Blocking Wifi and mobile waves

After reading the article http://goo.gl/CHVd9, I wonder if there is any material that would completely block the waves of wifi and cellular telephony?

I have read about the wallpaper: https://www.elektroda.pl/rtvforum/topic2290980.html
But she only blocks the WIFI

I tested food grade aluminum foil - I wrapped it tightly on my wifi router - it doesn't work, I didn't even notice a decrease in signal strength.

Someone wrote that even in a microwave oven there is no complete blocking of waves, because a mobile phone locked in a microwave oven still shows the range.

What material would actually block wifi and cellular waves? I am talking about a material that could be used to cover the walls in the bedroom and at least not be exposed to them during sleep.

Try a dense steel mesh.

The first question is what you want to achieve.

matt74ike wrote:

I tested a food grade aluminum foil - I wrapped it tightly on my wifi router - it doesn't work, I didn't even notice a decrease in signal strength.

I don't think this wrapper was airtight after all. You probably decided that cables passing through the foil do not matter. Unfortunately, this is not the case.

Did you check with this microwave oven? Because when it lets in waves, it can be dangerous ...

Tommy82 wrote:

The first question is what you want to achieve.

As I wrote in the last sentence, my point is not to be exposed to WIFI and mobile phone in the bedroom.

Added after 8 [minutes]:

Pawel2420 wrote:

I don't think this wrapper was airtight after all. You probably decided that cables passing through the foil do not matter. Unfortunately, this is not the case.

There is a power cord and one twisted pair cable - I didn't wrap them and I don't believe that wrapping them would change the situation significantly. I think food grade aluminum foil just doesn't dampen waves.

Added after 35 [minutes]:

otto25 wrote:

Try a dense steel mesh.

I do not have one and I must admit that I would prefer proven information that it makes sense to buy one.

I read a bit more about it and from what I found out, it is very difficult to completely suppress Wifi and cellular waves.

In metals, electromagnetic waves decay exponentially - the formula is given, for example, in a book by Jaworski and Dietłaf Physics - encyclopedic guide , in Wikipedia en: Epidermis en: Skin effect - examples (the latter gives an example of the depth of wave penetration into the metal, for Al foil it should be about 2.5um at 1GHz - at such a depth the amplitude decreases e-fold, i.e. from 20um = 0.02mm it should not noticeably pass the 1GHz wave); The penetration depth is inversely proportional to the root of the product of frequency, conductivity and magnetic permeability (the latter causes iron to dampen electromagnetic waves much more strongly than aluminum or even copper).

It is only worth remembering that if the cover has a hole, the waves can enter through the holes and reflect inside the cover, so that despite the small size of the hole, the waves in the middle are not much weaker. In particular, the gap at the junction of the foil transmits the waves - in order not to pass through, the edges of the foil must be densely connected (spacing at most 1/4 wavelength) electrically.

I have not been able to observe that the microwave oven suppresses the wave used by the mobile phone (although the signal indicator is poorly visible through these holes in the opaque diaphragm and I am not completely sure if I have seen it) - perhaps the absorption / reflection of the wave is resonant, only in around the frequency emitted by the oven magnetron. Besides, there are gaps when the oven door is closed ...

_jta_ wrote:

It is only worth remembering that if the cover has a hole, the waves can enter through the holes and reflect inside the cover, so that despite the small size of the hole, the waves in the middle are not much weaker. In particular, the gap at the junction of the foil transmits the waves - in order not to pass through, the edges of the foil must be densely connected (spacing at most 1/4 wavelength) electrically.

Hmm .. so I would have to think of a wave more like a fluid that can leak out through crevices? Only, by peasant reason, the wave that "leaked" through some hole should be very weak ...

matt74ike wrote:

After reading the article http://goo.gl/CHVd9 ..

If the conclusions drawn on the basis of this experiment were correct, then the GSM relay stations should be deserted. (Much greater signal strength) Well, unless only watercress is sensitive to electromagnetic radiation at this frequency
Second, for the experiment to be credible, it must be repeated several times, changing various conditions, e.g. humidity.
It is better not to expose yourself to electromagnetic radiation unnecessarily, but confining yourself to a shielded room is quite an exaggeration.
I omit that I once heard somewhere that being in a screened room does not have the best effect on a person - apparently such isolation has a negative effect on the psyche.

matt74ike wrote:

There is a power cord and one twisted pair cable - I didn't wrap them and I don't believe that wrapping them would change the situation significantly. I think simply food grade aluminum foil does not dampen waves.

Completely wrong assumption
Even very thin aluminum foil suppresses WiFi and GSM practically in 100%.
The cause of the leakage of RF energy outside there were cables passing through the foil. The piece of wire on the inside acts as the receiving antenna and the piece on the outside of the foil acts as the transmitting antenna.

Quote:

The devices, according to the calculations of the students, were to emit the same radiation as an ordinary cell.

Which cell (with Wi-Fi turned off) transmits waves with a frequency of 2.4 GHz or 5 GHz?

Has anyone tried to close a Wi-Fi router (or just AP) in a microwave oven or - would it be easier - a phone with Wi-Fi, but watching the range not of the cellular network, but Wi-Fi?

Pawel2420 wrote:

Completely wrong assumption
Even very thin aluminum foil suppresses WiFi and GSM practically in 100%.
The cause of the leakage of RF energy outside there were cables passing through the foil. The piece of wire on the inside acts as the receiving antenna and the piece on the outside of the foil acts as the transmitting antenna.

I did a test with a cell phone - I wrapped it in silver and it was really impossible to call this phone. So you are right, aluminum foil suppresses GSM and Wifi waves very well.

There is only one conclusion - if I really wanted to make a room free from GSM and WiFI waves, it would be enough to stick aluminum foil under the wallpaper and have external aluminum blinds lowered on the windows.

There is a problem with doors and window frames. They pass electromagnetic waves without any problems. Especially that a break for the cable in the foil that the router was wrapped was enough for this.

I propose to check if there will be Wi-Fi communication with such a wrapped phone.

As far as I know, a wave with a frequency of 2.4 GHz (i.e. used by microwave ovens and 802.11 communication, i.e. Wi-Fi) can be dangerous for people due to the fact that it is the resonant frequency of water (I will not remind us of the percentage of the human body made of it). Hence the heating effect of the products in the oven. But it is enough to compare the power of a microwave oven and a Wi-Fi router (limited by regulations) to conclude that to threaten a person, such routers would have to be placed next to each other several dozen, if not several hundred or several thousand, and each would have to transmit at a given moment, i.e. send a file to the connected device (I'm not convinced as to the last one, access points periodically send a beacon every fraction of a second, i.e. information about the existence of a network, but I think that the time needed to transmit such information is much shorter than the interval between them) .

markoz7874 wrote:

I omit that I once heard somewhere that being in a screened room does not have the best effect on a person - apparently such isolation has a negative effect on the psyche.

Surely, if you "heard somewhere", you will not provide a link to such information It's a pity, because it's very interesting - it would seem that a person in such a room should not feel worse ...

But if the wave passes through the hole into the inside, from which it can only come out through the same hole, then "peasant reason" should not be much weaker there (and it really is different - maybe the wave will bounce back like this right after it enters. that it will fly out, and then inside it will be weak, or maybe it will bounce many, many times - then inside it will be almost as strong). You can make sure that the holes do not let it through (and they probably do it in microwave ovens - after closing the door, gaps remain, but their sizes are selected so that there is a resonant reflection of the wave used in this oven) and additionally that the wave inside was absorbed (in the microwave oven: the water contained in the heated products absorbs the wave that is used there) - then the wave coming from the outside inside will be much weaker (in a microwave oven, the water inside causes little to escape outside ).

Kpc21 wrote:

There is a problem with doors and window frames. They pass electromagnetic waves without any problems. Especially that a break for the cable in the foil that the router was wrapped was enough for this.
.

Well, it seems to me that it is not about a cable break, but about the cable itself, which becomes the antenna - that's why my experiment with wrapping the wifi router failed, and with wrapping the cell phone it was successful.

https://www.elektroda.pl/rtvforum/topic2579884.html

AWllen wrote:

On Saturday, May 25, in the old Tonsil factory in Września, the historic anechoic chamber caught fire.

This is where the loudspeakers were tested, their characteristics were checked and improved. The large, square room was upholstered on all sides with polyurethane soundproofing foam. There was no echo in the chamber. In the ventricle, you can clearly hear the sound of blood flowing in the vein, the beating of the heart. After 5 minutes in such a room, you can go crazy due to the lack of any sound stimuli.

It is possible that it is similar with electromagnetic waves - a person is used to their presence and without them would feel "uncomfortable".

Another point is that in order to eliminate all electromagnetic waves from the room, not only would it have to be fully shielded, but there could be no electrical appliances or live wires inside.

matt74ike wrote:

Well, it seems to me that it is not about a cable break, but about the cable itself, which becomes the antenna - that's why my experiment with wrapping the wifi router failed, and with wrapping the cell phone it was successful.

It is probably more probable - after all, the blackbody model (and thus not emitting any radiation in the visible light range) is the only minimum size of the hole in a large "box", so on the same principle, wrapping the router with foil should shield it well. The wave is reflected inside the screen and is practically completely absorbed there.

One more tip: when I once made a ferrite antenna (i.e. I wound a coil on a ferrite rod and connected a capacitor to it) and retuning it, at some point the radio standing next to it fell silent - my antenna caught the wave and the radio did not get it. Maybe something like this? It's just that you need an antenna not for long waves, but for microwaves - "slightly" different technology. For microwaves, maybe some "antenna wall" that would let some of the wave pass through and the rest shifted the phase so that both parts met in out-of-phase and extinguished (this is how the antenna worked).

I just came up with a cheaper way:

It would be cheaper than wallpapering to create a mosquito net that blocks Wifi and GSM waves



The question is, what would it have to be made of, because it would have to be made of a mesh permeable to air and light.

Added after 6 [minutes]:

_jta_ wrote:

One more tip: when I once made a ferrite antenna (i.e. I wound a coil on a ferrite rod and connected a capacitor to it) and retuning it, at some point the radio standing next to it fell silent - my antenna caught the wave and the radio did not get it.

Hmm ... I admit that it sounds magical. I thought that your coil started to jam the radio waves, but I don't know - you might be wrong.

Added after 12 [minutes]:

Kpc21 wrote:

It is possible that it is similar with electromagnetic waves - a person is used to their presence and without them would feel "uncomfortable".

I once read about an experiment in which people were out of complete darkness - then the brain could not withstand the lack of stimuli and people in this experiment had hallucinations, delusions, etc.
But I believe that it may be different with GSM and Wifi waves, because our senses cannot perceive it and the brain should not theoretically complain about the lack of it. When we walk in the middle of the forest, where there is no cellular coverage, and especially Wifi, we don't feel bad :)

Kpc21 wrote:

Another point is that in order to eliminate all electromagnetic waves from the room, not only would it have to be fully shielded, but there could be no electrical appliances or live wires inside.

And this is where the above-mentioned idea comes in handy with the creation of a mosquito net that blocks GSM and Wifi waves. Then we would have the problem of eliminating all appliances and wiring in the bedroom from the head.

_jta_ wrote:

One more tip: when I once made a ferrite antenna (i.e. I wound a coil on a ferrite rod and connected a capacitor to it) and retuning it, at some point the radio standing next to it fell silent - my antenna caught the wave and the radio did not get it. Maybe something like this? It's just that you need an antenna not for long waves, but for microwaves - "slightly" different technology. For microwaves, maybe some "antenna wall" that would let some of the wave pass through and the rest shifted the phase so that both parts met in out-of-phase and extinguished (this is how the antenna worked).

I'm not sure if the antenna was splashing these radio waves, you probably had some power connected to it while tuning.
I used to play jokes with a radio microphone a long time ago.
When the radio microphone was aligned with the radio frequency, the radio went quiet, possibly due to a stronger signal from the radio microphone than from the radio broadcasting station.
You could then look from a distance at the client who was listening to this radio and, for example, when he wanted to adjust the setting of the station, the radio said to him, "don't touch me, and sit still", or similar texts.

There was no power supply - resonance was enough. And that was AM modulation (do you know what the difference between AM and FM?).

Copper wire mesh (or rope) - "fabric" with "eyelets" about a centimeter (you can smaller so that it does not let flies and mosquitoes pass), soldered at the wire junctions; on the edges taped with a ribbon of copper (or even better: copper-bonded iron) 15 cm wide, soldered to the wires - these ribbons are used to connect individual elements, you need to arrange them evenly so that there is no gap; on the floor, a sheet of metal, walls and a "ceiling" made of such mesh - are to create a "closed" surface; in the middle, antennas (tuned to popular bands) catching waves that hit there so that they do not fly inside ...

Each of these Alu foils or meshes must be connected to good quality grounding (max. 10 Ohm)
Otherwise it won't work.
Read Faraday's Cage

And after the lightning is gone, we fry elegantly in our microwave.

Congratulations on winning this year's "Golden Shovel".



Dig up the topic after almost seven years ... The archeology department is waiting for such talented people. Possibly a water supply repair service ...