Detecting RFI from an Uno

Is there any practical way to detect the amount of RFI a Uno puts out? Is there any simple device that can tell me how much “noise” (locally) I am emitting from an Uno?

Thank you

An "all wave" radio receiver will let you listen to the RFI, but cannot give you any actual numeric values. Use a wire antenna and move the wire around over the Uno.


There are a number of rtl-sdr spectrum analyzer projects available on the internet. This gives one a visual display of the radio spectrum over some range. This will be uncalibrated and the cheap rtl-sdr radios are prone to internally generated spurs, but it can give useful qualitative information.

Or you can use a high value (maybe 10MOhms or more)pull-up or pull-down resistor connected to one of the Analog pins and do some averaging with analogRead of that pin. The readings will fluctuate based on the local EMI

I wish you luck, you are taking on a major project. Try this link for some good information: From the above link: CATEGORIES OF INTERFERENCE There are two broad categories of interference; narrow band and broadband.

Narrow Band – this would include continuous wave (CW) or modulated CW signals. Examples might include clock harmonics from digital devices, co-channel transmissions, adjacent-channel transmissions, intermodulation products, etc. On a spectrum analyzer, this would appear to be narrow vertical lines or slightly wider modulated vertical bands associated with specific frequencies.

Broadband – this would primarily include switch-mode power supply harmonics, arcing in overhead power lines (power line noise), wireless digitally-modulated systems (such as Wi-Fi or Bluetooth), or digital television. On a spectrum analyzer, this would appear to be broad ranges of signals or an increase in the noise floor. Power line noise or switch-mode power supplies are the most common sources. Good Luck & Have Fun! Gil