I'd be a little skeptical about what's going on. Depending on the model of Duplexer and other factors. Proper troubleshooting requires the proper tools. First if the amp was rebuilt, did you check it when done with a Spectrum Analyzer to make sure it was clean and wasn't creating broadband noise or spurs. Either way that is the first thing you need to do now. Reducing from 40 to 25 watts shouldn't affect the desense in the first place...that isn't even a 3dB change in levels. I suspect you still have a problem with the amp and when it's at 40 watts you aren't as clean as you think.
You really need to get to the bottom of this....even though it appears you have temporarily cured your symptom, you didn't really resolve the problem because you still don't know what the problem was. In addition if you are spurious and reducing power helped you, who's to say that you aren't interfering with others, by having spurs or wideband noise that is reaching your antenna system. Go back with the proper test equipment and troubleshoot it and fix it proper, or hire someone who can. Gregg R. Lengling, W9DHI, Retired Administrator http://www.milwaukeehdtv.org K2/100 S#3075 KX1 S# 57 Politics is the art of appearing candid and completely open, while concealing as much as possible. -States: The Bene Gesserit View -----Original Message----- From: Tim Shephard [mailto:[EMAIL PROTECTED] Sent: Wednesday, April 21, 2004 11:45 AM To: [email protected] Subject: [Repeater-Builder] To adjust or not.... I service a public safety repeater. It's a master II. About 6-8 months ago I rebuilt the PA, replacing the two output transistors, caps, etc... I even added a couple of fans and it's been working great at around 40 watts. Lately we have been having some trouble which has been nicely termed the whale noise. After dispatch would transmit via a wire line, very infrequently we would have a noise come through or cover their transmissions. Yesterday I checked everything and found I was getting some desense, around 8db. I looked at the duplexer and it looks like it has not been touched in around 25 years. The shafts are rusty, cables look very fragile. So, I decided not to try and retune it because I feel something inside may snap and I'd be worse off then I am now. So I adjusted the transmit power down to 25 watts and no desense. We are planning to replace the radio system in the next year, so I don't' really want to invest in a new duplexer. What do you guys think? -Tim Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
