OFCOM re: International Commission on Non-Ionizing Radiation Protection (ICNIRP)

[David G4EBT]

Had an e-mail today from Ofcom, as I guess all other amateur radio licensees will have, a clip of which states:

Quote:

Dear Licence Holder,

We are writing to make you aware of some important changes that we are proposing to make to your Wireless Telegraphy Act licence(s) issued by Ofcom.

In February and October last year, we issued two public consultations on our proposal to formally require licensees to comply with the internationally agreed levels in the International Commission on Non-Ionizing Radiation Protection (ICNIRP) Guidelines for the protection of the general public from electromagnetic fields (EMF). We refer to these levels as the ICNIRP general public limits. In October, we also issued a Statement setting out our decision to formally require licensees to comply with the ICNIRP general public limits and we recently published an update on how we propose to implement that decision.

End quote.

Not really sure what the implications of that are in practical terms.

As I went off air 15 years ago, and only retain my licence out of sentimentality, it has no adverse consequences for me, so I can file it under 'burn before reading', but maybe it has significant consequences for many who are still active.

Just had a quick squint at the 'Manage Your Licence - EMF' pages:

https://www.ofcom.org.uk/manage-your-licence/emf

Here's a short clip:

How do I show Ofcom my equipment is operating within the ICNIRP general public limits?

You need to be able to explain the steps you have taken to ensure compliance with the ICNIRP general public limits and if requested, provide us with records demonstrating compliance.

Examples of an acceptable record include:

keeping a record of how you make sure your equipment never transmits above 10 W EIRP (or 6.1 W ERP) e.g. you may be able to demonstrate your equipment is not capable of or is set-up in a way which means it cannot transmit above 10 W EIRP (or 6.1 W ERP);
keeping the manufacturer’s instructions, or information from the installer of the equipment, to hand;

Documenting any calculations you’ve made to determine the compliance distance for your equipment (for example by printing the output from Ofcom’s EMF calculator);
keeping the results of any on-site EMF measurements you’ve made;

Keeping a record of the control measures you have put in place or how you may otherwise ensure that no member of the general public is present in any area in which the ICNIRP general public limits may be exceeded when transmissions are taking place.

When we say 'general public', we mean anyone who isn’t:

The licensee, owner, operator or installer of the radio equipment, OR
a worker who is already protected from EMF exposure under pre-existing health and safety legislation, including The Control of Electromagnetic Fields at Work Regulations 2016.

The general public can include family, friends, lodgers, neighbours, visitors and paying customers as well as other members of the general public of all ages.

End quote.

Just curious really, as an outsider looking in - I haven't seen it mentioned anywhere, but I guess it has been quite a talking point in amateur radio circles.

[Radio Wrangler]

Very, very few people have calibrated field measuring equipment, so almost everyone is going to rely on calculated values.

The RSGB seem to be working on pre-calculated situations which might get a lot of people off of the hook.

The email received seems dodgy in the 'Less than 10W eirp' bit - the actual legislation is in volts/metre and amps/metre at the point where someone could be exposed. It's really all in near field for the HF bands and that stirs a right hornet's nest of uncertainties.

For the moment, just keep a watch on Radcom.

David

[Sinewave]

I had this email today, had a quick scan of it, was hoping to see what others made of it too.

[HamishBoxer]

I am relieved to hear your thoughts David, thank you.

[eaglework]

Likewise I've just seen the same email but not done much more research yet.
Another point to note, aside from David's 10W eirp lower limit, is the excel calculator you can down load from ofcom has a lower frequency limit of 10MHz so won't be of any help on the lower amateur bands unless this means the limits aren't relevant under the 10MHz.
More reading required.....

[G6Tanuki]

The modulation-duty-cycle and amount-of-operation-in-any-six-minute-period factors are interesting get-outs; typically, a 100-Watt PEP SSB transmission has an effective duty-cycle around 30% (thats why you can drive 'linear' amplifiers relatively hard without them melting the valves as would happen if you did key-down CW to the same input).
And unless you're an 'alligator' - all mouth and no ears - who spends more time talking than listening - well, the Military-standard for power consumption assumes a 9:1 ratio of receiving-to-transmitting, I'd say 3:1 would be a sensible compromise for amateur operation - unless you're doing something like RTTY in which case you could be running 100%-output for quite a few of those six minutes.

Plugging the numbers into the spreadsheet [100 Watts PEP, 10MHz] would require a minimum separation of 4.77 Metres between my antennas and a member-of-the-public.

Given that my HF antenna is 25 feet above ground, I guess that means I'm in the clear. My VHF antenna [144MHz] is 12 Metres above ground, so that would seem to be OK too.

What happens for below-10MHz? The caculator doesn't give guidance.

One thing the spreadsheet's notes say but I don't understand:

"Enter EIRP (Watts) in cell D5. EIRP (watts) = ERP (Watts) x 1.64"

To me, identifying EIRP depends on a knowledge of transmitter-power *and* antenna gain. I wonder what the 'gain' of my end-fed longwire is? I suspect it's actually negative!

I too tried the spreadsheet (openable in OpenOffice, no need to buy Microsoft) and it seemed to give 4.77m for almost anything. There is nothing noted below 10MHz. Seems to me as a "cover an ass" bit of regulation. The worst my neighbours want is TV interference, well broadband interference anyway.

[eaglework]

To answer the G6Tanuki query:
One thing the spreadsheet's notes say but I don't understand:

"Enter EIRP (Watts) in cell D5. EIRP (watts) = ERP (Watts) x 1.64"



The 1.64 on the spreadsheet is the difference between the ERP of real world dipole and the EIRP of an isotropic dipole. Real world has a 2.15dB gain over the unreal/isotropic one.

Guess who has just passed his Intermediate exam!

[GMB]

The email received seems dodgy in the 'Less than 10W eirp' bit - the actual legislation is in volts/metre

... except for less than 10W eirp when it says "it's OK", so you don't have to work it out.

"Enter EIRP (Watts) in cell D5. EIRP (watts) = ERP (Watts) x 1.64"
To me, identifying EIRP depends on a knowledge of transmitter-power *and* antenna gain.

It does, but some antenna gains are expressed relative to dipoles so I think they are just reminding you of that.

I happen to know that the RSGB are working very hard on creating a more ham-freindly calculator and with the view that printing its output can be the filed documentation.

One thing that amazes me on all this (which by the way has been talked about for a long time - and 2 OFCOM consultations too) is that it has always effectively been a requirement to meet the ICNIRP standards. The NEW thing is having to have documenation to prove you thought about it. I get the impression that many people handn't!

[Vintage Engr]

I've also received the same info from Ofcom. As others have said, the RSGB/ Radcom are keeping a close watch on this, & reporting accordingly. I await with interest the final outcome.


Like David G4EBT, I'm very rarely on the air these days, but do keep the licence up to date.

Perhaps I'm more fortunate than most, as the 'General Public' are unlikely to come anywhere near any antennas that I might erect, as I'm over 800 feet ASL, and there are no roads / gardens/ public footpaths running anywhere near any of my kit. I guess the sheep deserve some protection though...! We actually had a visitor today, the first in over a year, so hopefully there is little risk.

[G6Tanuki]

Originally Posted by GMB

The NEW thing is having to have documenation to prove you thought about it. I get the impression that many people handn't!

Yes, Being able to demonstrate - with supporting screenshots/spreadsheets - that "I analysed the situation as defined within existing risk-regulatory frameworks and - where analysis showed action to be necessary - recommended/undertook suitable remediatory action(s) with due consideration to the underlying extent/probability-of-harm balanced against the costs-of-remediation" is how I will address this whole thing.

[I wrote-up a lot of this stuff in days-past]

[Panrock]

Originally Posted by Radio Wrangler

Very, very few people have calibrated field measuring equipment, so almost everyone is going to rely on calculated values.

Is it possible to hire this sort of thing?

Steve

[kellys_eye]

Well 1/4 mile to nearest neighbor and 25 metres from any public road makes this the 'burn before reading' document David exhorts!

Woo hoo!

[GMB]

For >30Mhz yes. Not sure there is the demand for HF stuff as there are not too many commercial users. But also it is hideously difficult to make such measurements.

The practical approach is to calculate the fields you are generating. Where there is some uncertainty then use worst-case assumptions about the unknowns. This is as much as OFCOM will expect.

If you are very keen or have a very weird setup then maybe try making some measurements to confirm the calculations. I am currently looking into ways to do this in a more DIY manner (and I know other people doing the same).

One thing to not be fooled by - there are loads of not entirely expensive field measuring gizmos that you will see advertised. Many look like they would be useful. But read and understand the small-print. Every one I checked out would be useless. The reason is that many of them have a very narrow agenda about their calibrated range. Don't be fooled by the "headline" specs.

[G6Tanuki]

Originally Posted by Panrock

Is it possible to hire this sort of thing? Steve

Sure - but a professional field-strength-measuring test-set with proper calibration-traceability will cost you a minimum of £200/day for a week's hire.

Which is why sane people will treat the whole thing as a proof-of-assessment paper-exercise, with screenshots and spreadsheets to show you've followed the specified procedures.

[GMB]

Well 1/4 mile to nearest neighbor and 25 metres from any public road makes this the 'burn before reading' document David exhorts!

Quite good, but anyone in your house must be considered - and don't forget visitors like postman etc.

But do not loose sight of the requirement.
It is about documenting the safety case!
You still have to write up that being miles from anyone is OK - and justify it.

[AdrianH]

I must be doing it wrong perhaps I need to read it more.

20 meters If I assume that I can get full power at the end of my co-ax to a simple wire dipole, I have 100 Watts peak output, even with a speech processor on I will see a typical average value of 70Watts on the power meter, x 1.64 gives me a EIRP of 114.8 Watts and a safe distance of 3.42 meters. So I will still have some loss in a LPF, cable, balun and connectors but the distance is OK to me.

2 meters I use typically 1 watt to an omni in the loft so no issue.

QO-100 operation typical measured power with a Bird throu line going to the feed is 33 Watts into a 1.05m dish. Assuming 70% efficiency gives me a gain in dBi of 26.3dB which equates to an EIRP of 14,125 Watts That is 14.125 Kilo Watts and a safe distance of 17 metres in front of it. Good job it points to an elevation of 23.4 degrees, I guess I need a more specialized calculator where I can find the gain drop off at various angles off the beam, typical 3dB beam-width is 7.12 degrees, so 3.06 degrees either side? of dead centre.

Adrian

[Panrock]

Very crudely, imagine a bare 1 kilowatt electric fire element (with no reflector) atop that mast in your garden. With all that space around it, it wouldn't warm you up much at ground level, would it?

Now replace it with an omni antenna (of similar radiating pattern) and feed in 1 kilowatt of RF. Apart from the fact that the RF heats tissue throughout the body rather than just the surface (as per infrared), the heating effect would be similar - and utterly negligible.

Am I missing something here?

Steve

[Colinaps]

It gives the same result for 1W as for 100W. Hmm.

Colin.

[GMB]

At low HF the problem is not heating but nerve stimulation.

Also, with all the interest in the ICNIRP document it seems the authors have been "improving" it. Already the HF limits have changed completely to what it was a while ago, and I think it is even possible that we have yet to see the final version.

I think you should also bear in mind that if the heating effect was such that you actually noticed the warming glow from the aerial then you are way way over the limit (so thinking of a 1kW fire up a pole may not give the right impression).

With HF aerials you have to consider near fields as the wavelength is much longer than the safety distances will be. So a typical problem is at the ends of wire aerials where the E field is very high - and these are often near the ground e.g in inverted V (and maybe tied to the fence? That is the kind of thing that will ask for trouble).