Devices for Measuring radiation

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Measuring Radio Frequency Radiation

There are many ways that an electronic device can unexpectedly generate electromagnetic fields.

First, at low frequencies (<100KHz) you primarily get magnetic radiation Low RF frequencies are generally in the range 20Khz to 3MHz, HF (High Frequencies) are 3-30MHz, and VHF above that to about 500MHz. Cellphones operate in the 700-900MHz and 1800-2100MHz regions (some LTE is outside this range), NFC sensors are at 13.56MHz, smart electric meters are typically 900MHz (plus Zigbee WiFi), WiFi is 2.4HGz and 5GHz, and WiGig is at 60GHz.

A month or two ago I started to revisit the topic of quieting down the appliances and adapters in my own house. What surprised me was the huge amount of noise emitted by the power adapters for charging USB, running Routers, etc. I ended up throwing most of them away.

The best way to see if a device is emitting electromagnetic signals is to use a Spectrum analyzer. This is basically a device which shows the entire frequency spectrum in one sweep, and some sweep all the way from 1MHz to 12GHz.

But a cheaper, and often more effective method, is to listen for interference using a shortwave receiver. Unfortunately, many of the receivers being sold in 2014 use a new digital chip which makes them almost useless for tracking down noise sources. I did find one radio on amazon which does work well, and is not too expensive (most of the 'meters' sold for this task cost hundreds of dollars). It is the WRX911 (or Tecsun R911 on Ebay). This is an old model now, and will eventually run out of stock.

Trevor Marshall, PhD

Q. are the “power adapters” you refer to above the same as surge bars or power strips? I am trying to visualize these devices.

A.#1 Power adaptors are commonly called converters, chargers, wall worts, power bricks, etc. They are the things you would plug into the power strips.

A.#2 Power chargers, as we call them, are actually transformers. They are electronic devices that take the 110V power from our wall outlet (in the US, anyway) and “transform” it into the lower power levels needed by our computers or other electronic devices.

Usually you can recognize them by their bulky/boxy shape. Some of these are made of a good enough quality that they don't produce excess “E-smog”. Many of them are very poorly made and some of them appear to be of concern..


I just received a catalog from “Less EMF Inc.” I can't believe the extortionate money that is charged for relatively uncomplicated equipment. And for just plain scams.

Anyway, I gave details for the $20 shortwave radio which helps you track down and get rid of devices putting low-level wideband noise onto the power lines. But when you are looking for Radio Frequency sources (like the ROKU problem), WiFi and Smart meters, then a Spectrum Analyzer is a real help. We have a gold-standard HP 8569B in the lab, but that originally cost tens of thousands of dollars, and weighs about 50 pounds.

There is a nice user-supported project, however, the “RF-Explorer” device, and associated software. For those of you who are technically inclined, preferably with a radio background, this device seems to do just about all one could want in a portable Spectrum Analyzer (15MHz to 2.7GHz).

The designer's website is at: RF designer's website

I have used it to look at radiation from my neighbors' DECT phones, (I was so horrified by our own that I immediately replaced it with wired phones), to look at the Smart-meter network in a little more detail, and generally to make sure there are no unexpected sources of radiation around (like the ROKU).

Here is a link to a convenient supplier: supplier

It is relatively expensive because it is pretty sophisticated. Note that I am not suggesting this is worth every member rushing out and buying, but if you know you want a spectrum analyzer, I have given this one a through checking-out, and you won't find anything much better at anywhere near the price.

- Trevor

Selecting a meter

the GS meters cover low frequencies, the Kaito radios cover the HF frequencies, and the RFexplorer covers the microwaves.

all the Cornets I have received have tested out well enough, so I haven't had to 'calibrate' any. They seem to be calibrated at the factory. I would not touch that setting, as it comes from the factory close enough for you to see what is going on.

You do need to throw out the antenna it ships with, however.

Trevor Marshall, PhD

Joyful: Since we are trying to get our sleeping area down to below -90 dB, there is a point where the Cornet isn't what we need to assess the levels. Yes, we can add filters and a booster, but each frequency range probably needs a different “test setup”.

For the cell tower range I'm using an RF Explorer to measure in the Faraday cage.

Prof. Marshall Measuring EM waves is very difficult. One has to understand many things which are not immediately obvious.

The first thing is the phenomenon of Boltzmann noise (Thermal Noise) level. All living objects, and most inanimate objects emit radiation at a very low (thermal noise) level.

The second thing is bandwidth. The wider the range of frequencies you are listening to, the greater is the level of Thermal Noise which accumulates.

For a 10GHz bandwidth of the Cornet, the lowest level which can be measured out of this thermal noise is about -75dBm. If you reduce the bandwidth to 1Ghz then you will be able to sense about -85dBm. Looking at even smaller regions of energy, such as the 4G region 600MHz-1GHz, allows even greater sensitivity.

I have designed amplifiers which work well with the original Cornet meters, giving 16dB or 20dB of amplification to its -65dBm sensitivity. But they don't read -80dBm, as the thermal noise level is higher than that. They read about -75dBm with no input signal. My colleagues with Faraday Cages have been sent these amplifiers, and a set of filters which reduce the frequency range and can increase the sensitivity to -85dBm, but only for specific sources - 4G, smart meters, and WiFi. They have many different filters in their grab-bags depending what they are measuring.

A Spectrum Analyzer will examine even smaller bandwidths, and reach down to around -132dBm. You need a spectrum analyzer to measure the radiation emitted by our CWS units, for example, no wideband meter can measure down to their -90dBm radiation intensity. A relatively simple spectrum analyzer is the various RF Explorer units, which now cover a range from frequencies from 150KHz to 6GHz in the various models available.

In my lab I personally use my (expensive) Hewlett Packard 8569B analyzer, which reaches above 100GHz with its waveguide adapters, several RF Explorers, and a Triarchy USB dongle which covers 1MHz to 8.5GHz. Each is best for a particular task.

Every frequency source needs a different antenna.

The new SDR (Software Defines Radios) are an inexpensive way to look at a range of frequencies. You can buy a dongle, and an assortment of antennas, for just a few dollars which connects to a computer (Windows, Mac Linux and Android) and allows you to tune from the bottom of the AM broadcast band (500KHz) to 1.8GHz. This takes you through the smart meter and 4G regions and well beyond the FM and TETRA radio sources. It does not reach WiFi at 2.45GHz, however, or the higher UMTS and 2G / 3G regions around 2Ghz.

In the lab I also have a KiwiSDR, and it covers lower frequencies from 4KHz to 30MHz. You can access these free of charge from all around the world from the list at http://SDR.hu

I see little to no advantage with upgrading to the new Cornets. If you have one measuring to -65dBm, it will seve you well for a specific type of peak, quick-and-dirty measurement.


The RFexplorer is the most accurate tool to figure out what your problem signal source is, is it TV? is it FM? is it Cellular? is it WiFi? Is it SmartMeters? DECT Phones?

The Cornet gives a quick answer representing the total of all those sources. By extending, or shortening the antenna we can get an idea of the FM/TV contribution, and we can switch on the audio, where the whine of a cell-tower is often quite obvious. The cornet is is a tool which is quick and accurate, but can't give as much information as the RFexplorer.

Trevor Marshall, PhD

alternative antenna

Prof. Marshall, .. is happy with using this antenna with the RF Explorer as well:

  Superbat 5dbi 700-2600Mhz 4G LTE Omni Directional Antenna    

alternative indicator

Joyful Nov. 2017 Using the KAITO radio as a low frequency detector, you can see if it is putting off a lot of radiation by doing as Prof. Marshall suggested. Take the radio in the house and find where the main stations are (the ones where the Kaito GREEN light goes on). Then take the radio out by the power feed to the light when it is on and tune to each station. If you get static on a frequency that you found a station on before, that means it's broadcasting noisy Esmog at that frequency.

If you can ask your power company where some of the new lights are installed, then you can do the same test at one of those locations. (And also use the sniffer for local UHF+Microwave levels.)

Notes and comments



home/special/emf/measure/meters.txt · Last modified: 11.21.2018 by sallieq
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