Re: Construction: how to shield CPU noise?


Guy Atkins
 

I added some shielding recently between the boards of the C. Crane Skywave radio, and have made similar additions to other portables before. My usual approach is to target the DSP chip first of all, and DC-DC converters or display driver chips if I can identify them.

Sometimes the extra screening works best if it is floating (not connected to a ground point), but usually grounding the shield is the way to go.

Construction-wise, I like to make up a sandwich of thin tin sheet metal with clear plastic tape on opposite sides for insulation. For the Skywave radio I didn't have any more tin sheet metal around so I used a layer of aluminum foil with the tape on both sides. Because I couldn't solder to the aluminum, I made a mechanical connection of a short length of wire under the tape, and then routed the wire to a ground point on the Skywave.

I'm not sure I noticed any noise level improvements with the Skywave, but I felt better knowing I'd added more extensive coverage than the minimal stock shielding. With other radios the improvement has sometimes been dramatic.

73,

Guy Atkins
Puyallup, WA

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