Talk:Velocity factor

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Factor of 1000[edit]

Factor of 1000 left out. Charles Matthews 18:51, 16 Oct 2004 (UTC)

Where's the maths on this page?! —Preceding unsigned comment added by (talk) 13:51, 1 May 2008 (UTC)

The maths for this topic is known as Telegraphers equations. Added link. --Catskineater (talk) 00:46, 22 August 2008 (UTC)
The maths on the page were both confusing and incorrect. I have fixed the transmission line equation per Telegraphers equations and added a clarifying equation for non-transmission line situations. (talk) 15:01, 23 February 2009 (UTC)
Oops, I have incorrectly flipped the fraction. Reverted that equation. (talk) 15:46, 23 February 2009 (UTC)


From what I can gather, this is simply 1/refractive index. Should we merge to refractive index? Oli Filth(talk|contribs) 19:02, 27 May 2009 (UTC)

No merge, please. Similarities can be seen in vacuum or in free air, but not for instance in electrical cables. Geof (talk) 13:18, 30 May 2009 (UTC)
Why are cables a special case? They're just EM waveguides. Oli Filth(talk|contribs) 13:24, 30 May 2009 (UTC)
Yes, but there's a lot things to be said about velocity of propagations in them. Group velocity, phase velocity, etc... What needs to be include here can be debated, but its certainly a distinct topic from refractive indices. Headbomb {ταλκκοντριβς – WP Physics} 15:55, 30 May 2009 (UTC)
If this article had a wider scope, then I could agree with you. But as it stands, the examples you gave are already distinct articles, and not specific to EM in cables. This article isn't attempting to cover such a wide range of ideas, but simply the relationship between v and εr, and gives that relationship a name. This relationship is already implied by the first section of the Refractive index article. As such, I feel that the relationship between the two concepts would be made much clearer and compact if we merged the relatively trivial amount of content here into that article. Oli Filth(talk|contribs) 16:07, 30 May 2009 (UTC)
I disagree. The refractive index page does not adequately cover the topic of wave propagation speed. It lists no equations and gives no "common" velocities. An explanation of (), or propagation velocity is required for an understanding of refractive index but they are not the same. --kf4yfd (talk) 15:24, 21 August 2009 (UTC)

No Merge: Wave propagation speed is not equal to refractive index. Refractive index is simply the ratio of the speed of light divided by the propagation velocity (). Wave propagation velocity is not a very complex subject and therefore the page will never be as large as refractive index, but it is not required to be. That said, wave propagation speed could use a cleanup/rewrite.

Refractive index: Velocity of Propagation:

--kf4yfd (talk) 15:24, 21 August 2009 (UTC)

Do not merge those are simply different notions, which might cross in a few formulas, not more. Materialscientist (talk) 05:38, 30 August 2009 (UTC)

I agree that now the article title has changed, a merge may no longer be appropriate. Under its original title "Velocity of propagation" it was rather too focused on the ratio, which (AFAIK) really was refractive index under a different name. Oli Filth(talk|contribs) 10:08, 30 August 2009 (UTC)

Error in formula[edit]

It sais: where c is the speed of light, L is ... But there is no c in the formula, only C (the capacitance) —Preceding unsigned comment added by (talk) 12:30, 2 June 2009 (UTC)

That's because some anonymous dolt deleted the c without considering why it might be there, and no one caught it. I've reverted the change. 0x30114 (talk) 20:45, 27 August 2009 (UTC)


There is some ambiguity present in the current definitions of "velocity of propagation". The first definition (1/sqrt(K)) is unitless, i.e. a fraction relative to the speed of light. The second definition (1/sqrt(LC)) is an actual velocity, in m/s. Which is correct? Oli Filth(talk|contribs) 19:12, 2 June 2009 (UTC)

Well, the difference arose in the first place because of an inconsiderate anonymous edit, which I've reverted (see above section). But anyway, velocity factor seems like a much better term to me, although I don't know what's common among engineers. 0x30114 (talk) 20:48, 27 August 2009 (UTC)


I downloadad ARRL Handbook.pdf the 2010 --- i was unable to locate the Table in the file. The file is crappy so i was not able to search it, however chapter 19 begins on page 370, and does not contain such a table. The publication Year of ARRL Handbook and the page of the Table yould be great. ... or even other / better / free sources. —Preceding unsigned comment added by (talk) 21:37, 8 March 2010 (UTC)

Requested move to Velocity factor[edit]

The following discussion is an archived discussion of the proposal. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the proposal was moved. --BDD (talk) 19:03, 10 September 2013 (UTC)

Wave propagation speedVelocity factor – Title disagrees with content. The title Wave propagation speed implies a speed (distance/time), while the content mostly describes velocity factor (the ratio of propagation speed to the speed of light). Reference 2 (General Cable) does not back up the assertion in the first line that wave propagation speed and velocity of propagation are synonymous with velocity factor. It says that VoP is a measure of speed, whether stated in distance/time units or as a percentage of c. A percentage of c such as '80% of c' is still a speed, not a ratio. The other reference that I am able to check, Chambers 1991, defines VoP as a speed, not a ratio. I believe that this article should be solely about the ratio, so VoP and wave propagation speed do not belong here. The relevant policy is WP:PRECISE, because the proposed title of Velocity factor unambiguously refers to the ratio and not the speed. Heron (talk) 10:57, 2 September 2013 (UTC)

The above discussion is preserved as an archive of the proposal. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Dielectric Constant[edit]

A section of this article reads: "the dielectric constant of the material through which the signal passes". Does that wording even make sense?

From what I understand the dielectric constant is a property of the "insulation" between the conductors of a cable. And the signal isn't "passing through" the insulation. But perhaps "material" here refers to the cable or medium as a whole?

The article may be correct but I have trouble parsing that sentence. I'm just a neophyte. R4p70r (talk) 04:32, 20 November 2013 (UTC)

Velocity factor formula is incorrect[edit]

The equation VF = (LC)^0.5 is incorrect. Because L and C are inductance and capacitance of of unit length cable, the formula gives the propagation velocity in the cable. That must be divided by the velocity of light c to get the velocity factor. Thus the correct formula is VF = (LC)^-0.5 c^-1 . Can somebody fix it? I can't edit wiki equations. Rubmum (talk) 18:11, 16 February 2014 (UTC)

What about in metals?[edit]

How do you find the VF for a copper wire where the relative permittivity is infinite? So if I have a 2m 14 guage AWG wire, how do I find how fast a 60Hz signal propagates through it? Thanks (talk) 05:56, 21 April 2016 (UTC)

Assessment comment[edit]

The comment(s) below were originally left at Talk:Velocity factor/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

The wave propagation speed (or velocity of propagation by redirect) page is a good start, but lacks references. More information and a less technical introduction are needed. This page was ranked as high on the importance scale due to velocity of propagation being a core concept in amateur radio. Understanding of this concept is required in order to properly calculate the lengths of antennas and feedlines. --kf4yfd (talk) 15:00, 23 August 2009 (UTC)

Last edited at 19:03, 10 September 2013 (UTC). Substituted at 09:52, 30 April 2016 (UTC)

Phase speed[edit]

Is the "speed at which a wavefront passes through the medium" (cited in the lede) the same as the phase velocity? (talk) 15:32, 9 February 2017 (UTC)

False positive source[edit]

Shigley's Mechanical Engineering Design: Engineering, Mechanical [1] appears to be a copy of this. Widefox; talk 13:29, 4 July 2017 (UTC)


Older versions included sound waves [2] but this was partly dropped from the text. Either we want to properly discuss it (if the term is actually used with sound), or completely remove it if not. Widefox; talk 13:33, 4 July 2017 (UTC)