On / Off Transition: Christmas Lights Causing RF Disturbances In Electromagnetic Field

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Having slower than usual internet access? Your seasonal display of twinkling lights may be causing interference with your Wifi router. Today’s electronically managed Christmas light-show controllers, available at many retail stores, also add to the potential for lights to transition at the same time, causing RF interference.


Strings of Christmas lights are unshielded, so when the electricity pulses through the cords electromagnetic radiation is created. The quantity and size, as well as a blinking function can all have an impact on the strength of the electromagnetic radiation.

The electromagnetic waves from the strings of décor actually merge together and the resulting wave produces a stronger magnetic field, called linear superposition. When the light waves move, the waves can arrive at the same point at the same time causing their amplitude to be combined. Therefor, one string of lights would emit less electromagnetic interference than a tree full of hundreds of lights because of the combined amplitude.

Increasing the distance between your Wifi router and a lighted Christmas tree will lesson the affects of the electromagnetic interference, because electromagnetic field strength diminishes with distance.

Ofcom, the communications regulator of the United Kingdom, has created a new Wifi-checking App, however the App only currently works in the UK. Turning Christmas lights on and off while running manual internet speed tests can help diagnose interference if you are experiencing issues.

Other common household items like lamps, baby moniters, cell phones, bluetooth gadgets, microwaves and other electronics can also produce interference, so singling out Christmas lights would be unfair, and may cause the Ghost of Christmas Past to pay us a visit and remind us how electromagnetic interference did not used to be such a household occurrence.


Article: “Amy Jones | HCTA”
Editor: “M. Danmole”
Image: “Fashion 507”

Amy Jones