Kevin, Nothing about duplexers is "for certain." While I agree that a PLL exciter is inherently less noisy than its multiplier counterpart, I never assume that it's okay to plan ahead for less than optimum isolation. Some duplexer designs are known to have better performance than physically identical designs from other manufacturers- the silver-plated copper cans from Decibel Products are one example. I feel that it's better to have a duplexer that is perfectly tuned and has absolutely zero desense, than a lower-performance duplexer that has only a little desense.
In an ideal world, KJ4SI should be able to buy a four-cavity BpBr duplexer and try it out for 30 days to see if it had zero desense- with the option to purchase two more cans and the appropriate jumpers at a discount for upgrading it to a six-cavity duplexer. 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kevin Custer Sent: Saturday, August 22, 2009 12:52 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] isolation Eric, Are you sure about your six-cavity recommendation? The MASTR II PLL exciter has 22 dB less side-band noise than a typical multiplier exciter - using 600 kHz TX to RX separation. Assuming his preamp isn't driven into a non-linear region (it shouldn't be), a good 4 cavity duplexer, like a WACOM WP-641, should give plenty of isolation... Kevin Custer > My CommShop calculates 99.65 dB is required. I'd definitely be looking at a > six-cavity BpBr duplexer for this station. > > 73, Eric Lemmon WB6FLY > > ---------------------------------------------------------- > Hope someone may have a program,commshop? What I need to know is what amount > of isolation with duplexers that is required for a GE m2 receiver with > .1...@12db and a m2 pll exciter,100 watt PA on vhf,600kc split?1/2in > helix,with 4pole db224 antenna at 70 ft. > > thanks kj4si
