In a story I'm working on, I need a fictional blues station in Portland, Oregon. Obviously, I don't want to use something that exists. Does anyone know of a database of call sign letters or something like that? Or are there rules I can follow that I can slightly break and make it work? (e.g. call signs are always 3 or 4 letters, and never 5 letters, so if I make it SOUND like a radio station, but make it five letters I'm safe.) I've done a few Google searches but the results have been pretty ambiguous. Thanks, C.