de WB2CPN 2005.04.20 Yep, Marty, the loop ranges had an AM audable tone on that one transmitter, but the five-tower adcock ranges didn't. The center tower was 1020 Hz freq ofset, and the hetrodyne was what the pilot heard. I still think it's all magic. Breck been working on a range simulator. It sounds like a good idea. 73 Clete