Bob, Point well taken and thank you. If I were to change the seperation to 1mhz and get the duplexer retuned would that provide enough isolation? I guess my question is will the duplexers work ok with a different band split? Thanks, Gary K2ACY
--- In Repeater-Builder@yahoogroups.com, "Bob M." <[EMAIL PROTECTED]> wrote: > > 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: Repeater-Builder@yahoogroups.com > > 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 Repeater-Builder@yahoogroups.com, "Bob M." > > <msf5kguru@> > > 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 <gary.paul@> > > wrote: > > > > > > > From: garyp609 <gary.paul@> > > > > Subject: [Repeater-Builder] Re: How to figure > > cable length for > > duplexer? > > > > To: Repeater-Builder@yahoogroups.com > > > > 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 Repeater-Builder@yahoogroups.com, 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: Repeater-Builder@yahoogroups.com > > > > > 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 >
