When You say you're hearing a "buzz" in the background indicates to me either severe line noise or, more likely, TV video from some high power station TV transmitter. Try a substitute simple home made ground plane antenna to rule out intermod generated from the antenna. If noise is still present, you probably have to add a bandpass cavity between your receiver and the duplexer Rx port to kill out of band strong signals. Most duplexers don't have good out of band rejection curves, usually only down -20 to -30 dB. Next thing to add would be a circulator between your TX output and the duplexer Tx port. I know these will add $$$ to your project, but in today's high noise RF environments, they are almost always a necessity. YMMV.
73's, George --- In Repeater-Builder@yahoogroups.com, [EMAIL PROTECTED] wrote: > > At 10/3/2008 00:10, you wrote: > >Here is the latest. I terminated the cable at the antenna with a dummy > >load and no desense. I hooked back up to the antenna and if listen to the > >receiver with the squelch > >open I hear a buzz in the background of the receiver white noise audio in > >addition to desense which doesn't show up when terminated. > > Sounds like you probably have a mix that's external to your hardware, but > still possible that the mix is occurring within the shielding of the LMR-400. > > Bob NO6B >
