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

Velocity Factor

  1. Sep 4, 2004 #1
    is the Velocity Factor is a factor to caculate the length wave(gama) or its only connected to the type of the cabe
     
  2. jcsd
  3. Sep 4, 2004 #2

    Integral

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Could you try rephrasing the question? Perhaps there are others on the board who speak your native language who will help you translate.
     
  4. Sep 4, 2004 #3
    I just want to know the meaning of Velocity Factor and if it influence the calculation of the length wave? :uhh:
     
  5. Sep 4, 2004 #4

    jcsd

    User Avatar
    Science Advisor
    Gold Member


    Your going to have to be alot clearer and give the context as what you are using is from what I gather the 'velocity factor' is engineering terminlogy referring to the speed of propagation of a signal as a fraction of c, though I could be wrong (and I think you mean wavelength not 'length wave').
     
  6. Sep 4, 2004 #5
    do you know if it influence the wavelength? :confused:
     
  7. Sep 4, 2004 #6

    Tide

    User Avatar
    Science Advisor
    Homework Helper

    Yes, the relative speed of the source and the detector influences the observed wavelength.
     
  8. Sep 4, 2004 #7
    what is formula to calculate the wavelength if Velocity Factor is 0.66
    and Er=1.2 for example
     
  9. Sep 4, 2004 #8

    jcsd

    User Avatar
    Science Advisor
    Gold Member

    ou have to be clearer 'cos I'm not exactly sure what you're talking about: what exactly are we delaing with? are we dealing with an electrical signal through a wire?
     
  10. Sep 4, 2004 #9
    yes! electrical signal through a wire
     
  11. Sep 4, 2004 #10

    jcsd

    User Avatar
    Science Advisor
    Gold Member

    You'd do a lot, lot better to post this on the engineering forum, but:

    wavelength = velocity factor*(the speed of light in a vacuum/frequency)
     
  12. Sep 4, 2004 #11
    where do you take under consideration the Er ?
     
  13. Sep 4, 2004 #12

    jcsd

    User Avatar
    Science Advisor
    Gold Member

    What is 'Er'?
     
  14. Sep 4, 2004 #13
    Code (Text):
    [tex]\epsilon_r[/tex]
    dialectrical coefficient
     
  15. Sep 4, 2004 #14

    jcsd

    User Avatar
    Science Advisor
    Gold Member

    I'll have to say I don't know how you'd go about calcualting or even if you can calculate it from the velcoity factor and the dialectric cooefficient ,though I think your not after the wavelength but the reflection coefficient.
     
  16. Sep 4, 2004 #15

    Tide

    User Avatar
    Science Advisor
    Homework Helper

    [tex]\lambda_{observed} = \lambda_{source} \sqrt { \frac {1-\frac {v}{c}}{1+\frac {v}{c}}[/tex]
     
  17. Sep 5, 2004 #16
    why you don't take under consideration [tex]\epsilon_r[/tex]
    the dialectrical element
     
  18. Sep 5, 2004 #17

    Tide

    User Avatar
    Science Advisor
    Homework Helper

    Because I don't fully understand your question. If you are talking about a transmitter and a receiver that are in relative motion with respect to each other then I presume the signal is propagating through empty space or possibly air whose dielectric constant is very close to 1. It doesn't make sense to me that one end of a cable would be moving relative to the other if that's the medium you are talking about.
     
  19. Sep 5, 2004 #18

    pervect

    User Avatar
    Staff Emeritus
    Science Advisor

    I think he's talking about the velocity of signal transmission along a coaxial cable, or possibly a transmission line.

    as in for instance

    http://www.nr6ca.org/vf.html

    If so, the velocity factor should be approximately c/sqrt(Er), where Er is the permitivity of the dielectric material relative to the permitivitty of free space.
     
  20. Sep 5, 2004 #19

    Tide

    User Avatar
    Science Advisor
    Homework Helper

    Oh, okay! I've never heard it called a "velocity factor."
     
  21. Sep 5, 2004 #20
    how come if Er=1.24 put it in the formula c/sqrt(Er) it never will be vf=0.666 for example :confused:
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?