Speaking of Seco-Larm. They have a twisted pair balun with built in ground loop isolation. You use the ground loop one at the camera, and use their regular balun at the other end.
Has anybody used this pair? EVT-PB1-V1TGQ EVT-PB1Q
Perhaps for a multiple building installation where ground loop is a real likelihood?
Did it work well for you?
Is there another manufacturer with a comparable product?
Maybe one that some of the distributors actually have in stock?