ATTENTION EVERYONE! Here are some easy ways to mitigate EMFs in our EMR-saturated environments.

Radiofrequency and Microwave Shielding

Submitted by A Radiofrequency Engineer

I’ve been an RF Engineer for over a couple decades, and everyone is always asking me about human exposure to RF. We live in an electromagnetic environment that is completely saturated with RF, and we are exposed to manmade electromagnetic fields from DC to daylight 24/7. My focus is on minimizing my exposure to the maximum extent possible, and these are the things that I do to accomplish that.

I try not to be paranoid and conspiracy theory about RF, although we never really know what the governments are up to. There’s also the possibility of other countries are up to no good too. With all this being said, let’s break it down and start with some basic math and principles, then we can talk about ways to minimize our exposure.

The first principle is electromagnetic flux density. This is a measure of power / area, or Watts / meter2. This is a measure of how much instantaneous power is in a 1 meter x 1 meter square. We will focus on how to reduce [attenuate] the amplitude of the electromagnetic flux density from 1 Watt/m2 to 0.1 Watt/m2 and even more desirable 0.01 Watt/m2.

The second principle is attenuation as a function of distance. Electromagnetic energy attenuates as 1/distance2. What does this mean? Let’s use a simple example.

If a cell phone is 1 inch from your head, the propagation attenuation is 1/12 = 1/(1*1) = 1.

If a cell phone is 2 inches from your head, the propagation attenuation is 1/22 = 1/(2*2) = .25. By simply doubling the distance we have reduced the electromagnetic flux density by a factor of 4!!

If a cell phone is 4 inches from your head, the propagation attenuation is 1/12 = 1/(4*4) = 0.0625.

If a cell phone is 8 inches from your head, the propagation attenuation is 1/12 = 1/(8*8) = 0.015625.

If a cell phone is 24 inches from your head, the propagation attenuation is 1/12 = 1/(24*24) = 0.00174 or about 0.002.

What does this mean? If we keep our smart phone 2’ feet away from us, we reduce the amount of electromagnetic energy we are exposed to by A LOT!!! How do we use this info? I try to keep my phone 2 feet away from me at all times. This means I simply set it down and I don’t keep it on my person. The further the better. When I talk to someone, I use the speaker phone and I keep it 24” from me.

When I drive in my car I try to keep my phone as high as possible in the car so it has line of sight through the window to the cell phone tower. Why? If you keep the phone on the floor, it has to transmit more power than it does if you set it on the dash. Keeping the phone on the dash simply minimizes the amount of power the phone has to transmit, and this minimizes the amount of electromagnetic flux density you are exposed to. I set my phone in the middle of my dash board. This gives me several feet of distance between myself and my phone, and it also gives the phone direct line of sight to the cell phone tower and the power it has to transmit is minimized. Remember, we are not trying to calculate exact values, we are simply trying to minimize our exposure using known attenuation principles.

The third principle is antenna reactive nearfield coupling. When an antenna is touching you, or is extremely close to you, the electromagnetic fields are coupling directly into you and you are a part of the antenna. The Reactive Nearfield distance is defined as 2D2/λ, where D is the largest dimension and λ is the wavelength. The diagonal of a smart phone is approximately 10 inches, which is approximately 0.25 meters. Since electromagnetics is exclusively metric, we will use 0.25 meters to keep the math simple. It’s very easy to divide something by 4, or multiple by 0.25. What does all this mean? If your phone is touching you, you are part of the antenna. If your phone is 2 feet away from you, it’s not coupling directly into you. I try not to get caught up in the exact calculation because this is all about minimizing our exposure, not trying to predict exact values.

The fourth principle is the dielectric constant and loss tangent of materials. These are physics constants set by nature and are out of our control. They determine a material’s reaction to electromagnetic energy. We are primarily interested in the loss tangent, which is essentially a material’s ability to convert electromagnetic energy to heat. In general, the higher the loss tangent the better. Lossy materials include bricks, concrete, plaster, and to a lesser extent wood, paper, and wood fiber and fiberglass insulation. I do not use metal to prevent exposure, EVER!!! Using metal is a bad idea because you can set up a resonant cavity and concentrate electromagnetic energy. Do not use metal to prevent exposure to RF, except in certain circumstances that I will cover later.

Another way to minimize exposure is to turn your electronics off when not in use. All electronics spew electromagnetic energy in the form of “EMI.” Put all of your electronics on power strips and turn the power strip off when not in use. This ensures the power supply isn’t doing it’s thing and spewing electromagnetic energy, and this will also reduce your electric bill!! Do not sleep with your smart phone next to your head at night. I leave my phone on the far end of the house at night and it basically can’t get any further from me. This takes advantage of 1/ distance2 and maximizes this attenuation.

The best way to minimize your exposure to RF is to attenuate it. One of the best ways I have found to attenuate electromagnetic energy is with a bookshelf. Yes, you read this right!! Paper has a fairly high loss tangent and it readily converts electromagnetic energy to heat. More paper is better. Let’s say for example there is a cell phone tower a half mile to the east of you. If you put a 6’ tall x 8’ long bookshelf on the east wall of your bedroom, the electromagnetic flux density will be reduced by 3 dB to 6 dB, or 50% to 75%. An electromagnetic flux density of 1 Watt / meter2 will be reduced to 0.25 Watt / meter2 – 0.5 Watt / meter2.

Let’s talk about this book shelf. The books on this shelf should be every size and shape possible, made by different publishers. Variety is key! We want to avoid flat surfaces on the surface that is facing the room and closest to you. Flat on the face that is closest to the wall is fine, because a flat surface will partially reflect some energy. We want our book shelf to look like a book shelf in a library. The face of the book shelf that is closest to us should be uneven. Big books are closer to the front edge, while smaller books are set back further from the front edge. Make sure one end of the book shelf is 2” – 3” further from the wall than the other end. The book shelf should not be a constant distance from the wall. If you know for sure there is not a cell phone tower to the west for 5 miles or less, you can use a metal backing on your book shelf. You can use metal in this case because the books will prevent a resonance from setting up inside the room because they are converting electromagnetic energy to heat.

If you are surrounded by cell phone towers and you want to put book shelves on all the walls, make sure the faces are very uneven, and make sure you do not set up a perfect square or rectangle with the book shelves. One end of a book shelf can be against a wall, and the other end should be 2” – 3” away from the wall. Be careful not to set up a resonant cavity in the form of perfect squares and rectangles.

If you want to use books under your bed, they should stand on edge so there is an uneven face closest to you and a flat face on the floor. Fill boxes with books standing on edge, and just slide them under there!! If you want to fill your attic with books, just try to prevent all the boxes of books from making a flat surface. Set some boxes up higher and set some lower. And remember books are heavy!! The good news is books are extremely cheap right now and you can buy a lot of books for a relatively small amount of money.

Brick, cinder block and concrete walls also attenuate electromagnetic energy. Their faces are also flat making the rooms they form candidates for resonant cavities. Use bookshelves to attenuate electromagnetic energy and prevent resonances from forming. Always have one end of a book shelf 2” – 3” further from a wall than the other end. Keep a bookshelf perfectly flat against a wall potentially sets up a resonant cavity, and this helps prevent resonances.

Imagine that, books!!!

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