Surprisingly, they are RF quiet.
A few years ago I bought the Harbor Freight 100 w solar power kit for use at Field Day. After I bought it, I learned that some charge controllers produce RF noise.
So before Field Day I hooked everything up in the backyard as a test.
Frankly, given it was harbor freight I expected the worst.
But I could not detect any RF noise from it.
Now, the supplied controller is a PWM controller, so it isn't very efficient.
But it DOES work.
73 de N8AUC
Eric