On Sep 2, 2009, at 3:16 PM, tahrens301 wrote: > Don - I can put the iso-tee in line, & feed the atten port > into the spectrum analyzer. It should show me if the xmtr > is having problems. However, the current antenna is a > perfect match - no reflected power at all, so I think the > xmtr 'should' be happy.
Remember also... (just saying as a side-note, may not apply to THIS situation)... that a 50 ohm dummy load and hardline that doesn't radiate is also a "perfect match". Sometimes you need to see if the antenna is REALLY radiating as it should be. (And this is difficult, but do-able.) If it looks like it doesn't perform as well as a similar or preferably the SAME antenna type at the SAME location, that's a great way to determine that there's "something wrong" and any such antenna is suspect from then on of horrible Passive IM mixes, or other site nastiness. You mentioned swapping in a "ham quality" antenna. It's a tempting troubleshooting technique, but if there are a bunch of transmitters on that site... don't leave it that way. All those joints on those floppy hunks of junk will EVENTUALLY bite either you, or more likely, someone else in the butt with a mix, as the antenna gets old and loose RF joints become little diodes... I'm still pretty sure you're fighting an external MIX of your own transmitter with "something"... in an active component of someone else's PA, in a rusty joint of that metal building, a loose/rusty bolt on the tower... and these things are a real PITA to find in a duplexed system, especially when you have "nice" gear like the DB antenna and good feedline and really WANT to assume everything's good, before you start ripping it apart, piece by piece... only to find that you've replaced EVERYTHING and the problem still exists. I'm tellin' ya... repeaters that have problems like this, WILL make you crazy. (This list is proof positive! GRIN!) :-) Or as a good friend puts it, "Passive Intermod, the devil's snack food." -- Nate Duehr, WY0X n...@natetech.com facebook.com/denverpilot twitter.com/denverpilot
