RF radiation from cell tower

Thread Starter

xchcui

Joined May 12, 2014
203
Hi.

I made some measurements(with emf meter)near few cell towers and i have noticed
that i get 2 values that is changing every few seconds.
For example i get 20uW/cm2 for few seconds and after that the value spikes
to 60uW/cm2 for some seconds and again it go down to 20uW/cm2 and so on.
What is the reason for this phenomenon?
Thanks.
 

KeithWalker

Joined Jul 10, 2017
1,681
To put it in very simple terms, the cell tower has two distinct functions. The first is to receive any incoming signals from cell phones and other cells. The second is to transmit those signals to the appropriate phones and cells to route the messages to their destinations. That is why you see two different levels of activity.
 

Thread Starter

xchcui

Joined May 12, 2014
203
Thanks,keithwalker.
But it doesn't make sense,do you mean that the 20uW/cm2
is the value for the receiving activity,while the 60uW/cm2
is the value for the transmitting activity?
I think that both value are of transmitting activity,but
i am trying to figure why it acts like that.
 

KeithWalker

Joined Jul 10, 2017
1,681
My previous answer to you was a very generalized one. The actual operation of the cellular phone system is very much more complex. I think you are approaching the question of signals from cell phone towers from the wrong end. If you really want to understand why, you will have to learn in detail how phones, towers and cells communicate and what frequencies, signal strengths and protocols are used by different components of a cellular networks. Then you may be able to rationalize your random measurements (but I doubt it!).
 

Thread Starter

xchcui

Joined May 12, 2014
203
Yes,a generalized answer is all than i need.I see no point to spend weeks of study only for that small question.
I know that cell tower uses pulsed rf radiation which is not constant,but changed hundred times in second.
So,at first i thought that the rf meter,which is much slower than the cell tower transmitting pulses,is just showing 2 values from hundred of values of those pulses,but next i wondered,why just 20uw/cm2 and 60uW/cm2 all the time,why the rf meter doesn't catch other values from the hundred pulsed values of the cell power.Is it possible that you may explain that?
 

Thread Starter

xchcui

Joined May 12, 2014
203
Okay.but why you must complicate the question.I just asked what are the two values that i got.May someone,please,relate to my post #5?
 

Alec_t

Joined Sep 17, 2013
12,000
i wondered,why just 20uw/cm2 and 60uW/cm2 all the time
Perhaps the system has a power-saving mode and only uses the higher power when traffic is particularly busy, or atmospheric conditions attenuate the signals unduly? Just a guess. Only someone with an in-depth understanding of cell tower operation is likely to be able to give you a definitive answer.
 

Yaakov

Joined Jan 27, 2019
2,911
Cellular towers use transmitters for two things: subscriber connections and backhaul. Backhaul is sometimes done over microwave links and sometimes over landlines.

The tower doesn’t broadcast, it only transmits when it is talking to a subscriber. All connections are point-to-point and intended for only the subscriber(s) currently using the cell.

Subscribers are handed off from and to cells as they move around (this is the special magic of cellular service) and so the total output of the site will vary with the number of connections.

It is completely expected that it will vary because of this. I am not sure exactly what you are measuring but without an instrument built for the purpose I wouldn’t count of any sort of “accuracy”.

There will also be a difference between close to and somewhat more distant from the site due to the antenna radiation pattern carefully optimized to work as a cell site.
 

Thread Starter

xchcui

Joined May 12, 2014
203
Perhaps the system has a power-saving mode and only uses the higher power when traffic is particularly busy, or atmospheric conditions attenuate the signals unduly? Just a guess. Only someone with an in-depth understanding of cell tower operation is likely to be able to give you a definitive answer.
It maybe just a guess,but it sound logical.The traffic busy option
sound more possible.
You just might have caught a gost!
Are you a paranormal researcher?
I have already caught two of them,but they didn't know
the answer to my question,they even didn't want to talk
until they see their lawyer,which sound as a nonsense,ghosts don't have a lawyers;)
Cellular towers use transmitters for two things: subscriber connections and backhaul. Backhaul is sometimes done over microwave links and sometimes over landlines.

The tower doesn’t broadcast, it only transmits when it is talking to a subscriber. All connections are point-to-point and intended for only the subscriber(s) currently using the cell.

Subscribers are handed off from and to cells as they move around (this is the special magic of cellular service) and so the total output of the site will vary with the number of connections.

It is completely expected that it will vary because of this. I am not sure exactly what you are measuring but without an instrument built for the purpose I wouldn’t count of any sort of “accuracy”.

There will also be a difference between close to and somewhat more distant from the site due to the antenna radiation pattern carefully optimized to work as a cell site.
Yes,i was expecting to get changing values,as you explained
and i wasn't expected to get accurate numbers either,but the main unexplained issue is that i get exactly the same numbers:few seconds 20uW/cm2 and few seconds 60uW/cm2.I was expecting to get changing values,but not the exacts values.Do you have answer to that?
 
Last edited:

Yaakov

Joined Jan 27, 2019
2,911
Yes,i was expecting to get changing values,as you explained
and i wasn't expected to get accurate numbers either,but the main unexplained issue is that i get exactly the same numbers:few seconds 20uW/cm2 and few seconds 60uW/cm2.I was expecting to get changing values,but not the exacts values.Do you have answer to that?
My point about the instrument not being designed for the measurement was addressing that. It seems to me there is a high chance of that quantization being an artifact of the device.
 

Janis59

Joined Aug 21, 2017
1,330
RE:""20uW/cm2 for few seconds and after that the value spikes to 60uW/cm2 for some seconds""
The modulation type is somewhat similar to FSK, means no radiated power when no transmittable information. Somewhat mean powe at average traffic, and peak power at full data-rate. Therefore the power is well indicator how many people are serviced at current second, what is all the time changing value. However, try to check the order, those hundreds of towers what am measured I had between 0.5 and 5 WATTS per m2 not a microwatts. Secondly, You should activate the frequency acquisition part in the measurer to see do the main impact is from tower, or, may happen, from nearly 50 Hz transformer sub-station or walky-talky just around the corner.
PS. Sorry, I was beat off the mind by Your choice of non-standard related units. 60 uW/cm2=0.6 W/m2, thus the standard says "acceptible"
 

du00000001

Joined Nov 10, 2020
50
Just a thought: the raised transmit power might be targeting new potential subscribers (mobiles) at the limits of range: this way the mobiles are enabled to assess when better switching to the next node (and to which one in case of multiple nodes within reach).
 

andrewmm

Joined Feb 25, 2011
1,240
A thought
did you have your cell phone on you ?

Phone towers,
use lots of "tricks" to get a signal to and from a subscriber.
all those antennas act as a phased array, which creates beams,
different powers can be sent to different beams, depending upon the power power the user needs .

They are a long way from a simple omni power source,
 

DickCappels

Joined Aug 21, 2008
7,263
Cell vary their transmitter power, and these days the antenna pattern too. If the cell is talking to more than one phone it might change its power and/or antenna pattern as it switches among phones.

In other words, there are many possible answers to your question. When I asked a software engineer why something was done a particular way, he looked at me and asked if I have children. "Yes, I do", I replied. He said then this explanation will make sense to me. He said "Its that way because that's the way it is."
 

wayneh

Joined Sep 9, 2010
17,149
I think the problem is a sampling problem. It's like picking random points on a map of a mountain range and reading the elevation at that point. The instantaneous cell tower power is like the elevation - it's all over the place. Only by seeing the bigger picture can the terrain be mapped out.

If you want to study the output power, I think you'd need a device able to capture the variations in real time. You can go slower but you need a LOT of samples to learn about the distribution. It's like learning about stock prices by looking only at the daily closing price. You probably need at least 100 days worth of data to estimate the variance.
 

anniel747

Joined Oct 18, 2020
601
Way more information on the type of tower would be needed to answer your question. Your measuring device make and model would also help.
 

PadMasterson

Joined Jan 19, 2021
26
I would also add that your meter my not be able to pick up these high frequencies the same for each band, so the response is not going to be the same. The signals are not broadband and unless your meter has a good high end front end, it could be getting radiation from it's antenna and some could be getting into the internal circuits due to a RF leaky case or even a harmonic of the case/antenna/cables, you name it. Your question is interesting, but the answers from that question are going to be all over the map due to the many reasons listed and the limited information on your setup, etc.
 
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