A Measurement of RF Field Intensities in the Immediate Vicinity of an FM Broadcast Station Antenna
R. A. Tell · 1976
FM broadcast antennas create some of the strongest RF exposures in our environment, requiring careful measurement for safety.
Plain English Summary
This 1976 technical report measured radio frequency field intensities directly around FM broadcast station antennas to understand actual exposure levels. The study documented RF field strengths in areas where people might be present near these powerful transmission facilities. This type of measurement work helps establish safety guidelines for workers and the public around broadcast infrastructure.
Why This Matters
This early measurement work represents crucial baseline research that helped establish our understanding of RF exposure levels around broadcast facilities. FM radio stations transmit at power levels ranging from hundreds to tens of thousands of watts, creating some of the strongest RF fields in our everyday environment. What makes this study particularly relevant is that it measured actual field intensities rather than relying on theoretical calculations. The reality is that people living or working near FM broadcast towers can experience RF exposures orders of magnitude higher than typical household sources like WiFi routers or cell phones. While FM radio frequencies (88-108 MHz) are lower than cell phone frequencies, the power levels are dramatically higher, making proximity to these antennas a significant exposure consideration that predates our current wireless world.
Finding
From an examination of the data it is clear that exposure intensities on FM broadcast towers can exceed the OSHA recommended safety level of 10 mW/cm2 by more than a factor of 10.
In their words
“From an examination of the data it is clear that exposure intensities on FM broadcast towers can exceed the OSHA recommended safety level of 10 mW/cm2 by more than a factor of 10.”
Figures from the Original Paper
Diagram extracted from the original research document.
Exposure Information
Specific exposure levels were not quantified in this study. Duration: about 20 minutes
Study Details
To measure radiofrequency field intensities in the immediate vicinity of an FM broadcast station antenna and evaluate potential exposure risks to personnel working on broadcast towers.
Measurements were made with an electric field energy density meter, model EDM-3, designed and develo...
The highest value of energy density measured directly under the towers on the ground was 0.032 uJ/m3...
Exposure intensities on FM broadcast towers can exceed the OSHA recommended safety level of 10 mW/cm2 by more than a factor of 10. The simplest method of control appears to be to turn off the transmitter while work which requires people to be on the tower is done. Television towers are also suspected of having very high levels near the antenna since they have significantly higher powers than FM broadcast stations. Standard broadcast AM towers may also be of concern because of high surface fields on the tower.
Show BibTeX
@article{a_measurement_of_rf_field_intensities_in_the_immediate_vicinity_of_an_fm_broadca_g6113,
author = {R. A. Tell},
title = {A Measurement of RF Field Intensities in the Immediate Vicinity of an FM Broadcast Station Antenna},
year = {1976},
}