: Re: [Repeater-Builder] Re: 220 Duplexer Tuning Help
> Maybe I'm missing something then. All I'm adjusting is the rod and turning > the coupling. > > There is a small hex cap on top of the coupling, that I didn't touch. > > The manufacturers tuning instructions for this model say to adjust an > external tuning stub, which I don't have. > > YOu may be missing something. I have the instructions for a wp652 but not the A version. There was a 450 mhz version that I seem to remember having some adjustments for the rejection notches under a cover on the top of each can similar to what you are describing. That may have taken the place of the reject stubs that are on the side of the cans. They looked similar to a pl-259 with a clear plastic rod sticking out of them and parallel to the cans. You may want to adjust the coupling loops for maximum output and then adjusting the large tuning adjustments for maximum pass. Then look under the covers and adjust the screws for maximum rejection. The notches for maximum rejection have to be adjusted last. A repeater group I was with had a 4 can 2 meter duplexer from them and we has lots of problems with intermod. The duplexer worked ok for a 30 watt repeater but many times it had lots of intermod from what seemed like about 100 transmitters within a 3 block radius. We sent it off the Wacom and had a band pass cavity put on the TX and RX side. This cleared up the problem . Noticed that in a catalog a year or so later that same design showed up. Seems like some duplexers just do not have much out of band rejection. Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
