Accession Number : ADA051717

Title :   Surveys of Electromagnetic Field Intensities Near Representative Higher-Power FAA Transmitting Antennas.

Descriptive Note : Final rept. 1974-1976,


Personal Author(s) : Larsen,Ezra B ; Shafer,John F

PDF Url : ADA051717

Report Date : Dec 1977

Pagination or Media Count : 115

Abstract : The National Bureau of Standards has completed surveys of electromagnetic field intensities near the antennas of typical FAA transmitters. These include aircraft radars, ground surveillance radars, instrument landing systems, navigation equipment and communication antennas. The surveys were made with rf radiation monitors having isotropic response patterns. Commercial monitors with thermocouple sensors were used to measure electric fields between 0.5 and 24 GHz and magnetic fields between 10 and 300 MHz. Probes designed at NBS with diode detectors were used for electric field between 100 kHz and 10 GHZ. These radiation monitors cannot measure (accurately) the pulse-peak field of a radar nor the field of a scanning antenna; therefore, most of the radar surveys involved fixed antennas. The intensity in the direct beam of air route surveillance radars was greater than 10 mW/ at distances within about 14 meters from the antennas. The intensity of airport surveillance radars was above 10 mW/ at distances within 15 meters, except for the newer ASR-8 model. The direct beam of aircraft radars exceeded 10 mW/ at distances ranging from 2 to 7 meters. If the time-averaging effect for antenna scanning is taken into consideration, these field values would be greatly reduced. Also, the near-zone beams of FAA antennas are not normally accessible to personnel. In accessible areas the measured fields were generally less than 1 mW/sq cm. (Author)

Descriptors :   *Antennas, *Electromagnetic fields, Field intensity, Radar antennas, Radio transmitters, Radio navigation, Surveys, Very high frequency, Microwave frequency, High frequency, Medium frequency, Probes

Subject Categories : Electrical and Electronic Equipment
      Active & Passive Radar Detection & Equipment
      Electricity and Magnetism
      Radio Communications

Distribution Statement : APPROVED FOR PUBLIC RELEASE