I recently installed 4 120W panels, used a Midnite Solar "Kid" controller. I have the noise in the VHF radios, one worse than the other, and to the extent that I can't squelch it when the panels are at any more than about 30% output. VERY annoying. I turn the controller off while underway so I can use the VHF's. Also annoying. I also wanted to use high quality gear, the Midnite Solar has a good reputation. Evidently this problem is known, I had sent the controller back in warranty for another problem and asked about the RFI. They apologized about the noise, and suggested I install ferrite cores, which I did with no appreciable change.
My understanding is that because a solar controller is rated as an electrical control device, not a radio device, it is not required to meet FCC part 15. I'm fuzzy on how the regulations apply here, but regardless, it is noisy. The noise is coming from the controller, the electronic switching part of the MPPT circuitry is what creates the noise. If the controller were rated as a marine electronic device, it would be required to not create RFI, but that drives up the cost of the equipment. It's already over $300.
I've not received any further offers of a solution from the manufacturer, I have sent another note that refers to this thread and the fact that others are having this problem. They do sell a "marine" version, AFAIK, the only difference is that the marine version is white, has a trunion mount, and has a battery temperature sesnsor.
At this point I can't recommend the "Kid" controller. Although it appears to be well built and the function/features are excellent, for me the RFI is a deal breaker. Perhaps I'll hear more from Midnite, we'll see. It seems to me that if they intend to market their product for a marine application, it should be compatible with other electronics, FCC part 15 notwithstanding.