Talk:Transmission line

message: In
Z_{in}\left(l\right)=\frac{V(l)}{I(l)}=Z_0 \frac{1 + \Gamma_L e^{-2 \gamma l}}{1 - \Gamma_L e^{-2 \gamma l}}
exponent 2 is due to back and forth reflection?
— Preceding unsigned comment added by 82.56.167.93 (talk) 07:48, 4 August 2014 (UTC)
replies: text: Yes, \scriptstyle{2 l} is the distance from measurement point to the load and back again and so \scriptstyle{e^{- 2 \gamma l}} is the phase delay for the round-trip, and \scriptstyle{\Gamma_{L} e^{- 2 \gamma l}} is the voltage amplitude of the reflected wave relative to that of the incident wave. --catslash (talk) 17:52, 4 August 2014 (UTC)
thread_title:  Input impedance of transmission line 

message: In
"Since most transmission lines also have a reflected wave, the characteristic impedance is generally not the impedance that is measured on the line",
for completeness sake, shouldn't it be:
Since most transmission lines also have reflected waves and standing waves...?
I am not an expert but I am just reading here and there and it seems to me that those 2 are different phenomena:
* reflected waves are due to unmatched lines (terminations);
* standing waves may be generated by reflected waves, which thing usually happens;
don't both of them contribute to the reasons why Z_{in} \ne Z_0 ?  
This way, the reasons why Z_{in} \ne Z_L  should be
* losses due to R and G of the line that we often neglect;
* reflected waves;
* standing waves;
— Preceding unsigned comment added by 95.237.220.142 (talk) 09:22, 6 August 2014 (UTC)
replies: text: The standing wave is due to interference of the incident and reflected wave.  It is not a separate phenomenon. The input impedance is a function of distance, ZL, Z0 and γ.  The last two are functions of R and G amongst other things, but are not additional parameters needing to be taken into account—they are already included.  SpinningSpark 14:24, 6 August 2014 (UTC)
replies: text: Agree with Spinningspark: Reflected waves are the cause, standing waves are the effect. If you say that the measured impedance is affected by reflected waves, that already implicitly includes anything related to standing waves too. --Steve (talk) 14:53, 6 August 2014 (UTC)
thread_title:   Input impedance of transmission line: the reason(s) why <math>Z_{in} \ne Z_0 </math> 

message: I'm not sure that I can agree with marking this article as American English.  The relevant passage of WP:RETAIN says;
:When no English variety has been established and discussion cannot resolve the issue, the variety used in the first non-stub revision is considered the default. If no English variety was used consistently, the tie is broken by the first post-stub contributor to introduce text written in a particular English variety.
The version pointed to by user:Jc3s5h is undoubtedly a stub, being merely a semi-automated copy-paste from the glossary of Federal Standard 1037C, along with hundreds of other stubs created in the same way at that time.  The first non-stub contribution is this edit by user:Heron.  That contribution is unarguably written in British English. SpinningSpark 03:53, 12 May 2015 (UTC)
replies: text: If you wish to change it, feel free. As you know, it's not that easy to spot which is the first non-stub version to use a national variety of English, what with all the wiki markup and author names that the spell-checker doesn't recognize. Jc3s5h (talk) 17:14, 12 May 2015 (UTC)
replies: text: Thanks for replying.  I'll leave it for a day or two to see if anyone else comments. SpinningSpark 19:19, 12 May 2015 (UTC)
thread_title:  Language version 

message: The figure of the transmission line element in the section of the Telegraphers equation is wrong.
The conductance of the line is modelled as a resistance, therefore the value of the conductance should be (1/G)*dz.  — Preceding unsigned comment added by Qvandenbrande (talk • contribs) 09:48, 5 August 2016 (UTC)
replies: text: It is correct is shown.  The symbol is a resister, but the text clearly states that G is the conductance per unit length.  We can specify a resister by its resistance or its conductance, but we use the same symbol regardless of whether we are specifying resistance or conductance.  Constant314 (talk) 14:01, 5 August 2016 (UTC)
thread_title:  Telegrapher's equation: Figure transmission line element error 

message: I have just removed this addition to the article
I have a number of problems with this:
* Primarily, it is uncited, especially problematic is the numerical values of line length at which the various approximations apply.  We definitely need a reference for that.
* The parameters Y, Z Y', Z' are all undefined.
* I might have been inclined to sort out the problems with the table formatting if that was the only problem, but as it stands, I though it best to remove it from the article.
* The addition opens with "we can also model..."  The ABCD parameters are not an alternative to two-port modelling, but one specific instance of them among many.  The AD-BC=1 requirement is a statement that the network is reciprocal and the A=D requirement is a statement that the network is symmetrical.  Analogous requirements exist for other forms of two-port parameters.  The requirements for reciprocity and symmetry could be stated more generally, and more clearly, without the need to invoke ABCD parameters. SpinningSpark 11:28, 23 November 2016 (UTC)
thread_title:  ABCD parameters 

message: I've noticed that in the examples there is a "Single-wire line" subsection. It points to unbalanced line, and also discribes the line as still being a two-line TL, just with the earth (or some other external thing) as the return. I feel that this should also mention single-wire transmission lines. Although one could argue that they are not truely transmission lines as they are more similar to dielectric waveguides (at least from what I understand), they should perhaps be mentioned as many authors cover them as "SWTs" or single wire transmission lines, and a reader could thus look them up and find them here, with an incorrect discription (For that specific type). There are a couple of IEEE references that could easily be pointed to, as well as perhaps a link to the article on the Goubau line?
TheUnnamedNewbie (talk) 16:26, 30 January 2017 (UTC)
thread_title:  Single Wire Transmission line 

message: A interested layman asking.  — Preceding unsigned comment added by Koitus~nlwiki (talk • contribs) 18:21, 21 November 2018 (UTC)
replies: text: j is the imaginary unit, \omega is angular frequency, and the expression j \omega is the imaginary part of complex frequency.  You are right, the article could be a lot better at explaining its notation. --SpinningSpark 18:34, 21 November 2018 (UTC)
thread_title:  What is j? What is ɯ? The article doesn't tell me. 

message: If you fixate on the black dots, it's not so easy at first to discern the "rightward" propagation. 
It might be useful to add the explanatory gloss that each arrow's magnitude follows the magnitude of the nearest arrow to the left a short interval later in time (globally uniform as illustrated, though you can build lines where the propagation velocity varies continuously). 
Perhaps "moving rightward with uniform propagation velocity down a lossless two-wire line of uniform construction". — MaxEnt 17:40, 26 September 2020 (UTC)
replies: text: Agree. --ChetvornoTALK 18:22, 26 September 2020 (UTC)
thread_title:  Rightward ho 

message: At frequencies below about 100 kHz, the phase velocity of signals in a transmission line with loss decreases.  As a result, at low frequency, the electrical length can be significantly longer than the physical length.  Because it amuses me, I plotted out the length of a typical polyethylene insulated RG58 Coaxial cable that would equal 1/5 of a wavelength (2/5 round trip).  That is the point at which, I switch from lumped models to telegrapher's equations.  Other people made use 1/4 or 1/3.  It doesn't change the plot very mush, since it is on a log scale. So, you could run a voice line to the bottom of the deepest ocean trench without worry to much about reflections, etc., but not across Los Angeles the long way. Cheers. Constant314 (talk) 20:11, 23 November 2020 (UTC)
replies: text: Wow!  I had no idea.  So a 1 Hz sine wave only travels through a coaxial cable at a rate of about 1000 miles/sec?  It would take 3 SECONDS to travel across the United States from coast to coast.  And a 10−6 Hz sine would only travel at a rate of about 1.8 MILES PER SECOND?  Holy crap that is weird. --ChetvornoTALK 21:09, 24 November 2020 (UTC)
replies: text: In the low frequency regime velocity goes as v = \sqrt { \frac {2\omega}{RC}}     so the velocity just keeps going down as the frequency goes down until, in the case, around a few microhertz.  That is where G starts to dominate ωC. Constant314 (talk) 21:33, 24 November 2020 (UTC)
thread_title:  A comment on wavelength in transmission lines 

message: I think that the tag on the lead is appropriate.   And then we have two following sections (Overview and Applicability) which have the kind of material that is missing from the lead.   I might try to tidy up unless someone else wants to.  Sincerely, North8000 (talk) 13:08, 24 November 2020 (UTC)
thread_title: Tagged lead and related

message: I don't think this edit was vandalism.  The edit summary was "Removed duplicate section".  The material removed from the lead is an almost exact copy of the "Overview" section.  It was copied there by user:North8000 a couple of years ago who I think intended to then edit it down to a summary, but didn't actually edit out very much in the end. SpinningSpark 17:25, 17 June 2022 (UTC)
replies: text: I reverted my revert.  Still, the explanation was sparse. Constant314 (talk) 20:09, 17 June 2022 (UTC)

text: I noticed that it got re-removed. In light of the unusual structure of this article (having the "overview" section, and the rest of the article consisting of a collection of specialized information and equations) I think it's probably best that way for now. North8000 (talk) 15:10, 18 June 2022 (UTC)
thread_title:  Duplicate section in lead