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Is it possible to measure the velocity of propagation utilizing a Keysight Vector Network Analyzer (VNA)?

Keysight VNAs do not directly provide the velocity of propagation measurement. As an alternative, the steps below outline a method to calculate the velocity of propagation based upon the physical length of the cable under test.

  1. Perform a transmission calibration (response, enhanced response, full 2-port, etc.)
  2. Connect the cable under test between calibrated ports.
  3. Measure S21
  4. Set the display format to DELAY.
  5. Record the delay.
  6. Measure the physical length of the cable.

Calculate the velocity of propagation utilizing the equation:
Vp (m/s) = cable length (m) / delay (s)

As an alternative, the user can measure the electrical delay of the cable, enter the velocity factor of the cable, and calculate the velocity of propagation as the ratio of physical length divided by the electrical length. To measure the electrical delay, perform steps 1 thru 3 as noted above, then perform the following steps:

  1. Set the display format to PHASE
  2. Utilize the Marker Function and and MARKER > DELAY to automatically set the electrical delay via the marker.
  3. Set the velocity factor for the cable under test via the CAL menu.
  4. Measure the physical length of the cable.
  5. Display the electrical delay of the cable via the SCALE - ELECTRICAL DELAY function.
  6. The analyzer should now be displaying both the Electrical Delay and the cable length.

Calculate the velocity of propagation utilizing the equation:
Vp (m/s) = cable length (m) / delay (s)

Either method should provide similar results.

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