It pretty much is that for the AM C-C Coupler, an adjustable, transformer isolating, Medium Wave RF Tuner, for matching very low impedance values. One of the best resources that I have is the 1979 book from Ernest Wilson, (The Panaxis Productions dude.), of Carrier-Current Broadcasting Techniques: The Wired-Wireless. I really need to get that scanned to .PDF. Thanks, for the links! Always good to have Part #15 broadcasting knowledge INFO out there.