zealand . SEE ALSO
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