Switching Power Supplies a More Common Noise Source than Power Lines, ARRL Lab Manager Says


ARRL Laboratory Manager and EMI Expert Ed Hare, W1RFI, told the HamRadioNow webcast recently that switching-mode power supplies are a more common noise source for radio amateurs than electrical power lines. HamRadioNow host Gary Pearce, KN4AQ, interviewed Hare on April 4 at the Raleigh, North Carolina, RARSfest, where Hare also presented a forum, “Tall Tales from the ARRL Lab.” Hare told Pearce that switching-mode power supplies are in — or provide power for — many home electronics these days.

“The old days of those iron transformers are gone,” Hare said. “Every single one of these is a switcher. We’re also seeing noise from pulse-width control motors.” Hare said the big culprits are “little wall warts,” not switching supplies designed to power Amateur Radio gear. Every TV you own has a built-in switcher, almost every device has a wall-wart, and a lot of these are imported, not necessarily meeting the FCC rules, so we’re seeing more reports involving those,” he said.

Hare also told HamRadioNow that a few LED-type lightbulbs that are becoming more common also can be noise-generators, as are “grow lights” used for cultivating plants indoors. He said that the ARRL Lab can work with manufacturers to correct these problems, but the Lab needs model numbers and “specific information about the problems amateurs are having, so that we can put some of our resources toward helping.”

Many interference issues can be resolved without FCC intervention, Hare said, noting that Commission enforcement is the last step, if other efforts fail. He told Pearce that he does not anticipate any immediate negative effects from the recently announced cutbacks in the number of FCC Enforcement Bureau field offices and personnel.

“[T]here’s a short list of who’s going to get closed down, but we’re going to continue to work with the FCC as we have,” Hare said. “We’ve been told by Laura Smith [of the FCC Enforcement Bureau] that she’s going to continue to be engaged in this. So we’re going to continue to send problems [in] that direction.”

Hare said the only area where FCC cutbacks could affect enforcement would be FCC field investigations, but “we’ll cross that bridge when we come to it,” he said.

Hams experiencing RF interference problems can contact the ARRL Laboratory by contacting Ed Hare or ARRL Lab EMC Specialist Mike Gruber, W1MG. The complete interview with Hare is in Episode 196 at — Thanks to Gary Pearce, KN4AQ/HamRadioNow