Ya you should be able to trim your coax so the transmitter "sees" 50 ohms, which should be every 1/2 wave. All this does it protect the transmitter, the standing waves are still there, they just gets dissipated/radiated by the coax.
Also with cans usually, if I have enough time on my hands, I tune them one way (higher frequency = cans marked TX), then the other (lower frequency = cans marked TX). Almost every time you'll get a different outcome. Which way you tune them in the end depends on your situation, weather your putting out lots of TX power and need the isolation, or if you care about receive sensitivity. I find that usually one side of the duplexer will have a better insertion loss than the other, while the other will have better null than the other. The one with better insertion loss I usually put on the RX side (I can simply bump the TX power by a dB to compensate for the extra loss). This of course only applies to cans where you can not set the insertion loss. For cans that you can change the insertion loss you can spend hours on fiddleing. If you take your transmitter and put it into a dummy load what's its TX power? Also no one mentioned this (I think), but check you cables and connectors, I had one that was bad, produced a bunch of swr, cans were fine. Jesse On 8/25/07, Ralph Mowery <[EMAIL PROTECTED]> wrote: > > > --- Jeff DePolo <[EMAIL PROTECTED] <jeff%40depolo.net>> wrote: > > > > When you put the Bird between the TX and the > > duplexer, you > > > have changed the > > > length of the jumper cable, which upset the > > tuning. > > > > Adding a wattmeter or any other length of cable > > between the transmitter and > > the duplexer Tx input port has no effect on the > > tuning of the duplexer. It > > may change the load Z the transmitter sees, which > > may make the transmitter > > happier (or sadder) depending on the resulting Z, > > but in no way does it > > alter the tuning of the duplexer itself. > > > > Adding or removing cable lengths between the > > transmitter and duplexer also > > does not change the VSWR as seen by the transmitter > > (minimal cable loss > > effects notwithstanding). > > > > --- Jeff > > > Jeff you have just made two statements that are the > exect opposit of each other. If changing the length > of cable makes a differance, then the swr as seen by > the transmitter must change. > > As some transmitters can not be tuned for impedance > mismatch, adding lengths of line may change the > impedance where the transmitter will produce the > maximan ammout of power out. > > If say the duplexer is setup for a 50 ohm load and the > transmitter wants to load into a 60 ohm load, then > changing the length of cable between the duplexer and > transmitter may let the transmitter see 60 ohms > instead of 50 ohms. The swr will not really change on > the line as a whole, but at a given point it may match > the impedance of the transmitter for maximum power > transfer. > > __________________________________________________________ > Moody friends. Drama queens. Your life? Nope! - their life, your story. > Play Sims Stories at Yahoo! Games. > http://sims.yahoo.com/ > >
