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OFCOM rules on EMF compliance for marine radio

Holders of marine radio licences are now required to show EMF compliance. Does this apply to me?

Vhf radio


The RYA has warned boat owners to be aware of new OFCOM measures designed to protect members of the public (which includes family and other crew) from the effects of being too close to powerful radio transmissions. Read their guidance here.

Does this apply to cruising sailors?

In theory, you could be asked to produce evidence that you have calculated the safe distance from your antennas (VHF & MF radio, radar etc) and taken steps to ensure that members of public are not put at risk. In practice, this is only likely to come up as part of examination for "coded" vessels - i.e. those used for commercial purposes such as chartering or training.

For sailing yachts, it is normal for radar and VHF antennas to be mounted well above deck level, so there is no possibility of crew coming within a few metres of a transmitting antenna. On a power boat, particularly with a fly-bridge, it may be more of an issue, and measures such as warning signs might be needed to show compliance.

Note that handheld VHFs have a maximum radiated power below the OFCOM limit of 6.5W, so they do not need to be considered for these purposes.

How do I calculate a "safe distance"?

OFCOM provides a basic calculator which you can find here, but you will need some technical information to use it, and it does not take account of losses such as cable runs, so it will tend to produce an overly cautious result.

An easier to use calculator, tailored to marine VHF, has been produced by a member of the Oban Sailing Club, which you can find here

A quick calculation for a yacht transmitting at full power (25W) with a typical masthead antenna, and a feed cable length of 20m and a duty cycle of 25% gives a safe distance of less than 1m, so clearly no protection measures would be needed. Printing out this calculation would cover you in the unlikely event of anyone asking.

I would suggest that anyone who has a radar or satellite dome mounted such that crew could be sitting with their head in close proximity might need to seek further professional advice, and maybe consider raising the antenna(s) well above head height. They will probably work better too!

Peter Forey

25 May 2021

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