No. 67 RF SAFETY CERTIFICATION

W3BE'S BE Informed!

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BE Informed No. 67

CERTIFICATION REGARDING RADIOFREQUENCY RADIATION SAFETY

John B. Johnston W3BE

When applying for an FCC amateur service license grant, you must use either FCC Form 605 or NCVEC Form 605. They both require signing, among other things, this certification:

I certify that I have read and will comply with Section 97.13(c) of the Commission’s Rules regarding radiofrequency radiation safety and the amateur service section of OST/OET Bulletin Number 65.

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Below are the text and tables that you must certify that you have read, and for which you must give your word to comply. You will need to understand the following terms in order to make these FCC documents meaningful.

amateur - A duly authorized person interested in radio technique solely with a personal aim and without pecuniary interest who carries out the purpose of self-training, intercommunication and technical investigations. Read Section 2.1.

amateur station – a station in the amateur service. Read Section 2.1.

antenna – a metallic device for sending and/or receiving RF electromagnetic field waves.

band – a continuous RF range.

cm – centimeter (.01 meters).

dB – decibel (10 bels); named in honor of Alexander Graham Bell. The term bel is seldom used.

decibel - ten times the logarithm to the base ten of the ratio of two power levels.

dipole - a radio antenna consisting of two metal conductors of rod or wire, oriented parallel and in line with each other, with a small space between them. Read BE Informed No. 65.

EHF - extremely high frequency; range 30–300 GHz. Read Section 97.3(b)(1).

Electromagnetic field – a physical combination of a magnetic field and an electric field. This phenomena is the basis of radio.

ERP - effective radiated power (in a given direction). The product of the power supplied to the antenna and its gain relative to a half-wave dipole in a given direction.

Exposure. Exposure occurs whenever and wherever a person is subjected to electric, magnetic or electromagnetic fields other than those originating from physiological processes in the body and other natural phenomena.

Frequency - The number of occurrences of a repeating event per unit time. An RF electromagnetic field wave is an oscillation, and therefore it has a frequency.

Gain (of an antenna). The ratio in decibels, of the power required at the input of a loss-free reference antenna to the power supplied to the input of the given antenna to produce, in a given direction, the same field strength or the same power density at the same distance. When not specified otherwise, the gain refers to the direction of maximum radiation. Gain may be considered for a specified polarization. Gain may be referenced to an isotropic antenna (dBi) or a half-wave dipole (dBd).

General population/uncontrolled exposure. For FCC purposes, applies to human exposure to RF electromagnetic fields when the general public is exposed or in which persons who are exposed as a consequence of their employment may not be made fully aware of the potential for exposure or cannot exercise control over their exposure. Therefore, members of the general public always fall under this category when exposure is not employment-related.

GHz – gigahertz; 1 billion Hertz.

Half-wave dipole antenna – one whose length in feet is approximately 468/frequency in MHz. Read BE Informed No. 65.

HF - high frequency; 3–30 MHz.

Hz – Hertz; the unit for expressing frequency. One hertz equals one cycle per second.

kHz – kilohertz; 1000 Hz.

Isotropic antenna – uniform radiation in all orientations.

Joule - The energy expended in passing an electric current of one ampere through a resistance of one ohm for one second.

M – Meter; a length of approximately 39.37 inches.

MF - medium frequency; 300–3000 kHz. Read Section 97.3(b)(5).

MHz – megahertz – 1 million Hertz.

MPE - maximum permissible exposure. The rms and peak electric and magnetic field strength, their squares, or the plane-wave equivalent power densities associated with these fields to which a person may be exposed without harmful effect and with an acceptable safety factor.

Oscillation - The repetitive variation, typically in time, of some measure about a central value or between two or more different states.

PEP – Peak envelope power; average power supplied to the antenna transmission line by a transmitter during one RF cycle at the crest of the modulation envelope taken under normal operating conditions. Read Section 97.3(b)(6).

Radio - the transmission of signals through free space by modulation of oscillating electromagnetic field waves.

Repeater - An amateur station that simultaneously retransmits the transmission of another amateur station on a different channel or channels. Read Section 97.3(a)(40).

rms - root-mean-square; the effective value, or the value associated with joule heating, of a periodic electromagnetic wave. Obtained by taking the square root of the mean of the squared value of a function.

RF – Radiofrequency. A rate of oscillation in the range of about 3 kHz to 300 GHz.

Super-high frequency (range 3–30 GHz).

Station - One or more transmitters or receivers or a combination of transmitters and receivers, including the accessory equipment, necessary at one location for carrying on a radiocommunication service, or the radio astronomy service. Read Section 2.1.

Transmitter - An electronic device that generates an RF alternating current, which when applied to an antenna, propagates RF electromagnetic field waves.

UHF - ultra-high frequency (range 300–3000 MHz). Read Section 97.3(b)(9).

VHF - very-high frequency (range 30–300 MHz.) Read Section 97.3(10).

W – watt; one joule per second, a measure of the rate of energy conversion.

Watt – A unit of electrical power.

Wave - A disturbance that transfers energy from point to point.

Wavelength – Distance from crest to crest in the line of advance of a wave.

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Section 97.13(c) says:

§ 97.13 Restrictions on station location.

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(c) Before causing or allowing an amateur station to transmit from any place where the operation of the station could cause human exposure to RF electromagnetic field levels in excess of those allowed under §1.1310 of this chapter, the licensee is required to take certain actions.

(1) The licensee must perform the routine RF environmental evaluation prescribed by §1.1307(b) of this chapter, if the power of the licensee's station exceeds the limits given in the following table:

Wavelength band	Evaluation required if power¹ (watts) exceeds
MF
160 m	500
HF
80 m	500
75 m	500
40 m	500
30 m	425
20 m	225
17 m	125
15 m	100
12 m	75
10 m	50
VHF (all bands)	50
UHF
70 cm	70
33 cm	150
23 cm	200
13 cm	250
SHF (all bands)	250
EHF (all bands)	250
Repeater stations (all bands)	non-building-mounted antennas: height above ground level to lowest point of antenna <10 m and power >500 W ERP building-mounted antennas: power >500 W ERP

¹ Power = PEP input to antenna except, for repeater stations only, power exclusion is based on ERP (effective radiated power).

(2) If the routine environmental evaluation indicates that the RF electromagnetic fields could exceed the limits contained in §1.1310 of this chapter in accessible areas, the licensee must take action to prevent human exposure to such RF electromagnetic fields. Further information on evaluating compliance with these limits can be found in the FCC's OET Bulletin Number 65, “Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields.”

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Operations in the Amateur Radio Service (From OET Bulletin #65)

In the FCC's recent Report and Order, certain amateur radio installations were made subject to routine evaluation for compliance with the FCC's RF exposure guidelines. Also, amateur licensees will be expected to demonstrate their knowledge of the FCC guidelines through examinations. Applicants for new licenses and renewals also will be required to demonstrate that they have read and that they understand the applicable rules regarding RF exposure. Before causing or allowing an amateur station to transmit from any place where the operation of the station could cause human exposure to RF radiation levels in excess of the FCC guidelines amateur licensees are now required to take certain actions. A routine RF radiation evaluation is required if the transmitter power of the station exceeds the levels shown in Table 1 and specified in 47 CFR § 97.13(c)(1). Otherwise the operation is categorically excluded from routine RF radiation evaluation, except as a result of a specific motion or petition as specified in Sections 1.1307(c) and (d) of the FCC's Rules, (see earlier discussion in Section 1 of this bulletin).
The Commission's Report and Order instituted a requirement that operator license examination question pools will include questions concerning RF safety at amateur stations. An additional five questions on RF safety will be required within each of three written examination elements. The Commission also adopted the proposal of the American Radio Relay League (ARRL) that amateur operators should be required to certify, as part of their license application process, that they have read and understand our bulletins and the relevant FCC rules.

TABLE 1. Power thresholds for routine evaluation of amateur radio stations.
Wavelength Band            Transmitter Power
                                                     (watts)
MF
160 m                                           500
HF
80 m                                             500
75 m                                             500
40 m                                             500
30 m                                             425
20 m                                             225
17 m                                             125
15 m                                             100
12 m                                               75
10 m                                               50
VHF (all bands)                            50
UHF
70 cm                                             70
33 cm                                           150
23 cm                                           200
13 cm                                           250
SHF (all bands)                           250
EHF (all bands)                           250

   When routine evaluation of an amateur station indicates that exposure to RF fields could be in excess of the exposure limits specified by the FCC (see Appendix A), the licensee must take action to correct the problem and ensure compliance (see Section 4 of this bulletin on controlling exposure). Such actions could be in the form of modifying patterns of operation, relocating antennas, revising a station's technical parameters such as frequency, power or emission type or combinations of these and other remedies.

   In complying with the Commission's Report and Order, amateur operators should follow a policy of systematic avoidance of excessive RF exposure. The Commission has said that it will continue to rely upon amateur operators, in constructing and operating their stations, to take steps to ensure that their stations comply with the MPE limits for both occupational/controlled and general public/uncontrolled situations, as appropriate. In that regard, amateur radio operators and members of their immediate household are considered to be in a "controlled environment" and are subject to the occupational/controlled MPE limits. Neighbors who are not members of an amateur operator's household are considered to be members of the general public, since they cannot reasonably be expected to exercise control over their exposure. In those cases general population/uncontrolled exposure MPE limits will apply.
   In order to qualify for use of the occupational/controlled exposure criteria, appropriate
restrictions on access to high RF field areas must be maintained and educational instruction in RF safety must be provided to individuals who are members of the amateur operator's household. Persons who are not members of the amateur operator's household but who are present temporarily on an amateur operator's property may also be considered to fall under the occupational/controlled designation provided that appropriate information is provided them about RF exposure potential if transmitters are in operation and such persons are exposed in excess of the general population/uncontrolled limits.
   Amateur radio facilities represent a special case for determining exposure, since there are many possible antenna types that could be designed and used for amateur stations. However, several relevant points can be made with respect to analyzing amateur radio antennas for potential exposure that should be helpful to amateur operators in performing evaluations.
   First of all, the generic equations described in this bulletin can be used for analyzing fields due to almost all antennas, although the resulting estimates for power density may be overly-conservative in some cases. Nonetheless, for general radiators and for aperture antennas, if the user is knowledgeable about antenna gain, frequency, power and other relevant factors, the equations in this section can be used to estimate field strength and power density as described earlier. In addition, other resources are available to amateur radio operators for analyzing fields near their antennas. The ARRL Radio Amateur Handbook contains an excellent section on analyzing amateur radio facilities for compliance with RF guidelines (Reference [4] ). Also, the FCC and the EPA conducted a study of several amateur radio stations in 1990 that provides a great deal of measurement data for many types of antennas commonly used by amateur operators (Reference [10] ).

Amateur radio organizations and licensees are encouraged to develop their own more detailed evaluation models and methods for typical antenna configurations and power/frequency combinations. The FCC is working with the amateur radio community to develop a supplement to this bulletin that will be designed specifically for evaluating amateur radio installations. For example, the supplement will contain information on projected minimum exclusion distances from typical amateur antenna installations. The supplement should be completed soon after release of this bulletin. Once the amateur radio supplement is released by the FCC it will be made available for downloading at the FCC's World Wide Web Site for "RF safety." Amateur radio applicants and licensees are encouraged to monitor the Web Site for release of the supplement. The address is: www.fcc.gov/oet/rfsafety. Information on availability of the supplement, as well as other RF-related questions, can be directed to the FCC's "RF Safety Program" at: (202) 418-2464 or to: rfsafety@fcc.gov.

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July 16, 2011

Supersedes all prior editions

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