Well, everything you plug in changes the impedance, including what you *measure* it with. Calculate? Does not compute! More a problem would be any reflections from bad terminations, AKA standing waves.
You can observe the impedance by applying a square wave from a very low impedance source, and the initial current tells you the impedance, much like if you had a 300M Meter roll of coax and applied a battery to it: After a couple seconds, the reflected current from the other end might knock you on your butt unless it is terminated, but until then, the current flowing reflects that characteristic impedance. Of course, your cables are shorter, so you need to be really fast, and then there are the active devices attached to the cable, which can have all sorts of nonlinear effects that the impedance simplified concept cannot describe.
UDB
Re: UDB
