Is it a top mounted loop or side mounted loop on the cavity? Changing the loop shape can also pull in the notch closer to the pass frequency. Changing its length also has an effect on insertion loss, coupling and the pass to notch spacing. A network analyser becomes very useful in determining what effect you are having when modifying the loops.
Are the 8 cables individually connectorized? Maybe a photo would help. I have seen many versions made by Sinclair and they were built with stubs to the mid 70s. Too bad Jim Morrison retired. After that, the company's help dissappeared. It returned for about a year (2000/2001) when I breifly returned and knew where all the old docs were. Harold --- In [email protected], Jim Brown <[EMAIL PROTECTED]> wrote: > > > > > > >If the tunable stub is connectorized, then just add a 90 degree > >connector in line to make it a bit longer. > > > > > > No connectors on the tuning stub. The coupling loop is built into the > stub and it extends at a right angle from the loop insert. A single N > connector opposite the tuning stub couples to the harness. I am not sure > if the center conductor inside the notch tube will unscrew from the > connector/loop assembly. It looks like it is soldered to the loop and > connector. > > >It depends on the version of the old stub Q202 duplexer you have. > > > >Is it side mounted or top mounted loops and are there 4 or 8 pieces of > >coax being used? Is the harness connectorized with separate Ts or is > >it one assembly? The coax lengths should be a little longer but I > >think 2" is too much if I remember correctly. You should still be > >able to make it work with that cable harness. > > > > > > The harness is made up of 8 individual cables with all cables the same > length except for one that couples from the junction of the antenna > output cable and the receiver connection. (transmitter connection is > also longer). I have tried extending the cables with an elbow connector > on each of the cavities that won't tune with no change in the tuning > characteristics. > > >A good working stub Q202 is better than a new Q202 with capacitor loops. > > > >Harold, VA3HF > >--- In [email protected], Burt Lang <burt@> wrote: > > > > > >>> > >>> What you are experiencing is the symptioms of insufficient capacity to > >>> pull the notch down low enough on the low pass side. The capacity > >> > >> > >range > > > > > >>> of those "tuning stubs" is determined by the length of the center rod > >>> inside the plastic stub. They are 3/16 (I think) diameter brass rod > >> > >> > >with > > > > > >>> a threaded end. Sinclair had several lengths available, the longest one > >>> being about 6in long. There is probably nobody left at Sinclair that > >>> even remembers that part as that design dates back to the 1950s or 60s > >>> and was superseded by the Johanson trimmer design in the late 1960s. > >> > >> > >You > > > > > >> should be able to get a local machinist to make you a longer one using > >> the one you have as an example. > >> > >> Burt VE2BMQ>>> > > > > > Thanks for the inputs - > > 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/
