Kevin, I am using your coaxial matching section on a couple of antennas with good results. Great article on RB and not too hard to build
--- In Repeater-Builder@yahoogroups.com, Kevin Custer <kug...@...> wrote: > > Russ Hines wrote: > > > > Thanks, guys, a good topic and one that always seems to come up. And > > it sparks more questions and comments, of course. > > > > The cable length issue is a brother to "if you don't like your VSWR, > > change the point along the transmission line where you're measuring > > it." By changing the length of the line, we're creating a > > transmission line transformer (a good thing) but we're limited by its > > length (not so good). It seems to me the mentioned > > circulator/isolator at the output of the xmtr is a better fix, as > > reflections coming back from the duplexer is absorbed by the > > circulator's load, the xmtr is generally happy, and we're no longer > > limited where we can put things in a rack or elsewhere. > > > > For amateurs, coming up with usable VHF circulators seems to be > > difficult and usually expensive, and coax always seems to be cheaper. > > Has anyone had luck finding a source for reasonbly priced VHF > > circulators, or success in rolling their own? > > > > Also, I noted in the pamphlet Kevin referenced that the unused > > duplexer port was left open (Figs. 1 & 2). I guess if the isolation > > is already greater than the load's return loss, it doesn't matter, at > > least at the reject frequency. But it seems to me one could possibly > > create problems for oneself by not terminating the unused open port. > > Just a thought. > > > > Maybe I work better knowing there's a load there. ;-) > > > > Your comments, please. > > > > 73, Russ WB8ZCC > > > > I think we all agree that a real impedance matching device is the best > approach, but hams (generally speaking) are cheap. Many will spend two > days hacking on a piece of RG-214 before spending fifty or a hundred > bucks on a different (better?) solution. > > Allan Crites and I are currently in discussion which will be used as the > basis of a RB web article that will explain exactly what is happening, > why it happens, and why an 'optimized' cable length can be used to > transfer power ending up with the stated loss of the duplexer and have > little reflected power toward the transmitter - so long as the duplexer > is tuned properly and exhibits good return loss on the frequency it's > designed to pass. > > Kevin Custer >
