On Dec 1, 2010, at 1:36 PM, Dick Flanagan wrote: > Wasn't that an old rectifier tube?? You thinking of the 5U4GT? :-) :-) 5Z4GT, also a rectifier type, is a real call sign. I don't know about 5U4GT. Can Canadians pick CK722 as a call sign? :-P 73 Chen, W7AY