How can I measure/what instrument should I use to identify/measure the RF signal strength in a "noisy" environment?

For example, I want to measure the RF signal strength of my device at a particular spot in a convention hall, while there may be external wireless routers/personal devices emitting 2.4 GHz as noise too.

Is there a gadget that can identify the different RF signals in a noisy environment?

  • The answer will depend on just what you mean by "signal strength". Do you want to know the total RF power in some band? Or do you want to know the power specifically in your signal, excluding noise? The latter is a lot harder. – Phil Frost - W8II Aug 6 '16 at 17:32

Is there a gadget that can identify the different RF signals in a noisy environment?

Not in general. One radio's signal is another radio's noise, especially in the case of high-bandwidth digital signals. The problem is essentially the same as wanting one radio to receive every type of signal in the environment. Which is theoretically possible (as long as each modulation is already known to the radio), but as far as I know not something that's been done.

You can get a spectrum analyzer, or a SDR receiver, which will give you a plot of power vs. frequency vs. time (waterfall plot). (The difference between the two for this purpose is that a spectrum analyzer is calibrated, giving measurements in absolute units, and much more expensive.) This will show you the strength of the signals, but it won't let you tell the difference between different protocols or devices (unless you know when particular devices are transmitting and can match up the timing).

If you just want to figure out which channels are least-occupied, or find the signal-to-noise ratio for a particular configuration (have your device transmit, see how far it sticks up above the background), then this is sufficient.

  • 1
    Also note that distinguishing signals is hard, and there's whole military departments dedicated to what is called SIGINT, doing nothing but that all day. – Marcus Müller Aug 3 '16 at 18:00

If you're purely interested in 2.4GHz Wi-Fi signals then I can recommend the free Ekahau Wifi Heatmapper for Windows. http://www.ekahau.com/wifidesign/ekahau-heatmapper Of course this doesn't pick up any non-802.11 signals but may still be of great help.

Heatmapper doesn't support GPS in the free version but if you have a floor plan then you just walk around and left-click at corresponding locations where you're walking and the program figures out how the signal fades.

Example neighbourhood 2.4GHz Wi-Fi map: enter image description here

As you can see I first walked around the block (the dark-green line) and then let the program do its thing. It also picked up heaps of other nearby access points (around the edges of the screen) but was unable to properly give them a location on the map.

Super simple.

Alternatively, look for a wardriving app for your mobile phone.

  • That's great for WiFi, but the OP may have been speaking about a different kind of device. All sorts of different devices use the 2.4 GHz ISM (Industrial, Scientific, and Medical) band: WiFi devices, baby monitors, garage door openers, microwave ovens, etc. – rclocher3 Aug 3 '16 at 22:47
  • @rclocher3 thanks for the distinction, I've updated my answer. OP does speak about 'wireless routers/personal devices' but yes, there is no guarantee that other 2.4GHz signals are involved too. – captcha Aug 3 '16 at 22:58
  • Please also remember that non-amateur radio is off-topic; this question is on-topic only insofar as it can be answered from a theoretical perspective. – Kevin Reid AG6YO Aug 4 '16 at 2:07

I used MetaGeek Wi-Spy for that purpose.

It is not cheap solution but it can recognize various signal sources, not only WiFi.

You could your mobile/cell phone for free

Personally I use Android, and use an app called "WiFi Overview 360"

It will give you a good indication of the various signals and details

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