FM Radio interference

[john banks]

I get FM radio interference from my laser machine's 36V DC power supply which powers the stepper motor drivers (whether the stepper motors or the drivers are plugged in or not). It has an EMI filter on its mains supply.

Suggestions to fix? Although we could use internet or digital radio, the finding of interference is unwelcome and should be fixed.
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[john banks]

Would a ferrite core clipped onto the cable likely be a useful addition to the EMI filter that is shown?

[Michael Hunter]

To be effective, the filter on the mains input needs to be very close to the PSU (only a few inches of cable between them). If the in-between cable is longer, then a ferrite (biggish one) might help.
A ferrite on the 36V output would probably help a lot. If possible (cable length allowing), get a big ring ferrite and wind the cable through it to get at least one full turn and preferably two.
Size-wise, 20mm+ diameter and 25 to 30mm long, with a hole for the cable of 12 to 15mm diameter.

In general, "solid" ring ferrites are more efficient than the split ones, though the split ones in a plastic cover/clip (as sold for HiFi etc.) are much more convenient to use.

[john banks]

Thanks Michael. Lots of information there to allow me to improve this!

[matthew knott]

Move the radio, or tune it to Radio1, that way the interference will become a welcome break :)

[john banks]

She likes Radio 2. I'm a Radio 4 man.

For our North American readers, forgive this parochial discussion of our state funded radio services. I hate the state poking its beak in as much as Ron Paul, but in this case it does quite a good job, and I work in a state funded health system. Like a turkey voting for Christmas I am.