I thought that's what Skipp was saying but I wasn't sure. I think (without looking) the -8920 is good for 80dB.
Gonna redo the duplex test with a different iso-tee, just on the off chance that something is amiss there. Mike WM4B From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Jeff DePolo Sent: Wednesday, October 08, 2008 1:03 PM To: [email protected] Subject: RE: [Repeater-Builder] Re: Desense has me pulling my hair out! (Was DB4060 Duplexer Cables > Skipp, > > > Please explain your first statement. if I can't see it on the > spectrum analyzer, then what is it? Not to step on Skipp's toes, but I think what he was getting at is that spectrum analyzers have a limited dynamic range, probably around 80 dB. So you can only see noise/spurs down as low as 80 dB below carrier. If you crank up the gain (i.e. reduce the attenuation) on the spectrum analyzer higher, you will start to overload it with the carrier unless you have something (filter) to attenuate the transmitter carrier. It's quite easy to have low-level spurs and broadband noise that aren't immediately discernable on the spectrum analyzer, yet they're still strong enough to cause you problems at sub-microvolt receive levels. > If I lower the power enough, the desense goes away. just as > I'd expect. It's a matter of scale, after all. Does the desense "taper off" as you reduce power, or does it suddenly disappear at some power level? That can be a big clue. > 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. That's good information. As I mentioned in a previous post, I'd suggest trying duplex desense tests with a good external load rather than the one built into the 8920 just to rule that out too. --- Jeff WN3A
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