> Doesn't the isolator typically installed at the transmitter
> output spin off any anything reflected from the duplexer (or
> the feedline) into it's load?
The generic answer is "yes", but the qualified answer is that isolators,
like everything else, have a finite bandwidth, so if the energy is far
removed from the design frequency of the isolator, it doesn't do its job as
well. At far-removed frequencies, some of the power incident on the output
power (i.e. what's coming back down the hose) gets reflected at the isolator
due to a poor match, some will makes its way around to the reject load, and
some will make it 240 degrees around to the transmitter.
As an example of the limitations of an isolator, a UHF isolator on a UHF
repeater isn't going to isolate your PA very well from highband signals
coming down the line. A bandpass cavity between the isolator and the
duplexer will.
--- Jeff
