Ian, Since I don't have a network analyzer or a tracking generator, I have consistently used the S meter method to tune my cavities for both the transmit and receive side.
It is not recommended to tune duplexers with power applied, because you wind up getting little arcs that leave black carbon spots on the metal contact areas. BUT with all things said, I find I can always get a few more watts out of the transmit side by tuning with power applied for max RF out. My gut feeling is that things change a little under the influence of the high RF levels. Art - KC7GF Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/