I have been faithfully using a coil of coax as a common mode choke for
a while without any idea if it is really doing any thing.

Googling turns up more url's than I can follow. I would appreciate any
suggestions as to how might measure the effects of the common mode
choke. 30 to 17 meters is my favored range of operation. I have a
pretty well equipted shack.
John Ferrell W8CCW