The Big Clamp On that I measured is 1+/- ID. Using the area of a circle the RG-393 just makes 4 t. So make it fit. Tom W3FRG Does anybody know if 4 turns of RG-393 (.390 OD) will fit INSIDE of the big clamp on ?? I believe the big clamp on is aprx 1” ID. Tnx..... Jim VE7RF