OT very but urgent!

[Lobster]

Sorry for the OT post but would really appreciate the advice,and I know people here will have the answer...

I've just received a text message from a friend who's working in the Middle East today doing repair work on big radio masts. He's just been sent 50m up a mast with live microwaves (for mobile phones), with VHF radio transmission for TV and radio on the same mast 50m above that; having been assured it was perfectly safe to do so but has subsequently found out that this was pure supposition. Ha bloody ha.

Understandably he's now very worried and upset. He's asked me to find out anything I can about UK guidelines, radiation risks etc; what he's likely to have done to himself and if there's anything he can do now? Apparently this is a main mast for the whole country so presumably it's going to be pretty powerful.

If anybody could point me at some guidelines or has any helpful advice I can relay back to him urgently I'd be really grateful. Anything else I need to ask him?

Thanks David

[Adrian C]

Googling about, the NRPB (National Radiological Protection Board - now part of the health protection agency) has this document on the effects and their recommendation.

links at

[Lobster]

Thanks a lot for that - as it happens I'd just located that in parallel. Reading what I've found so far, it looks to me that as a layman (as is my zapped friend) and the rather vague info I have, in the short term (ie right now!) we're not likely to be able to make to much sense of official guidelines: I'm hoping someone out there will have real-world experience of this stuff and will be able to offer some advice?

(It sounds as if he didn't get physically burned, ie didn't suffer from direct heating effects so hopefully that's a good sign?)

Thanks David

[Bill]

In message , Lobster writes

You might try asking on uk.tech.broadcast some very knowledgeable people on there.

[Andy Dee]

No-one here can say if that was safe or not.

If he was 50m below the main VHF aerials, then there is no need to worry. Field strengths directly behind these would certainly be higher than that which is considered to be safe, although some are adequately screened so that one is able to climb through safely but not linger there. Cellphone panels have little radiation back towards the mast. The powers are also much lower than broadcast. As long as he was not in front of these panels, then there is little risk. Same goes for dishes. Cellphone antennas using "co-linears" (an omni-directional vertical) are renowned for high field strengths but that doesn't extend far above and below.

Physical exposure to high levels of non-ionising radiation causes the body to heat-up so hopefully, he didn't notice anything like this whilst on the structure.

HSE publishes exposure limits but unless a hazard meter is available, this cannot be checked.

In the UK, each mast has a safety survey which shows the field strengths and lists the measures to be taken when work is to be carried out at each height.

If your friend is a trained rigger, he should know all this anyway. If he is not, then what is he doing working on transmitter masts?

A

[Lobster]

Many thanks for that advice Andy, much appreciated: sounds reasonably encouraging.

He's a trained rope-worker for sure, whether that normally covers transmitter masts I have no idea - but pretty sure this is the first time he's been asked to work on one, anyway. But God knows what rules and regs apply in the country he's working in :-( Wouldn't be my first choice of employer/employment, that's for sure...

Any further comments from anyone much appreciated.

David

[Vernon]

For future reference, the first signs that you are being irradiated is usually tingling in the ears, and as others have said if he was behind the antennae he was probably safe, in front of them NOT. most are highly directional to ensure they get max range.

[Dave]

As a licensed radio ham, I have to ask the question of 'why the tingling in the ears?'

Dave

[Derek Geldard]

Ask on uk.tech.broadcast

My info is 35+ years out of date although the physics doesn't change.

Personally I'd say that if he kept out of the useful beam (the antenna's didn't point towards him like a searchlight) and he was 50m away then he'd be alright.

The principal risk is of R.F. heating affecting the eyes in particular causing cataracts and some other organs to a lesser extent.

There is no risk of hidden long term damage. If he'd cooked himself I think he'd know about it, but if they'll take risks like that the question is what else are they taking chances with.

Accidents have occurred with radio towers over the years, If the transmitter was suddenly energised whilst he is up there he could end up panicking and fall off scrabbling to get out of the beam. Proceadures have been evolved to avoid that possibility.

Derek

[dennis]

If he only got as far as the mobile phone bit and didn't hang about in front of a microwave link i don't see there is a problem. In general the power is radiated away from the mast so being inside or below it means low power levels.

[Paul Martin]

According to the US Military, "RADHAZ is a DADHAZ".

[Bill Wright]

So far I don't think we've had a response covering the future symptoms that might develop. If he endured the exposure without being aware of any ill effects, does that mean there will be no future problems?

Bill

[geoff]

In message , Bill Wright writes

I hope not - I spent a lot of time up telecom towers when I worked in Indonesia

Nothing wrong with me

No sireee e e e

AArgh

[John Rumm]

Chances are the base station ERP is only going to be a couple of watt. The antennae are somewhat directional - but don't have a huge gain, so short term exposure risks are going to be tending to zero. (you are probably exposed to stronger field strengths from your own mobile given the proximity to the aerial even if the power is a maximum of 600mW - the inverse square law comes to your rescue).

Non ionising RF hazards tend to be fairly self evident at exposure - burns, localised heating etc. There may be some risks in high RF fields for people fitted with pacemakers, but otherwise normally healthy folks there is not much to fear.

Ask him to stop worrying... Its wise to be cautious, and think about the levels he is exposing himself to, but not something to panic about.

[<me9]

Having worked in that field for 35 years, 50 metres below an active VHF/UHF aerial should be ok, unless it is very poorly designed/faulty. The aerials are designed to radiate out from the mast, and the field strength below or above them should be quite low. Our normal proceedure was to reduce power to climb through the aperture of the aerial. For some aerials this was inadequate and required removing power completely. 50 metres above/below should be ok. it is when outside the mast in line with the aerial the field strength is highest, as they are designed to put the signal out away from the mast.

If he didn't feal heated up or any othe symptoms (nausea) he'll almost certainly be ok as long as it is a one off.

[Andrew Gabriel]

Certain body organs are particularly susceptable to damage from even a small amount of radiation induced heating and/or their composition makes them more susceptable to absorb the energy. Lenses in the eye form cataracts, but I believe that's pretty instant (same effect as cooking egg white). Kidneys are another, but it can take you a few days to realise kidneys have stopped working (or even longer if they haven't completely stopped). Also depends on the wavelength, at what depth below the skin the heating effect takes place.

[Fredxx]

All those effects are from direct RF heating tissue. Fortunately for the OP's friend the levels required to do damage are actually quite high. Most wavelengths are either reflected by flesh (water), and of the transmitted power into the body, it's quickly absorbed. I wasn't aware that cataracts formed so quickly. One would have thought more cataracts would be formed by standing close to fires.

My instinct does suggest that working behind mobile radio aerials would pose little danger, the maximum power emitted would be in the region of 30W forward. As long as he stayed within the confines of the mast, I doubt there would be much power in the VHF band, especially 50m away from those aerial.

I would say that he ought to take more care though, and only climb a mast which has been surveyed for field strength. It seems this one hadn't?