It looks to me that the extra cavities were added to a regular duplexer. The receive side has the T connector connected to the notch cavity thru a length of cable to make a pass band network along with the notch. This has the effect of skewing the normal pass of the notch filter on one side (making for a steeper notch on one side) and at the same time forming somewhat of a pass band filter with the length of cable between the filter and T. The extra stub I believe is used to try and make the notch steeper on one side so as not to overlap on the TX side with the close spacing.
They may have reduced the coupling of the notches in order to try and make them steeper for the close spacing and then added the extra cavities to make up for the inadequate coupling in the primary filter cans. Or they may have just thought that "more is better". Or they may have added the extra filters because of the botched job of trying to make a close space duplexer and not getting the cables right. 73 Gary K4FMX > -----Original Message----- > From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of skipp025 > Sent: Monday, May 28, 2007 2:03 AM > To: Repeater-Builder@yahoogroups.com > Subject: [Repeater-Builder] When 4, 6 or 8 Cavities just won't due... > > Re: When 4, 6 or 8 Cavities just won't due... > > Another Ebay gem: > > DB PRODUCTS 9-CAVITY RADIO REPEATER DUPLEXER-100DB-HAM > Ebay Item number: 250120910164 > > I don't know to be impressed or just laugh at all the > hardware (number of cavities used). > > cheers, > skipp > > > > > > > Yahoo! Groups Links > > >
