Martin, The other 40dB is hiding in the lower regions of the sweep. I'll try to describe what to do from memory but I may be a bit off target. The bottom of the sweep should look a bit wide and ragged, not a smooth line. Drop the Reference level down to -40 or -50. You should now see the bottom of the sweep and see a smooth, well defined line on the trace.
Milt N3LTQ Quoting cruizzer77 <[email protected]>: > > > Thanks guys I'll have another go tomorrow (it's 0.30 a.m. in my place now). > > Concerning the isolation question I was obviously wrong, I came up > with the idea because the duplexer is a commercial tetra duplexer of > which I had the factory test certificate filed and only remembered > something like 80 dB. So I hooked it up (in factory condition) and > only got 40 dB difference between the high point of the curve to the > low when I looked at it in the spectrum analyzer with the tracking > generator on (same value on both legs). My first calculation was 40 > + 40... In the meantime I dug out that spec sheet and indeed there > are values of > > Rejection (Ant - RX Port) : -80 dB > Rejection (Ant - TX Port) : -80 dB > > Now what am I doing wrong in this case? Somewhere there are missing > 40 dB each... I have to admit that I don't have double-shielded > cables available at the moment, first need to get some, but that > can't make such a difference can it? > > 73 > Martin > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > >
