> 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
