What is the worst source of RF exposure for most people? In 2011 a division of the World Health Organization (WHO) classified using mobile phones as a "possible carcinogen" due to high RF exposure while talking on a mobile phone next to your head. You can reduce this exposure a lot by using headphones, earbud, or speaker so you can hold the phone away from your head.
For more about cell phone use see:
What are RF Electromagnetic Fields? RF means "Radio Frequency" which includes electromagnetic fields from mobile phones, cell and mobile phone towers, radio and TV towers, Wi-Fi, and microwaves. Physically, these are electric and magnetic fields vibrating faster than 3 kHz and usually moving together as waves. For Electromagnetic Fields (EMFs) from home wiring and power lines see AC Fields in Homes.
What does the RF meter measure? Our RF Meter measures the RF field strength in Volts per meter (V/m), and the time-average RF power in uW/m2. That is the "RF Exposure" that people are exposed to. It can measure it at frequencies from 150 MHz to 10 GHz, but it does not display the frequency. An RF meter does not measure static or low-frequency fields from magnets, the earth's magnetic field, power lines, or home wiring, for those you would use a different meter: see Gaussmeters at top of page.
What is frequency in Hz, kHz, MHz, or GHz? Frequency in Hz is how many waves per second. kHz is a thousand waves per second, MHz is a million waves per second, and GHz is a billion waves per second. So 1000 Hz = 1 kHz, 1000 kHz = 1 MHz, 1000 MHz = 1 GHz. Higher frequency is not necessarily worse than lower frequency. Higher frequency is not the same as higher RF exposure.
Explain the units of Average RF power. Our RF meter displays the Average RF power in uW/m2 (microWatts per meter square).
The "u" stands for "micro" (1 millionth in standard scientific notation).
Another widely used unit is "Watts per meter square" (W/m2), so 1 W/m2 = 1 million uW/m2
Our RF meter can measure from 1 to 100,000 uW/m2 (which is up to 0.1 W/m2).
Other standard scientific prefixes are sometimes used in other documents, for example: 1 mW/sq.cm = 10 W/m2 = 10 million uW/m2
This RF meter provides a much more accurate Average RF power reading than most RF meters. Most RF meters use a simple formula which only computes continuous wave (CW) RF power from the V/m, which vastly overestimates the average power of most modern digital RF signals transmitted in digital bursts. Our RF meter displays a far more accurate true time-averaged power reading using 1024 samples, which is much more accurate for modern digital RF signals than other RF meters in this price range. This meter is also easier to use, very wide bandwidth (covers a wide range of frequencies), and very sensitive (it can measure and display very weak RF signals).
What is considered a safe level of RF exposure? There are varying opinions about this from experts around the world:
New Zealand has a 500 meter (1/3 mile) buffer around mobile phone towers where no one is allowed to live. At this distance from a large cellular phone base station tower with many antennas on it the exposure is roughly around 5000 uW/m2 at ground level. Most other governments allow a much higher level of RF exposure (see next question).
In 2005 a group of German doctors wrote an open letter to the President of Bavaria, in the forward it recommends that public exposure should be below 10 uW/m2 average RF power (which is near bottom of the "Average" scale on our RF meter).
A list of RF levels and guidelines is shown at:
What are government safety standards for RF exposure? Different countries have different standards and it also depends on the frequency and length of time of the exposure. In the USA the limit for RF average power exposure of the public is:
2 W/m2 (=2 million uW/m2) at frequencies of 100 MHz to 400 MHz
2 to 10 W/m2 (=2 million to 10 million uW/m2) at frequencies of 400 MHz to 2000 MHz
10 W/m2 (=10 million uW/m2) at frequencies of 2000 MHz to 5000 MHz.
Some countries have lower limits than US: in Canada it is 3 W/m2 (3 million uW/m2) at 1800 MHz (Safety Code 6, 1997).
In Italy, Switzerland, Poland, and China it is 0.1 W/m2 (100,000 uW/m2) at 1800 MHz.
If our RF meter is showing below its maximum average reading of 100,000 uW/m2 then these government standards are being met (usually by a wide margin). However, some studies have found adverse health effects at levels far below these government standards (see other questions on this page). Our RF meter can measure much lower exposure levels: from 1 to 100,000 uW/m2.
Where are cell towers located? www.antennasearch.com shows locations and frequencies of many towers and antennas in USA.
There is a cell phone tower near my house, what is our RF exposure, and should we be concerned? As mentioned, New Zealand has a 500 meter (1/3 mile) buffer around mobile phone towers where no one is allowed to live. RF exposure at ground level at 500 meters from a large cellular phone base station tower with many antennas is roughly about 5000 uW/m2, and about 10,000 uW/m2 at 100 meters from the tower, but this exposure can vary a lot, it can be less for many towers, and can be measured using the RF meter.
RF exposure will depend on the distance from the tower, your height above ground compared to the tower antenna height (being closer to the antenna height is worse), the number of carriers and operators using that tower, the average power transmitted, frequencies, antenna patterns, type of walls and roof material in your building, metal objects in your vicinity, etc. You can get some general info about most towers in the USA, such as the tower location and frequency, from www.antennasearch.com . You can also measure the RF exposure using the RF meter and compare it with other locations.
There is an antenna on the roof of my apartment building or nearby building, what is my RF exposure? First, find out what type of antenna and what its used for: some antennas are for receiving only (like TV antennas on houses, satellite TV, and some satellite internet antennas), those would not transmit anything so they would not cause any RF exposure nor show anything on the RF meter. See if the building address is found at www.antennasearch.com which gives some information about many transmitting antennas in the USA. Ask the owner of the building or the antenna what type of antenna it is. If it is a cell phone antenna then see the above FAQ about antenna towers near your house. Antenna beams usually direct more power horizontally than downwards, so you could have more exposure on an upper floor of a nearby building, than on a lower floor in the same building as the rooftop antenna.
Could there be a cell phone antenna on the wall of my building? Sometimes a cell phone company has been allowed by the landlord to place an antenna on the outside wall of an apartment or office building, which exposes the occupants in the nearest room to high RF fields. These antennas may be as small as a shoe-box and painted the color of the exterior of the building to blend in. These antennas can be located using the RF meter, since the fields get stronger as you approach the antenna.
Can the meter measure RF power from cell phone towers, TV and radio broadcast towers? Yes, except not AM radio towers since AM frequencies are below the frequency range measured by this meter.
If I want to reduce RF exposure from a nearby tower or antenna, what can I do? Aluminum siding will block most RF radiation. RF waves travel mainly in straight lines from the source and are blocked by metal, so you actually only need the aluminum siding on the sides of the house facing the tower. In attic areas you can staple chicken-wire to block rays from the top of the tower from entering the house from above. Aluminum mosquito screens will block RF and can be used over windows. Conductive paint is available which will block RF. Conductive fabrics can be used over walls or ceilings or for curtains, drapes, or shields (conductive fabrics are usually copper color or gray color and are very flexible and can be sewn like most fabrics). Aluminum venetian blinds (vertical) in front of windows will block some RF. Aluminum foil also blocks RF. These all work due to the high frequency of RF; the RF can still go around these shields but is much reduced in strength. (But these methods would not block 60 Hz magnetic fields from power lines, measured with an AC gaussmeter).
Can the RF meter measure WiFi and Bluetooth? Yes. Distance reduces RF exposure, so you could place the WiFi router away from children's bedrooms, and turn off WiFi devices like laptops at night if they are close to the bed. Different WiFi devices emit differing amounts of RF power. WiFi routers that need to cover a wider area like schools often radiate at higher power, and could be placed farther away from where children sit. Bluetooth radiates lower power than WiFi.
Can the RF meter measure TV or radio sets in my home? No, since TV and radio sets are receive-only and do not transmit any RF power, so there should not be any RF coming out of a home TV or radio antenna. Two-way radios however can transmit and could be measured by this meter.
Can the RF meter measure Ham Radio antenna transmissions? Not most ham radio transmissions, since they are usually below the 150 MHz frequency which is the lowest frequency measured by this meter.
What is the RF exposure while using a mobile phone next to your head? A typical mobile phone produces about 25 W/m2 average power on the outside surface of your head, and 3 W/m2 average power for parts of your brain near where the phone is held (add six zeros to get uW/m2). The peak V/m is around 300 V/m on the outside and about 100 V/m on the inside of the head. For a child their head is smaller and their brain still developing, so this very high exposure is of even more concern.
Mobile phones are tested for SAR which measures how much RF power is absorbed in the head. It does not consider other possible effects besides heating. Also, the government assumes that adult users will not use their phones for longer than 30 minutes per day, and children even less.
Is there an easy way to reduce RF exposure? For mobile phone conversations you can use an earbud or speaker so the phone is not next to your head. You can use the RF/Cell Tower Meter to measure areas where you spend a lot of time, and if they are below 10uW/m2 Average, and you don't live near any AM radio towers, then you should have very low RF exposure.
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