Next question what channel spacing are you tuning them for ?
Merrill KG4IDD On 1/28/2010 8:56 PM, tahrens301 wrote: > Hi Merrill, > > Yep, that's what the label says. > > Now, gotta figure out why they aren't > living up to specs. > > Tnx > > Tim > > > > --- In [email protected], Merrill<kg4...@...> wrote: > >> Tx-Rx model 28-41-05 "Vari-Notch" pseudo-pass, notch >> duplexer. >> This is the appx two RU duplexer for wide split repeaters, >> Comprised of five of the two inch square cavities. >> Tx-Rx manual says 2.5 mhz spacing. >> Tag says Tx 1.5 dB insertion for 76 dB isolation, and Rx is 1.1 dB for >> 110dB(Tx is 76dB at Rx and Rx is 110 at Tx) >> Three cavities on Rx, two on Tx. >> >> >> >> On 1/28/2010 8:28 PM, tahrens301 wrote: >> >>> Hi Rob, >>> >>> Sorry, I forgot to put the model number in the original >>> posting! >>> >>> It's 28-41-05 >>> >>> It has 3 of the blocks in the TX line, and 2 in the >>> RX. It's in a 2 1/4" thick rack panel. >>> >>> I opened one up, and it looks like a helical resonator >>> with a silver slug that goes in and out, and the BNC >>> connectors have a loop that is 90 degrees to the larger >>> coil and has an air variable cap to ground. >>> >>> thanks! >>> >>> Tim >>> >>> >>> >>> --- In [email protected], "Rob Lee"<rob@> wrote: >>> >>> >>>> The duplexer that you have may not be a "Vari-Notch" unit. Your description >>>> sounds like a "30 series" unit (Model number will start with a 30 e.g. >>>> 30-36-01A) >>>> >>>> The 30 series VHF duplexers are specially designed to work with repeaters >>>> that exhibit problems when connected to high selectivity duplexers. This >>>> design uses three standard notch type filters on the transmitter side which >>>> provide excellent noise filtering while maintaining a relatively low VSWR >>>> over a wide frequency range. This helps minimize transmitter sensitivity to >>>> cable length between the duplexer and the transmitter and also reduces the >>>> potential for transmitter spurs. >>>> >>>> The receiver portion of the duplexer incorporates three pseudo bandpass >>>> filters to give isolation to the transmit carrier and reduce interference >>>> and intermodulation caused by other nearby transmitters. >>>> >>>> Because different types of cavity filters are used for the transmit and >>>> receive sides of the duplexer, it is important that the correct model be >>>> used. Model numbers are different for units designed for either the >>>> transmitter higher or lower than the receiver frequency. >>>> >>>> I have tuning instructions if this sounds like the unit. >>>> >>>> Rob K7TGU >>>> >>>> >>>> ----- Original Message ----- >>>> From: "tahrens301"<tahrens@> >>>> To:<[email protected]> >>>> Sent: Thursday, January 28, 2010 15:37 >>>> Subject: [Repeater-Builder] VHF Vari-Notch Duplexers - 2" x 2" x 4" ??? >>>> >>>> >>>> >>>> >>>>> Well, I thought this thing was tuned up, >>>>> but obviously something is wrong. >>>>> >>>>> These are a set of the 2x2x4" cavities... >>>>> have a plunger in the front, and a variable >>>>> cap adjustment on the back. Also, a pair of >>>>> BNC connectors on the capacitor side. >>>>> >>>>> The plate says Duplexer Vari-Notch, >>>>> 147-174 >>>>> >>>>> It also implies that the TX has a 1.5dB >>>>> insertion loss, but darned if I can get >>>>> only about 4.5. >>>>> >>>>> I've talked to the guys at TX/RX, and they >>>>> are looking for a book on them, but nothing >>>>> yet. >>>>> >>>>> Anybody have any tuning instructions/info on >>>>> them? >>>>> >>>>> The plunger is marked 'pass low', and the cap >>>>> is reject high. Pretty much self explanatory, >>>>> and they tune ok, but the insertion loss is >>>>> higher than it appears it should be. >>>>> >>>>> Thanks, >>>>> >>>>> Tim >>>>> >>>>> >>>>> >>>>> >>>>> ------------------------------------ >>>>> >>>>> >>>>> >>>>> Yahoo! Groups Links >>>>> >>>>> >>>>> >>>>> >>>>> >>>> >>>> >>> >>> >>> ------------------------------------ >>> >>> >>> >>> Yahoo! Groups Links >>> >>> >>> >>> >>> >>> >> > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > > >
