Electro Magnetic field Exposure, OFCOM & RSGB

[CambridgeWorks]

Moderators, please move to different section if you need to.

Did a forum search just now and nothing on this subject found.
Not being a member of RSGB for many years, but a long term member of RAOTA I just saw mention of the EMF exposure and OFCOM in the latest edition of OTN. "The Presidents piece" Page 4
As not currently active on the air, I was not aware of it.
Whether this link is the first step for further research, I don't know. But it has further links within.
Certainly looks set to affect all radio amateurs who transmit.

https://rsgb.org/main/technical/emc/emf-exposure/

Rob

[G3PIJpeter]

The ICNIRP Guidelines 2020 to which the RSGB response refers is at

https://www.icnirp.org/cms/upload/pu...Prfgdl2020.pdf

I have followed this subject closely since my son was diagnosed with leukaemia (AML - successfully treated) at the age of 19 in 1998. There remain many unknowns in this area and it is likely there are synergistic effects with other factors in the environment - plus, of course, genetics.

Peter

[trh01uk]

Its astonishing how long this topic has been running for. It was a hot topic when I started as a graduate engineer in 1977. No doubt it was hotly debated when radar engineers found they could cook their meat pies at the end of a waveguide during WWII!

Its telling that in the paper that Rob posted they had to include these comments:

"Within the guidelines, “evidence” will be used within this
context, and “substantiated effect” used to describe reported effects that satisfy this definition of evidence.
The reliance on such evidence in determining adverse
health effects is to ensure that the exposure restrictions
are based on genuine effects, rather than unsupported
claims."

The amount of wild claims in this field is quite astonishing - with the latest of course being that 5G mobile systems have caused the coronavirus outbreak. And I note that latest Ofcom consultation is largely aimed at the 5G conspiracy theorists.

It looks like radio amateurs have been caught up with this in an unfortunate way. Its not likely any sensible amateur is likely to ever get anywhere near the limits listed in that paper. I think you would have do something like pump 400W into a yagi high gain antenna and then stand in front of it, to actually put yourself in harm's way. Unfortunately, proving that you are "doing no harm" will be a very different matter - and I can see why the RSGB is objecting to these new regs as being way over the top.

Richard

[Oldmadham]

Even so, you still only have 400 watts--- antenna gain claims notwithstanding!
Different frequency range, but an open fire could pump out well over that, & people have survived them for millenia.

[Hartley118]

Look after your eyes.

I’ve known of a couple of engineers who spent a lifetime in the radar industry and suffered severe eyesight problems in later life. Unlike most sources of warming, RF energy generates its heat locally, typically when it meets some human tissue, and the local temperature rise depends on the thermal capacity of that tissue. The cornea has very limited thermal capacity and is easily damaged. An experienced microwave engineer, explaining it to me, once likened it to the frying of the white of an egg, a once transparent fluid becoming opaque once cooked.

A sure route to blindness is the instinctive move to look down a waveguide without previously checking whether the transmitter is locked off.

Martin

[GrimJosef]

The sad fact, of course, is that severe eyesight problems in later life are, well, an unfortunate feature of later life. Unless RF engineers are developing disproportionately high levels of eye disorders, in the same way that miners got above-average levels of lung disorder, or asbestos workers got mesothelioma, our own experiences of a couple of unfortunate people aren't going to prove cause and effect.

Cheers,

GJ

A little optimism...
1. Hardly anyone will know about it, I didn't until I read this thread (thanks OFCOM, I am a registered Radio Amateur, you have my email address)
2. "Everyone" is now used to "buffering" and occasional "pixelation" on TV that my occasional transmission interfering with their (badly designed) kit won't register.

[Hartley118]

It’s not of course any sort of of proof: just a bit of cautionary evidence. Equally there are many engineers who’ve spent a lifetime in RF fields of lower frequencies without any ill effects. There’s no sinister mystery about it, just locally generated heat.

But do avoid looking down a waveguide unless you know it’s dead.

Martin

This must be buttock covering in the extreme, "we can't possibly give anything real and tangible, it's down to you to prove a negative" (which can't be done).

Me? I am going to be vigilant, informed and possibly more aware than most about the "dangers" of RF. And just carry on...

If cavemen had to do a risk assessment (apart from "we are very hungry and there is some food") before a hunt we wouldn't be here.

[G3PIJpeter]

It's one thing for rules and regulations to be laid down and it's another for them to be policed. I had several visits from the GPO in 1962 when G3PIJ was reported for interfering with next door's TV via its 'rabbits ears' set-top aerial. Nowadays, everything has been outsourced to incompetent outfits staffed by two men and a dog. If we are reasonable in our behaviour and cannot be accused of being negligent, then I think it's a case of "Carry on regardless".

- Peter

[trh01uk]

Originally Posted by Oldmadham

Even so, you still only have 400 watts--- antenna gain claims notwithstanding!
Different frequency range, but an open fire could pump out well over that, & people have survived them for millenia.

Well, lets take a few numbers here. Assume 400W is fed to a yagi antenna with a gain of 10dB. I am thinking here of operating on 2m, so our frequency is 145MHz.

At a distance of 10m from the antenna - and making the perhaps simplistic assumption that the antenna is a point source, the simple equation (30*P)^0.5 / r will give the field strength at distance r in V/m, where P is the radiated power. In this case P = 4000W (due to 10dB gain from the antenna) and lets take r as 10m, which many people would assume to be a pretty safe distance.

The field strength comes out as approx 35V/m. If you look at the attached field from the ICNIRP paper we had posted previously, this Fig.2 is the maximum field strengths allowed averaged over a 30 minute period. At 145MHz, its actually 28V/m approx. So nominally, in this notional situation we are over the limit.

However there are a couple of caveats here....

1. Who is going to transmit steadily for 30 minutes, and stand there in the full beam for that period? Most amateurs would get bored after 2 mins and head off for a cup of tea.....

2. Most yagi antenna as mounted well out of reach, often on a house roof or a mast of some kind. Actually standing in the beam would require some acrobatics.....or a very tall ladder in most practical cases.

So I conclude that while its possible to generate these high field strengths, in practice most amateurs are unlikely to breach the limits, unless they are doing something very odd indeed.

Richard

I do wonder why and how they reached those figures.

[G3PIJpeter]

Originally Posted by trh01uk

Well, lets take a few numbers here. Assume 400W is fed to a yagi antenna with a gain of 10dB. Richard

Let's look at a piece of wire on the HF bands and have a go at a few more numbers.

The effects of RF fields at HF are much less well established than the basic heating effect (mugs of cocoa in waveguides in 1945) but there is some statistical evidence about influences on cell membrane permeability at a biochemical level. The IEEE paper at http://emfguide.itu.int/pdfs/C95.1-2005.pdf contains (Table 9 page 25) the usual sort of guidelines for uncontrolled exposure at 3-30 MHz i.e.

Electric field strength = 823.8 / f (volts/metre)

Magnetic field strength = 16.3 / f (amps / metre)

RMS power density = 1800 / f^2 (watts / square metre)

So how do we interpret these figures for 400 watts into a low half-wave dipole or an end-fed wire? My intuitive (but likely faulty) reasoning runs as follows.

The close-up field strength depends on the current in the aerial wire and the value of this current varies inversely to the voltage as we move towards the end of the wire: electric field strength goes up as magnetic field strength goes down, roughly maintaining watts (power density) as amps x volts . . . (?) However, 400 watts into a half-wave of wire (136 feet at 3.5 MHz) is not all going to be concentrated at the spot where you are standing. The inverse square law says that intensity decreases with the square of your distance from each segment of the aerial. I suppose that you could cut the aerial wire into an infinite number of segments and use calculus to sum the intensity at wherever you are standing. That’s where the exposure guides come in.

Risk: 10 people are currently dying each day from Covid-19 while 30 people are dying each day from prostate cancer and 30 from breast cancer. 1500 people a year die in road ‘accidents’. The causes in these cases are clear. The case for a causal connection between any specific illness and HF RF is not clear and, so far as I know, any specific effect has yet to be demonstrated. There are some statistical correlations but sources conflict. 400 years ago, we’d be burning people at the stake for putting wires up in the air - let’s hope at the very least that we are spared this fate.

- Peter

400 years ago, we’d be burning people at the stake for putting wires up in the air - let’s hope at the very least that we are spared this fate.

Nearly, burning 5G masts??

[G3PIJpeter]

Originally Posted by merlinmaxwell

Nearly, burning 5G masts??

Well, there you go - we do not 'progress' into the future in a straight line. The pendulum of history swings back and forth and so here we are again back in the pre-Enlightenment era of un-reason.

However, continuing with the subject of this thread, most of us are stuck with a bit of wire in the air and a 100 watt SSB / CW transceiver attached to it with a less than perfect power transfer. Unless you wrap the entire aerial round your body and transmit (duty cycle <50%) for a week, I suspect that your cellular function is likely to chug on totally unaffected - with the exception that you might just be that 0.05% of the population who might be susceptible for one DNA reason or another (with added serendipitous pollution synergistic effects) to suffering a nasty response that manifests itself as an identifiable disease.

- Peter

[Refugee]

Originally Posted by merlinmaxwell

Nearly, burning 5G masts??

There is some logic there.
Those masts run at a pretty modest power and the aerials are pretty high up and out of the way.
The masts do not spread cherryade virus.
Burning them will not do any good.
The logic is:-
It is spread by zombies with touch screen hand sets that live half their lives welded to the sides of their faces. They transfer the virus to the ready to eat fruit in supermarkets with one finger from the s touch screen. Yuck.

[dsergeant]

For most amateur stations as said above we won't get anywhere near the ICNIRP limits. I operate QRP, 5W to my simple antennas, so can sit comfortably.

As for 5G, having just encountered a couple of the anti-5G crowd on a different forum it is impossible to reason with them, they can't seem to understand the truth.

[Radio Wrangler]

Originally Posted by G3PIJpeter

The effects of RF fields at HF are much less well established than the basic heating effect (mugs of cocoa in waveguides in 1945) but there is some statistical evidence about influences on cell membrane permeability at a biochemical level. The IEEE paper at http://emfguide.itu.int/pdfs/C95.1-2005.pdf contains (Table 9 page 25) the usual sort of guidelines for uncontrolled exposure at 3-30 MHz i.e.

Electric field strength = 823.8 / f (volts/metre)

Magnetic field strength = 16.3 / f (amps / metre)

RMS power density = 1800 / f^2 (watts / square metre)

Need to stress that f is the frequency in MHz otherwise it turns out a million times more onerous than necessary!

[Radio Wrangler]

We had an anti-cellphone mast protest in our village years ago. It was quite remarkable to see the number of protesters holding phone handsets to their ears.... especially the kids!

They really haven't got a clue

Once someone swallows a conspiracy theory, it seems that any information they receive (Apart from information from bona-fide conspiracy theorists, whose lack of credentials has been carefully checked) becomes part of an ever expanding cloud of cross-linked conspiracy theories.

We live in a time when there is solid evidence that believing conspiracy theories is no obstacle to reaching even the highest positions.

David

[trh01uk]

Originally Posted by merlinmaxwell

I do wonder why and how they reached those figures.

Well, its all set out - in grim detail - in the paper originally posted. Hard work ploughing through it all though - and you probably need a very good understanding of E-M fields and how they are measured to really grasp it all!

Richard