ARE EMISSIONS FROM RADIO AND TELEVISION BROADCAST ANTENNAS SAFE?

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Radio and television broadcast stations transmit their signals via RF electromagnetic waves.  There are thousands of radio and TV stations on the air in the United States.  Broadcast stations transmit at various RF frequencies, depending on the channel, ranging from about 540 kHz for AM radio up to about 700 MHz for UHF television stations.  Frequencies for FM radio and VHF television lie in between these two extremes.  Broadcast transmitter power levels range from less then a watt to more than 100,000 watts.  Some of these transmission systems can be a significant source of RF energy in the local environment, so the FCC requires that broadcast stations submit evidence of compliance with FCC RF guidelines.

The amount of RF energy to which the public or workers might be exposed as a result of broadcast antennas depends on several factors, including the type of station, design characteristics of the antenna being used, power transmitted to the antenna, height of the antenna and distance from the antenna.  Note that the power normally quoted for FM and TV broadcast transmitters is the “effective radiated power” or ERP not the actual transmitter power mentioned above.  ERP is the transmitter power delivered to the antenna multiplied by the directivity or gain of the antenna.  Since high gain antennas direct most of the RF energy toward the horizon and not toward the ground, high ERP transmission systems such as used for UHF-TV broadcast tend to have less ground level field intensity near the station than FM radio broadcast systems with lower ERP and gain values.  Also, since energy at some frequencies is absorbed by the human body more readily than at other frequencies, both the frequency of the transmitted signal and its intensity is important.  Calculations can be performed to predict what field intensity levels would exist at various distances from an antenna.

Public access to broadcasting antennas is normally restricted so that individuals cannot be exposed to high-level fields that might exist near antennas.  Measurements made by the FCC, EPA and others have shown that ambient RF radiation levels in inhabited areas near broadcasting facilities are typically well below the exposure levels recommended by current standards and guidelines.  There have been a few situations around the country where RF levels in publicly accessible areas have been found to be higher than those recommended in applicable safety standards.  As they have been identified, the FCC has required that stations at those facilities promptly bring their combined operations into compliance with our guidelines.  Thus, despite the relatively high operating powers of many broadcast stations, such cases are unusual, and members of the general public are unlikely to be exposed to RF levels from broadcast towers that exceed FCC limits

Antenna maintenance workers are occasionally required to climb antenna structures for such purposes as painting, repairs, or lamp replacement.  Both the EPA and OSHA have reported that in such cases it is possible for a worker to be exposed to high levels of RF energy if work is performed on an active tower or in areas immediately surrounding a radiating antenna.  Therefore, precautions should be taken to ensure that maintenance personnel are not exposed to unsafe RF fields. 

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WHAT IS THE FCC’S POLICY ON RADIOFREQUENCY WARNING SIGNS? FOR EXAMPLE, WHEN SHOULD SIGNS BE POSTED, WHERE SHOULD THEY BE LOCATED AND WHAT SHOULD THEY SAY?