How to easily measure radiation from cell phone masts, Wi-Fi etc. How to choose an economical, reliable and easy to use high frequency radiation meter. Which are the necessary features. How to use the meter to spot radiation sources and reduce your radiation exposure.
Not the type of meter you are looking for? Please check our guides on low frequency meters (measure radiation from power lines, cables, transformers, electric devices laptops etc), radioactivity meters (measure radiation from radon gas, granite counters, nuclear accidents etc) or check the frequently asked questions about electromagnetic field meters!
We advise you to read all the following information about how to use a high frequency meter and which are the important features to look for, but if you are in a hurry to see the recommended meters go straight to the high frequency meters comparison tables at the end of the article.
What do high frequency meters measure?
They measure electromagnetic fields (radio waves, micro waves etc) from cordless phones, wireless modems (Wi-Fi), cell phone masts, mobile phones, baby monitors, wireless laptops, smartphones, printers, keyboards, speakers, game consoles, Bluetooth devices, microwave ovens, wireless alarm, fire detection and temperature control systems, radars, TV and radio antennas (depending on their frequency range).
Were do we usually record high wireless radiation levels?
- In houses close to cell phone or broadcast towers (most burdened areas are those that have windows facing the antennas)
- In apartments and offices were a multitude of wireless signal from Wi-Fi, cordless phones etc is recorded devices from neighbors
- In densely populated areas because of the presence of more cell phone masts
- On the upper floors of buildings because they are more exposed to wireless radiation from all high frequency sources
- Laboratories, diagnostic centers, recording studios, etc should also check for high frequency radiation levels, because they have electronic equipment that is sensitive to electromagnetic interference
How to use the high frequency meters
- Measure close to the walls, the ceiling and the floor adjacent to neighboring apartments, so you can locate the wireless devices of your neighbors (eg cordless telephones, Wi-Fi Internet modem-routers, DECT phones etc), which will probably produce higher radiation values in certain areas of your premises.
- This way you can avoid the electromagnetic hotspots you detect or ask your neighbor to move his wireless devices to another location.
- You can also use shielding materials (eg use a shielding fabric over a couch or bed when you identify a strong signal from below, use shielded bed canopies, paint the walls with EMF shielding paints etc.).
- If you detect cordless phones you can ask your neighbor to replace it with a low-radiation cordless telephone whose base emits only time when you talk to the phone and not on stand by mode.
- Also, measure the radiation close to the windows and walls that are facing outdoor areas to check if you have significant radiation from the outside (i.e. cell phone masts).
- If there is an obvious or hidden cell phone mast nearby you will record higher radiation levels close to external walls or windows in the mast’s direction.
- Windows are the most vulnerable point of penetration because they do not reflect high frequency radiation (unless they have reflective or mirrored or low-e glass, which is coated with metal oxides for thermal insulation purposes). Windows can be easily shielded using EMF shielding curtains or window films, which reflect more than 99% of wireless radiation.
- Walls reflect/absorb part of the external wireless radiation depending on the thickness and type . Walls and roofs can be shielded by painting with an EMF shielding paint.
More tips about using high frequency meters
- High frequency electromagnetic waves are either vertical or horizontally polarized. Try to rotate the meter in all directions when measuring in a certain area.
- Indoor measurements might vary significantly from point to point mainly to reflections in the furniture, appliances and building materials.
- Metallic objects might amplify the high frequency fields, creating local radiation hotspots.
- Try to take multiple measurements at different times during the day and during the year. Cell phone masts vary their transmission power depending on the demand and every year some kind of new signal (3G, 4G etc) gets added to their transmission. Also, regular maintenance works on cell phone mast might slightly change the transmission angle, which could lead in great difference of radiation levels. In addition, you might locate a Wi-Fi modem or other WI-Fi enabled device that works only during certain hours of the day. Finally, your neighbours might purchase a new wireless device or other outdoor antennas might be added any minute changing dramatically your EMF exposure. This is why you have to check regularly.
- Most of the high frequency meters are reliable for “far field” measurements ( roughly more than 3 times their wavelength in meters) which means that you can take wrong measurements when you really close to the radiation source, which is closer than 2 meters for most modern radiation sources (cell phones, WiFi, DECT etc)
- Do not cover the antenna with your hands or other objects when measuring.
- You might notice excessive radiation values when moving the meter quickly. Try to make slow and steady movements.
- Hold the meter at arm’s length.
What features to look for in an RF meter
A reputable company or country of manufacture could mean better quality and extended operating life. Being more geographically close might be helpful if there is a malfunction of the meter or you need to send it back for recalibration.
This is the average price of the meter sold by the various online sellers shown on the bottom of each table.
High frequency meters are characterized as single axis, triple axis, omnidirectional, isotropic, directional etc according to the type of antenna/sensor they have.
In high frequency measurements most meters measure in 1 axis, which means you have to turn the meter in all directions to approximately calculate the total (3 axis) radiation.
Some meters have a directional (logarithmic) antenna (see on the photo to your right the antenna used by Gigahertz meters). These meters are also single axis but the directional antenna helps you find the direction of radiation penetration so you can easily locate the radiation source.
Some meters offer 3 axis measurements which means they use three single axis antennae to compute the overall exposure.
Some have omni-directional antenna which provides a 360 degree horizontal radiation coverage.
An isotropic antenna is a theoretical antenna that has a 360 degree vertical and horizontal coverage, so meters that claim they have isotropic antennas, should give the most accurate measurements. In real life when they say isotropic they usually mean omnidirectional.
Both 3 axis and omnidirectional antennas help you perform quicker and more accurate measurements but help less in locating the source compared to directional antennas.
To conclude, single axis antennas are the poorest choice, directional antennas are better for locating radiation sources and a 3 axis or an omnidirectional or an isotropic antenna will give you more accurate measurements. Combining directional and an omnidirectional antenna (as the HF35EC does) combines all the benefits.
Frequency range (MHz)
Each wireless radiation source emits in a certain frequency (the number of oscillations or wave cycles that pass a particular point per second). The higher the frequency, the higher the energy and the shorter the wavelength of the wave (frequency=speed of light/wavelength).
Frequency units used are Hz (Hertz) and Khz=1000Hz, MHz = 1000000Hz and GHz = 1000000000Hz
High frequency meters should be able to record radiation at least in the 800MHz-2500Mhz frequency range, were most modern radiation sources (cell phone masts, smaprtphones, Wi-Fi etc) emit.
If you are interested in measuring TV or Radio broadcast signals you should choose a meter that measures down to 100MHz or below.
If you interested in measuring radar signals you should choose a meter that measures above 3000MHz, but for many reasons we do not think it is necessary:
- a meter that measures in a wide frequency range will probably detect more sources but it usually provides less accurate measurements and makes it also more difficult to figure out where the radiation comes from
- test show that many meters which claim to measure up to 8GHz cannot often detect or measure most higher frequency sources, so they are useless (see more information below).
- wireless sources above 3GHz are still relatively rare, so you probably do not really measure higher frequencies
Here is a table list of the most common radiation sources and the frequencies they usually emit (might differ from country to country):
|Source||frequency range Mhz|
|Baby monitors||49 , 900, 2400|
|Cell phones and cell phone masts||900,1800,2100|
|DECT (cordless phones)||1800-1900
|WLAN (Wi-Fi) modems, tablets etc||2400-2500
Units of measurement
High frequency radiation meters measure electromagnetic field power density (in mW/m2 = milliwatts per square meter = 1000 μW/m2 = 1000 uW/m2 = 1000 microwatts per square meter or W/cm², or W/m²) or high frequency electric field intensity (in V/m = Volts per meter), or both.
Some meters also measure magnetic field strength in A/m (ampere per meter) or μA/m, mA /m but this not really needed.
Some meters meausure in dBm, the power ratio in decibels (dB) of the measured power referenced to one mill watt (mW). It is a convenient measure of absolute power because of its capability to express both very large and very small values in a short form. But for most non technical users who just want to check their area for common wireless radiation sources, dBm is only confusing. The same goes for dBW, which is referenced to one watt (=1000 mW).
Units can be converted from one to the other:
V / m = SQRT [(μW/m2) * 0,000377]
These conversions are not valid very close to the radiation sources (near field measurements = roughly less than 3 times their wavelength in meters). The near field is less than 2 meters for most modern radiation sources (cell phones, WiFi, DECT etc) For example a Wi-Fi modem transmitting at 2400MHz has a wavelength λ=c/f (were c= 299792458 and f= 2400000000Hz) = 0,12m which means far field is >3*0,12 =0,36m.
You find ready unit conversion calculators here:
For easier comparison to the recommended radiation limits we prefer the meters that measure in μW/m2 (=uW/m2) or V/m
The high frequency meter should be able measure values as low as 1 μW/m2 (=0,02 V/m) so you can compare them to even the lowest recommend safety limits.
Being able to measure up to millions of μW/m2 (were usually the legal limits are) would be great but not necessary, as most common radiation sources emit up to a few thousands of μW/m2.
Some meters have signal attenuators, or preamplifiers so that they can extend their measurement range.
There are also meters that don’t give an exact measurement but only a measurement range and usually have some warning lights depending on the radiation levels. If you don’t care about the exact radiation levels but only to get a warning for high radiation levels this could helpful.
The measurement span is something that many people don’t pay too much attention and they end up buying a meter that cannot measure what they need. This is especially true for many meters that supposedly measure all types of radiation, but in reality they only detect very high power sources. For example the famous Trifield Meter can only measure very high levels of high frequency radiation, meaning it cannot detect most common wireless radiation sources.
What are the safe levels of high frequency radiation?
The legal exposure limits to non-ionizing electromagnetic radiation today are in most countries aligned with the limits set by the International Commission for the Protection against Non-Ionizing Radiation Protection (ICNIRP), which recognize only the thermal effect of radiation and do not take into consideration other non thermal, effects such as the production of stress proteins, increased activity of free radicals, calcium outflow, increased permeability of blood-brain barrier, platelet aggregation, increased production of histamine etc.
The past few years many scientific bodies have proposed new exposure limits to protect the public from artificial electromagnetic fields, based on recent research showing that non-thermal radiation levels can lead to serious long-term health effects.
The differences in the proposed safe limits are quite remarkable as you can see on the table below:
|SCIENTIFIC BODY||Proposed safety limit|
|in μW/m2 = uW/m2||in V/m|
|ICNIRP (International Commission for the Protection against Non-Ionizing Radiation Protection)||2000000-10000000||27-62|
|Seletun Scientific Panel (recommendations of international scientific panel)||170||0,25|
|European Parliament STOA (Science and Technology Options Assessment = Organization Valuation Sciences and Technologies of the European Parliament - recommendation of Dr. Hyland, Options Brief and Executive Summary, PE Nr. 297,574 March 2001)||100||0,2|
|German Building Biology Institue IBN (Institut für Baubiologie + Ökologie Neubeuern - Recommendations for the bedrooms)||10||0,06|
|BioInitiative Working Group (international team of scientists that reviews data from over 2000 studies on the effects of electromagnetic fields)||3-6||0,03-0,04|
|Austrian Medical Association||10||0,06|
|Radiation levels in nature||<0,000001||
Generally, the recommended exposure limits are below 200 microwatts / m2 (=0,27V/m).
The average population exposure indoors from all high frequency sources according to European surveys were below 100 microwatts / m2 in Europe until 2010 (European Health Risk Assessment Network on Electromagnetic Fields Exposure, Report on the level of exposure in the European Union).
Our opinion is that values> 500 microwatts / m2 (0,43 V/m) are high.
Ideally we recommend that you record values <100 μ/m2 in all areas and <10 μW/m2 in your bedroom.
Detailed information about the proposed and permitted levels can be found in our article "Safe Exposure Limits' .
Most international safety standards take into account the Average radiation power (RMS = root mean square = the square root of the arithmetic mean of the squares of the samples), usually measured over a period of 6 minutes.
On the other hand Building Biologists or scientists that recommend lower precautionary safety limits, claim that the important measurement for high frequency radiation is the Peak signal radiation levels.
This is especially important for digital signals (Wi-Fi, cell phone masts, DECT etc) which have a pulsed waveform (a lot of time they are not transmitting) and so the average power is many times lower than the peak power. This for many scientists underestimates the radiations levels compared to their the biological effects.
For older analogue or continuous wave signals, average and peak levels are similar.
Peak hold measurement means the meter retains the highest readings, so you can easily measure the highest radiation value in a given area.
Some meters also distinguish between pulsed and non pulsed radiation levels, giving another way of determining the safety of your area. Also the German Building Biology Institute recommends much lower safety limits for pulsed radiation (they consider extreme levels >100μW/m2 for pulsed and >1000 μW/m2 for all signals).
The BioInitiative Report concludes that:
"There is substantial scientific evidence that some modulated fields (pulsed or repeated signals) are bioactive, which increases the likelihood that they could have health impacts with chronic exposure even at very low exposure levels.
Modulation signals may interfere with normal, non-linear biological processes.Modulation is a fundamental factor that should be taken into account in new public safety standards; at present it is not even a contributing factor. To properly evaluate the biological and health impacts of exposure to modulated RF (carrier waves), it is also essential to study the impact of the modulating signal (lower frequency fields or ELF-modulated RF).
Current standards have ignored modulation as a factor in human health impacts, and thus are inadequate in the protection of the public in terms of chronic exposure to some forms of ELF-modulated RF signals. The current IEEE and ICNIRP standards are not sufficiently protective of public health with respect to chronic exposure to modulated fields (particularly new technologies that are pulse-modulated and heavily used in cellular telephony).”
So Peak signal measurements are more important biologically but if you do official measurements you will also need to measure average value and also have a meter that records data.
Data logging is more important in low frequency magnetic field measurements. For high frequency measurements it is useful if you want to measure following most official measurement guidelines that measure the average radiation over a period of a few minutes.
A digital display gives you more accurate readings and has a more modern and professional look. Analogue displays are rather outdated, but are usually cheaper and will also do the job.
Not a necessary feature but is helpful when measuring in dark areas or in houses with no working lights.
Audio signal which increases volume according to the radiation value, is helpful but even more helpful is the acoustic demodulation of the wireless signals, that some meters offer.
Audio signal demodulation means the meter will make a different sound according to the radiation source. This feature is a must when you want to identify what kind of device or antenna is to blame for your elevated radiation levels!
See in the video how to locate cell towers in the area, cordless phones and modem-routers of your neighbors and other wireless devices using a meter with audio signal and a directional antenna!
Audio alarm is helpful for finding radiation hotspots but not necessary when you have audio signal. Some meters also allow to set the alarm threshold yourself.
Higher accuracy is good but it is more important for professional users and not for amateurs. Also, manufacturers show their accuracy data in various ways, making it difficult to distinguish the ones with crappy accuracy.
Due to the nature of high frequency waves propagation the accuracy of high frequency meters is not very high and it is also difficult to reproduce measurements especially in indoor areas. Most manufacturers mention accuracy in dB (decibels) and not in percentages. For example, an ordinary amateur meter accuracy is +/-6dB which translates to -75% to + 200%. Commercial grade models might have a + -3dB accuracy which translates to -50% to + 100%.
The Electric Power Research Institute in its 5000$ report “Consumer-Grade Radio-Frequency (RF) Exposure Meters” sates that:
“Because of differences in design, reliability, and functionality, direct comparisons of meters is difficult, especially because meters are designed for so many different applications.
One common function of all the meters is to detect the presence of an RF field, but some meters provide little more information than that. Some meters are not able to detect RF fields below a set field strength while others are tuned to a certain frequency range.
Consumers need to recognize that each meter’s performance can vary dramatically at different frequencies, distances, and orientation. Such variations can be significant and may limit interpretation of measurement results."
The most important to have in mind is that some some tests show that the accuracy is often not what is claimed by the manufacturers.
So choosing more accurate meters could be more helpful in theory than in practice.
Batteries and battery life
If you plan to use the meter a lot then you should definitely take into account the battery type and life of the batteries used, because changing batteries frequently could elevate the operating cost significantly. Some meters are rechargeable so you don’t have to purchase new batteries every little while.
Low battery indication
Warns you about low battery so it helps you not run out of batteries unexpectantly.
Auto power off
Helps you avoid battery loss when you accidentally forget the meter on.
A good quality plastic case is very helpful for professionals or for those those who frequently measurements in various locations.
If you need to check that everything works well in the future you might consider sending it for calibration (or recalibration if the meter was originally calibrated). This is especially important for professional users. In that case you should choose a manufacturer that offers this service. Also it would be better if the manufacturer is geographically close to you.
The longer the warranty the better, especially if the meter is expensive.
We try to we recommend reputable companies, with good customer service, that can ship the meters worldwide.
Being more geographically close might be helpful if there is a malfunction of the meter, so we usually recommend one seller from the USA and one from Europe.
Also, buying from an overseas company means there will be some extra shipping costs and possible tax charges in the customs office.
Finally, please be sure to check all the mentioned features (warranty, prices etc) also in the sellers page, because they could be different from those mentioned in the following comparison tables or have changed since the time this article was written.
Some tips for professional users
- There are meters in the market that are targeting professional users and are priced very high, though they seemingly offer the same features.
- Some times, the increased price is justified by some extra features such as frequency analyzing, higher accuracy, data logging capability etc. Make sure you really need those features before you spend extra money on them.
- On the other hand, more expensive meters usually also mean higher overall quality, more professional design, longer and more reliable operation, longer warranty, better service and the potential to get your meter recalibrated, which are important for professional users.
- And your clients will value your service more if you use a high end meter, rather than a cheap one.
- We suggest you try to avoid all in one combination meters. They do not perform well in all types of measurements.
- Also, using more meters will make a better impression to your clients, than doing all the measurements with only one meter.
- While smaller and lighter meters are easier to transport, bigger and heavier meters look and feel more professional.
Basic high frequency meters
The basic low cost meters presented below will measure correctly most common high frequency radiation sources but not with great accuracy, might not detect all the frequencies claimed by their manufacturer or have the expected sensitivity.
Since they are low cost they have their place in the market, but do not expect them to perform as professional meters.
Some manufacturers, have no problem admitting their meters limitations. As Cornet (USA) admits in one of their manuals “(our meter) is designed for quick living environment RF radiation evaluation and is for reference use only. Official RF safety radiation measurement procedure is complicate and should be handled by trained technical person with lab instruments”.
The German Consumer Protection Organization (WILA Bonn) commissioned IMST GmbH (an accredited EMC testing facility in Germany) to test low cost meters that could measure up to 8GHz.
The results showed that all meters performed poorly in frequencies above 3GHz which means that the advertised very wide frequency range is not valid.
Also the claimed sensitivity of the meters was not as promised. In most cases they could not measure values lower than 10μW/m2 which are recommended by the Building Biology Institute and BioInitiative Working Group.
The German report “Electrosmog meters put to the test” concludes that:
“It is good to maintain a healthy skepticism toward offers that promise amazing performance at extremely favorable prices.
And it is always good to remember that professional testing equipment never combines RF and ELF measurement probes in one single meter or fits an RF antenna into the meter casing.
Antennas/probes that are integrated into the meter casing are also a great source of errors.
Prefer meters with a digital display and an external measurement antenna. A highly directional logarithmic-periodic antenna (which looks like a Christmas tree or fish skeleton) is very useful in determining the direction from where the RF radiation originates."
So to conclude all of the basic high frequency meters below have their limitations (we try to highlight them in the following tables).
Their main advantages are their low price and their basic functions.
Also, due to the fact that their antenna is inside the meters case, most of them have a very small size. Smaller and lighter meters are easier to transport. They are also great when you want to take measurements discreetly.
And if you don’t see a low cost frequency meters in the following tables, it is most likely that we have rejected it because it does not fill some basic criteria (frequency range, measurement span etc).
For professional use or for more accurate and reliable measurement you should invest in other type and/or more expensive meters (see advanced meters below).
Advanced high frequency meters
A company that provides reliable, even low cost, meters for professional and amateur users is Gigahertz Solutions (Germany).
All of their high frequency meters have a directional antenna (logarithmic – periodic) that helps you locate the radiation sources.
Some of Gigahertz meters provide a second antenna which is isotropic (meaning it receives radiation from all directions), making measurements more accurate and expanding their frequency range.
Most of their meters also have audio signal which is different according to the radiation source, so they help us identify which is the problematic radiation source.
And all their products features completely concur with the information supplied on the corresponding data sheets which unfortunately is not valid for many low cost high frequency meters.
Building biology's associations worldwide recommend Gigahertz equipment for the easy evaluation or professional analysis of EMF / RF pollution.
All meters developed and produced by Gigahertz are manually aligned and calibrated during the manufacturing process and the VDE (the German Association for Electrical, Electronic and Information Technology) monitors their quality control system with annual inspections.
Finally, we have personally used Gigahertz meters in hundreds of EMF surveys and know from first hand that they are very easy to use, sturdy, reliable and accurate.
Also, Gigahertz has great customer care and offers calibration services!