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RF Safety Program

- Guidelines for Compliance -

Understanding Site Requirements for

Radio FrequencyElectromagnetic Fields

Robert LangstonAmateur Call W2ENY

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OVERVIEW

Requirements Dates 1997 FCC 97-303 Order 1997 OET65 Guidelines Exposure Levels Antenna Proximity Exclusions and Compliance Control of Non-Conforming Sites

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REQUIREMENTS

October 15, 1997– All new, modified and renewal sites

September 1, 2000– All sites must comply

Regions required to ensure compliance Comply with the spirit and precautions

outlined in the standards Use common sense where not specific

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1997 FCC Order 97-303

The standard sets RF Exposure Levels Occupational and General Public levels differ Limits are averaged exposure over time Shared responsibility for

compliance in co-located sites

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FCC SPEC and ENVIRONMENTS

Controlled Environment Limits– Exposure at some level is possible– Persons trained to know exposure is

possible Uncontrolled Environment Limits

– Exposure at some lower level is possible– General Population – Oblivious to knowing they’re being exposed– 1/5 the Controlled level

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1997 OET 65 Guidelines

Evaluating Compliance with FCC rules Prediction Methods Multiple Transmitter Sites Sample Calculations Measurement Techniques Controlling Exposure

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EXPOSURE vs FREQUENCY

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RF Exposure and Absorption

Maximum Exposure averaged over time– Controlled: 6 minutes– Uncontrolled: 30 minutes

Exposure measured as:– Power Density (mW/cm²)

Absorption measured as:– Thermal heating effect (Watts/Kilogram)

Sites may include other signals

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ANTENNA PROXIMITY

Behind the Antenna– Front to Back ratio usually 30dB– Factor of 1000 times

Above, Below or Beside Antenna – Signals are greatly reduced– Isolated by 30 to 40dB– Factor of 1000 or better

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TYPICAL ANTENNA

This is a FRONT VIEW Mounted from back side Cables attach from back or

bottom Antenna is Covered

– Fiberglass or Plastic– NO ELECTRICAL SHOCK HAZARD– NO EXPOSED ELEMENTS

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FRONT/SIDE VIEW

Front to Back Ratio Side Nulls Over and Under Nulls Above, Below and Side

signals are reduced

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Control of Fields Time Averaging

– Based on Transmit vs. Receive– Duty Factors

Spatial Averaging– FCC Spec. is a whole body average

Elevate or Re-Orient Antenna Boundary Restrictions Fencing, Signs and Access Control

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Duty Factor by Mode

ModeDuty Factor

Notes

Conversational SSB 20% Note 1Conversational SSB 50%[A1] Note 2Voice FM 100%FSK or RTTY 100%AFSK SSB 100%Conversational CW 40%Carrier 100% Note 3

Note 1: Includes voice characteristics and syllabic duty factor. No speech processing.Note 2: Includes voice characteristics and syllabic duty factor. Heavy speech processor employed.Note 3: A full carrier is commonly used for tune-up purposes

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Averaging

For example, if a 1,500-watt PEP amateur single-sideband station (with no speech processing)transmits ("worst case") two minutes on, two minutes off then two minutes on again in any six-minuteperiod (the averaging time period for controlled exposure), then for controlled exposure situations theeffective power would be:

1,500 W X 0.2 (20% from Table 2) X _ (4 of 6 minutes) = 200 W

For uncontrolled exposures the averaging time is 30 minutes and the total transmission time during any 30-minute period would be 20 minutes out of 30. The result would then also be:

1,500 W X 0.2 X _ (20 of 30 minutes) = 200 W

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AveragingAnother example might be a 500-watt CW station that is used in a DX pileup, transmitting 15

seconds every two minutes (45 seconds for six minutes) the result would be the same for either controlledor uncontrolled exposure:

500 W X 0.4 (40% from Table 2) X 0.125 (45 of 360 seconds) = 25 W (controlled)

500 W X 0.4 X 0.125 (225 of 1800 seconds) = 25 W (uncontrolled)

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TriBander EstimatesTABLE 5. Three-element "triband" Yagi assuming surface (ground)reflection

Distance (meters) from any part of the antenna for compliance with eitheroccupational/controlled or general population/uncontrolled exposure limits

14 MHz, 6.5 dBi 21 MHz, 7 dBi 28 MHz, 8 dBi

Power(watts)

con. unc. con. unc. con. unc.

100 1.4 3.1 2.2 5 3.4 7.5

500 3.1 7 5 11.2 7.5 16.7

1,000 4.5 10 7.1 15.8 10.6 23.7

1,500 5.5 12.2 8.7 19.4 13 29

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VHF/UHF EstimatesTABLE 8. VHF 1/4 wave plane or mobile whip antenna at 146 MHz (estimated gain 1 dBi) assuming surface (ground) reflection

Transmitter power (watts) Distance (m) to complywith occupational/controlled exposure limit

Distance (m) to complywith gen. population/uncontrolled exposurelimit

10 0.5 1.1

50 1.1 2.5

150 2 4.4

TABLE 9. UHF 5/8 wave ground plane or whip antenna at 446 MHz (estimated gain 4 dBi); main beam exposure, assumes surface (ground) reflection

Transmitter power (watts) Distance (m) to complywith occupational/controlled exposure limit

Distance (m) to complywith gen. population/uncontrolled exposurelimit

10 0.6 1.3

50 1.3 2.9

150 2.3 5.1

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Sloper

TABLE 16. Quarter-wave half-sloper antenna(estimated average gain 6.7 dBi); main beam exposure,assumes surface (ground) reflection

Distance (meters) from any part of the antenna for compliance with eitheroccupational/controlled or general population/uncontrolled exposure limits

7 MHz 14 MHz 21 MHz 28 MHz

Transmitterpower(watts)

con. unc. con. unc. con. unc. con. unc.

100 0.7 1.6 1.4 3.2 2.2 4.8 2.9 6.4

500 1.6 3.6 3.2 7.2 4.9 10.7 6.4 14.3

1000 2.3 5 4.5 10.2 6.9 15.2 9.1 20.2

1500 2.8 6.2 5.6 12.5 8.4 18.6 11.1 24.8

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RF SAFETY EQUIPMENT

Personal Monitors Narda Survey Meter Model 8718 E-Field Probe 8722B (0.3-300%

Standard)– Isotropic Polarizationless 300KHz thru 40GHz

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So What Happens If... FCC: License Revocation

– Chance about Zero OSHA: $300 Fine per offense

– Chance about Zero Public Liability / Lawsuit Do you love your neighbor? Does your neighbor need the

money?