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 Repeater-Builder@yahoogroups.com, 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
>
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