Velocity Factor

1. Sep 4, 2004

edieber

is the Velocity Factor is a factor to caculate the length wave(gama) or its only connected to the type of the cabe

2. Sep 4, 2004

Integral

Staff Emeritus
Could you try rephrasing the question? Perhaps there are others on the board who speak your native language who will help you translate.

3. Sep 4, 2004

edieber

I just want to know the meaning of Velocity Factor and if it influence the calculation of the length wave? :uhh:

4. Sep 4, 2004

jcsd

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').

5. Sep 4, 2004

edieber

do you know if it influence the wavelength?

6. Sep 4, 2004

Tide

Yes, the relative speed of the source and the detector influences the observed wavelength.

7. Sep 4, 2004

edieber

what is formula to calculate the wavelength if Velocity Factor is 0.66
and Er=1.2 for example

8. Sep 4, 2004

jcsd

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?

9. Sep 4, 2004

edieber

yes! electrical signal through a wire

10. Sep 4, 2004

jcsd

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)

11. Sep 4, 2004

edieber

where do you take under consideration the Er ?

12. Sep 4, 2004

jcsd

What is 'Er'?

13. Sep 4, 2004

edieber

Code (Text):
$$\epsilon_r$$
dialectrical coefficient

14. Sep 4, 2004

jcsd

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.

15. Sep 4, 2004

Tide

$$\lambda_{observed} = \lambda_{source} \sqrt { \frac {1-\frac {v}{c}}{1+\frac {v}{c}}$$

16. Sep 5, 2004

edieber

why you don't take under consideration $$\epsilon_r$$
the dialectrical element

17. Sep 5, 2004

Tide

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.

18. Sep 5, 2004

pervect

Staff Emeritus
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 [Broken]

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.

Last edited by a moderator: May 1, 2017
19. Sep 5, 2004

Tide

Oh, okay! I've never heard it called a "velocity factor."

Last edited by a moderator: May 1, 2017
20. Sep 5, 2004

edieber

how come if Er=1.24 put it in the formula c/sqrt(Er) it never will be vf=0.666 for example

Last edited by a moderator: May 1, 2017