Too many Christmas lights may paralyze your WiFi, but here’s how to fix it

Christmas lights may be crippling your WiFi, or at least that was the takeaway from headlines circulating earlier this week.

The claim isn’t simply fodder for the #WarOnChristmas debate. It’s based on some basic principles of physics.

But how bad is the problem and should you toss those twinkle lights in the trash so you can stream Love Actually without interruption? The answer depends on where your WiFi router is in relationship to the holiday lights and the size of those sparkling strands.

WiFi uses radio waves to communicate. Radio waves fall into a family of radiant energy known as the electromagnetic spectrum. Microwaves, infrared beams, visible light, ultraviolet rays and gamma rays are all part of this family. Like relatives arguing at the holiday dinner table, sometimes these waves interfere with each other.

The biggest pest for WiFi tends to be microwaves. If you stick your router next to a microwave oven and warm up a bowl a soup, you might notice a few connectivity issues. That’s because high-powered microwaves often operate at a frequency — 2.4GHz — used by most WiFi devices. Switch on the microwave, and your laptop can no longer distinguish between the WiFi signals and energy being produced by heating your Hot Pocket. Cell phones, bluetooth gadgets, some baby monitors, and cordless phones (remember those?) can create the same problem and interfere with your download speed.

Back to holiday lights. Their incandescent and LED bulbs emit light. Also, their wires are typically unshielded, meaning the electromagnetic radiation created by electricity pulsing through the cord can produce a very weak electromagnetic field.

More lights may mean a stronger field, thanks to a physical concept called linear superposition. Light waves, like all forms of electromagnetic radiation, moves in waves like water.

An animation of a beam of white light being dispersed by a prism into various waves of colored light. Photo via wikimedia.

If two of those waves arrive at the same point at the same time, their amplitude or strength can combine. When that merger is constructive, the resulting wave looks bigger — ocean waves would look taller and light waves would create a stronger magnetic field.

The animation shows two wave pulses traveling in opposite directions. When they converge, their collective amplitude is greater than that of the individual waves. Animation courtesy of Dr. Dan Russell, Grad. Prog. Acoustics, Penn State.

Visible light from your holiday decor isn’t messing with your WiFi because the two don’t work on the same frequency. The primary culprit is the electromagnetic radiation from the wires or LED electronics, which can shed interference in the range of radio and WiFi frequencies.

It’s hard to predict the points where electromagnetic waves from twinkle lights may constructively merge, but electromagnetic field strength diminishes with distance, so you may want to move your WiFi router or laptop desk if they are placed right next to a festivus tree decked in fairy lights.

If you want to find the best spot for your router, then you could move it to different areas in your house and then check your connection speed here. Another option is a new WiFi-checking app from Ofcom — the United Kingdom’s communications regulator. A press release announcing the app this week set off a media storm about fairy lights and WiFi. Note: This new app only works in the United Kingdom.

Engineers are also designing materials that can protect WiFi and other communication devices from electromagnetic issues. These shields would only permit intended WiFi signals to interact with a device while blocking all other interference. NASA has a facility dedicated to creating these materials for satellites, and the National Science Foundation sponsors a nationwide research collective of three universities and 20 companies to achieve the same goal.

Why the fuss? Well, electromagnetic interference isn’t just a household nuisance; it can also be harnessed as a weapon. As William Radasky explains for IEEE Spectrum, a briefcase-sized radio weapon could cripple a communications network:

And, unlike other means of attack, EM weapons can be used without much risk. A terrorist gang can be caught at the gates, and a hacker may raise alarms while attempting to slip through the firewalls, but an EM attacker can try and try again, and no one will notice until computer systems begin to fail (and even then the victims may still not know why).

However, if you’re mainly worried about the worst interferers of household WiFi, check out this great list by Samuel Gibbs in The Guardian.