Clairification - only one cavity connections was described, four cavities were required for the DB HB duplexer. I regret the misinformation. Allan Crites WA9ZZU
--- On Sun, 6/28/09, wa9...@arrl.net <wa9...@arrl.net> wrote: From: wa9...@arrl.net <wa9...@arrl.net> Subject: RE: [Repeater-Builder] Re: Help with Duplexer To: Repeater-Builder@yahoogroups.com Date: Sunday, June 28, 2009, 11:43 PM Eric: I wonder if you are aware that any BP two loop cavity can be made into a BP/BR cavity by using only one of the 2 loops, having a coaxial "T" connector on the loop, with a tuning capacitor (in the form of a O.C. transmission line) connected to one side of the "T" and on the other side a 1/4 W.L. transmission line connecting to a "T" connector on the main line. The tuning capacitance parallel resonates the loop inductance for the notch freq. and the cavity is tuned for the pass freq. This was an original Sinclair design. I view having a tuning cap in series internally with the loop as a cost reduced version and probably better performing. Several years ago DB made a BP/BR duplexer for Motorola on HB by using a BP 2 loop cavity with a coaxial "T" connector on both loops, one side of the input "T" was connected with a 1/4 W.L. coax to a jct box containing a variable air cap series connected to the cc of the one coax and to the cc of another 1/4 W.L. coax which connected to the output "T". The cavity tuned the BP freq., and the air variable tuned the notch. 73 WA9ZZU --- On Sun, 6/28/09, Eric Lemmon <wb6...@verizon. net> wrote: From: Eric Lemmon <wb6...@verizon. net> Subject: RE: [Repeater-Builder] Re: Help with Duplexer To: Repeater-Builder@ yahoogroups. com Date: Sunday, June 28, 2009, 10:44 PM Ron, Your Q202G must be an earlier version, with a different method of adjusting the notch. A Sinclair bandpass cavity uses two loops, so the cavities you have are not bandpass. A photo would be helpful. 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@ yahoogroups. com [mailto:Repeater-Builder@ yahoogroups. com] On Behalf Of n4sfu Sent: Sunday, June 28, 2009 6:39 PM To: Repeater-Builder@ yahoogroups. com Subject: [Repeater-Builder] Re: Help with Duplexer Eric, Thanks for the reply. The Sinclair Q202G duplexers that I have do not have the tiny threaded cap next to the loop connector. 1 set of cans are labeled as High pass while the other set is marked as Low pass. I did notice a plate on top of all 4 cans that has noting going to it but cannot fing anything else that shows it can be changed other than the tuning rod. I do currently have these tuned at 146.715/146. 115. 73 Ron Hill N4SFU --- In Repeater-Builder@ yahoogroups. com <mailto:Repeater- Builder%40yahoog roups.com> , "Eric Lemmon" <wb6...@...> wrote: > > Ron, > > If you really have a Q202G (I'm guessing that "Q020G" was a typo) cavity > set, they are not bandpass. What suggests that they are bandpass? The > standard Q202G BpBr duplexer has only one loop per can, and a blank plate is > installed where a second loop would be. A tiny threaded cap next to each > loop connector covers the notch adjustment. Be aware that a Q202G duplexer > that was in commercial service will probably have the high-split harness > that measures about 12" between the centers of each tee, and will not tune > down to the 2m band. The harness drawing is found here: > <www.repeater- builder.com/ sinclair/ sinclair- q202-g-cable- harness.pdf> > > 73, Eric Lemmon WB6FLY > > > -----Original Message----- > From: Repeater-Builder@ yahoogroups. com <mailto:Repeater- Builder%40yahoog roups.com> > [mailto:Repeater-Builder@ yahoogroups. com <mailto:Repeater- Builder%40yahoog roups.com> ] On Behalf Of n4sfu > Sent: Saturday, June 27, 2009 7:13 PM > To: Repeater-Builder@ yahoogroups. com <mailto:Repeater- Builder%40yahoog roups.com> > Subject: [Repeater-Builder] Help with Duplexer > > > > I dont usually post on the forum but rcv the emails everyday and follow all > posts. I recently purchased a 4 can set of Sinclair Q020G cavities not > knowing until I had them tuned and connected to the MSR2000 that they are > Bandpass only. Needless to say that desense will not permit the rcv of weak > signals at all say 5 miles away. Does anyone know of a good place to acquire > a couple of the notch cavities with the cables to go with this set or of a > good set of BP/BR cavities at a reasonable price to complete this repeater > installation. We are located in South GA and are locating this repeaer on > 146.715 mhz. All help is appreciated. > Ron/N4SFU >
