Harold, the cavities are the welded type and the loops penetrate the top. The cavities have an extra hole on the other side so a band pass coupling system with an input and an output loop could be used. But the hole on the opposite side is covered with a plug, and only one connector/capacitor stub is used per cavity. The capacitor stub extends away from the cavity at right angles across but not touching the adjacent cavity.
The original cables were the 10.5 inch dimension that you mention, and I wound up with 12.5 inch cables to make it work. I suspect 12 inches even would work as well as there is some room left on the rods to do some more tuning. The cables were RG-213, by the way - I just left the high-pass side of the duplexer alone since it tuned up just fine with the 10.5 inch cables. So just modified the low-pass side cables to make it work on 147.76/147.16. Thanks again for the help and comments. 73 - Jim W5ZIT >According to the information I have, all the cables between the T's >should be the same length. For the VHF ham band, the cut length of >RG214/u should be 10.5" long then trim to add the N male connectors >without making it shorter. > >Was your duplexer top or side mounted loops? If they are the side >mounted type with the spun cavities (non welded top type) there may be >higher insertion losses due to the oxidation of the mating junction of >the resonator to the can. To resolve this problem I usually loosen >the 6 bolts that hold the resonator to the can and clean the contact >surfaces by just mechanically rubbing the two surfaces together. To >do it properly, the cans have to be disassembled which is allot of work. > >The resonator invar rod tunes the pass freguencies and the stubs tune >the reject frequencies. > >Harold > >--- In [email protected], Jim Brown <[EMAIL PROTECTED]> wrote: > > >>> >>> Jim - W5ZIT wrote: >>> >> >> >>>> >I am trying to move a Q 202 G from the 170 mHz range down to the >>> >>> >147 mHz > > >>>> >range and have run into a problem on the notch tuning. The high pass >>>> >tuning works like a charm and has a good pass and notch >>> >>> >characteristic. > > >>>> >The low pass side is another story. The pass tuning works fine, but I >>>> >can't get a notch. With the tuning rods all the way in, it is >>> >>> >starting > > >>>> >to notch, but only about 20 db. >>>> > >>>> > >>>> > >>> >>> >>> Eric - WB5FLY wrote: >>> >> >> >>>> >Jim, >>>> > >>>> >Sinclair makes two harness assemblies for that duplexer. The >>> >>> >jumpers are > > >>>> >about two inches longer in the low-range harness, and that makes a >>> >>> >world of > > >>>> >difference. You can order the low-split harness directly from >>> >>> >Sinclair. Go > > >>>> >to: >>>> >www.sinctech.com >>>> >Make it very clear that you want the "low range" harness, as some >>> >>> >of the > > >>>> >Sinclair sales folk seemed to be unaware of its availability, the >>> >>> >last time > > >>>> >I called them. A year or so ago, that harness cost about $145. >>> >>> >It's all in > > >>>> >one piece, with crimped connections. As I recall, the low range >>> >>> >was for > > >>>> >136-150 MHz, and the high range was for 150-174 MHz. >>>> > >>>> >Most Bp/Br cavities will have one notch above and one notch below >>> >>> >the pass > > >>>> >frequency. I have tuned several Sinclair duplexers of this design, >>> >>> >and they > > >>>> >all tuned up perfectly once the correct harness was installed. >>>> > >>>> >73, Eric Lemmon WB6FLY >>>> > >>> >>> >>> >>> Eric - I took your advice and built up a couple of jumpers to go from >>> the cans back to the tee in the harness on the low pass side and made >>> them 2 inches longer than the old ones as you suggested and presto - >>> nice deep null with the tuning rods. >>> >>> Thanks to all for the feedback, and thanks to the list for helping to >>> solve this problem. >>> >>> 73 - Jim W5ZIT >>> >> >> > > > > > > > > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
