Ofcom EMF risk assessment & UK SOTA

Just thinking about some stickers for my vehicle for when parked and chatting on the local UHF repeater.

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I’m just thinking that before getting too upset, it might be worth checking the calculator and see what distances you’re looking at for your setup(s).

Many of us use a telescopic pole to get the antenna up higher and in many cases this might be more than enough to be compliant. All you need then, is a print out of the calculator with your values entered, or perhaps an electronic copy on your phone, and you are sorted should it ever be needed.

I tested various low power options for the 2 m band and that came back as the antenna required to be ca 1 m away, so not a problem if you have it up a 6m pole!

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Wire HF antennas may be more problematical, they often approach the ground at their ends. In an area where public access is permitted I can see no basis for being able to create an enforcible no-go area. Wonder if a method statement stating transmission would cease if anyone came too close would suffice. Or will we all have to start carrying extra poles :frowning:

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I used the calculator to see what the worst-case [i.e. minimum] separation distance [‘R’ in the Ofcom spreadsheet] would be for my FT857 running 50W on 2m to my Diamond X50 collinear on my chimney, and it’s about 4m.

As the 3D radiation pattern is somewhat doughnut-shaped you would need to be in a ‘cherrypicker’ at the same height as the X50 to get that power density.

I think it would be reasonable to argue – without doing another calculation - that, since the power density drops off as you go above or below the horizontal plane around the colinear [e.g. a line from the X50 to the public road outside my house], the R value will be bigger there than the worst-case 4m.

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Sounds like a perfect excuse for adding 4m to your pole :rofl:

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Very good Andy - I did an ICNIRP calculation myself using software provided by a German Amateur in 2018. The calculation was based on my proposal to erect a Hexbeam at 12m for 20m-10m and my 4m/6m 5+5 yagi at 10m AGL using 200 watts output. The reason I did this calculation was for my own use in case I needed to counter an argument against a neighbour who was opposing a planning application. His garden border is approx 60m from the mast. The opposing neighbour who house itself is approximately 90 metres from mine, was alleging that the level of EMF from my antennae could be a danger to his health, citeing this as a valid reason for rejecting my planning application, which of course it is not.

In the event after receiving the request from the neighbour stating that in his opinion an ICNIRP assessment should be mandatory, the planning officer confirmed there was no requirement AT THAT TIME for me to produce one, therefore my calculations remained confidential and so not in the public domain. At that power level with the gain on those two antennae there was a considerable margin of safety in my favour to the objectors boundary and also to my nearer neighbours.

What this means though, if the request to provide an EMF calculation was made after the change is made to our licence conditions, I would anticipate that vexatious neighbours are likely to contact OFCOM to insist that to satisfy themselves from a safety point of view, that an EMF calculation should be provided.

What I would like to know, and I will be querying this with the RSGB to ask the question of OFCOM, is if the assessment was provided to OFCOM would the results be confidential to them and the licencee - or would they furnish the results to the vexatious complainent or publish them in the public domain.

73 Phil G4OBK

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The spreadsheet (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwj_5IL72rvsAhVKUhUIHe1iDqIQFjAAegQIARAC&url=https%3A%2F%2Fwww.ofcom.org.uk%2F__data%2Fassets%2Ffile%2F0018%2F204057%2Femf-calculator.xlsx&usg=AOvVaw11_HrdbtFRs-c4yX-EvGZK) seems to imply that for HF - certainly with a wire antenna with little gain it would be quite difficult to exceed the limits ( A linear is still on the wish list …) . Also of interest is what happens when the numbers are plugged in for a 4G cellphone running on one of the higher LTE bands - I had a guess at 0.25 w at 2600 MHz - and it came up with 7cm. I’m not sure that I always keep it that distance away - at the very least it would imply that there was a significantly smaller safety margin than when using amateur gear.

Interesting reading about planning permission - we had a battle to get planning permission for a polytunnel as we live in an AONB so have given up with the idea of a mast (I use trees to hold the wire up but I don’t think it would work too well for a beam and rotator …) 73

Paul

Hi Paul

As a serial planning permission applyer having been successful with 8 planning applications in Lancashire, Scotland and Yorkshire, in some cases against much opposition, if you need advice, regarding wording etc in “planning officer speak” I can send you the necessary information, although the RSGB Planning Committee guidance (if you are a member) is pretty good.

Like you I use a tree and my house and a fence to support wire aerials, but hams who haven’t operated with a directional antenna on HF don’t know what they’re missing - even something with only 3-4 dBd of gain makes such as difference. Not just in the strength of your signal out but more importantly on receive, with all the created and uncontrollable RF smog now around us, most of it coming from other peoples homes.

If one is serious about ones hobby one must strive to achieve the best result to enhance ones station performance with good aerials, and not cow down to neighbours who believe they have a “right to a view”, which no one does in the UK. The Council planning officer can be your friend and should not be feared.

PS Living in an AONB may make things a little more difficult shoudl you apply for a mast and beam, although I am aware of others in AONB and National Parks have been successful.

73 Phil

What you want to do is not contact anybody as that will only open Pandora’s box.

Put the numbers in for your equipment, including the necessary duty cycle for TX/RX and equipment duty cycle (50% for CW, 20% for unprocessed SSB etc.) , note the numbers and date. Job done.

I considered that when we moved here last year - especially as the bungalow is only 21m ASL - but I didn’t want my wife and neighbours to think the place looked like a taxi rank HQ.

Hang on, Andy - I thought you said you were gonna put this thread on mute. Couldn’t resist taking a peek, eh?

I’m not doing anything until the RSGB consultation with OFCOM is complete, the EMF calculator is completed and is official, and then I will do the necessary calculations. By then I may have made changes to my antennas anyway!

73 Phil

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I now live in an AONB [Arnside & Silverdale] - the regulations say you’re not to have road-facing TV aerials or satellite dish. My survey shows half the villagers are non-compliant. Can you imagine the reaction from householders if Ofcom told them they can’t watch TV any more.

Thanks Phil, yes I am an RSGB member and may well take advice in the future but would need something with a small visual footprint that I could also get past the garden manager! I’m almost certain to have neighbour objections too so it all needs careful consideration, at the moment my eccentricity is tolerated by the estate who ignore the wire between the trees, if neigbours make a fuss I may well lose what I have got! Very little RF smog here (No VDSL but an optical fibre) but there is still loads of ferrite around the shack trying to keep things clean from a gazillion of switched mode power supplies and LED lights. 73 - and thanks for the calls when I am activating - was hoping to do Great Whernside tomorrow but am doing a grand tour of the great roundabouts of Darlington instead as my son prepares for his driving test next month. Paul

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Yes Andy they would be very upset! Where I live the TV signal is 5 and 9 on an aerial in a loft and 5 and 9+++ on an aerial outside. The TV transmitter is above Bilsdale (near TW-001 and TW-002) which transmits Tyne Tees / NE Cumbrian news. Most people living around me hail from West and South Yorkshire and Lancashire (in my case). As a result we like to watch Yorkshire TV news, not Tyne Tees. To get Yorkshire on a normal sized 12 element TV aerial the signal is around 5 and 2 - or it was when it was analogue a few years since… To get a good picture needs an outside high gain larger yagi aerial and to feed more than one TV, a masthead preamp is required. The fact that several near neighbours have these on their roofs on 12 and 15 feet long poles was given as one of the reasons given for allowing planning permission for a 12m Tennamast and aerials. A 18m lattice Versatower would have been my first choice with an Optibeam 9-5 or 11-5 yagi, however that would never have got passed. One needs to be realistic if you want to stand a good chance of success.

73 Phil

I did. And I did. But there was a notification from your good self and I was wondering how I could be notified about something I had muted. So I clicked it and was a notification of an older reply from before the muting.

I too was wondering about this. After my superficial first use of the Ofcom calculator there appears to be nowhere to enter that kind of data. I would think human tissue exposure to EMF, i.e. the dose, would be a function of the duration of the radiation.as well as its power density.

I conclude - in the absence of information to the contrary - that the Ofcom calculator assumes the distance threshold [‘R’] involves 24/7 exposure with 100% duty cycle, e.g. your typical mobile phone mast - and that’s a far cry from your typical amateur radio usage

Trip to Specsavers needed?

I did say clearly I had made only a superficial look at the calculator.

Anyway, it’s good that you found the means to enter the duty cycle. I’m still not happy about equating a one-off 6-minute transmission of whatever duty cycle with a 24/7 transmission of the same duty cycle and EIRP. Surely the latter must have a much higher ‘dose’ than the former.

So lets form a queue at Specsavers!

OTOH, as Moderator, I would much rather that the snarky comments be held back, that includes you, Andy! :grinning:

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