I’ve been using these DC-DC converters for charging cell phones in my car and in the house (more in this blog) and they work fine. But when I plug my phone in, my FM radio station gets a lot of RF interference. I admit that the station, KSBR, which is low power and far away, has a weak signal, and that makes the problem worse. If the station was a powerful commercial station, the problem would probably be less, or not a problem if I moved the charger a few feet away from the radio.
But I like playing, er, experimenting with ferrite toroids and the like, so I decided to try putting RF interference suppressors on the cables. Most of us have seen the big plastic cylindrical thing on cables next to the connectors. This is a cylinder of ferrite. It’s like putting 4 or 5 toroids next to each other on the cable. These are effective at choking off and absorbing the RF interference coming out of the equipment by way of the cable.
I found some reasonably priced snap-on RFI suppressors at All Electronics. At $0.75 each, I can get a dozen for about ten dollars US and snap them on to both ends of the cables. I have already put the small ends of cables through a larger toroid, and it helped some. But I still hear some interference when it’s charging. So I ordered one size for larger cables and one for smaller cables. I guess they will arrive early next week.
