Radiation from Wireless LAN vs Bluetooth PAN

snipped-for-privacy@stonyx.com hath wroth:

A bit of trivia first:

- Sunlight generates about 1000 watts of power per square meter (or 100 milliwatts/cm^2).

- The maximum RF exposure limit is 1 milliwatt/cm^2 for an uncontrolled environment. Therefore, standing in the sun exceeds the FCC exposure limits by 100 times.

Sure. The FCC limits for SAR (specific absorption rate) is 1.6 watts per kilogram. Most current cell phones run around 0.25 watts/kg. The Class I 100meter headsets run about .005 watts/kg. The Class II 10m Bluetooth devices run about 0.001 watts/kg. 802.11 devices are not normally worn and are therefore not tested for SAR. Incidentally, the reason the Class I and Class II are not exactly 10 times difference is that the wearable Class I devices tend to be physically larger and therefore support more sophisticated antennas.

802.11 devices are tested for RF field safety limits not SAR because they are not worn. See: | a simple calculator. Use 0.035 watts for 802.11 xmit power and 0.010 for Bluetooth. Note that such field calculations assume a continuous transmission as in broadcast FM/TV. This is not the case with Bluetooth and 802.11 as the transmitters are not always on. Actual 802.11 and Bluetooth exposure will be less as multiplied by the duty cycle (% of time on the air). This is NOT the case with SAR calculations, which include duty cycle.

FCC exposure guidelines: |

Supplement: | Radio Supplement: | Supplement: |

The real pity is that none of the 802.11 devices can reduce their transmit power to the minimum required for adequate communications. Every other technology approved by the FCC since about 1985 has required transmitter power control, but not 802.11. This is to reduce interference, but would have beneficial effects on reducing overall radiation.

When the access point says +15dBm transmit power, that's the power coming out of the coaxial connector on the access point. It's the same no matter who manufactured the unit. My measurements show that it can vary from +12 to +17dBm depending on manufacturer, but there's no way to know that without a mess of test equipment.

What does have an effect on radiation is the antenna. The more gain, the larger the field intensity, and therefore the larger the exposure. Small antennas, with a gain of less than 8-10dBi aren't going to make much difference in the safe area. Highly directional dish antennas with 24dBi gain are obviously different. Since much of the indoor RF exposure comes from reflections, it's difficult to pass judgment on a given arrangement without also including the room in the calculations.

For example. My wireless access point is sitting on my desk about 2 ft in front of me. The 8dBi omni antenna is hanging from the ceiling about the same distance but over my head. I'm not worried because most of the radiation goes out the window and over my head. There's plenty of RF, but it's not going in my direction. Worry about antenna location and physical separation, not antenna size.

You may find this article quite informative: |

was written by a local RF Engineer who is far more knowledgeable and experienced than most. It should give you some numbers as to what to worry about, and what to ignore.

Also, thank you for asking the right question. Very few people asking about RF exposure bother to ask for numbers. If you know the numbers, you can make informed decisions. Anything less is just FUD. If I've missed something or you have additional questions, please ask.

I suspect you'll be disappointed. IME wired beats wireless by a large margin. Some houses are more difficult than others, but there's usually a way...

And is known to cause cancer. So then the question is what happens at lower levels of exposure but perhaps for even greater periods of time (ie wireless is around us in winter when we tend to be out of the sun, and at home, at night)? Not sure comparing with a known cancer causing agent is a good comparison tool.

But we don't actually know the effects of prolonged exposure at any number levels. Again I'm here, I use wireless, but my point is that we really don't know. No one has studied the effects of say a 2,4Ghz at what 30 milliwatts on a young child in the house. (who would be monster enough to do such an experiment, except of course a nerdy father wanting to use the internet in various places around the house and he isn't checking the impact on the kids) .

fundamentalism, fundamentally wrong.

To be fair, we also don't know the effect of prolonged exposure to a vast array of things, including vegan yoghurt, teletubbies and plasticine. There's a zillion modernish inventions we simply haven't been around long enough yet, compared to say the effects of prolonged exposure to volcanoes, the sun's rays and fish.

Actually, I'm pretty certain you're mistaken about this but its 22:30 on a sunday and my STFW fingers are tired.... :-)

Someone also studied the effect of living in high-radon areas, ingesting aluminium salts, living under pylons and mobile phone radiation. No animals were harmed in the making, because the studies were in-situ, with pre-existing groups of people in pre-existing exposure scenarios. You'd study the effect of 2.4Ghz radiation in much the same way and you can bet your bottom dollar that somewhere, some poor b*gger is living next door to a massive radar-type installation. Over here, it'd be some chavs, with any luck. Mark McIntyre

rico snipped-for-privacy@hotmail.com (Rico) hath wroth:

Actually, it's an excellent analogy if we ignore resonant and frequency dependent absorptive effects. The sun belches most of its energy in the visible spectra region, but spews considerable amounts of noise at lower frequencies including the microwave bands.

at the above graph, the sun generates 10E-4 Watts/sq-cm or 0.1 milliwatt/sq-cm in the microwave region. FCC limit for uncontrolled environments is 1 mw/sq-cm. Therefore, the sun generates 1/10 of the FCC limit. If I compare this to a typical 35mw wi-fi radio, with the stock 2.2dBi rubber ducky antenna, I get the same RF level as the sun at a distance of 0.7ft. Therefore, you're getting the same amount of RF from your laptop as from the sun.

It's also presumed that most of the biological effects of RF is due to localized heating. The sun can certainly do much more IR heating than a local RF source.

Incidentally, the standard method of calibrating microwave receiver noise figure is to point the dish at the sun and compare it with "empty" sky:

's LOTS of RF coming from the sun.

As for comparing wireless exposure with a known cancer cause, isn't that what all the FUD is about? The open question is "does RF cause cancer" or more specifically "Do cell phones, Wi-Fi, BlueTooth, and such cause cancer". If the sun can cause cancer, why not all these others? In theory, all you have to do is simulate with RF the exposure one gets from the sun necessary to cause cancer and you've proven that cell phones cause cancer.

What we know, what's codified into regulations, and what's commonly accepted, are quite different. For example, different countries have radically different exposure standards.

Actually, I could probably find some animal tests of the sorts. I was involved in one such study in an odd way. The researchers were getting inconsistent results on exposing bacteria to RF fields. They wanted my help calibrating the test setup. The RF source worked as advertised, but the home made antenna and cable were a useless dead short. They had generated months of test results without ever exposing the target with RF.

When I fixed the feed and antenna, and corrected some RF field strength calculations, the test proceeded on for months. Results seemed to show internal structure effects on the bacteria after about

100 generations as compared to a non-irradiated control culture. They were about to submit for publication when I suggested they compare the results with with the original data. They were exactly the same. The effects were eventually traced to contaminated glassware.

I'm not suggesting that all such studies are this bad, but it does make me wonder. Incidentally, the last line of all such studies is always "More research is necessary".

This doesn't lend to a secure feeling when you consider one agency OKed Vioxx etc. Seriousily these regulations at least in the US as you know are heavily influanced by the affected industry.

And no doubt (at least in my mind) sopme short term studies have been done, but people tend of course to live into their 70's. In my case I was an adult when Apple first started selling micro computers, so my exposure would be less then that of a new born today.

Of course not, I'm not saying any of the investigations done so far are in error. I'm sure as you note above more then a few are shall we say not

100%, but I would say today they may be the minority. Again I'm not suggesting even a moment here that we should not be using these nifty gadgets they keep coming up with (well wireless mice and keyboards, but for another reason then rf issues). I just wonder if in fact we aren't impacting the genome (might be postive, kids a generation or three out might end up smarter on average then we are or stronger).

fundamentalism, fundamentally wrong.

rico snipped-for-privacy@hotmail.com (Rico) hath wroth:

Industry has an effect on the regulatory process? Methinks not. My personal experience demonstrates that politics and legal issues far outweigh any technical issues. If some industrial giant wishes to influence regulations, they purchase, lease, or rent a politician, who then uses his political influence to change the numbers. The very last group with any effective input are scientists and technology people.

I don't suppose mentioning that every county has a different cellular tower ordinance would help you feel more secure.

RF has been around since Marconi in 1902. Is that long term enough? The problem with studying long term effects is NOT in the duration but in the isolation of a suitable control group. Where on this planet can you find an area that has a similar lifestyle to the typical urban dweller, but without the exposure to RF fields? How can you maintain such a control group for extended periods? Would you entertain the possibility that the reason there have been no long term RF studies is because they cannot be accomplished on this planet?

You have a right to be paranoid. However, constant fear of the unknown is not a great way to go through life. You could also take a conservative position:

's when someone "warns" the rest of the world of their fears and aprehensions, that I have problems. If you know something about RF exposure, including anecdotal incidents, then I'm all ears. If you're just afraid, it's not really very useful.

I think that's a bad analogy and a huge leap. Do you have any real evidence that radiation exposure limits have actually been "heavily influanced by the affected industry"?

Long term studies have been done. It's unlikely that any really serious effects would only show up after such long periods of time.

Was Macaroni sending microwaves in '02? I didn't realize, I thought it was long wave stuff though indeed rf, but then he wasn't doing it in my grandfather's house

Again though, we are now bring the xmitters into our houses, not just in the environment in general.

We are supposed to be frightened, don't you watch the news etc. Terrorists are hiding under the bed, bin Laden is lurking behind that tree in your back yard etc. The terror alert level is purple... and on it goes. The political system thrives on us being afear'd

I'm not afraid, but I think it is legitimate to ask these questions given the number of gadgets now entering our lives and homes.

(ot), could you take a look at my DD-WRT question in the group?

fundamentalism, fundamentally wrong.

That you think the federal regulatory process is not influanced by politics speaks volumes of how little you understand the workings of the system we have here. I'm not talking some great conspiracy, but those political contributions are not out of the goodness of big industry's heart. Congress is indeed for rent, they are rented daily. Agency heads do not 'po' Congress if they like their agency to be funded and on it goes. I seriousily can't beleive you are not aware of how the process works in this country.

They have? How? Bluetooth and Wifi in the home haven't been around long enough for long term studies to have been done.

fundamentalism, fundamentally wrong.

True, but all that matters is radiation strength, and the transmitters we're now bringing home can be very weak when compared to external sources.

I think I actually understand it pretty well (your insult notwithstanding).

Contributions don't go to regulators.

Some are; most aren't.

While Congress does have some influence in regulatory bodies, it's much less than you seem to think.

Again, I think I actually understand it pretty well, even though I don't subscribe to extreme hand wringing.

Long term studies of radiation from other consumers devices have been done, notably mobile phones, as well as long term studies of radiation from non-consumer devices.

Marconi duplicated many of Heinrich Hertz's experiments while still in Italy. Hertz's spark propogation experments were done with a full wave circular loop antenna, with metal balls at the ends to show the spark and act as somewhat of a capacitor. The approximate resonant frequency of his loops were about 300MHz. Not exactly microwaves, but close enough.

Your house is your castle, not your shield room. Worry about high power broadcast transmitters, not low power.

If one wants funding for any government activity, one needs to tie it to anti-terrorism or there's no money available. (Don't ask me for details). Say the magic words, and the money will flow.

Agreed. Asking questions is the first step to research. However, what are you going to do when research isn't possible? For example, the long term RF exposure tests just aren't practical due to lack of a comparable long term control group (without RF).

I did. No clue. Besides, politix is more fun.

I think you ought to take all your wifi and bluetooth stuff and put it in the middle of you living room, build a fence around it say a 3' radius and not let anyone get close to it,, then you would do your testing and such in a 'controlled' area, then come back and post the results, say in 30 years,

Or,, better still, buy up a stock of 'radiation badges' and have everyone wear one and have them checked and logged for 'over exposer"

Bob NA6T

Early microwaves.

"Surprisingly enough, some of the first electromagnetic experiments conducted by Heinrich Hertz in 1886 and also by Marconi used frequencies near the microwave region - some around 500 MHz and some even in the multiple GHz (Gigahertz) region."

J.C. Bose followed Heinrich Hertz with microwave experiments in the 5 mm region (about 30GHz) in 1895.

experiments use most of the common waveguide components in use today. Don't get the idea that microwaves are a recent invention. They were the original radio physics and only replaced by lower frequencies when scientists and inventors discovered that the lower frequencies were more useful for long range communications via ionspheric refraction.

Microwaves have been around longer than HF/SW broadcasting.

[POSTED TO alt.internet.wireless - REPLY ON USENET PLEASE]

Nah -- just go with tinfoil hats. :)

Shame on you! Surely you know that using actual facts in a Usenet pissing contest is contrary to Usenet guidelines! LOL

I was seriously considering manufacturing an RF dosimeter. It seemed like a good idea until I discovered that I would either need to build a pocket spectrum analyzer, or an ultra sensitive and broadband bolometer (fancy thermometer): |

way, nobody would be able to afford one, so I guess I can skip the business plan and marketing research phase.

Then, I discover that's it's already been done: |

| looking output. | 'll read through the 102 page test report when I have time.)

Well, there it is. Now buy one so I can borrow it.

Don't laugh jeff, I met a fellow from one of the cell tower servicing companies that has something similar to what was pictured.

This was about a year ago, and it would beep when the levels were to high (like next to the TX, etc). I didn't see a name but he said his company was testing them to see if they were any good. He mentioned that a few of the employees had been claiming "radiation posioning' and getting workers comp, so the company was trying to see if there really was a problem

He also mentioned to me that the only time he had ever heard it go off was when he walked in from of a 6' tx/rx dish that was working, and he also said he knew better....

Christ, I'm 60 years old, had a vasectomy when I was 30 and been using "IT" as a sports model since then,, bring on the radiation,,,,,,,

Bob Smith NA6T

(I'll read through the 102 page test report when I have time.)