USB RF noise?

I’ve been trying to use an MSF atomic time signal radio receiver, and I can get a clean signal with a power supply, but if I power the Uno R2 through the USB socket, I get a lot of radio interference and cannot pick up the time signal.

Does powering the Uno R2 through the USB socket normally generate RF noise or could there be a problem with that specific board?

Is this a DCF60 or 77 type of receiver?, If so I think there are some app notes about using 1, the larger antenna, and 2 using shielded cable to remote the ferrite antenna for best operation and away from the noisy processor. The Arduino is a real noise box, takes my favorite NPR station off the air pretty completely. If not pleze pardon my ignerant untrushun...


It's that sort of receiver, yes. I have set it running with a custom shield with an Adafruit 4-digit 7-segment display on it to show the time, and it's picking up just about every minute when powered by a 9v supply, so I don't think it's any problem with the wiring to the radio, it's only happening when it's powered by USB.

You mean that USB supply which is generated inside of that box with a ton of RF sources (some people call those PCs)?

Yeah, my PC puts out tons of RF hash as I discovered when I tried using my scanner within a 10 foot radius one day.

A USB “wall wart” not connected to a PC would probably be less of an issue, but really any SMPS is likely to produce a bit of low-frequency (<1MHz) noise.

If your USB cable does have a large ferrite EMI suppression toroid at each end, then try getting one that does.

In general any computer power supply is noisy across the entire RF spectrum, and analog circuitry should have a separate supply or good filtering (LC low pass).