Total posts : 45366
Hi Neil Radio 8z:
After thinking about your post for awhile a question has arisen.
It seems to me the obvious reason you put the Ramko FM25 in a metal box, since of course it comes originally in a plastic box, is to shield it from leaking or receiving RF.
But it sounds like the hum problem is a matter of the antenna being too close to the transmitter, which would suggest the RF is penetrating the metal box.
Although separating the two improves the situation, why can’t the metal box be the solution in the first place?