April 25th, 2012, 11:31 AM
We live on the top floor of a block of flats. They have accepted to install a digitalTV repeater, the power is 30 W.
Is it dangerous, where can I find information?
The firm declares that the safest place is just beneath the station as the beam is directed away, but I do not believe them.
Is it possible to screen the ceiling and walls? I read that aluminim foil is good to that purpose, and it's cheap.
Can I buy an instrument to check radiations?
Any suggestions?
Thanks
You have nothing to worry about, despite some of the alarmist reporting you see in the mainstream press. Until you get up to ultraviolet frequencies (that's six orders of magnitude or so higher than your TV repeater's frequency), you can't directly break any chemical bonds, so there can't be any biological effect from the RF directly. A subtlety is that heating of tissue can convert, as a consequence of entropy increasing, some of that low-frequency energy (such as produced by your transmitter) into damaging higher-frequency energy, which is why meat cooks. But as long as your tissues aren't being warmed noticeably, you are safe, despite claims by many wackadoodles out there.Originally Posted by logic
30 W is not a lot of power, and it falls off at least as fast as the inverse-square of distance. Plus, as they told you, there isn't much transmitter power directed downward (they design it this way, because it is desirable to direct the energy toward the vast majority of paying customers). You will get much more radiation from the light bulbs in your home. If you don't fear your light bulbs, you should fear the TV transmitter even less.
I'm not sure why you wouldn't believe them. It makes economical sense and is not technically difficult.
If you never want to receive any radio signals yourself (e.g. mobile phone?), I suppose you could do that. And don't forget to use the left over foil to make yourself a hat and a pair of underpants.Is it possible to screen the ceiling and walls? I read that aluminim foil is good to that purpose, and it's cheap.
Logic,
I doubt you need to "screen" your domicile. The amount of radiation you will be exposed to is not much more than you are exposed to daily walking from your flat to the corner shop. We are constantly bombarded with this type of energy. You are being iradiated simply sitting in front of your computer and typing. I doubt you have anything to fear. However should you choose to cover the interior of your home with aluminum foil I would recomend putting an additional layer of wall paper over it. Aluminum foil walls are so unsightly.
Thanks, dmwyant, of course the aluminum foil would not be exposed. So they are really effective.
We were worried about children being exposed all day to radiation. We read that, in another town, young people living near a radio transmitter had developed leukaemia. That is no laughing matter, no object of cheap sarcasm, I hope.
Could you give me some technical details about the range of dangerous frequencies or a link where I can get this info? what kind of instrument can measure the intensity of radiations, can I find one that's good for all frequencies?
Thanks
Last edited by logic; April 26th, 2012 at 01:14 AM.
When you read something like that, you need to look very closely at the evidence. Some people may have developed leukemia. This does not mean they developed it because of the radio tower. There are no scientific studies that establish any such link.
Note that radio transmitters tend to be in the tens of MW range, so a lot more than this repeaters. Although you would also need to consider the fact that radiation levels fall off with the square of distance and radio masts tend to be pretty tall.
But more importantly, as Harold says, there have been no scientific studies that show any such link. Leukaemia cases tend to cluster (because they are largely random) and people will always try and look for a cause. A large piece of poorly understood technology (transmitter, power station, chemical plant, etc) will tend to get the blame even if there are just as many clusters in locations without these things.
I think there have been some studies showing slight correlation between overhead power cables and leukaemia cases. But, again, there is no evidence of causation. It is more likely they are indirectly connected by some other factor (e.g. power cables lower the value of housing, leukaemia is commoner among the poor).
can you answer that?
...correlation has not been proved.
When your child has a station 24h/day a few cm. over his head, I think you would rather be safe than sorry, I hope.
You could try googling for "rf field strength meter". But I'm not sure how you would use/interpret the results. Compare the level indoors with out on the street? If there is a higher level indoors, turn off all your electrical and electronic equipment (turn off the main circuit breaker, ideally) and measure again. If that makes a significant difference ask your neighbours to do the same. I would guess that there is more RF radiation from the wiring in your flat than from this repeater. I assume there are a few metres from head height, say, to the repeater? Certainly more than the distance to your computer, TV, fridge, Wi-Fi access point, cordless phone, mobile phone, microwave, etc.
I think electrical wiring doesn't emmit as much radiowave as handPhone or a WiFi, because I was told that if the wiring is too short compared to the wavelenght of the power signal (50/60Hz frequency) then the wire couldn't emmit radiowave (reference: post in ScienceForum about "Physic of brain: can the brain emmit radiowave at 13Hz? why not?") , so radiowave from handPhone & WiFi and TV repeater should be the only radiowave that can be detected...
We should be worry if the TV repeater could interfere with any electrical equipment in the house...
The roof, of course, is ferroconcrete. Isn't that a Faraday cage? Or RF slips through it?
Do you know the frequency of a DTV repeater?
1m away from 30W is not little as compared to 1 Km from MW, is it?
What is the name of the instrument Field strength meter?
Thanks
That is a good point: the wavelength at 50Hz is about 6,000 km - not many houses have that much wiring! However, the electrical supply also has a lot of higher frequencey noise (from attached equipment, etc) which will be radiated. But you are right; devices which intentionally radiate will put out a lot more power.
Luckily, the repeater (and all the devices in the home) will have been rigorously tested to ensure this is not the case in order to be certified for use.We should be worry if the TV repeater could interfere with any electrical equipment in the house...
Something similar to this might serve your purpose.
Amazon.com: Extech 480836 3.5GHz RF EMF Strength Meter: Home Improvement
definitely will go right thru the concrete cage... TV signal is in MHz frequency.
I think they are about 600MHz (but I am more an audio than RF guy). Which, at 49cm, might make the ferroconcrete an effective Faraday cage (don't know what the typical spacing of the iron is)
30W @ 1m would be equivalent to 30MW at 1km (if my mental arithmetic is right) all other things being equal. Which of course, they aren't. At 1km, the transmission can probably be approximated as omnidirectional whereas your repeater is highly directional.1m away from 30W is not little as compared to 1 Km from MW, is it?
BTW digital transmitters tend to use lower powers, I think, so are probably in the kW rather than MW range.
Um... field strength meter (that is all I know it as). Or do you mean a specific make? Can't help with that, I'm afraid.What is the name of the instrument Field strength meter?
But: You Have Nothing To Worry About.
Thanks, Harold, very helpful: one review there says that RF in sleep should be less than 1.0 μW/mēSomething similar to this might serve your purpose.
Amazon.com: Extech 480836 3.5GHz RF EMF Strength Meter: Home Improvement
and 0.1 for digital pulse radiation.
I suppose that for children it should be even lower, considering it is not a casual exposure as when you open a fridge. That does not sound good news.
Videos on YouTube show that in sight of cell tower radiation reaches 900. Wow! We got a cell tower just in front of us!
thank you all for precious info.
P.S. We are taking into consideration moving to the North Pole
Last edited by logic; April 26th, 2012 at 10:32 AM.
Although that is obviously a serious piece of measuring equipment, the fact that "related items" include books on ghost hunting, detox diets and a "cancer cure" (*) says something about how serious a problem this is.
(*) If I were in charge, the author of this would be on trial for fraud, if not manslaughter.
They are about to re-make the outer plastering on the building. The original chicken-wire of the stucco is in glass fiber, I suppose it is no good.
If we replaced it with iron-chicken wire I suppose that would be the solution to all problems, as we are also surrounded by other stations (TV ,cell-phone , police etc, as we are in the highest part of the town).
50 cm chicken wire is no use for plaster, usually it is 5 - 10 cm, this size would be effective also for cell-phone frequencies ( I suppose 0.8 - 2.7 GHz)?
what is the size that is good for all frequencies used in transmission, 5mm?, I suppose the smaller the better?
Last edited by logic; May 15th, 2012 at 02:46 AM.
I hear covering your walls with tin foil works well
congrats for your promotion!
Not.
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