# Talk:Velocity factor

(Redirected from Talk:Wave propagation speed)

## Factor of 1000

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 144.32.126.15 (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. 12.174.19.210 (talk) 15:01, 23 February 2009 (UTC)
Oops, I have incorrectly flipped the fraction. Reverted that equation. 12.174.19.210 (talk) 15:46, 23 February 2009 (UTC)

## Merge?

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)
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 (${\displaystyle v_{\mathrm {p} }}$), 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 (${\displaystyle v_{\mathrm {p} }}$). 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:
${\displaystyle n={\frac {c}{v_{\mathrm {p} }}}}$ ${\displaystyle v_{\mathrm {p} }={\frac {1}{\sqrt {\kappa }}}\ }$

--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

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 84.197.182.66 (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)

## Ambiguity

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)

## Sources

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 88.215.113.163 (talk) 21:37, 8 March 2010 (UTC)

## Requested move to Velocity factor

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

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

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)

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 71.139.160.208 (talk) 05:56, 21 April 2016 (UTC)

## Assessment comment

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

Is the "speed at which a wavefront passes through the medium" (cited in the lede) the same as the phase velocity? 178.39.122.125 (talk) 15:32, 9 February 2017 (UTC)

## False positive source

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

## Scope

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. 13:33, 4 July 2017 (UTC)