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VNA insertion phase measurment for cable assembly

Question asked by shan on Apr 21, 2008
Latest reply on Apr 30, 2008 by shan
Hi I m a new member. I m a testing technician and I use E8801A model Agilent PNA.
Can anyone please explain how to do the phase measurment and delay using this VNA in order to phase match cable assembly in a group of cable assemblies.

I briefly explains what I did.
1.Start Freq 360 MHz Stop 380 MHz
2.VNA was set to do S11,S21,S22, and S21 phase measurment.
3.Measurment: S21, Format: Phase, Marker 370 MHz
4.Did full 2 port Calibration and connect DUT (Cable).
5.Displayed SAW tooth form graph.
6.On electrical delay menu following settings were displayed
    Delay =0ns
    Velocity factor = 1 (actual cable has VF 0.77)
    Cuttoff frequecy 450000Hz
    Coax was ticked
    Wave guide was unticked
7.Phase offset menu setting: 0

8. selected marker function menu and select delay.
9. A flat line was now oberserved with phase value in degrees. What will  be the explanation of this value oberserved. Why it changes every time I select marker function menu and press delay tab.

9. Now electrical delay menu displayed 6.5ns.

How do I use or interpret this graph to phase match cable assemblies to each other within +/-2.5 degress.
Looking forward to anyone's  reply with detailed explanation
Thanking you