Hi Merrill, Yep, that's what the label says.
Now, gotta figure out why they aren't living up to specs. Tnx Tim --- In Repeater-Builder@yahoogroups.com, 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 Repeater-Builder@yahoogroups.com, "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:<Repeater-Builder@yahoogroups.com> > >> 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 > > > > > > > > > > >
