Eighty-five years ago this month, the August 1941 issue of QST carried this hint, sent to the magazine by W3QY, to get rid of a pesky case of broadcast interference (BCI). Even though he was running less than 100 watts on 10 meter AM, he was coming through the radios of rowhouse neighbors on their AC-DC broadcast radios. His antenna ran close to the power lines, and he suspected that’s how the interference was getting in to the sets, especially since the tuning dial didn’t make any difference. Moving the antenna wasn’t possible, so he tried filtering. Experimenting on his own set, he built this filter, which did the job. He reported that he provided one for his neighbor, who was also overjoyed.

You can see W3QY’s QSL card, with a picture of his homebrew station, at this eBay listing.