I've run into a problem that baffles me. I have two sets of WACOM WP-641 4 can Duplexers. They have been tuned to TX on 146.96 mHz and RX on 146.36. One set was tuned in a Professional Lab, the other I tuned myself. They tune very well with excellent rejection ~90db. When I duplex into a dummy load running 100W, I can inject a signal with an iso-tee and there is vertually zero desense to the receiver. When I hook it to an antenna it instantly experiences 30db of receiver desense. I can lower the power to 3 watts or less and still have 20db desense. I have a GE Mastr II repeater, but I've used a separate Transmitter and receiver and experience the same results.
I'm using double shielded RG214 for testing. I've also used 1/2" heliax for testing from the duplexer to the antenna. I've used 3 different antennas. 2 different colinear and a j-pole. The antennas all have less than a watt reflected out of 65W forward. I've used separate antennas on the TX and RX Cans with the same results. When I terminate either TX or RX into the dummy load the desense disappears. It appears that when the reactive component is introduced everything goes to pot. It doesn't make any sense to me. Any Ideas? I'm stumpted.. :-( Thanks, Bliss
