harmful Radio waves ... suddenly no one talk about it

[Zero999]

I took a class on bioelectrics once and looked at the data. The effects from all this EM stuff is either nonexistant or on the order of .01% increase in cancer rates.
In other words, its not really worth worrying about if any effects even do exist.

This might be correct for everyday situations - but there is no such qualification in statements like these.

I could specify a set of conditions that anybody here with RF experience would get cold shivers, so there IS a point at which danger exists - where my question still stands: "Where do you draw the line?"


Let me throw this very specific scenario out there for comment:
Conditions:
 * Type of energy: Unmodulated carrier RF
 * Frequency: 2.4GHz
 * Exposure time: 1 hour
 * Power:
    1uW - - - - - - - 1mW - - - - - - - 1W - - - - - - - 1kW - - - - - - - 1MW - - - - - - - 1GW

Where do you draw the line?

Sorry,but that isn't specific at all.

Are you talking about real power ( I^2R) or EIRP?

OK - let's go for EIRP

If real power,what kind of antenna? (The signal strength in any direction,of an isotropic radiator fed with 1kW will look like that of  a 30dB gain antenna fed with 1W in its direction of maximum directivity .)

N/A

How far away?

For a number, how about 1m.

Anything else needed?

Where do you draw the line?

You asked that question before and I provided you with the answer, and the answer has not changed. I suggest you read it.

A response was posted, but the question was not answered.

Note that at 2.4GHz the answernhas been very well studied, and that domestic microwave ovens leak up to 1W and that people stand very close to those. I would not put my eyeballs anywhere near a domestic microwave oven with unknown provenance.

... yet here you acknowledge the very issue I have been trying to address.  On these, your very own words: "anywhere near" I ask - just how close do you mean?



My point in all of this is rather simple - and I have tried to make it clear.  At some point much, if not all, radiation - both ionising and non-ionising - becomes harmful.  I simply want to know when that transition occurs - and if it's a fuzzy line, just how fuzzy it is.

Yes, I know there will be a number of parameters - frequency, power, duration, distance, etc., etc., etc. and certainly the conditions are not likely to be commonly occurring (we would hope) - but nobody here seems to want to look past the simplistic answers.

That's still not enough information.

Does the beam spread or is it concentrated energy?

For example, a couple of minutes of exposure to near IR, UV and visible light from the sun will not cause any damage, even on clear day, at the top of a mountain, at midday on the equator, but concentrate the energy using a magnifying glass or parabolic mirror and it can cause severe burns.

[Brumby]

That's still not enough information.

Does the beam spread or is it concentrated energy?

For example, a couple of minutes of exposure to near IR, UV and visible light from the sun will not cause any damage, even on clear day, at the top of a mountain, at midday on the equator, but concentrate the energy using a magnifying glass or parabolic mirror and it can cause severe burns.

If I have it right, the parameter you're homing in on here is W/m² - and it is certainly key to answering the question quantitatively, but for the sake of argument, let's just pick an average microwave antenna that you might find in a place like this:



But before this continues into farce (and I'm sure some will say 'too late'), I would like to cut to the chase...

Even if all the parameters you wish to throw down as a challenge are defined - would you then attempt to answer the question?

I somewhat suspect the answer is 'not really'.  If so, this highlights the point that I have been trying to show - that we can are fairly clear about very low levels being safe and very high levels being unsafe, but we don't have much confidence in defining the risks over the transition zone or even where the transition zone starts and ends.

[Bob F.]

I took a class on bioelectrics once and looked at the data. The effects from all this EM stuff is either nonexistant or on the order of .01% increase in cancer rates.
In other words, its not really worth worrying about if any effects even do exist.

Be careful what you say.  Srbel may put you on his ignore list!   

And not even with any warning whatsoever!  Now that can't be fair surely?  I think you should apply for compensation - clearly your Human Rights have been violated...  Oh, the inhumanity! 

[vk6zgo]

That's still not enough information.

Does the beam spread or is it concentrated energy?

For example, a couple of minutes of exposure to near IR, UV and visible light from the sun will not cause any damage, even on clear day, at the top of a mountain, at midday on the equator, but concentrate the energy using a magnifying glass or parabolic mirror and it can cause severe burns.

If I have it right, the parameter you're homing in on here is W/m² - and it is certainly key to answering the question quantitatively, but for the sake of argument, let's just pick an average microwave antenna that you might find in a place like this:



But before this continues into farce (and I'm sure some will say 'too late'), I would like to cut to the chase...

Even if all the parameters you wish to throw down as a challenge are defined - would you then attempt to answer the question?

I somewhat suspect the answer is 'not really'.  If so, this highlights the point that I have been trying to show - that we can are fairly clear about very low levels being safe and very high levels being unsafe, but we don't have much confidence in defining the risks over the transition zone or even where the transition zone starts and ends.

Parabolic dish antennas are designed to convert diverging rays into parallel rays ( OK ,wavefronts are not really rays,but it is how such reflectors are explained,both in optics & antenna descriptions)

Imagine ,a Parabolic dish used as a receiving antenna:-

Parallel rays from the remote station strike the dish,are reflected at an angle depending upon its curvature at that point,& all converge at the focal point of the Parabola,where the feed device,(let us assume,a dipole) is situated.

The transmit case is the converse of the above.
The RF signal is radiated from the dipole into the dish,& is reflected as parallel rays which then proceed to the remote receive antenna.

There is only one “focal point” with such an antenna,& that is where the feed device is situated.

Even if it were possible to "focus RF signals to a point"somewhere in mid-air using such antennas,there is nowhere in Communications where such a thing would be useful.


Note on EIRP:-
Say the dish has a specified gain of 28dB &,the dipole has a gain of around 2dB,both  w.r.t Isoptropic,for a total gain of 30dB.
If the dipole is driven with 1 Watt of RF,to the remote receiver the signal strength received is the same as that which would be supplied by an Isotropic antenna driven with 1kW.

Remember,however,the original 1W is all you have to work with,distributed across the whole area of the Dish.

If you suspend yourself 1m in front of the dish your body will only intercept some of that 1 Watt.
To the signal,you are  two dimensional---parts of your surface area which don’t face the antenna don’t count.

I don't think your question is something that can be easily resolved.
The RF Exposure Rules are extremely conservative,for that very reason.

Frequency is important-----I have spent longer than 1 Hour within a few metres of the base of an MF Radiator fed with 60+kW.& longer than that on another occasion working in close proximity to a HF curtain Array fed with 50kW.
I have also spent the best part of an hour behind VHF antennas fed with 10kW (EIRP 100kW).

I would be very wary of Microwave signals at such levels.

Quite apart from the fact that high gain antennas usually make it unnecessary to produce extreme levels of real power at Microwave frequencies,most people  do not spend a lot of time in front of such antennas because by their very nature they are "up in the air".

Maritime & Military people are more likely to be exposed to high levels of Microwave RF power,due to the fact that RADAR does produce real power levels in the kW region,as witness folks getting eye damage by looking down waveguides.

[Brumby]

I appreciate your effort in examining the scenario in detail, but you could have stopped with this:

I don't think your question is something that can be easily resolved.

I most certainly agree - but however easy or difficult it may be, the implications of getting it wrong are somewhat of a concern.

The RF Exposure Rules are extremely conservative,for that very reason.

That is reassuring - but my interest has been just how conservative they are, which is only really going to be apparent when the range of transition from safe to unsafe has been defined.

We certainly seem to know enough to keep safe enough - but I don't think it can be said we know everything.

[Zero999]

At low frequencies, it just not possible to focus the radiation into an intense beam because the wavelength is so large. I'd also suspect the wavelengths much larger than the human body are low risk because they won't be absorbed, unless you're in the near field or near something which could act as an antenna.

[vk6zgo]

At low frequencies, it just not possible to focus the radiation into an intense beam because the wavelength is so large. I'd also suspect the wavelengths much larger than the human body are low risk because they won't be absorbed, unless you're in the near field or near something which could act as an antenna.

Normal antennas do not "focus" the radiation "into an intense beam",as there is no practical purpose in so doing.
Maybe an "Evil Genius" might do that,but we are dealing with normal Communications & Broadcast Antennas.

[Richard Crowley]

Normal antennas do not "focus" the radiation "into an intense beam",as there is no practical purpose in so doing.
Maybe an "Evil Genius" might do that,but we are dealing with normal Communications & Broadcast Antennas.

A great many antennas focus RF beams. Every parabolic dish and directional antennas of several varieties "focus" radiation.
There are excellent reasons for focusing RF both at the transmitting end and at the receiving end. 
Everyone who watches satellite TV understands that.  Anybody who has seen microwave dishes has seen it at work.
The definition of "intense" is ambiguous and undefined.

[Zero999]

At low frequencies, it just not possible to focus the radiation into an intense beam because the wavelength is so large. I'd also suspect the wavelengths much larger than the human body are low risk because they won't be absorbed, unless you're in the near field or near something which could act as an antenna.

Normal antennas do not "focus" the radiation "into an intense beam",as there is no practical purpose in so doing.
Maybe an "Evil Genius" might do that,but we are dealing with normal Communications & Broadcast Antennas.

But an antenna can convert the radio waves into electricity which can cause nasty burns.

Take a person who's 1.75m standing near a huge 1MW 1MHz transmitter. All will be fine because the wavelength is 300m and they're a tiny fraction of that. Now put the person between two 150m long metal poles, forming a ¹/₂ wave dipole and they'll get zapped.

[vk6zgo]

Normal antennas do not "focus" the radiation "into an intense beam",as there is no practical purpose in so doing.
Maybe an "Evil Genius" might do that,but we are dealing with normal Communications & Broadcast Antennas.

A great many antennas focus RF beams. Every parabolic dish and directional antennas of several varieties "focus" radiation.
There are excellent reasons for focusing RF both at the transmitting end and at the receiving end. 
Everyone who watches satellite TV understands that.  Anybody who has seen microwave dishes has seen it at work.
The definition of "intense" is ambiguous and undefined.

The "focussing" is between the feed point and the dish itself---the signal leaves the transmitting dish as parallel rays,which do not converge again (in fact,they diverge) until they reach the receiving antenna.
The region of the most intense RF energy is directly at the feedpoint.

Many people believe that 'gain antennas" have real power gain,& that 1kW EIRP can perform the same amount of work as 1kW of real power (including cooking unwary passers-by).
This is,of course,nonsense,as it implies "over-unity".

Our hypothetical "Evil Genius" would have to approach the problem from another direction.

Perhaps an array of collinear elements (covering an area equal to that of a dish),fed with high power & mounted directly in front of that dish.
At the "focal point"would be another small dish,firing through a hole in the middle of the main dish,then some other hardware producing an adjustable focal point he could use on "Mr Bond".

[Brumby]

The RF Exposure Rules are extremely conservative,for that very reason.

Here's a question:

If it is so darned difficult to define a scenario, then how is it possible for the "RF Exposure Rules" to have any practical meaning?

[helius]

There's a well-known logical fallacy called the Argument Of The Beard. It goes something like: We would like to prove that there is a real difference between being clean-shaven and being bearded. But no one can agree just how many face hairs must one have, or how long they must be, to be a beard. Any precise definition would be arbitrary, for we could ask, What is the reason you do not draw the line a little lower, or a little higher? and you would have no good answer. So, we cannot show any difference between clean-shaven and bearded. Thus the fallacy.

It's commonly accepted that there are safe levels of RF, and there are dangerous levels of RF. They are sufficiently different in terms of their effects that it is easy to tell between them (just like beards). The fact that there are intermediate levels which are not obviously safe or obviously dangerous can't affect that.

[Brumby]

From what you have said, the "Argument Of The Beard" is based on an opinion.  Defining safe levels of RF exposure is, to my mind, directly associated with measurable impacts on human health.

It's commonly accepted that there are safe levels of RF, and there are dangerous levels of RF. They are sufficiently different in terms of their effects that it is easy to tell between them (just like beards). The fact that there are intermediate levels which are not obviously safe or obviously dangerous can't affect that.

My prime interest is in those intermediate levels.

[Alexei.Polkhanov]

There's a well-known logical fallacy called the Argument Of The Beard. It goes something like: We would like to prove that there is a real difference between being clean-shaven and being bearded. But no one can agree just how many face hairs must one have, or how long they must be, to be a beard. Any precise definition would be arbitrary, for we could ask, What is the reason you do not draw the line a little lower, or a little higher? and you would have no good answer. So, we cannot show any difference between clean-shaven and bearded. Thus the fallacy.

It's commonly accepted that there are safe levels of RF, and there are dangerous levels of RF. They are sufficiently different in terms of their effects that it is easy to tell between them (just like beards). The fact that there are intermediate levels which are not obviously safe or obviously dangerous can't affect that.

Solution is simple.

In Hegelianism that later was developed into Dialectical Materialism this is described as transformation of quantity into quality. https://www.marxist.com/science-old/dialecticalmaterialism.html#Quantity and Quality.

For this case of harmful radio waves we should use analogy of nuclear reaction - if we have few atom of Plutonium they will emit some electrons that will set other atoms in chain reaction but if we don't have many atoms of Plutonium reaction will die out. If we have enough - we have an explosion. So in case of RF radiation if organism is exposed to amount of power that is small enough that it can heal itself faster than it receives damage then we definitely say it is NOT harmful and otherwise it is harmful. Now that amount of RF radiation became very clear definitive quantity. Following this idea we can calculate which hair will make beard, which atom of plutonium will make it go bOOOOm and we know what amount of RF power will cause harm.

[VK5RC]

For measurable effects the "beard" issue is not a problem, the standard measure is the LD50. The lethal dose that kills 50% of an aged standardised population. For ionising radiation these levels to approximate values (order of magnitude) are known.  RF radiation can heat and can therefore kill/main but those levels are exceptional but again reasonably known. The idea that at levels of uncertainty, i.e. whether  you get burns or not, does  not mean that there is uncertainty of effect e.g. it gives you cancer. (or NOT)

The other good place to look for RF safety is in the epidemiological data, in the last 15-20 yrs the number of people sticking a small and modestly powerful RF transmitter right next to their head for hours a day has skyrocketed. perhaps 100,000x compared to  1960s levels, yet the number/distribution of illnesses has NOT followed such a trend.

In my mind the most dangerous aspect is the bus I have seen people nearly walk into while talking on the phone.