Skipp,
Doing that produces some interesting noises in the receiver. It will go from full-quieting to complete garbage without much movement. Tapping, beating, and banging seem to have little to no effect. I think I'm going to tear them down again and reclean all the mating surfaces. I MUST have missed something. 73, Mike From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of skipp025 Sent: Tuesday, October 07, 2008 11:57 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables Something I would try, which I would not recommend to others is to rotate the tuning plungers and maybe the cap(s) with the unit under power making trouble. I have used this method to find grunge makers, which turned out to be plunger pitting, capacitor problems and hydroscopic sourced breakdowns. If you try the above, reduce the tx power to the min you need to confirm grunge/desense and keep your tx keydown times to a minimum value. Don't try the above unless you're sure or willing to trust the RF PA final is a fairly rugged beast/circuit/device. I'm willing to take the mentioned test gamble in 99.5% of the more common situations. If you are smart, quick and careful... you might be able to catch the source of trouble if it has a mechanical contribution. s. > "Mike Besemer \(WM4B\)" <[EMAIL PROTECTED]> wrote: > 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:Repeater-Builder%40yahoogroups.com> > [mailto:Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> ] On Behalf Of skipp025 > Sent: Tuesday, October 07, 2008 5:49 PM > To: Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.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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