From: Mike Manes <manes at attglobal.net> Doesn't there have to be a chunk of ferrite inside the WG in the magnet field as well? Yes. And if it's an isolator, doesn't there have to be a 3rd port where the return power is dumped? No. The three port thing is a circulator. You can make an isolator with a 3 port circulator and a matched load. -John 73 de Mike W5VSI