Pot-Growing Lights Are Interfering with Local Radio Waves in Colorado

Alyssa Bereznak

We all know that a good ol’ cellphone jammer can shut down mobile service for miles. But did you know that the lamps used to grow marijuana indoors can interfere with radio waves?

As The Coloradoan reports, Boulder resident Tom Thompson recently discovered this peculiar reality when he set out to track down what was interrupting his ham radio — which he uses to communicate with friends across the country.

Thompson, a retired electrical engineer, crafted a portable antenna and began roaming the streets to see what made its signal cut out. Eventually he discovered the offenders: the growing collection of high-powered lamps that residents are using to grow the now-legal pot indoors. 

It appears that this is not a novel problem. Though Colorado legalized recreational use of the drug only five months ago, medical marijuana is legal in 22 other states (plus the District of Columbia). As weed laws loosened, amateur botanists took to growing pot indoors, to avoid thieves, insects, and inclement weather.

And growing pot indoors requires high-powered lighting. How high powered? High Times recommends using 1,000-watt high-pressure sodium lamps along with 400-watt metal-halide lamps. Of course, that’s for mass scale production, and would be pretty overkill for a casual home grower, as many experienced commenters have noted below. In small households, you’d usually find just one lamp under 1,000-watts. Some even use incredibly energy efficient LED lights that avoid intense energy drain.

Many of these particular types of lights employ electrical ballast to limit the amount of current they use. Ballast circuits can cause electrical noise: They radiate radio energy. With so many of these lamps in the area, ham radio operators are essentially trying to work amid a human-made thunderstorm.

Add up the wattage of every weed-growing household in America and, well, local radio stations don’t really stand much of a chance. The problem has become so severe that the American Radio Relay League, representing America’s 720,000 licensed ham operators, filed a federal complaint. ARRL spokesman Sean Kutzko told The Coloradoan that the problem states are — surprise! — Colorado and California.

The Federal Communications Commission seems to be less concerned about the interference of grow lights than it is about cellphone jammers. A representative told The Coloradoan that it’s aware of the problems but didn’t say the government organization was going to do anything about it.

In the meantime, Thompson found a very Boulder-esque way to solve his problem: He bought every perpetrator he could track down a $20 cable shield to block the interference.