Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Propagation velocity through coax's with different velocity factors?

  1. Mar 10, 2014 #1
    Hi everyone,

    I have been studying transmission lines and it got me thinking.

    If we have a series circuit which has two equal length transmission lines with the same Zo but with different velocity factors how does this effect the wave velocity through the circuit?

    Do the waves travel faster through one line and then slow down and bunch up in the other?

    Does the mismatch in velocity factor produce reflections even through the Zo and length of each line is identical?
  2. jcsd
  3. Mar 10, 2014 #2


    User Avatar
    Science Advisor

    The reflections on a line are due to changes in line impedance.
    There is no reflection at a change in velocity factor unless there is also a change in impedance.
  4. Mar 11, 2014 #3


    User Avatar
    Gold Member

    When velocity factor changes, wavelength changes so there is no bunching.
  5. Mar 11, 2014 #4


    User Avatar
    Science Advisor

    The constant here is the period, frequency or pulse repetition rate.

    There is a good analogy with traffic on a road that has an increase in speed limit.
    The vehicles are further apart, but they still have the same time period between vehicles and the same number of vehicles per hour.

    The length of the road or transmission line is not important.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook