Surely this stuff only really needs such consideration for operating at home. ie where your neighbours / family members might be located while you are operating in the shack and possibly not in sight of them.
Out portable operating for SOTA, if anyone gets close enough to be potentially infringing on the compliance distance, you will (a) see them coming, and (b) stop operating, realising that they probably want to talk to you.
I’ve only just noticed this post and a thought occurred to me, which I then checked out. The answer to your problem with using RG174 on 80m is that the specifications for that coax type available online only go down to 5MHz (and up to 1GHz). Here’s a graph of attenuation by frequency for RG174 A/U, data gleaned from the specs, taken from a handy online source:
It would seem that the RSGB calculator does not extrapolate linearly downwards from the lowest frequency in the specs, and simply assumes that the coax is not capable of being used at any frequency outside of its’ specifications. But I’ll wager people do use it on 80m anyway…
Hi Andy as the models can only predict theoretical results (with all sorts of real world variables likely to be at play), I would apply the worst case version - ie the largest exclusion zone. You couldn’t be criticised for doing that.
No. It needs to be done for all your operating circumstances. Off topic for SOTA, but a potential vulnerability is for amateurs who operate /m from their car in built up area. Pedestrians or cyclists could pass quite close to the antenna.
How do you know what the compliance distance is if you haven’t done “this stuff”?
ISTR we did compliance checks for our contest gear when the power limits changed. On 2m with a 10m mast and a 10m long 17ele Yagi and 1kW you could stand about 2m from the mast and be OK. I may remember this wrong, I’m using the wrong computer at present to review this.
As it takes so little time to run the calculator, I couldn’t resist, Andy.
Assuming CW, 10m of Ultraflex-7 feeder and Yagi is horizontal …
I read that as meaning, it someone were standing at the same height as your Yagi (maybe on some rocks) there would need to be 44.5m from the beam direction. However, with the Yagi at least 7.6m up (10m in your case), they could stand right next to the pole.
To be fussy, the model probably doesn’t take the length of the Yagi into account. Assuming your 10m-long Yagi is attached to the pole at its mid point, we would need to add 5m onto the radius of the EZ, to get 49.5m.
The ‘takeaway’ from your Yagi example and mine is, for a horizontally-polarized Yagi, the EZ below the the plane of the Yagi rotation ‘cones’ in. With a 10m high one, folk are safe to walk about below it [from an RF point of view, not a it-falling-over-in-the-wind point of view].
That is what I recall now, right up by the pole was kosher. In reality we have typically 25m of either LDF4-50 or FSJ4-50 feeder, 4m along the boom, 11 down the mast (rotator loops) and about 10m left along the ground to the station. We’re on a slope with high ground behind us. So for someone to be at the same height as the beam, they could stand on the higher ground behind us. But that’s about 2km distant so again no problem.
Now we are on private land but there are walkers and cyclists who go past on the track. My XYL (bless her) was looking at a photo of us on the May 2m contest and I was wearing T-shirt, shorts, wellies and some kind of wide brimmed hat. She described me as looking like some kind of Wurzel Gummidge but not from a kids TV program but a more a zombie/psycho/slasher/horror film Wurzel. And I’m the good looking one in the photo! So our appearance is enough to deter visitors from approaching too close 
This raises an interesting point, which does not appear to be taken into account by EMF exposure calculators such as that provided by the RSGB, but which may be (I would hazard the guess that it must be) taken into account by medical physics research studying the effects of long-term (seconds to hours, days, etc.) exposure to EMF fields by people/animals/instruments remaining static and unmoving in those fields at given distances from the antenna in question while the antenna is radiating.
It would seem to be obvious that a person standing, say 5 meters away, from an antenna would experience roughly the same amount of “radiation effects” (given that HF is non-ionizing, and VHF barely so, exceptions of course for Yagis/beams…) if:
and so on.
One thinks of the unfortunate soldiers brought in to try to remove parts of the reactor core during the clean-up at Chernobyl: get in, do what you can, get out: in 90 seconds flat. Any longer, and you run the risk of permanent injury or worse - much worse.
Thoughts?
It’s all non-ionising. Ionising radiation starts at higher energy ultraviolet and X-rays.
Definitely ionising radiation. In this case also from sub-atomic particles.
… so, UHF and SHF much so? No!
Phew! Well done Richard for getting to it quickly. Alarms bells were ringing when I read Rob’s comment. The [non-science literate] general public already fears the word “radiation” [equating it with nukes and reactor melt downs] and we don’t want them to put RF in the same box.
A ‘blue’ photon has twice the energy of a ‘red’ photon (as its energy is proportional to its frequency) - which is why you don’t want blue lights on when you’re trying to sleep. You could bombard someone with billions of RF photons - they could get RF heating - but not one of them will cause ionization. But just a single UV, gamma or X-ray photon could cause ionization.
Rob, it might seem obvious to you but I think it’s wrong for several reasons. This is a complex situation. You are dealing with a (human) animal which has natural mechanisms for ridding excess heat (blood flow, sweating) for heat generated internally (e.g. in our ~25% efficient muscles) and externally from the environment. See my previous discussion on this:
The medical models/experiments on which the RF heating limit is based will attempt to take in the heat in (due to the RF) versus the body’s ability to remove the excess heat. If, during the 7-minute test period the former exceeds the latter, the body (part) temperature will rise. If the temperature exceeds some critical value for that time, cell damage will result. Your 1000W case is more likely to cause this situation within the 7-min test period than the 100W case.
You are conflating two different situations. Your 1000W & 100W RF cases are about RF heating of the body. The reactor core case is about very-energetic gamma and x-rays whose ionizing effects would have been shredding the DNA of Alexei Ananenko, Valeri Bespalov and Boris Baranov, the three brave men who made up Chernobyl’s so-called ‘Suicide Squad’.
Well, @G4TGJ and @G8CPZ ,I did ask for thoughts … and you did not disappoint.
Understood that EM radiation below UV/X-rays is non-ionizing, this is not news to me.
I’m not science illiterate - the thoughts of several are better, at least from a STEM-literate community like this one, and I’m certainly not equating HF/VHF radiation with higher-energy EM radiation like UV/X-rays, even though the “general public” may not be au fait with the differences between these various frequency ranges of EM radiation and particulate radiation (e.g. alpha, beta, gamma).
I am aware of the heating properties of HF radiation, and of the medical uses of HF radiation in providing low-level “deep-heating of bodily tissue.”
So, the discussion now turns on the heating effects of HF radiation, and the ability of the body to effectively dissipate the heat generated by HF EMF fields in the bodies of persons exposed to HF EMF fields, as in standing close to HF antenna systems radiating HF waves. Is it assumed by the EMF “safety” calculators that, regardless of the HF power radiated (up to the amateur radio power limits), the body can effectively dissipate the extra heating caused by the EMF field surrounding the antenna? If so, then duration of exposure is not an issue.
Thoughts?
No, it isn’t. And that’s the very purpose of having the calculator.
There isn’t a simple relationship between the RF power of your transmitter and the RF heating effect in an animal (e.g. a human bystander). As I just said above “This is a complex situation”.
I’ve given my interpretation of the RF dosage vs heating effects [implied by the small print in the model] in the link I just gave. I’m no expert. You have a complex chain of energy transfers: from the rig (power level, mode, duty cycle, etc), antenna feeder, antenna (many types, gain, directionality, etc), position and distance of bystander w.r.t. the antenna. Most of this is above us non-specialists so probably best to accept the models/calculator as approved by Ofcom, plug in the numbers and comply with the results. In all but a few cases I get ‘low-power compliant’ so bystanders can sit next to my setup in confidence.
100% - of course, and I’m as aware of the complexity of the situation as the next guy. I’m just interested in some of the background thinking behind the standards of compliance - I’m not arguing against them at all. Good to hear from somebody who knows what they’re talking about, thanks.
I hope you don’t mean me [I just sound like I know what I’m talking about]. I’m just ‘seeking the truth’ like the next guy.
Understood.
So, the heating effect IS taken into account, by linking the field-strength at a defined power and EIRP and distance from a particular antenna setup, with the degree of heating experienced by a human bystander, with reference to standard results gleaned from various models and lab results. Got it now.
So, Here am I operating somewhere from my bike, car, bus, caravan, park etc., etc.,
a. Whats the chance of someone from OFCOM dropping by and saying; “Excuse me Mr Perry can we see your Ofcom EMF RA please”?
Or;- Someone passing by asks you if you’ve done a RA on the little whip you’ve got stuck on top of the car, caravan bike, etc.,
Or:-
b) Someone suddenly collapses, or goes home claiming to be cooked or suffering from exposure to radio waves, … And you getting the blame - (because they worked for OFCOm and took down your callsign.)
a. Unannounced, nil [notwithstanding the witty joke I made in Part 1 about an Ofcom ‘swat’ team dropping from a helicopter around your summit activation]. How would they even know where you are away from the home address?
b) Nil [to someone making that causal connection between the two, and proving it].
So, for those reasons I anticipate a large number of UK amateurs won’t bother to determine their use-case EM compliance because they know there will likely be no consequences.
I’ve done the work - not for fear of a knock on the door - but because:
BTW: I imagine the chances of a home visit are low to nil. A written request by Ofcom to provide documentary evidence might be a bit more likely.
Andy, just for clarification I was criticising you or anyone else 
