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Ofcom EMF Licence changes - 2020

John Rogers M0JAV

“Implementation of measures to require compliance

with international guidelines for limiting exposure to

electromagnetic fields (EMF)”

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Proposed Licence Condition:

“Licensee shall only establish, install, modify or use Relevant

Radio Equipment if the electromagnetic field exposure levels

produced by the Relevant Radio Equipment are below the basic

restrictions in the relevant tables for general public exposure

identified in the ICNIRP Guidelines in any area that is accessible

to the general public”

Ofcom want to foster a climate of compliance not a “high handed”

enforcement approach, but they would act against reckless individuals

Ofcom proposals for limiting exposure to EMF

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To comply, you perform an assessment using any appropriate combination of the following:

1. Following manufacturers’ guidance/instructions

2. Establishing consistency with pre-assessed compliant configurations

3. Performing desk-top calculations

4. Making sure that people are not present in areas where ICNIRP reference levels are not met, before transmitting

5. Taking measurements

Then keep records of what you have done, and when.

– Aim should be Compliance by Design

How can amateurs Demonstrate Compliance

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• Electromagnetic energy can be absorbed by body and cause a temperature rise, or tingling nerves

• ICNIRP gives guidelines for limiting exposure including:

– Basic restrictions and reference levels for

– two levels of limits Occupational and General Public

– for two types of exposure Local and Whole-body

– for three measures peak, averaged for 6 minutes and for 30 minutes

What is that all about ?

When Transmitting:

Amateurs can be in the occupational

zone

General public outside the

occupational zone in the compliance

zone

Zone shape is antenna dependent

Potential

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How Guideline reference levels are calculated

> 6 minute exposure < 6 minute exposure

41 page document guideline document

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ICNIRP Reference Levels for General Public Exposure

Need to compare Electric

Field, Magnetic Field and

Power Density with

recommended maximum

exposure levels (frequency

dependant) to determine

compliance in near and far

field conditions

Then there are limb

current limits

Ofcom calculator is conservative but if separation maintained you will be Compliant

• Input PEP including feeder losses, antenna gain and EIRP multiplier

• Derives average power including modulation factor and Tx/Rx ratio

• Calculate separation to stay below recommendations at operating power level

• Keep people out of the non compliant zones while transmitting

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Using the Ofcom Calculator - RSGB frontsheet

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8 Flowchart to Demonstrate Compliance

Keep a

Record of

results

EMF

Employ

any

Needed

Mitigations

Done

Inherently

Compliant

Normally

Compliant

Compliant

Separation

achievable

?

Are

Exposure

Zones

Accessible

?

Is EIRP <

10W ?

Calculate

Exposure

Zones

Use

RSGB /

Ofcom

Calculator

Y

Y

Y

N

N

N

1 Screening Evaluation

Pre-assessed Configurations,

power, antenna, height, orientation

2 Calculate Separation

needed for compliance – use

RSGB/Ofcom calculator based on

far field so it is

deliberately conservative

3 Advanced methods

near field modelling,

compliant power contours,

other mitigation measures to help

achieve compliance…

Advanced

methods if

needed

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• We should all aim to be “Compliant by Design”

– Follow Manufacturers Instructions and Guidelines

– Follow Ofcom and RSGB advice - Radios will perform better if you do

• Configure/operate station using pre-evaluated guidance

• Run the Ofcom calculator to give compliant separation

• Implement mitigations if required to demonstrate compliance

– Turn down the power

– Adjust antenna type / position / height / limit operating beam headings

– Don’t transmit if a person is in a potential exposure exceedance zone

• If compliance not demonstrated, use advanced modelling

and/or revise mitigations until compliance is demonstrated

Good Practice to achieve Compliance

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Research - V/UHF Compliance Zones, 70cm Yagi

Ofcom calculator vs NEC 5 Clay ground

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• Identify differing ICNIRP compliance requirements over amateur licence frequency range – Exposure assessment is NOT just about field strength at a point

• Develop modelling tools for: – computing electric and magnetic fields (e.g., latest NEC 5)

– analysing data to determine exposure (e.g., Mathematica)

• Establish range of amateur antenna types / configurations to be evaluated

• Apply modelling to establish guidance on achieving ICNIRP (UK), FCC(US) compliance – Contour maps to show exposure from antenna at given power

– Contour map showing max power for compliance at location

– Minimum height / separation guidance

• Prepare guidance on RF Safety with Ofcom / PHE

EMF Guidance & Tools – Research jointly with ARRL

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Thank You!

Any Questions?

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Research - EMF exposure contours for dipole

E Field H Field

Dipole Inverted V

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• Develop an increasing number of pre-assessed off-the-shelf

configurations so compliance is demonstrated by meeting that

configuration: - – HF dipole [beam] – no part of any radiating element less than Z m AGL for W

power [range of X, Y & frequencies]

– Ground mounted vertical – X m separation for W power [range of X, Y &

frequencies]

– Power < W Watts, and you can’t touch antenna with extended arms is Okay

• Good practice – Matching at antenna to limit feeder radiation

– Radiating elements as high as practical

– People not too close to antenna when operating

• Training – Improved syllabus

– Documentation prepared and website updated

Proposed guidelines and training