Monday, April 13, 2015

Ham Radio Vs. Marijuana Growers

According to AARL, the average age of a ham radio operator is over 50. They don't say how much over 50 and some nations have admitted their median ham age is almost 80. You would think that mature demographic would have some non-recreational interest in medical marijuana. But that has not been the way things have gone. Marijuana growers and ham radio operators have actually become mortal enemies. The AARL even posted an article on identifying these growers, and how to deal with the problem from both a legal and technical point of view here.

the conflict stems from a simple fact about grow lights. Like many forms of fluorescent light, they produce RF interference (RFI).  In the last decade, digital high-intensity discharge (HID) ballasts have largely replaced traditional coil magnetic ballasts. The HID ballasts typically operate on 110-270V circuits. The target target output frequency from the ballast is 50-120Hz. But your household electricity typically operates on 60Hz.  not the obvious problem. Fluorescent tubes are non-linear devices, and generate harmonic currents in the power supply. The arc within the lamp can generate RFI as well, which can be conducted through power wiring!  More here, here and here.

The RFI is usually in bands between 1.8 MHz and 30 MHz and it's strong enough you don't need special gear to detect it. You can find a bad grow light with a handheld AM radio. These aren't 40 watt bulbs either. Grow lights are usually High pressure sodium (HPS) or metal Halide (MH) and easily 1000w per lamp. Lab tests at the AARL have revealed that many grow light makes and models violate FCC part 15 and/or part 18. The units often operate on a timer making it even more obvious what the source of the RFI is. Even for marijuana growers in Colorado, this presents an unexpected legal problem with the FCC instead of the FBI. I found an article on that details the ease at which police can now find indoor growers.
"One narcotics officer from the San Francisco Bay Area turns his car radio to 560 AM when he checks out potential indoor grows. He’s checked out seven indoor marijuana grows since learning about the RFI issue. All seven times, the car’s radio showed significant interference from the ballasts inside of the grow location. "
This unnamed police officer is finding marijuana growers, not with helicopters, thermal cameras, NSA stingray transcripts, automatic number plate recognition, video surveillance, or phone taps but with the stock AM radio in his cruiser. Notably, the AARL, still primarily focused on ending RFI, listed in that same article how a grower might reduce the RFI affordably with simple AC line filters and toroids.

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