At 8/4/2010 14:37, you wrote: >---- Doug Hutchison <[email protected]> wrote: > > Does the length of coax connecting cable between repeater and filters > > matter? > > > > Doug > > >As long as the filters are working correctly, the cable length from the >duplexers to the radios tx and rx does not matter. Having said that, >remember that the shortest length of double shielded coax or HELIAX cable >that will reach without kinks or physcial loads (binds) on the connectors >should be used. This has nothing to do with impedeance matching, but >rather cross talk thru cable leakage.
Double-shielded cables aren't going to leak enough to be a concern. You do want to keep the length short to minimize loss. BTW, I once measured the isolation between a pair of ordinary RG-58 cables on a VNA from 50 to 500 MHz. Unless the cables were twisted together, I didn't see any coupling between them down to at least -90 dB. When they were twisted together, I think there was ONE frequency around 500 MHz where there was -65 dB coupling. > On this same note (and knowing I'm going to stur up a hornets nest) I > strongly advise against using the LMR type cables for ANY full duplex > system. Any double sheilded cable which uses dissimular metals in the 2 > (or more) shields will eventually cause rf noise . No argument here. Bob NO6B
