Science Fair Project Encyclopedia
Low-power broadcasting is the concept of broadcasting at very low power and low cost, to a small community area. These stations tend to serve small towns, if not completely rural areas in the United States, largely because they cannot fit into large cities already crowded by full-power stations. The terms Low-power broadcasting and Micro-power broadcasting are sometimes used interchangably. However, the former term is more often used to describe stations who have applied for and received official licences. The latter is more often used to describe stations that have not applied for such licences and broadcast illegally.
The Prometheus Radio Project is an advocacy group for LPFM.
LPFM classes in the United States:
- Class L1 (LP100) is from 50 to 100 watts ERP.
- Class L2 (L10) is at least 1 and up to 10 watts ERP.
- Class D is 10 watts TPO or less, regardless of ERP, and are no longer issued for LPFM services (since 1978), though they are still issued for broadcast translators.
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 antennas, or may use carrier current methods to ride on power lines. These signals cannot pass through transformers, 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 highways and airports, and occasionally other tourism attractions such as national parks. Only governments may have licenses for TIS/HAR stations, and music is disallowed.
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