As someone else mentioned, 77dB is nowhere near enough isolation, especially at 600 kHz spacing. You need at least 90dB with double-shielded coax between the duplexer and radios. As with so many other things in life, more is better. This also translates to more bucks.
You may need a six-cavity duplexer, depending on the design, to get that kind of isolation, especially with that spacing. One more cavity on each side could give you enough isolation, but with a bit more insertion loss. I think you should have done some reading, homework, and question-asking before buying that duplexer. Bob M. ====== --- On Fri, 7/25/08, garyp609 <[EMAIL PROTECTED]> wrote: > From: garyp609 <[EMAIL PROTECTED]> > Subject: [Repeater-Builder] Re: How to figure cable length for duplexer? > To: [email protected] > Date: Friday, July 25, 2008, 8:12 PM > Thanks for the info. I will call call Telewave for an > education. The > TPRD1454 shows 77db of isolation and a minimum of a 1 meg > split. I am > running .600 split here. > 73's > Gary K2ACY > > --- In [email protected], "Bob M." > <[EMAIL PROTECTED]> > wrote: > > > > Telewave is VERY responsive to e-mails and even phone > calls. I've > had technical questions about their duplexers on several > occasions > and have sent e-mail to their only public e-mail address. > Usually I > get a reply later the same day or first thing in the > morning from a > man named Ray Collins. Turns out he's the president of > Telewave and > very nice to converse with. Highly recommended. > > > > I will offer this, however. Celwave (and possibly > other > manufacturers) seem to have "cut lists" which > specify the lengths of > coax you need between cavities and from the last cavity to > the TEE > connector. Telewave doesn't seem to have them; I've > asked in the past > and I'm always told they make each cable set on the > shop floor when > the unit is attached to expensive analysis equipment, > starting with > some known (but un-publicized) length, just to get it > close, then > they "trim to fit" until the unit performs as > they want it to. In > actuality, they may have a bunch of cables all made in > various > lengths by 1/4 inch increments, then select the right ones > to get the > desired performance. > > > > You probably wanted a TPRD1454 unit, if they make one, > as that > would have the right cable lengths and configuration for > the 2 meter > band. > > > > Bob M. > > ====== > > --- On Fri, 7/25/08, garyp609 <[EMAIL PROTECTED]> > wrote: > > > > > From: garyp609 <[EMAIL PROTECTED]> > > > Subject: [Repeater-Builder] Re: How to figure > cable length for > duplexer? > > > To: [email protected] > > > Date: Friday, July 25, 2008, 7:09 PM > > > Jim, > > > Thanks for the response. The duplexer is a > Telewave > > > TPRD1554. They > > > are brand new and bought from Tessco tuned. The > cable on > > > the RX side > > > is marked 11" in black marker on the > connector and the > > > TX side is > > > marked 11 1/2 ". Both cables terminate at > the T. I > > > just want to feel > > > assured that they are the right length as I feel > my > > > performance > > > should be much better and want to rule out the > duplexer. > > > Gary K2ACY > > > > > > --- In [email protected], Jim > Brown > > > <w5zit@> wrote: > > > > > > > > What kind of duplexer is it? I have > several older > > > Sinclair 2 meter > > > duplexers that were up in the 170 mHz range that > I moved > > > down to the > > > ham band, and I had to replace each 10.5 inch > cable that > > > went from > > > the can to the Tee with a cable 12.5 inches > long. Turns > > > out for > > > those older models that piece of cable was part > of the > > > tuned circuit > > > for adjusting the nulls. > > > > > > > > All duplexers are not made the same, so I > think you > > > need to be more > > > specific. Interesting on the frequency you are > using. > > > We are just > > > putting one on the same frequency here in central > New > > > Mexico - HI. > > > > > > > > 73 - Jim W5ZIT > > > > > > > > --- On Fri, 7/25/08, garyp609 > <gary.paul@> > > > wrote: > > > > From: garyp609 <gary.paul@> > > > > Subject: [Repeater-Builder] How to figure > cable length > > > for duplexer? > > > > To: [email protected] > > > > Date: Friday, July 25, 2008, 5:46 PM > > > > > > > > Output frequency is 145.450 & input is > > > 144.850. How do > > > I figure out > > > > > > > > what length the cables should be between the > rx side > > > and tx side > > > that > > > > > > > > connect to the T-Connector? Thanks and > 73's ! > > > > > > > > Gary K2ACY
