How to Test WiFi Network Tools for Signal-to-Noise Ratio (SNR)

by James T Wood

The tools that you can use to perform a Wi-Fi site survey will provide a signal-to-noise ratio, and that defines the power of the primary signal as compared to the rest of the background noise on that radio channel. However, if you want to determine the accuracy of your Wi-Fi network tools, you'll need a consistent signal generator that will provide a defined amount of noise, so you can compare the reading from the network tool to the actual SNR.


Test your Wi-Fi Network Tools without any interference. Find a location where no interfering Wi-Fi signals are, so that you have a baseline from which to test your adapters and SNR. A deep basement provides a good, signal-free area. If you can't find a naturally signal-free space, you can create one by lining the walls of a room with aluminum foil. All radio signals from outside the room will be deflected, so the only source of Wi-Fi signals will be inside the room.


Add your Wi-Fi signal in the form of a configured access point or router. Test the tools again from no more than 10 feet away with no obstructions between you and the Wi-Fi device. You should show a very high SNR with all of the tools. Anything greater than 40 decibels is indicative of a high quality signal. Your tool should provide you with a SNR that is equal to the dB microvolt output of your router minus the noise level. Note that the higher the SNR is, the stronger the signal, but raw signal and noise strength numbers are expressed in dBm and negative numbers. A noise of nearly zero is over anything less than -100 dBm.


Power on the signal noise generator and set it to interfere with your Wi-Fi signal. Generators like those from DBM Corp and Noisecom are able to maintain a preset SNR per your determination. The AirHORN tool transmits at 17 dBm, which will yield a negative SNR number since Wi-Fi routers transmit much less power.


Test the Wi-Fi tools again with the known noise value and compare the results. You should see the SNR that is equivalent to your setting, if you're using the DBM Corp or Noisecom signal generator. If you're using the AirHORN tool, subtract 17 dBm from the signal strength you found in the first test, with no interference. For example, if you had a signal strength of -45 dBm, you should read a SNR of -62 dB with your Wi-Fi testing tools.


  • check Routers and adapters with multiple-in, multiple-out capabilities can mitigate the effects of a low SNR.

Items you will need

About the Author

James T Wood is a teacher, blogger and author. Since 2009 he has published two books and numerous articles, both online and in print. His work experience has spanned the computer world, from sales and support to training and repair. He is also an accomplished public speaker and PowerPoint presenter.

Photo Credits

  • photo_camera Thomas Northcut/Photodisc/Getty Images