There are more than 500,000 licensed amateur radio operators in the United States and many more throughout the world. Consequently, there is potential for human exposure to radiofrequency (RF) electromagnetic fields due to amateur radio stations. Because of its responsibilities under the terms of the National Environmental Policy Act (NEPA), the Federal Communications Commission (FCC) has an interest in ensuring that FCC-regulated transmitters do not expose the public to levels of RF energy in excess of accepted RF safety guidelines. Since 1985, human exposure to RF fields has been one of several environmental factors considered by the FCC in evaluating potential environmental impact from facilities and equipment it regulates.1 More recently, as discussed later, the FCC has proposed to adopt new guidelines for evaluating human exposure to RF energy.
In order to obtain data on the potential environmental impact of transmissions from amateur radio stations, personnel from the FCC and the U.S. Environmental Protection Agency (EPA) measured electromagnetic fields at several stations in southern California in July, 1990. Measurements of electric and magnetic field strength were made in areas near antennas and transmitting equipment in order to determine potential levels of exposure to RF radiation for amateur operators and other individuals who may be present in the immediate vicinity of amateur stations. Some measurements of operator exposure to 60-hertz magnetic fields were also made because of interest by the EPA in the extremely-low-frequency (ELF) electromagnetic environment. Data obtained as a result of this study will assist the FCC in determining how to ensure compliance with new RF guidelines that may be adopted in the near future.
Nine amateur stations were selected for this study based on several factors, including availability of the operator during the study period, the variety of antennas and equipment at the station, the variety of available frequencies, and accessibility of the transmitting site. Participation in the study was voluntary. The southern California location was chosen primarily because of its proximity to the EPA laboratory in Las Vegas, Nevada, where the EPA personnel, measurement vehicle, and most of the measuring equipment were located.
It was desired to obtain as representative a sample of amateur installations as possible so that comparisons with other typical amateur stations could be made. However, it is recognized that no two amateur facilities are likely to be identical. Multiple frequency bands are allocated for amateur use between 1.8 MHz and 250 GHz, and the maximum allowable power for an amateur station is 1500 watts peak envelope power (PEP).
The stations visited ranged from simple to complex, and measurements of fields due to transmissions from vehicular-mounted antennas were also included. Electric
FCC policy on RF exposure can be found in 47 CFR 1.1307(b).