Ofcom EMF safety calculator & ICNIRP Guidelines

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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by pete_uk »

I'm not going to get my thong in a twist given the amount of time I spend transmitting.

Expect it to be used by some 'Karen' to complain about someone giving her a STD or somthing.
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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by 5973Laterz »

It will likely be somewhere between -3dB and -6dB "gain" READ : loss antenna. Expect between 1/2 and 1/4 input power actually being radiated. But I imagine you need to find some kind of calculator, in mine which sounds similar more than 1/2 the total wire in the antenna is in the coil ! Close to 20m worth.

Somehow it just does not ring true that the necessary clearance distance is so... with such low power.

Lower frequency operation needs clarification I think.
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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by Andy »

Yes, I did a fag-packet guesstimate and plumped for 6 dB when all the losses are included.
Lower freqs does indeed need looking at. So does the tiny amount of time we are actually transmitting. I'm only on TX for about 15 minutes per week! Not enough to boil an egg!
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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by Transwarp »

5973Laterz wrote: 11 Mar 2021, 12:05 You have a good point with the small gardens. I think your 160m band vertical will probably have very poor efficiency if it is a 1/4 wave reduced, I would be surprised if 2-3W is radiated from 10W going in so you can probably base EIRP on that as well.. it is 100pct a negative gain antenna.

Does field strength somehow reduce with lowered frequency ? I think not. I thought that it was VHF and microwaves that were more hazardous to
humans. (wavelengths more easily penetrate and heat tissue, please do correct me)

Unless you are on a hunting mission in the neighbourhood (and likely to be the local annoyance) it is a rather spoilt hobby from home with the high persistent broadband noise floor.
1.6 to 30mhz is shortwave RF and shortwave diathermy is a medical treatment used I think on the muscles. In the US some the machines they use for this operate around 27mhz, it's not just giga freqs that can be a hazard.
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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by WhiteNoisePoetry »

OK just for a giggle lets look at two cases.

CB SSB at 12w PEP.

Firstly, there's duty cycle to consider (not made that clear in the OFCOM spreadsheet).
Processed SSB is generally rated at 50% duty cycle, so that 6 watts thermal heating power = 10w eirp = automatically compliant. And remember, that has to be taken over a 6 minute duration, so a typical back
and forth QSO especially the quick fire sort then takes down the cycle even more.

Even running a home station and a 5/8 vertical means sod all. There's no real gain in a 5/8th despite marketing
bullshit. Just a slightly modified angle of take off and a fraction of db gain (yes really). So you can take that as
being a 0db gain antenna. Result = automatically compliant = no exclusion zone required.

Foundation licence holder running 10w to G5RV / Dipole / Bit of wet wire etc.

None of these antennas has any genuine gain. Treat as 0db. Assuming 10w of processed SSB which is treated
as 50% duty cycle = 5w average heating power = 5w x 1.64 to get the eirp = 8.2w eirp = automatically compliant
and no exclusion zone required.

Man on Top Band with based loaded vertical.

Firstly, the efficiency of a shortened vertical is essentially determined by the fact that coil losses compared to
actual radiation resistance become significant.

Typical figures of a 16m tall base loaded vertical would be in the order of 68% efficient.

Therefore 30w of processed SSB has a duty cycle of 50% = 15w of thermal heating power (which is
what these regulations are all about).

30w x 50% = 15w x 1.64 = 25w (rounded up) x 68% efficiency of the antenna = 17w eirp.

20w x 50% = 10w x 1.64 = 16w x 68% efficiency of the antenna = 11w eirp.

17w x 50% = 8.5w x 1.64 = 14w x 68% efficiency of the antenna = 9.5w eirp = compliant, no need to have exclusion zone. So you need to set the rig to 17w output and your signal will lose 2.2db.

Of course, a 16m base loaded vertical is assumed here. If it's smaller then you can use a bit more power.

These examples are only to show what you can use to be be carefree and not worry about exclusion zones at all !

If you run higher power or erp then you can still do whatever you want if no member of the public enters
an exclusion zone.

ISSUES OPENING UP OFCOM SPREADSHEET.

Download and save it first. The open it with normal software. Don't try to use it online because it becomes
read only in most "apps" or like many "apps" on cell phones, they are only viewer and not editors.

Below 10Mhz ?

You won't have to worry about that until middle of next year. That's because OFCOM are having difficulty
making a spreadsheet simple enough to take into consideration factors such as shortened verticals that
often get used on the LF bands, or that most antennas are very low compared to wavelength and shoot
most RF in the sky, where no bugger is going to be standing in the way anyway ;-)

Apparently there's some headbanging going on about how to best incorporate such things so that dummies
can use the spreadsheet properly, hence the delay.

- WNP -
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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by Transwarp »

Could you repeat what you've typed please? I didn't hear it properly :eh:
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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by MrWeetabix »

from a post on an FB group I am in regarding the latest OFCOM guidance...

"These suggestions at the bottom of the Ofcom EIMF flow-chart sound hopeful?

It's almost saying "If you can't get the separation distance, then you aren't transmitting when anyone's nearby - ARE YOU - Nudge Nudge Wink Wink!"

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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by Transwarp »

I'd like to know how many millions of radio folk suffered from health problems or death due to prolonged RF exposure over the last 50 years. That's ham, CB, Taxi, business radio operating.
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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by Ant »

Andy wrote: 07 Mar 2021, 13:25 Call me a conspiracy nut if you want, but I'm beginning to think Ofcom wants to get rid of the amateur bands completely so they can gobble up more spectrum to flog to the Telcom industry. Sticking onerous and confusing regs on us will drive plenty out of the hobby completely. When we are down to a rump of barely active moaners they will petition government to withdraw the allocations.
I'd better get me pills.
I saw the same comment on the vintage radio forum and wondered if it were you. We get about don't we :)
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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by MrWeetabix »

Bottom line, without the manpower to come and perform checks and enforce anything, nobody is going to get a knock on the door.

These regs are nothing more than protecting OFCOM from potential prosecution in the future. If your neighbour gets a brain tumour and convinces some ambulance-chasing solicitor there's a case to pursue against you then all OFCOM now have to say is that they issued guidance on EMF compliance and it was the sole responsibility of the License holder to ensure they were compliant with that. As it stands at the moment, any claimant could potentially sue OFCOM for damages as they don't include EMF safety regs in any license.

When they're brought in, OFCOM will be able to step back in any claim and legitimately not be responsible.

Over and above that we all know Derek doing 100w into his Random wire isn't going to cause any health issues with anyone, but at some point in time ANY case is won regarding RF causing harm (in ANY spectrum, not just HAM radio) then that will cascade down to claims in other areas fast because some solicitors/lawyers are opportunist leeches (think about all this PPI crap and investment refunds stuff over the years).

This is OFCOM protecting their collective asses against legal action, it has nothing to do with safety.
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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by paulears »

I don't think we can blame OFCOM as they didn't create the need for this - it's a public driven reaction to complaints constantly received on RF. Made worse by the recent Brian frying 5G is causing.

If we look at it seriously, none of this is even new. Mast operators and every microwave operator has been calculating field strength for years. The Forces and the Post Office/BT were very proactive in this. As the licensing authority OFCOM have to have in place frameworks to meet the worldwide efforts to quantify emissions and any possible health implications. You can't blame the FA for having a rulebook for football, full of what-ifs, and setting out what is OK and what is not. Now it's done and circulated to every licensee, they can indeed claim everyone knows - something they could not be sure of before. It might be considered arse-covering, but that nowadays is a fact of life when we live in a blame culture.
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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by Ant »

Transwarp wrote: 25 Mar 2021, 12:09 I'd like to know how many millions of radio folk suffered from health problems or death due to prolonged RF exposure over the last 50 years. That's ham, CB, Taxi, business radio operating.
Just coming back to this. So probably no one as an operator/user suffered from health problems or death due to prolonged RF exposure, as they'd usually be outside of the radiating zone and most of us probably don't have a prolonged duty cycle.
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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by Transwarp »

MrWeetabix wrote: 02 Apr 2021, 09:15 Bottom line, without the manpower to come and perform checks and enforce anything, nobody is going to get a knock on the door.

These regs are nothing more than protecting OFCOM from potential prosecution in the future. If your neighbour gets a brain tumour and convinces some ambulance-chasing solicitor there's a case to pursue against you then all OFCOM now have to say is that they issued guidance on EMF compliance and it was the sole responsibility of the License holder to ensure they were compliant with that. As it stands at the moment, any claimant could potentially sue OFCOM for damages as they don't include EMF safety regs in any license.

When they're brought in, OFCOM will be able to step back in any claim and legitimately not be responsible.

Over and above that we all know Derek doing 100w into his Random wire isn't going to cause any health issues with anyone, but at some point in time ANY case is won regarding RF causing harm (in ANY spectrum, not just HAM radio) then that will cascade down to claims in other areas fast because some solicitors/lawyers are opportunist leeches (think about all this PPI crap and investment refunds stuff over the years).

This is OFCOM protecting their collective asses against legal action, it has nothing to do with safety.
Interesting points. I take from this then that this could leave individual radio hams, especially those with a few antennas installed, fair game for private claims against them from their neighbours stating they've started suffering health problems.
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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by Ant »

I think it would be very hard to prove an amateur radio antenna has caused health issues. Even if Ofcom were to set up camp outside your house, you'd need to be keying up for extended periods with sufficient power. I read nothing more into this than Ofcom ensuring all amateurs are aware of assessments and risks.
Shack? Shack is a poorly built building in a third world country, which is on the brink of collapse. I'm not calling mine a shack...

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Re: Ofcom EMF safety calculator & ICNIRP Guidelines

Post by Jon_D »

It will just give credence to the ignorati in society who have a grudge against individuals who happen to be amateur licencees. Remember the TV programme a few years back about a woman who stated that the antennae of a local operator (3 element beam) had caused 6 neigbours to contract cancer?

Regarding this OFCOM business I wrote this on another forum...."An interesting mathematics point, is that if the algorithm doesn't work for frequencies below 10Mhz, how then is it correct for those above? That's the same as stating that "2 + 2 = 4" over 10Mhz but doesn't add to that under 10Mhz. The formula is patently incorrect, and we should all ingnore it until OFCOM gets it sorted"
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