Instructables

How can I block wifi signals?

I'm doing a science experiment to see what wifi does to health, so I need to block it. I want to make a box holding cell cultures or something to see what happens. 

Vyger3 years ago
Metal screen material that you can get at your hardware store will work pretty good for blocking most low power wifi signals. It has to be metal screen though and not fiberglass or plastic. Brass would probably be the best but really any metal material will work. You have to make sure that there are no areas that you miss such as if you staple it to a wood frame the screen has to cover the wood completely. To join pieces together use thin wire like telephone wire or the wire strands from the inside of an extension cord. You can get a large sowing needle and actually sow it together. Remember it has to be on the bottom too, complete 360 coverage. To check how well it works put your cell phone inside and try calling it. If you still get some signal through it add a second screen layer but leave a little space between the two. Its a form of a Faraday cage. Its the reason some people cannot get a phone signal standing next to a window, it has metal screens and blocks the signal.
ANDY! (author)  Vyger3 years ago
I tried that and I don't think it works or not very well.
BrianB77 days ago

2.4 GHz is on the high end of the radio frequencies and the 5 GHz is on the very high radio to low microwave frequencies. If you want to block electromagnetic frequencies(Wifi) , use bodies of water. The only thing that can get through them is extremely low frequencies (ELF) which broadcasts at about 1 hertz, nowhere near 2.4 gigahertz. ELF is what navy subs use to communicate with others.

An interesting study on cress seedlings was done by 9th grade Danish students. The experiment was repeated by a young Michigan boy, Aiden Fitchett, an article in TriCity Times. You also might want to take a look at the recent studies at the BioInitiative Report 2012.

One of the problems "proving" wireless signals are biologically harmful is "replication" of effects. The problem is genetics of plants/cells/animals vary, as do human weaknesses and strengths. Some people can smoke all their lives and never get cancer, while others get cancer from 2nd hand smoke...just to help understand radiofrequency radiation risks.

To understand the science and how people treat the science on RF see at YouTube Dr. Ted Litovitz giving a talk to U.S. Congress in 2001. It will help to understand the controversy and what it means to take no precautions.

Interestingly, recently the CDC actually issued a stronger warning of RF from cell phones, esp. for children, and then it flip-flopped and RETRACTED it. Within a few days. There is much political pressure to not find any harm, and to not acknowledge biological damaging impacts, sad to say. Fascinating topic.

ron24703 years ago
gather various materiels that u suspect will block the signals. put a sample of each of those materiels in the microwave 1 at a time for an equal amount of time. the one that feels the hottest absorbs the most radiation and therefore blocks the most signals
Uhhh, no. According to Wolfram Alpha, WiFi is at 1.46MHz and the "microwave" band is 300 MHz to 300 GHz which would would make any results from that test invalid.
Nope, not quite sure where that website got it's info from, but WiFi (a common term referring to 802.11 wireless data) lives at 2.4gHz and 5gHz. It's most definitely microwave communications, in fact microwaves themselves are one of the worst WiFi interferes as they "broadcast" in the 2.4gHz ISM band along with WiFi (and Bluetooth, and WiMax, etc.)
ANDY! (author)  ron24703 years ago
water?
eirlandes3 years ago
no sure. but the yapper zapper works with phone jammer signals.
Layers of aluminum foil will do. Did anyone else here about the studies done in various countries about phones cutting your sperm count in half and your mobility by 3! I figure if i make a faraday cage i will prevent becoming infertile. I know that it will also prevent me from getting texts but who cares you can still take your phone Out when you want to text or read texts that didnt make it to your phone xue to the faraday cage the texts will come later . Ifs probaly not worth your fertiliy
rickharris3 years ago
Come and experiment here - I think this area is a black hole for RF signals - Poor phone and my wifi hardly penetrates a single brick wall.
ANDY! (author)  rickharris3 years ago
IF you buy me a plane ticket maybe I would...
CameronSS3 years ago
http://en.wikipedia.org/wiki/Faraday_cage

Aluminum foil should do it. If you want to watch it in progress, screens work too (old satellite dishes, the mesh on the microwave door, for example), but the mesh has to be sized properly for the frequency/wavelength you're trying to block.
ANDY! (author)  CameronSS3 years ago
How about a metal container like a coffee can?
Aluminum foil may not do it. The skin depth for aluminum at ~1 MHz (WiFi) is about 100 µm. Since that is also a typical thickness for retail foil, you'll only get about 37% (1/e) attenuation or so.

For a decent Faraday cage, he'll want to use perforated aluminum sheet, at least 500 µm thick, which will give five e-foldings of attenuation (0.0067).
Would multiple layers help in this case? A la 37%^n for n layers?
Yes. Calculus is your friend :-) You can treat each layer independently, and the attenuations simply multiply.
yeah, use aluminum foil