XP OS version A.09.80.20 capable make signal of S22 from 0 to -10db by setting source attenuation.
But on Win7 Os Version A.10.xx unable set source attenuation to achieve the same signal what XP PNA made?
More than likely, the WinXP build has a user preference disabled that mathematically offset for source attenuation (Meas: Mathematical offset for source attenuation). See this link for more info on the Preferences.
I had another Old model of PNA which had same situation, now I had uncheck the (Meas: Mathematical offset for source attenuation) but causing the PNA source unlevel.
Source power setting (-17dBm)
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