# Mesh to block or reduce wireless cell signals

I want to block or reduce the amount of wireless cell signals coming into my house through my window(s) by using some type of mesh (screen). I could use a sheet of metal but then I wouldn't be able to see through the window. I am initially planning on standard window screen made of aluminum (not fiberglass), and I would ground the screen to an earth ground outside my house. The wireless signals are from a new cell tower across the street from my house. It has 3G, 4G and is supposed to get 5G. So the frequencies I believe would be 850MHz-1.9GHz for 3G, 700MHz-2.6GHz for 4G and 2.5-30GHz for 5G. What would be, or how would I calculate the maximum hole size to block these signals? Does the thickness of the screen matter? Would I be trying to interfere with the frequencies or the amplitudes of these signals? PS: My house has metal siding but the roof is asphalt. My EMF meter typically has higher readings throughout the house the higher it is to the ceiling. Any other suggestions would be greatly appreciated.

• Put down the EMF meter. Ignore it. Worry about things that matter, like your friends and family. Your EMF meter is an uncalibrated toy, suitable only for creating fear and concern where none should exist. – JRE Sep 2 '20 at 17:56
• Because it has been scientifically proven that wireless signals have an adverse effect on our bodies. This non-ionizing radiation has different effects as ionizing radiation, but it still has adverse effects. – JCRisn Sep 2 '20 at 18:18
• Wireless signals have not "been scientifically proven that wireless signals have an adverse effect on our bodies." You'll have to cite something better than the advertisement for your EMF meter. – JRE Sep 2 '20 at 18:25
• Where is it proven? By whom? If it is proven dangerous, why they are not banned yet? – Justme Sep 2 '20 at 18:28
• The mesh in aluminum screening should be small enough to effectively shield all the frequencies up to 30 GHz. You should probably get a spectrum analyzer, though, and test to see what frequencies are present and at what levels inside your home. You don't need to earth ground the screens. They will be reflecting the RF, not shorting it to ground. – mkeith Sep 2 '20 at 18:37

Mesh attenuates in the range 10dB to 50dB. For anything more than that you'd need sheets of 1mm to 2mm thick, made of copper or steel.

It is not true that holes smaller than the wavelength block or shield an EM wave. Also, findings of the Faraday cage -not box- for electrostatic fields (familiar to many from Physics classes) are often misleadingly extrapolated to electromagnetic fields.

Brick, wood, cladding all attenuate but do not shield, so it's not just your windows but also the walls, blank doors.

Metal chimneys and vents will also guide waves inward.

When testing our RF circuits we use a shielded chamber, made of copper plate. Even the door has a copper coil, installed like a draft stop. It provides more than 100dB attenuation, which is adequate to perform sensitive noise measurements in our circuits. Supply and network cables leading into the chamber are throttled with chokes.

Cell towers transmit at 40dBm or more. That's one transmitter at one frequency. Add a few up, at different bands, and from different towers, and you can see how an attenuation of 20dB does not accomplish much if you are close to the source.

As for your question, here are some examples of materials with attenuations higher than mesh.

https://aaronia.com/shielding-materials/?gclid=Cj0KCQjwhb36BRCfARIsAKcXh6FF4fIEuC859ZNxsboV7l0x20du8nL3yp8NBj_2bn1OHYt-71i8ZBwaAo3jEALw_wcB

From an engineering standpoint I'd say you will be throwing too little money at a problem for which there is too little evidence.

You pointed to a shielding paint. The manufacturer, Yshield (Germany), reports their in-house RF tests with 40dB attenuation after 1 coat, and 50dB & 60dB after resp. 2 & 3 coats. These are notable numbers.

For 60dB, $230 covers perhaps 150 sqft of wall/ceiling. Do the math for your home: a 2000 sqft 2-story home has 3400 sqft of surface needing coverage, and costs$5200 (very ball-park).

This is the attenuation through the paint, and does not account for imperfections in a realistic space (doors, windows, other orifices etc..)

Another issue is entrapment of EM waves: whatever gets in, or originates from within, is reflected between walls until it decays away. With purely reflective protection there is no EM escape. The report does not split the attenuation between absorption and reflection, but they do quote the resistivity. Absorbers would be the carbon paint, the furniture etc. and -ironically- human bodies.

You still need to cover the windows, which require a metallic foil. Metallic heat and UV shields also provide EM attenuation. Some office buildings with darkened windows are notorious for poor cell phone reception inside. (And I don't believe the foil is grounded)

The supplier you mention has those as well:

https://slt.co/Products/RFShieldingPaint/ShieldingPaint-YShield-HSF54.aspx

• This is a good answer. But 20 dB of attenuation is pretty substantial. Nothing to be scoffed at from an exposure perspective. – mkeith Sep 2 '20 at 21:10
• @mkeith Yes, agreed. Also note that the first meter (!) in free space, at 1GHz and above, is already at least 30dB attenuation. I'm just making an esoteric point that if someone is worried about EMI, then 20dB around a cell tower is not much cushion & comfort. – P2000 Sep 2 '20 at 21:16
• @P2000 & mkeith Thank you for your answers. I will look into the examples posted. There is a paint (for the walls and ceiling) which claims to attenuate radio frequencies (as perhaps mentioned in another post about guitar pickups). It is black and is carbon based and needs to be grounded, "provides protection against RF radiation, microwave and also from low-frequency electric fields if grounded properly". It claims an attenuation of 39 dB. It is expensive. Do you two think there is truth to the claim? slt.co/Products/RFShieldingPaint/… – JCRisn Sep 2 '20 at 22:31
• I don't know. It is possible to make conductive paint that can help shield against EM waves. But the paints I have seen were all metallic, not carbon-based. I doubt any thin substance will be effective at blocking or shielding low frequency EM waves or fields. It may be possible for a carbon based coating to absorb radiation also, but I believe it would need to be thick. In anechoic chambers, it is common to use carbon impregnated foam pads to absorb EM waves. But they have a LOT of carbon in them. – mkeith Sep 2 '20 at 22:52
• Thank you P2000 and mkeith for answering my question. You two are a breath of fresh air in a smoke cloud of naysayers. Since the paint is to be grounded, it would seem it absorbs rather than reflects. My house is wired... no wireless router, no wireless keyboard, no cordless phone, no wireless TV, disabled everything wireless. No microwave oven... try using an EMF meter while a microwave oven is operating, at 10 feet away the EMF's are horribly high! The detector the Sears tech. uses is, well, useless in my view. My home environment was rather EMF clean until that cell tower was built. – JCRisn Sep 3 '20 at 20:30