The problem occurs into both the antenna system and the -8920 with two totally different repeaters. There is no external PA. I've already said that the duplexers are bad. they're the only common component. This is all basic troubleshooting!
Mike WM4B From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of skipp025 Sent: Tuesday, October 07, 2008 5:49 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables > Please explain your first statement. if I can't see it > on the spectrum analyzer, then what is it? Don't know until you nail down the exact cause, which a service monitor might not always clearly indicate, regardless of type and how you use it. > No circulator/isolator in line during test. VSWR is > indetectable between the TX and the cans. Doesn't matter... I've seen and found gremlin generation in well matched cavity and combiner systems. Especially High-Q cavities (most the larger diameter types). Telewave 8 and especially 10 inch cavities seem to be more often prone to gremlin issues when used in tx combiner and antenna systems. Other brands and cavity sizes can also crap up a system when there's a reason or cause. > If I lower the power enough, the desense goes away. just > as I'd expect. It's a matter of scale, after all. I would point an evil eye toward the duplexer, antenna feedline and the antenna. The obvious trick would be to swap out one or more of the mentioned until the problem goes away. > By the way. the symptoms are both the same with 2 separate > repeaters (I amended my first post to say that), so unless > they both have the same problems, the issue is not the with TX. Are you using the same power amplifier with both repeaters? A Circulator might help you quickly locate and/or fix the problem. Type of duplexer, power amplifier, feed-line and antenna you're using? s.
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