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Essex Ham

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Ofcom EMF Licence Conditions Changes

Posted: 08 Mar 2021 10:28 AM PST https://www.essexham.co.uk/emf-licence-changes.html


As we advised some months back in our interview with Leslie G0CIB, Ofcom is likely to introduce a new licence clause. Ofcom started writing to
(emailing) radio amateurs at the start of March 2021 notifying them of a
change to the licence conditions regarding EMF and safe exposure limits.
All radio amateurs will be required to comply with the new conditions
around not exposing members of the public to perceived unsafe levels of RF.

This page contains a very basic summary of what radio amateurs need to
know. This is our interpretation of the situation only, and amateurs are advised to do their own reading and research.
What is changing?

Until the 18th of May 2021, nothing.

Ofcom will be making a final decision on changing our licences on the 18
May 2021
What is being proposed?

A change of wording to the amateur radio licence conditions affecting any transmissions at powers over 6.1 watts ERP (or 10 Watts EIRP) to state that licence holders will have to comply with the ICNIRP limits about exposure
of radio signal field strength to members of the public.
How will that affect radio amateurs?

All radio amateurs who transmit more than 6.1 watts e.r.p will need to
carry out an assessment to make sure that members of the general public are
not exposed to field strengths greater than the limits specified by a body called the ICNIRP.

This potentially affects your antennas at home, your in-car/mobile setup
and when you operate out-and-about /P. It will also affect amateur radio
clubs at club venues and on field days.
How do I comply with the new rules?

In one of the following three ways:

Calculate your field strengths and make changes if needed This is the
route that most of us will likely go down
Measure your emissions and make changes if needed This involves special
and expensive measuring equipment, so not ideal
Ensure you never radiate more than 6.1 watts ERP This is not practical

What should I do?

For many amateurs, its a case of using an online calculator to enter how
much power youre putting out on various amateur bands, and the calculator telling you the safe distance.

As long as members of the general public cant stray into the unsafe zone
and stay there for longer than the allotted length of time, then theres no problem.

Amateurs are likely to need to retain a copy of the calculations (perhaps
with a copy of their licence), so that if theres a knock on the door from Ofcom, you can present the calculations and demonstrate no risk to the
general public.



Ofcom EMF Changes Leslie G0CIB Interview





How do I calculate the safe distances?

Ofcom has released a calculator (as an Excel spreadsheet). RSGB has
released an amateur-friendly version:

RSGB / Ofcom Calculator
Ofcom Calculator

Example of Ofcoms EMF Calculator

Youll need to type in several bits of information, to calculate the safe distance in meters. The important data is:

Transmit power
Frequency


By adding in amateur radio specific information to the calculator, we can reduce the calculated distance. Factors affecting amateurs include:

Mode (SSB, FM, etc) Taking SSB as an example, when we talk quietly, we
radiate less power than when we shout
Transmit time We can specify our measurements based on a 6 minute period.
As we will spend some of that six-minute period listening, we can specify
what percentage of a sample 6 minute period we spend transmitting
Antenna gain This of course affects the ERP
Co-ax loss Some power is lost in the feeder, reducing the amount of power
we radiate from the antenna
Antenna height off the ground Obviously affects how likely the public are
to be in the unsafe zone

What if theres a chance of members of the public being inside the unsafe
zone?

Then you potentially need to make changes this could be: a) raising the
height of the antenna, b) taping or fencing off areas, for example on a
field day, c) displaying warning signs, d) reducing the power, e)
repositioning the antenna to a better location.
Will this affect Foundation?

Yes. Foundation licence holders can transmit up to 10 watts. Power is
measured at the feed point of antennas, and antennas have gain. ERP
(Effective Radiated Power) is the power multiplied by the antenna gain, so Foundation can easily exceed 6.1 watts ERP.

If you have not already done so, you will need to carry out an assessment
to check that your radio equipment operates within the ICNIRP general
public limits.
Can I have an example?

Pete M0PSX has prepared an example assessment of this home setup. He has a 2m/70cm colinear white stick antenna on the roof.

To try out this new rule, I entered details of my setup into the RSGB calculator:

Mode: FM Voice  Mode factor 100% (uses the full 50 watts when transmitting) Frequency: 145MHz
Power: Radio has a maximum of 50 watts output
Antenna gain: 3dB
TX percentage in 6 minutes: 50% transmitting (3 minutes)
Co-ax loss (6m run of RG213 feeder) -0.5dB
Height of antenna feed point from ground: 9m


In reality, I rarely transmit at 50 watts, and probably for less than 3
minutes every 6 minutes, so this is a worst case.

The RSGB spreadsheet returned a separation distance of 2.3 metres.

I entered details of 70cm my radio can only transmit 20 watts on 70cm. Seperation distance was 1.3m.

A member of the public would have to me on my roof to be within 2.3 meters
of my antenna. Therefore, no risk. Print out my calculations. Job done! Im
only required to check this again if I change my setup.
Where do I get more information?

Guidance from Ofcom: https://www.ofcom.org.uk/manage-your-licence/emf
Guidance from RSGB: https://rsgb.org/main/technical/emc/emf-exposure/

See Also:

Our interview with Leslie G0CIB


Disclaimer: This is our interpretation of the situation only, and amateurs
are advised to do their own reading and research, and form their own
opinion on how to interpret Ofcoms proposed changes.The post Ofcom EMF
Licence Conditions Changes first appeared on Essex Ham.

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XPost: uk.radio.amateur

On 09/03/2021 08:51, Essex via rec.radio.info Admin wrote:

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Ofcom EMF Licence Conditions Changes

A change of wording to the amateur radio licence conditions affecting
any transmissions at powers over 6.1 watts ERP (or 10 Watts EIRP) to

The proposed wording I have seen says "where powers of more the 10 W
EIRP" are authorised, and doesn't say anything about the actual
configuration of the equipment. The UK amateur licence, in all forms, authorises more than 10 W on most bands. (However the RSGB does seem to
be taking the view that equipment capabilities can be used as a let out.)

Ofcom has released a calculator (as an Excel spreadsheet). RSGB has
released an amateur-friendly version:

RSGB / Ofcom Calculator
Ofcom Calculator

Both these calculators only generate far field solutions. Separation distances from amateur HF transmitters, in UK gardens, are unlikely to
ensure that people are outside the near field. The RSGB's latest
response to the consultation acknowledges that there may be hot spots in
the near field.

Antenna gain  This of course affects the ERP

Both of these are only valid in the far field, as noted in the RSGB
response.

Antenna gain: 3dB

Is this dBd or dBi. I suspect it is dBd, but I believe the spreadsheet requires dBi, which will be higher. On the other hand, it also assumes
gain from ground reflections, which will only have an effect much more
into the far field than the distances in the example.

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