|
|
|
|||||||||||
|
Scroll down or select a link to jump to:
Cell phone shields
Cell phone, mobile phones, and cordless phones produce both magnetic fields and radiowaves (microwaves). Most cell phone shielding devices are designed to reduce the radiowaves. But you can test for either, if you wish. The tricky part about measuring the radiation from a cell phone is that the emission strength varies widely over time. There will be strong bursts of varying intensity, followed by quiet periods. This makes it hard to compare "apples to apples". Also, because you are measuring up close to the source, you must use a near field meter AND you must maintain the postion of the meter very precislely. First, you must have a proper meter. To check for magnetic field emissions, an AC Gaussmeter will work. Most AC gaussmeters will have an internal probe. Simply position the gaussmeter on the phone. Note carefully where the meter is positioned. Make a call and watch the readings. Notice the highest and lowest readings, and make a mental note of the "average" reading. Now, insert the magnetic shield, and repeat.
Return to Cell Phone Shields
Shielding fabrics can accomplish 3 things: shield radiowaves, shield electric field, grounding. Each requires a different test set-up.
Return to Shielding Fabrics
Shielded clothing will reduce your exposure to radiowaves. Their effectiveness is easy to test with an RF meter. It also helps to have an RF source which produces a steady emission (such as a key fob, or radiowave remote control). Using background levels can be tricky if the levels vary widely. First, put on the shielded garment. With the RF source, activated, make a measurement just outside the garment. Now position the antenna of the meter inside the garment and repeat the measurement. Try to plan ahead, so that the meter does not change position while you place the garment over it. Return to Shielded Clothing
There are many ways to do this test. Here is perhaps the simplest: Using a long extension cord laid straight out on the floor, plug in a high current device such as a hair dryer. The hair dryer must be at a good distance from the place where the test will occur. Place your AC Gaussmeter directly on the wire. First measure with the hair dryer off (Is there a lot of background field? If so, do the test in a different location.) Now, turn on the hair dryer and note the gaussmeter reading. Finally, slip the magnetic shield between the meter and the cord and see the difference in the meter reading. Remember: this is a test of the shielding performance of the material itself. The size, shape, and position of the shield in your application will all affect total shield performance. Return to Magnetic Shielding
The HARApad is very easy to test. You will need a gaussmeter and a laptop computer. Make a "bridge" with 2 piles of books which is tall enough to span your gaussmeter. Place the laptop on the bridge. Turn on the laoptop and make a measurement of the magnetic field with your gaussmeter. Note that the strength of the field varies with position. Now, without moving the meter, slip the HARApad into position and repeat the measurement.
WaveCage and Signal Tamer are tested using an RF meter. First, set up the RF meter in a fixed position. Unplug the wi-fi router and measure the background levels of radiation with your RF meter (if there are other RF sources nearby, such as cell phones, cordless phones, iPads etc., move them away). Next, turn on the wi-fi router and measure its radiation output. Finally, put the wi-fi router inside the shield, and re-measure. Return to Computer Shields
Remember that Stetzer filters reduce "dirty electricity", not the 50/60 Hz electric and magnetic field emitted from wires and appliances. So you can't use a standard electric or magnetic field meter to check performance. Instead, use the Stetzer Microsurge Meter. Find an outlet where nothing is plugged in. Plug the meter into one of the openings and notice the reading. (allow a moment for the meter reading to staibilize). Last, plug a filter into the other opening in the outlet and watch the meter reading go down. Return to Stetzer Filters
Shielding paint will reduce radiowave signals. One-sided shields can be tricky, not because the signal comes through the shield, but because it can come around the shield. To eliminate this, you can create a shielded enclosure. First, you need an RF meter. Next find a cardboard box and paint the entire surface, either inside or outside, and allow it to dry. Now, make a measurement outside of the box. Next put the meter inside the box (with a small flashlight if necessary). Look through a small hole in the box to read the meter. The levels will be greatly reduced. Return to Shielding Paints
Canopies will shield radiowaves, so you need an RF meter and a steady RF source such as a key fob. Note: please don't call us asking why your cell phone or laptop bars don't change*. This is not a valid way to test for shielding performance. Set up the canopy, and set the RF source in a fixed position outside the canopy. Make a measurement with the RF meter outside the canopy. Now, put the meter inside the canopy and repeat the measurement. Return to Shieldng Canopies
Smart Meters produce a mix of emissions. Most people think of microwave (radiowave) emissions. But there will also be magnetic fields, electric fields, and dirty electricity produced by the Smart Utility Meter. Smart Meter shields address the radiowaves. You will need a special kind of RF meter for this job because the emitted signal from the Smart Meter is a very short, very fast burst. The detector needs a fast reaction time to pick up the signal reliably. The Acoustimeter and the High Frequency Meter are both well suited for this purpose. Set your detector in a fixed position near the Smart Meter. Make measurments over a few minutes, looking for the highest readings you get during the bursts. Without moving the detector, apply the shield, and repeat your measurments. Return to Smart Meter Shields
* Cell phones and laptops can operate on a very small fraction (1/millionth to 1/billionth) of a strong signal. You know this is true because you can be miles away from a cell tower and still get reception. At this distance the signal from the tower is very weak. Shielding material may reduce the signal by 99% or more. But this means that 1% (or less) of the signal still comes through. 1% of a strong signal is plenty for the device to still operate, and won't even reduce 1 bar. But 99% reduction is still way better than no reduction!
 [email protected]
Copyright 2015-2017, Less EMF |
To check for radiowave emissions, use an 
