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Radiofrequency and Microwave Radiation |
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Evaluating RF and Microwave Exposure |
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RF energy includes frequencies ranging from about
3000 cycles per second (3 kHz) to 300 billion cycles per second (300 GHz).
Microwaves are a subset of radio waves and includes frequencies ranging from around
300 million cycles per second (300 MHz) to 3
GHz. RF exposures are directly linked to
absorption and distribution of RF energy in the body, and the absorption and
distribution are strongly dependent on body size and orientation and on
frequency and polarization of the incident radiation. A common measure of exposure is the Specific Absorption Rate
(SAR), the rate of energy absorption in tissue, measured in watts per kilogram
of tissue.
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C95.3-2002,
IEEE Recommended Practice for Measurements and Computations of Radio
Frequency Electromagnetic Fields With Respect to Human Exposure to Such
Fields, 100 kHz-300 GHz. This standard revises and develops
specifications for preferred methods for measuring and computing
external radiofrequency electromagnetic fields to which persons may be
exposed.
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Evaluation and Control of Personnel Exposure to Radio Frequency Fields —
3 kHz to 300 GHz. NATO Standardization Agreement (STANAG)
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Radiofrequency Radiation Dosimetry Handbook (4th Edition). Durney, C.H., Massoudi,
H. and Iskander, M.F. (1986) , United States Air Force Research
Laboratory Technical Report USAFSAM-TR-85-73, Brooks Air Force Base,
Texas USA. This handbook includes basic electromagnetics, dielectric
properties, methods of calculation, thermal responses of man and animals
and an overview of safety standards. Based on the earlier versions of
this report, most RF standards
(e.g., ACGIH, ANSI, ICNIRP) include exposure limits which change with frequency and based
on Specific (frequency and species) Absorption Rates expressed in Watts/kilogram of body
tissue.
- Degraded Instrument Performance due to Radio Interference: Criteria and Standards, 369 KB
PDF, pages. Raymond F. Feldman.
From American Conference
of Governmental Industrial Hygienists (ACGIH): Applied Occupational and
Environmental Hygiene, 8(4):351-355, Copyright 1993, Cincinnati, OH. Reprinted with permission.
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Field Service Memo — Electromagnetic Radiation and How It Affects Your Instruments. OSHA Cincinnati Technical Center. (1990, 20 May)
The purpose of this field service memo is to
provide OSHA compliance officers with basic principles of
electromagnetic (EM) radiation. It discusses the effects of radio
frequency interference (RFI) on the operation of industrial hygiene
instruments, explains why special isotropic probes are used for making
non-ionizing radiation surveys, and emphasizes the need for special
attention in measuring radio frequency fields.
Radio and Television Broadcast
Stations
- Evaluating Compliance with FCC
Guidelines for Human Exposure to
Radiofrequency Electromagnetic Fields. Federal Communications
Commission (FCC) Office of Engineering Technology (OET) Bulletin 65 (1997, August),
380 KB
PDF,
84 pages. This revised OET Bulletin 65 offers guidelines and
suggestions for evaluating compliance. However, it is not intended to
establish mandatory procedures, and other methods and procedures may be
acceptable if based on sound engineering practice.
- Supplement A: Additional Information for Radio and Television Broadcast Stations, 451 KB
PDF, 43 pages.
- Supplement C: Additional Information for Evaluating Compliance of
Mobile and Portable Devices with FCC Limits for Human Exposure to
Radiofrequency Emissions, 186 KB PDF, 57 pages.
Amateur Radio
- Evaluating Compliance with FCC
Guidelines for Human Exposure to
Radiofrequency Electromagnetic Fields. Federal Communications
Commission (FCC) Office of Engineering Technology (OET) Bulletin 65 (1997, August),
380 KB
PDF,
84 pages. This revised OET Bulletin 65 offers guidelines and
suggestions for evaluating compliance. However, it is not intended to
establish mandatory procedures, and other methods and procedures may be
acceptable if based on sound engineering practice.
- Supplement B: Additional Information on Amateur Radio Stations, 548
KB
PDF, 65 pages.
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The FCC's New RF-Exposure Regulations.
American Radio Relay League (ARRL) The FCC regulations (based upon IEEE and NRPB exposure guidelines) identify
Maximum Permissible Exposure (MPE) derived from the Specific Absorption Rate
(SAR) at which tissue absorbs RF energy, expressed in watts per kilogram (W/kg).
From a safe SAR, the Standards and regulations set MPEs that vary with
frequency. Human-body resonances fall in the frequency range from 30 to
300 MHz and are the most strictly controlled. The regulations define two primary
RF-exposure environments"controlled/occupational" and "uncontrolled/general
public." In a "controlled" RF environment people know that RF is present and can
take steps to control their exposure. This applies to areas where you control
access. The limits for controlled environments are evaluated differently (less
stringent) than those for uncontrolled environments.
- FCC RF-Exposure Regulations -- the Station Evaluation.
American Radio Relay League (ARRL)
The power-density and
field-strength formulas and tables give the compliance distance in the
main beam of the antenna, at any angle.
The tables based on antenna
modeling have calculated the horizontal compliance distances at ground
level, and at first and second story exposure levels.
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Measurements of Electromagnetic Fields at Amateur Radio Stations.
American Radio Relay League (ARRL) OET Report ASD-9601 (1996, January), available as a 145 KB
PDF, 70 pages. The report describes a joint measurement study of
environmental radiofrequency (RF) fields in the vicinity of nine amateur
radio stations that was conducted by the FCC and the U.S. Environmental
Protection Agency (EPA) in southern California. Measurements of electric
and magnetic field strength were made in areas near amateur antennas and
equipment in order to determine typical and "worst case" exposure
levels.
Cell Phones
Stations
- Evaluating Compliance with FCC
Guidelines for Human Exposure to
Radiofrequency Electromagnetic Fields. Federal Communications
Commission (FCC) Office of Engineering Technology (OET) Bulletin 65 (1997, August),
380 KB
PDF,
84 pages. This revised OET Bulletin 65 offers guidelines and
suggestions for evaluating compliance. However, it is not intended to
establish mandatory procedures, and other methods and procedures may be
acceptable if based on sound engineering practice.
- Supplement C: Additional Information for Evaluating Compliance of
Mobile and Portable Devices with FCC Limits for Human Exposure to
Radiofrequency Emissions, 186 KB PDF, 57 pages.
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