If you're getting a general RF hash then it may be radiated noise, which no filter is going to fix. I have the same problem with my electronic cigarette, the processor throws out RF junk like crazy. The answer in that case is to switch off while using the radio. With the solar controller I could identify the source as a low frequency switching noise.
But hey, trying caps certainly won't hurt!
"The cure for anything is salt water... sweat, tears, or the sea" -- Isak Dinesen
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