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Why RF meter show only part of the RF radiation?

posted Feb 1, 2016, 5:49 AM by Amir Borenstein, No Rad   [ updated Feb 25, 2016, 12:42 PM ]
Q - Have a query please regarding comment about the ED88T meter on website in the limitations section which says, "Will show only part of the RF level when measuring multi frequency sources, or several source at once (like most RF meters)." 
To clarify, does this mean if your lounge or bedroom that is actually receiving radiation from three or even four neighbors in different directions, each neighbor in turn likely having multiple sources such as wifi, DECT and numerous other Bluetooth or wireless devices such as iPod docking bases, internet TV and wireless printers etc, all of which the majority of neighbors may now have) the meter would not pick up the sum total of all of that radiation from all of those devices of all of your nearby neighbors, but only whichever single frequency is most predominant in whatever room you are measuring in?  (If this is how the meters work, then the combined total of so many lesser amount frequencies from so many sources and directions could seemingly be quite astronomical?  For instance if there was wifi router radiation coming in at 2.45GHz at a level of 1.9 V/M but also something radiating at 5.8GHz but at 1.0V/M would it only read the 2.45GHz and give level for that and fail to capture the 5.8GHz and/or any other combined frequencies present at lower levels than the 2.45GHz?)  I think I read this somewhere before on a website about meters but not sure if that is what the person meant.  
Thank you for your clarification.
Best wishes,
P.S.  If it is as stated above, are there any meters that do read the sum combined total of all of the different frequencies present in any spot in a room that you are measuring?
Lets start at the end -  To my understanding there are no meters today ,  that can measure the sum combined total.
The CORNET ED78S and the CORNET ED88T does a very nice job, while taking into consideration the limitation.
Now for the long explanation:
RF radiation measuring is very complexes. 
The accumulation has to be done over different frequencies, over the display time (in this meter 0.5 seconds) and over the number of sampled (in this meter 3500 every half a a second). Even the geographical position of the meter influence the measurement. There are so many variables , I will try to explain the most important.

Sampling rate and Calculation of the leveled displayed:
Then what meters is the way you calculate the level you display, in this meter the displayed value is the highest peak that was found over half a second (most meters sample much less, profession meter usually sample less than 10 times each second).  
If there was a higher peak during this half a second which the meter did not pick up in one of his 3500 samples, this will be missed and will not effect the measurement or displayed value.

Geographical location of the meter
On the geographical level, if the meter is in between 2 sources that emit in the same time and the same level and the same frequency in the direction of the meter, most meters will show less than the 2 combined levels, usually even lower than one of the emission. But the human body would be effected by both. 

Measuring different frequencies at the same time
This meter is a broadband meter which means it is influence by a wide range of frequencies. But there are a lot of technical issue and limitation that makes it very hard to same all of them up in a linear may. 

Accuracy is not the full story
As strange as it may sound, I think that the accuracy of a meter is the least important factor.
The most important factor is the sampling rate. The second is the way that the info is calculated and presented.
Therefor, according to my perception, the CORNET ED78S and the CORNET ED88T are the best home use meters on the market today.
I think that a meter should be used to scan the house, walls, windows, floor and ceiling in order to find EMF sources and penetration point.
Later on it should be used to understand what emit which type of EMF, when and why (so you can reduce your exposure).
The CORNET's meters are great for that.

I hope this info helps