Ofcom EMF Licence Conditions Changes

As we advised some months back in our interview with Leslie G0CIB, Ofcom has now  introduced 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 has changing?

The licence was updated on the 18th of May 2021 to include new wording about field strength.

The change of wording to the amateur radio licence conditions affects any transmissions at powers over 6.1 watts ERP (or 10 Watts EIRP), and is designed to ensure that licence holders will have to comply with the ICNIRP limits about exposure of radio signal field strength to members of the public.

How does 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:

  1. Calculate your field strengths and make changes if needed – This is the route that most of us will likely go down
  2. Measure your emissions and make changes if needed – This involves special and expensive measuring equipment, so not ideal
  3. Ensure you never radiate more than 6.1 watts ERP – No-one’s preferred option

What should I do?

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

As long as members of the general public can’t stray into the “unsafe zone” and stay there for longer than the allotted length of time, then there’s no problem.

Amateurs are likely to need to retain a copy of the calculations (perhaps with a copy of their licence), so that if there’s 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:

Example of Ofcom's EMF Calculator
Example of Ofcom’s EMF Calculator

You’ll 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 members of the public are to be in the ‘unsafe zone’

What if there’s 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's Colinear AntennaPete 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 (according to the spreadsheet)
  • 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! I’m only required to check this again if I change my setup.

Where do I get more information?

See Also:

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 Ofcom’s proposed changes.


  1. Brian 15 March 2021 Reply
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