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BE Informed No. 2.8

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GOTA Experience 

As Our

License Qualifier

John B. Johnston W3BE

Q. We want to expand our amateur service community by bringing youngsters and as many other citizens as possible to our hobby. Exams scare off a lot of folks. People don't learn to drive a car from memorizing multiple-choice answers from the owner's manual; they practice driving a car. Likewise, the GOTA on-the-air experience we provide to unlicensed and under-licensed persons is superior to memorizing the VECs' answers to a lot of superfluous questions. GOTA experience facilitates personalized hands-on training by mentors at real amateur stations. How about using GOTA experience as our license qualifier?

A. You apparently observe that our amateur service Section 97.301 spectrum allocations have the capacity to accommodate very large influxes of additional stations, indeed.

   Our amateur service community seems to have embraced the notion of GOTA experience. To replace testing with GOTA experience, no changes would be required to the international Radio Regulations. Those RRs should, however, be taken into account within our needed regulatory revisions; in particular, the scope of ITU-R M.1544 minimum qualifications of radio amateurs. It recommends that any person wishing to operate an amateur station have certain theoretical knowledge. That seems to encompasses a GOTA operator.      

Q. How about requiring our VEs to give examination element credit for a GOTA experience.

A. Simple enough. Section 97.505 element credit already incorporates the fitting rubric. Just expand that section and add new sentences to require our Section 97.509 administering VEs to give credit for the GOTA experience.

Q. That GOTA sounds like an excellent project for our radio club members to offer at our club station. 

A. Yes, personalized hands-on training by active seasoned amateur operators at real amateur stations should be a lot more direct, effective, and responsible use of two highly valuable public resources: our allocation of electromagnetic spectrum and our technical and operational experts.  Personalized GOTA student operator mentoring should help expand our amateur service community, bring home license qualification training, and buildup our clubs' memberships. 

Q. Our clubs should each obtain a stack of free club station licenses for its mentors to loan out to GOTA student operators who just want to give ham radio a try before investing their time and effort in memorizing the answers to the exam questions. They would use that call sign until they receive a call sign of their own, or lose interest.

A. Your suggestion does provide a workable trail: call sign - ULS - license trustee mentor - student operator. The onus, however, would be entirely upon your Section 97.5(b)(2) club station licensee to impose, on a case-by-case basis, any operational or technical limitations necessary to assure compliance with the rules.

Q. What should be covered in the GOTA experience curriculum?

A. GOTA experience should result in the person acquiring the operational and technical qualifications required to perform properly the duties of an amateur service licensee.

Q. Would the question pools be helpful as a GOTA guideline?

A. Possibly, but those Section 97. 523 question pools cover a broad range of topics, some- if not most - of which may be of little interest to the trainee, then or later on. The mentor should purposefully tailor the GOTA experience to the person's interests and intended usage so that he/she can get underway with his/her own amateur operator/primary station license grant without unnecessary delay and irrelevant baggage.

Q. Would all of the GOTA experience consist of actually engaging in over-the-air amateur station intercommunications?

A. Not necessarily. The curriculum would depend upon the trainee's intended use and his/her prior related experience.

Q. GOTA experience as a license qualifier will be more effective than answer memorizing only if all mentors carefully monitor their trainees progress and follow up using their expertise to correct their trainees' errors and misunderstandings.

A. Yes. A major disillusionment with the current system is that the Section 97.509 administering VEs' work is predominantly accounting in nature. Theses VEs, moreover - quite disappointingly - do not seem to follow up an examination using their own expertise to enlighten the examinee as needed, even though their incorrect answer choices pin down for them the specific areas where it is that their examinee's technical and/or operational knowledge is faulty. This inaction tends to signal that the VEs do not firmly accept that such knowledge is all that essential. 

   Our Section 97.507 preparing VEs, moreover, seem to be caught up in a 1960s-era incentive licensing time warp. The Element standards that they should be using are codified in Section 97.503: prepare written examinations such as to prove that the examinee possesses the operational and technical qualifications required to perform properly the duties of an amateur service licensee. Element 2 is supposed to be concerned with the privileges of the basic Technician Class operator; Element 3 with the privileges of the intermediate General Class operator; and Element 4 with the expert Amateur Extra Class operator.

   If, in their Element 2 questions, the VEs have accurately identified the operational and technical qualifications required to perform properly the duties of a Technician Class operator, there should be little need for additional qualifications for the General Class and practically none for the Amateur Extra Class. There are very small differences between the three classes in duties to be performed.

Q. But it is the FCC rules that stipulate 35 more questions for the General test and 50 more questions for the Extra. So our Elements 3 and 4 pools have to be padded with hundreds of unessential questions just to fill the voids.

A. There is your roadblock. Somewhere during the period starting with the 1983 initiation of the volunteer examiner system, our VEs should have called this inconsistency to the attention of our regulator and advocated for more reasonable numbers of examination questions. The VEs are the persons who are supposed to have identified the operational and technical qualifications required to perform properly the duties of each class of operator. So they should best know the proper number of questions to ask on the written examinations that they prepare and administer. Perhaps Section 97.503 should be divested of specifying numbers of questions.

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March 20, 2017

Supersedes all prior editions

BE Informed No. 1.1

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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.

   Here 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. Section 2.1.

   amateur station – a radio station operated by a duly authorized person interested in radio technique solely with a personal aim and without pecuniary interest. Read SEC. 3. [47 USC 153](2) of the Communications Act. An amateur station consists of all of the transmitters, receivers and combinations thereof, and all accessory apparatus, at any one location, necessary for carrying on radio-communications in any of our three amateur radio services. Read What Is an Amateur Station? BE Informed No. 1.15.  

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

   band – a continuous radiofrequency 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.

   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 regulatory 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.  

   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).

   RF – Radiofrequency

   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 radio-communication service, or the radio astronomy service.

   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(b)(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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   With regard to possible excessive RF exposure, Section 97.13(c) says: 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 Section 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 Section 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 Section 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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   The amateur service section of OST/OET Bulletin Number 65 says:

Operations in the Amateur Radio Service

   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 Section 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 Section 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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FCC Opens Docket: Our regulator calls for renewed discussion on both the currency of its RF exposure limits and possible policy approaches regarding RF exposure.

   The FCC is looking forward to developing a complete record to determine whether the current rules and policies should remain unchanged, or should be relaxed or tightened.  It says:  

   Periodic review of the government’s rules and regulations to ensure they have kept pace with current knowledge and changing needs is an important characteristic of good government, and we here will advance the process of providing a comprehensive review and modification, where appropriate, of this Commission’s various rules pertaining to the implementation of the National Environmental Policy Act (NEPA) requirements for environmental reviews, specifically those reviews related to health and safety of radiofrequency (RF) emissions from radio transmitters.  

   Our actions herein are intended to ensure that our measures are compliant with our environmental responsibilities and requirements and that the public is appropriately protected from any potential adverse effects from RF exposure as provided by our rules, while avoiding any unnecessary burden in complying with these rules.  This document is divided into three parts: a Report and Order (Order) and a Further Notice of Proposed Rulemaking (Further Notice) in ET Docket No. 03-137, and a Notice of Inquiry (Inquiry) in a new docket, ET Docket 13-84

   In the Order we conclude several technical and semantic issues initiated in 2003 that revise and update our regulations implementing NEPA; in the Further Notice we propose to further update and revise our procedures and treat all services equally; and in the Inquiry we request comment to determine whether our RF exposure limits and policies need to be reassessed.  The purpose of the Order and Further Notice is to advance ET Docket 03-137 with respect to how to demonstrate compliance with NEPA and our RF exposure limits, but that proceeding does not reach the issue of whether our exposure limits are appropriate.  Since consideration of the limits themselves is explicitly outside of the scope of ET Docket 03-137, we propose with the Inquiry to open a new docket to consider those limits in light of more recent developments. 

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Rule Adopted

   In the Order in ET Docket No. 03-137, at para. 77, our regulator says: It should be helpful to licensees to codify our earlier adopted policy with regard the use of occupational/controlled limits at amateur radio stations. This policy was established in the RF Report and Order of 1996, but was not incorporated in the rules at that time. It allows amateur stations to be evaluated with respect to occupational/controlled exposure limits as long as appropriate training and information has been provided to the amateur licensee and members of his or her immediate household. We here codify this policy be adding a paragraph to new sub section 1.1310.

3. Section 1.1310 is amended to read as follows: 

§ 1.1310 Radiofrequency radiation exposure limits.

   (a)  Specific absorption rate (SAR) shall be used to evaluate the environmental impact of human exposure to radiofrequency (RF) radiation as specified in § 1.1307(b) within the frequency range of 100 kHz to 6 GHz (inclusive). 

   (b)  The SAR limits for occupational/controlled exposure are 0.4 W/kg, as averaged over the whole body, and a peak spatial-average SAR of 8 W/kg, averaged over any 1 gram of tissue (defined as a tissue volume in the shape of a cube). Exceptions are the parts of the human body treated as extremities, such as hands, wrists, feet, ankles, and pinnae, where the peak spatial-average SAR limit for occupational/controlled exposure is 20 W/kg, averaged over any 10 grams of tissue (defined as a tissue volume in the shape of a cube). Exposure may be averaged over a time period not to exceed 6 minutes to determine compliance with occupational/controlled SAR limits.

   (c) The SAR limits for general population/uncontrolled exposure are 0.08 W/kg, as averaged over the whole body, and a peak spatial-average SAR of 1.6 W/kg, averaged over any 1 gram of tissue (defined as a tissue volume in the shape of a cube).  Exceptions are the parts of the human body treated as extremities, such as hands, wrists, feet, ankles, and pinnae, where the peak spatial-average SAR limit is 4 W/kg, averaged over any 10 grams of tissue (defined as a tissue volume in the shape of a cube). Exposure may be averaged over a time period not to exceed 30 minutes to determine compliance with general population/uncontrolled SAR limits.

   (d)(1) Evaluation with respect to the SAR limits in this section must demonstrate compliance with both the whole-body and peak spatial-average limits using technically supported measurement or computational methods and exposure conditions in advance of authorization (licensing or equipment certification) and in a manner that facilitates enforcement. Numerical computation of SAR must be supported by adequate documentation showing that the numerical method as implemented in the computational software has been fully validated; in addition, the equipment under test and exposure conditions must be modeled according to protocols established by numerical computation standards or available FCC procedures for the specific computational method.

   (2)  For operation within the frequency range of 300 kHz and 6 GHz (inclusive), the limits for maximum permissible exposure (MPE), derived from whole-body SAR limits and listed in Table 1 of paragraph (e) of this section, may be used instead of whole-body SAR limits as set forth in paragraph (a) through (c) of this section to evaluate the environmental impact of human exposure to RF radiation as specified in § 1.1307(b), except for portable devices as defined in § 2.1093 as these evaluations shall be performed according to the SAR provisions in § 2.1093 of this chapter

   (3)  At operating frequencies above 6 GHz, the MPE limits listed in Table 1 of paragraph (e) of this section shall be used in all cases to evaluate the environmental impact of human exposure to RF radiation as specified in § 1.1307(b).

   (4)  Both the MPE limits listed in Table 1 of paragraph (e) of this section and the SAR limits as set forth in paragraph (a) through (c) of this section are for continuous exposure, that is, for indefinite time periods.  Exposure levels higher than the limits are permitted for shorter exposure times, as long as the average exposure over the specified averaging time in Table 1 is less than the exposure limits.  Detailed information on our policies regarding procedures for evaluating compliance with all of these exposure limits can be found in the most current edition of FCC's OET Bulletin 65, “Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields,” and its supplements, all available at the FCC’s Internet Web site: http://www.fcc.gov/oet/rfsafety

   Note to Paragraphs (a) through (d): SAR is a measure of the rate of energy absorption due to exposure to RF electromagnetic energy.  These SAR limits to be used for evaluation are based generally on criteria published by the American National Standards Institute (ANSI) for localized SAR in Section 4.2 of “IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz,” ANSI/IEEE Std C95.1-1992, copyright 1992 by the Institute of Electrical and Electronics Engineers, Inc., New York, New York 10017.  These criteria for SAR evaluation are similar to those recommended by the National Council on Radiation Protection and Measurements (NCRP) in “Biological Effects and Exposure Criteria for Radiofrequency Electromagnetic Fields,” NCRP Report No. 86, Section 17.4.5, copyright 1986 by NCRP, Bethesda, Maryland 20814.  Limits for whole body SAR and peak spatial-average SAR are based on recommendations made in both of these documents.  The MPE limits in Table 1 are based generally on criteria published by the NCRP in “Biological Effects and Exposure Criteria for Radiofrequency Electromagnetic Fields,” NCRP Report No. 86, Sections 17.4.1, 17.4.1.1, 17.4.2 and 17.4.3, copyright 1986 by NCRP, Bethesda, Maryland 20814.  In the frequency range from 100 MHz to 1500 MHz, these MPE exposure limits for field strength and power density are also generally based on criteria recommended by the ANSI in Section 4.1 of “IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz,” ANSI/IEEE Std C95.1-1992, copyright 1992 by the Institute of Electrical and Electronics Engineers, Inc., New York, New York 10017.

   (e) Table 1 below sets forth limits for Maximum Permissible Exposure (MPE) to radiofrequency electromagnetic fields.

Table 1—Limits for Maximum Permissible Exposure (MPE)

Frequency range
(MHz)

Electric field strength
(V/m)

Magnetic field strength
(A/m)

Power density
(mW/cm2)

Averaging time
(minutes)

(A) Limits for Occupational/Controlled Exposure

0.3–3.0

614

1.63

*(100)

6

3.0–30

1842/f

4.89/f

*(900/f2)

6

30–300

61.4

0.163

1.0

6

300–1500

 

 

f/300

6

1500–100,000

 

 

5

6

(B) Limits for General Population/Uncontrolled Exposure

0.3–1.34

614

1.63

*(100)

30

1.34–30

824/f

2.19/f

*(180/f2)

30

30–300

27.5

0.073

0.2

30

300–1500

 

 

f/1500

30

1500–100,000

 

 

1.0

30

            f = frequency in MHz              * = Plane-wave equivalent power density

   (1)  Occupational/controlled exposure limits apply in situations in which persons are exposed as a consequence of their employment provided those persons are fully aware of the potential for exposure and can exercise control over their exposure.  Limits for occupational/controlled exposure also apply in situations when a person is transient through a location where occupational/controlled limits apply provided he or she is made aware of the potential for exposure. The phrase fully aware in the context of applying these exposure limits means that an exposed person has received written and/or verbal information fully explaining the potential for RF exposure resulting from his or her employment. With the exception of transient persons, this phrase also means that an exposed person has received appropriate training regarding work practices relating to controlling or mitigating his or her exposure. See § 1.1307(b)(2) of this chapter. The phrase exercise control means that an exposed person is allowed and also knows how to reduce or avoid exposure by administrative or engineering work practices, such as use of personal protective equipment or time averaging of exposure.

   (2)  General population/uncontrolled exposure limits apply in situations in which the general public may be exposed, or in which persons who are exposed as a consequence of their employment may not be fully aware of the potential for exposure or cannot exercise control over their exposure.  For example, RF sources intended for consumer use shall be subject to the limits for general population/uncontrolled exposure in this section.

* * * * *

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Proposed New Rule

   In the Further Notice, Section 97.13 was proposed to read as follows:

§ 97.13   Restrictions on station location.

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   (c) * * *

   (1) The licensee shall ensure compliance with the Commission's radio frequency exposure requirements in §§ 1.1307(b), 2.1091 and 2.1093 of this chapter, where applicable. In lieu of evaluation with the general population/uncontrolled exposure limits, amateur licensees may evaluate their operation with respect to members of his or her immediate household using the occupational/controlled exposure limits in § 1.1310, provided appropriate training and information has been supplied to the amateur licensee and members of his/her household. Other nearby persons who are not members of the amateur licensee’s household must be evaluated with respect to the general population/uncontrolled exposure limits.  Appropriate methodologies and guidance for evaluating amateur radio service operation is described in the Office of Engineering and Technology (OET) Bulletin 65, Supplement B.

   (2) * * *

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Q/A

Q. What was the power rule prior to the changeover to PEP output measurement? 

A. Copies of the pre-changeover rules show the power rule formerly specifying:

   Each amateur transmitter may be operated with a power input not exceeding 1 kilowatt to the plate circuit of the final amplifier stage of an amplifier-oscillator transmitter or to the plate circuit of an oscillator transmitter. An amateur transmitter operating with a power exceeding 900 watts to the plate circuit shall provide means for accurately measuring the plate power input to the vacuum tube or tubes supplying power to the antenna.

   So, it was 900 watts DC into a transmitter vacuum tube plate circuit unless the transmitter had on hand the means for accurately measuring 1,000 watts. That regulation must have been sufficient for the straightforward low-power CW and AM amplifier and amplifier-oscillator vacuum tube, measurement-deprived, ham-built transmitters back in the day. 

Q. What was the basis for 1,000 watts?

A. Possibly it was to promote a more harmonious spectrum coexistence with early commercial radio systems. Whatever it was, the 1 kW standard took on a life of its own and became our 1,000 watt legacy.

Q. For a CW emission, 1000 watts key-down makes sense. But for AM, an ammeter measures only the carrier power. Some hams seem to recall a 2,000 watt rule for SSB, although I think that was more a rule of thumb to comply with the average power rule rather than a codified regulation. 

A. No, the rule expressly prohibited exceeding 1,000 watts, or 900 watts if the former value could not be measured accurately. It wasn’t until the 1950s - when hams began showing interest in SSB and other emission modes - that the need for accurately measuring a rapidly varying DC plate current became a necessity. The advent of solid-state technology concurrently rendered obsolete the rule exclusively for vacuum tube transmitters.   

   The availability of transmitter peak-envelope-power output measuring means made possible the changeover to the present regulation: Regardless of the emission mode, no station may transmit with a transmitter power exceeding 1.5 kW PEP. So, the point of power measurement was relocated to the transmitter RF output, away from the often-dangerous DC high voltage final vacuum tube input. Today’s 1.5 kW PEP output limit is, therefore, more or less an artifact carried over from our 1,000 watt legacy.  

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September 25, 2015

Supersedes all prior editions