I don't have a coordinated pair at this time, and someone on my local repeater mentioned something about uncoordinated/unprotected/test/"community" pairs in 144 and 440 bands.. so if you know what they are, that's probably where this repeater will live until I get coordinated (if I get coordinated - NE Texas is pretty packed up).. So until I get more information, I guess I should be focusing on isolating the 2 digital rigs.
_____ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of skipp025 Sent: Friday, October 05, 2007 4:51 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: duplexer isolation and reciever noise budget Before I give you an answer I'd want to know where the repeater is going to be placed. Operation in the 146 and higher portion of the band is going to be a heck of a lot easier than a repeater in the 145 segment. both aprs and winlink radios on the same antenna are going to require some serious and unique protection methods. To talk about the cavity size question/issue... you'll notice the cavity Q is much higher for "most" larger diameter cavities. So pretty much anything you are going to want to hunt down is going to be the larger high Q cavities on the order of 8 inch min typical. s. > "John B" <[EMAIL PROTECTED]> wrote: > I'm attempting to design a system that will have a VHF repeater (freqs > not yet determined) sharing an antenna with 2 packet radios (APRS on > 144.39 and Winlink on 145.05, either of which may be active as a > digipeater at any time). > > I'm currently considering a bandpass-only "quadplexor" to isolate the > radios from each other.. each radio running through a bandpass filter > tuned to its frequency only (that includes the transmitter and > receiver for the repeater), on the theory that it is a lot easier to > pass one frequency than it is to reject 3 others. > > Assuming that none of the transmitters run more than 50w, how many DB > down do I need to be outside of the passband to minimize desense for > any of the 3 receivers ?? > > Any other suggestions on how I might handle this hookup would be > greatly appreciated. I'm nearing completion my trailer-mounted 40ft > crank up tower, and I'm having some problems budgeting space for a > filtering system with 12 bandpass cavities without cutting into > general cargo space. >
