Making Waves: RFI – My Unwanted Visitor

Considering the number of switching supplies these days powering everything from cell phone chargers to computers and televisions, you’d think radio frequency interference (RFI) would be a bigger problem. I dabble in ham radio just enough to notice that, except for a few birdies, overall HF spectrum is generally pretty quiet.

Our channel 6 transmitter just south of the border is most vulnerable being low band VHF, relatively distant for most US homes, and dependent on AM receivers for video. We do occasionally get the viewer phone call suggesting we fix the swirling video noise on his TV. I’ve never received any confirmation that anyone followed my suggestions to turn off appliances or even circuit breakers to find the source of the noise—just an occasional repeat call to say that the noise in Lakeside is still there, suggesting my work there remains.

Recently, though, I was surprised to find that my brand new Sears DieHard power tool “Multi-chemistry” battery charger produces enough RF to effectively overcome all incoming signals at home, pretty much DC to daylight. The entire AM band sounds like hash, the FM band is a screechy mess, and many of the ham bands have multiple carriers rapidly sweeping through all frequencies as heard with my fan dipole antenna some 60 feet away. I can’t imagine that this Made in China beauty, model 315.259260 passed FCC Part 15 subpart B testing, but I haven’t yet filed a complaint.

Have you discovered a similar hash transmitter in your home or neighborhood?