Talk:Coaxial cable/Archive 1

Archive 1

questions

From what I remember, there is a SiO2 material used within some coaxial cables which tend to make users find a way to curl the coaxial cable in a loop before going around wall corners. Could someone add discussion on this? --Cyberman 07:18, 11 July 2005 (UTC)

Plain coaxial cables are also used quite everyqhere carrying small audio signals both between devices and inside devices. Practically all instruments, microphones and PA systems using electronic amplification use coaxial cables everywhere. Even computer CD drives' audio connect and headphones have coaxial cables,

This seems to me to be the most common use and one which the article is practically leaving out entirely, speaking mostly about rf and other hf signals!

• The wire you are talking about is single-conductor shielded cable, not coax. Coaxial cable has a dialectric suited to low loss at high frequencies, a specfied characteristic impedence, and so on, and can be used for transmition-lines. While coax could be used for audio, the single shielded cable will be smaller, more flexable. But yes, there should be a link out to shielded cable and some detail there. Meggar 20:18, 2005 Jun 5 (UTC)

• Sharp turns are bad for any low loss cable (fiber, coax, whatever). Usually sensitive cables have a rated bending radius. If a cable has to make a 90 degree turn, that turn must not exceed the bending radius. This is especially true for very stiff cable. Sometimes to prevent damage, rather than make a 90 degree turn, they will make a 270 degree turn in the opposite direction, forming a loop with a radius larger than the cable's minimum bending radius. Perhaps this is what you saw. --ssd 16:11, 28 December 2005 (UTC)

Coax use in Amateur radio

A bit of detail probably too much for the article... I changed the coax use table to indicate that amateur radio uses RG-58 and RG-8 (and ladder line). Actually, amateur radio probably uses every variety of coax made, including ones not specificially mentioned in this article for various special purposes. However, normal connections between typical manufactured amateur radios and typical antennas uses 50 ohm coax. Most television applications use 75 ohm or 300 ohm cable, meaning RG-59 (most common), RG-6 (rarely, possibly long antenan runs), and twin-lead (usually in short runs from inside antennas). Cable mismatches can cause impedance mismatches; in a TV picture, this might be seen as a ghost image. In a radio transmitter, this would cause bad SWR. --ssd 21:21, 28 December 2005 (UTC)

I don't see the need to list those used by amateur radio. Why not list them used for TV, ECG machines, MRI scanners, satellites etc? I'm a ham myself, but I don't see why there needs to be section on what types of cable hams use. I'd suggest such information might be more appropriate in the entry for amateur radio. Drkirkby (talk)

Text flow

"Signal propagation in coaxial cable" had the best text flow, while a lot of the other sections feel like fact accumulation. So I added stuff there. Maybe we could reorder like this: Hardcore signal propagation: TEM. Softcore: Losses, capacitance, leakage and what to do about it (so that the facts do not hang in the air). Sorry for not using preview enough.

Thank you for error correction. But the dielectric has somewhere to be air. At least a small seam.--Arnero 20:21, 20 January 2006 (UTC)

Differences in coaxial cables

For example, RG-223 and RG-58 are both 50 ohm coaxial cables (see http://www.scanlancables.com/Coaxial%20Cables/RG%20Coaxial%20Cables.htm) so are there any physical differences?

One semantic difference appears to be the military specification: M17/28-RG058 fo RG-58 vs. M17/167-00001 for RG-223. Does this imply an actual physical difference? I am asking because a machine I am using came with RG-223 cables which I lost and I recently bought RG-58 cables from RadioShack to replace them.

According to http://www.colemancable.com, RG-223 has a double braided shield, thicker inner conductor and lower loss than RG-58. The difference would only be noticeable if you were using a very long cable run. --Heron 21:11, 14 March 2006 (UTC)

Coaxial v.s. Component/SVideo/Composite

So as I understand it, coaxial cables are used for RF signals; for things like, say, Direct TV; where you use to connect the satelite signal to a direct tv-receiver? I was wondering if coaxial cables could also be used in place of video-cables like Composite, S-Video, or Component cables; if they yield better quallity? Also, could you use those video-cables (s-video or component) in place of the coaxial cables; if that yields better quality? I ask this question because I've read that in terms of video quality; the component is best, then S-Video, then Composite, and finally, Coaxial. But I've also heard that Coaxial cables are not to be used for video, but rather only for RF signals; that it shouldn't be grouped together with the other cables. So which is it? Can Coaxial be grouped in with the rest of the video cables; and is it in fact the worst; and if these are both true, can the coaxial cable be used in place of cables like s-video or component, or vise-versa? —The preceding unsigned comment was added by 67.164.209.137 (talk • contribs) .

Video cable is 75 Ohm coax. Does this answer some of those questions? [1] Meggar 04:35, 23 May 2006 (UTC)

To put a finer point on it, "coaxial" is simply a way of designing your cable; basically, it means that the round signal conductor shares its center with the round shielding/return conductor; they share an axis so they are "Co-axial". And yes, essentially all video cables are designed as 75-ohm coaxial cables, even if they're not one of the standard "RG-xx" registered designs such as RG-59 or RG-6. S-video cables contain two 75-ohm coax cables: one for the luminance (brightness) signal and one for the chrom (color) signal. RF cables (with those screw-on F connectors on them) are a single 75-ohm coaxial cables.

Atlant 12:17, 23 May 2006 (UTC)

To regroup your "types" (someone correct me if I count wrong)... component uses 3 (or 4?) coax cables. S-Video uses two. Composite uses one. The remaning way to transmit video is as RF modulated to channel 3 or 4 over a coax. --ssd 12:52, 23 May 2006 (UTC)

Well, you can transmit modulated video on a wide variety of channels, not just #3 or #4, but that's a nit. ;-) "Component video" can use 3, 4, or 5 coaxial channels, depending on which encoding style we're talking about. The kind that comes out of a DVD player uses three channels (YCbCr), SCART uses 4 channels (RGB+Sync) (plus 2 for S-video as well!), and computer monitors use 5 channels (RGB, H- and V-sync).

Atlant 13:12, 23 May 2006 (UTC)

Perspective needed?

While it may be technically excellent, I would argue that this article fails to convey the true significance of coax cable. It is one of the fundamental electronic technologies of the modern age--the original fat pipe. Entire industries were built on it. Doesn't this article need a piece about the historical significance of coax cable that makes this clear? —The preceding unsigned comment was added by 68.33.60.226 (talk • contribs) .

Our anonymous critic is right; the article is biased towards utilities including telephone companies that used to run co-ax across continents, and towards Ethernet in offices that have since given up that practice. It pays little attention to local CATV companies running millions of miles of local cable, and to millions of little cables connecting VCRs and other home and industrial equipment. I just now corrected this bias slightly, in the "uses" section. Perhaps the intro to the article should mention some of these uses, but it is already an excessively long intro and other matter would have to be demoted into the various sections.

As for expanding the timeline into a proper history including Heaviside and other theoretical contributors, well, who wants to do the writing? Jim.henderson 03:24, 5 November 2006 (UTC)

Knowing little about coaxial cable and the like, my opinion may not be terribly valuable, but I have to agree with the above statements. This article could be made a bit more user-friendly, taking into account the bulk of the technology's use, in home electronics installations. Links on how to connect consumer equipment, cable boxes, tivos, etc., will seem pedestrian to the technical-minded, but may not be out of place here.

With all that aside, the one thing that prompted me to make my first contribution to wikipedia was the reference to coax's first televisual use at the 1934 Berlin olympics, an event which definitely did not occur. The olympics were held in Berlin in 1936, with no events taking place in 1934, as the games had not yet been divided into summer and winter sessions. I cannot comment on coaxial cable's role in the event.

Once I take the time to register, I will probably be known as Anachrophile, though not necessarily. Thanks for indulging me, and my apologies if my formatting creates a great mess. —The preceding unsigned comment was added by 24.63.0.53 (talk) 04:51, 18 December 2006 (UTC).

vertical and horizontal

i cant transfer a v and h signal at the same time on this cable>>> is there something wrong with "me" or with the cable? —The preceding unsigned comment was added by 63.243.163.202 (talk) 17:58, 6 March 2007 (UTC).

10Base5 is not RG-anything

Ethernet 10BASE5 cable looks a bit like RG-8 (not RG-8X as the 10BASE5 article currently says) but it is not. It's not PE dielectric, the shield is different, the velocity factor is different. It's about the same outer diameter, that's really about it. Paul Koning 01:13, 14 April 2007 (UTC)

10BASE2 I think can be RG58 but not necessarily (and often is PTFE instead). Paul Koning 14:35, 14 April 2007 (UTC)

Yes, 10base2 was commonly RG58 anywhere fire-resistance wasn't an issue (like in our offices).

Atlant 20:10, 14 April 2007 (UTC)

Typo in specs table

Specs table lists RG174/U as having both dielectric and external diameter as 0.1 inch. Self evident typo, Belded specs center conductor 0.018 inch (0.46mm) diameter, center dielectric 0.061 inch (1.55mm) diameter, overall outer 0.110 inch (2.79mm) diameter. Zeeglen 18:05, 13 May 2007 (UTC)

RG

Is it "radio grade" or "radio guide" or just a two letter designation that doesn't stand for anything? The article says "radio grade", the disambiguation page for RG says "radio guide" and the ITT Reference Manual for Radio Engineers just shows it as a two letter code. Paul Koning 14:36, 14 April 2007 (UTC)

I suspect that that's an after the fact construction. It's all part of the JETDS thing. You have several unit indicators that are radio related that use G as the second character: CG and RG for cables, SG for signal generator, UG for RF connectors(including waveguide flanges). CG, RG, and UG have all been discontinued. The only other xGs are PG for pigeon related articles, and TG for "positioning device" Jim Lux 137.79.6.96 23:42, 14 June 2007 (UTC)

Sounds right. So I removed the "radio guide" thing. Paul Koning 00:10, 15 June 2007 (UTC)

Patent 514,167

I took out the picture taken from that patent because it doesn't show a standard coax cable. The cable has an interrupted shield rather than a continuous shield, and the shield isn't grounded.

Reading the patent (by Tesla) is interesting. It specifically argues that a coax cable is a bad thing due to cable losses, and it says that it is important to have a shield broken into segments shorter than the wavelength (which is incorrect).

So while it's a historical curiosity, it's not a good illustration for this article (except, perhaps, as an example of how early students of the subject got all confused).

Paul Koning (talk) 21:29, 23 January 2008 (UTC)

Balun

05:35, 13 May 2007 Meggar (Talk | contribs) (24,202 bytes) (balanced lines and twisted pairs out, coax article)

I have the feeling that the text not clearly shows that a lot of coax cables are far from ideal (ok 80 dB in some freuquencies are already quite good). Baluns are not needed for ideal coax cables, but then why are we talking about losses, ideal cables have none. I have the feeling, that removing the balun link increases the confusion around the topic: Leakage.

And I have the feeling that Meggar does not understand leakage, otherwise hesheit would have added some alternative text or edited the balanced pair intro of the paragraph. Arnero 10:10, 13 May 2007 (UTC)

Yes. The deleted text went too far into ideas such as shielded balanced pair, but there should be references to alternatives and conversnions. Coax is not an island unto itself; it lives in a world. Jim.henderson 15:05, 13 May 2007 (UTC)

I couldn't find the deleted text, but I added a section back in, that I hope is the right balance between too much detail and nothing. Oh, also, the above is wrong. Baluns have nothing to do with ideal or non-ideal coax. It has to do with coupling between the coax shield and something else outside the coax. It doesn't matter how ideal your coax is, you still might need a balun. (Although some coax might have a built in balun of sorts.) --ssd (talk) 06:58, 24 June 2008 (UTC)

Leakage section is difficult to read

I came to this page to understand more about the leakage phenomenon, but I found this section very difficult to understand. While I appreciate the author´s efforts, it comes across as being written as a non native English speaker, perhaps even a computer translation from a foreign language. I have an engineering background, so it´s not just the tech terminology or concepts. --83.191.22.137 08:03, 8 June 2007 (UTC)

I did what I could to clean up the section, though my knowledge is more from practice than theoretical, so I was forced to leave in parts that are not obvious to me. It still needs work in the more advanced bits. Courtarro 22:37, 22 July 2007 (UTC)

"Leakage is the passage of electromagnetic fields through the shield of the cable." I don't think so.. Leakage is the passage of electromagnetic fields "TO" the shield of the cable. It's the dielectric that makes coax lossy. That is why air dielectric coaxes have the least amount of loss. The absolute worst is hard urethane, better is polyurethane foam, air is best as far as practical home use goes. Many commercial applications use air dielectric hardline charge with gases such as Hydrogen, Nitrogen or Helium. Gases do 3 things; help dry up any condensation, minimize arc-over and improve the dielectric properties. It's not 100% Shield, 1/2" Hardline is 100% shield and it's only a touch better than #9913 @100 feet. I've seen Mil-Spec coax with 2 shields and a mylar foil wrap that aren't any better then a good chunk of Belden #9913 or Pro-Flex both of which are air dielectric. Before I go editing I'm going to do some research on it. (I could be wrong and I won't say it never happens) But it does make sense otherwise Balanced line losses wouldn't be so low (air dielectric).. You might think thats bubkiss because balanced line is not shielded. Well, that's just the way it is. Coax which is unbalanced is lossier than ladder line which is balanced. Let me look into this subject a little and if I can find some creditable information to better explain it I'll add it. BTW I don't use coax below 30Mhz.. All my HF antennas at home are 450 ohm ladder line. I've even used 75Ohm twin lead coax using both the center conductors and grounding the shield. It works quite well also. Oh, --Dp67 | QSO | Sandbox | UBX's 21:16, 28 September 2007 (UTC)

Oh, forgot to mention.. A true balanced antenna and balanced feedline is not grounded.. Unlike coax which is grounded. --Dp67 | QSO | Sandbox | UBX's 21:20, 28 September 2007 (UTC)

The statement "Leakage is the passage of electromagnetic fields through the shield of the cable." is correct. The dielectric losses you're talking about are dissipative losses. Leakage is a radiative loss, and refers to the fact that imperfect shields cannot prevent some of the RF energy inside the cable from radiating into space, nor can they completely prevent RF outside from getting in. Thus the first paragraph appears correct to me. The rest of it could use some work, though. For example, the second paragraph talks as if gaps in the shield were the only mechanism for leakage. That ignores the role of skin effect and skin depth, which is what the first paragraph is really about. Palmpilot900 (talk) 03:02, 15 February 2008 (UTC)

I have fixed a lot of the leakage section, but the intro paragraph is still wordy, awkward, and overdetailed. Perhaps someone braver than I can delete more of it.  :) --ssd (talk) 07:01, 24 June 2008 (UTC)

Article is still not accessible to novices

This article may be technically correct, but it wasn't of much use to me as an a complete novice, because it assumes the reader understands basic concepts, such as data transmission. In this case, I understand that electricity requires 2 wires for a circuit : e.g. 2 wires go from the plug to my kettle, inside a rubber sheath, and the article states that coaxial cable is an electrical cable. I can see a central core and and outer shield in the diagram. The text states data is transmitted along the central core. So is data transmisison not like an electric circuit, does it only require a single wire ? Is the function of the outer shield purely to prevent interference or does it provide the the equivalent of the second wire ? These issues need to be adressed, as Wikipedia should be accessible to novices - experts don't need it. So please explain terms and concepts in language accesible to somebody with common sense but little training in the area. Dumb it down while retaining accuracy. Rcbutcher (talk) 17:42, 22 May 2008 (UTC)

There is already early on a link to the transmission line article, which explains what the crucial difference between a HF signaling cable and a cable for powering a kettle is. May be that should be made even more prominent. Wikipedia is aimed at people who know how to follow links and therefore do not need to repeat introductory basics in each article. Markus Kuhn (talk) 13:42, 23 May 2008 (UTC)

Believe me, I'm not mentally lazy and I knpw how to follow links, but I couldn't figure out what the relationship was between the central core and the outer braid (e.g. similar to 2 power wires, or totally different, with the braid purely an insulator), or whether all the action concerned the central core only. If only the central core was functional, how does only 1 wire get the job done, where is the earth ? Perhaps a small amount of basics does need to be repeated explicitly in potentially complex articles - what is a no-brainer to some can be a brain-breaker to others. Clicking to go to another page to get necessary prequisite information is a negative as one starts feeling lost. This is intended as helpul feedback rather than criticism. Rcbutcher (talk) 14:18, 23 May 2008 (UTC)

I agree with Rcbutcher, the article could use a little more elementary explanation. Kuhn, WP articles are also supposed to stand on their own. There are a lot of complaints that WP is too specialized and inaccessible. Although the subject here is inherently tech, the wide use of coax in home cable TV and networking means nontechnical people want to know about it. I think the article could back off and include a brief elementary explanation of the operation, covering the points Rcbutcher mentioned. This would be useful and of interest to a much larger number of readers than the technical details, which have a limited audience. Thanks for the courteous feedback, Rcbutcher. --Chetvorno^TALK 00:27, 6 March 2009 (UTC)

Added 'How it works' section to provide an elementary explanation. --Chetvorno^TALK 17:41, 8 March 2009 (UTC)

Merge/Link to page "Ethernet over coax"?

I think Ethernet over coax should be either merged or at least linked, not sure… ycc2106 (talk) 13:08, 10 June 2009 (UTC)

Hi Cy21. I oppose a merge. The original article (EoC) needs a lot of tidying up. If the tidied up version is much shorter, it may have a place here, but coax is important in it's own right. In many ways EoC is a slightly unusual use of coax (the information is digital, packeted, etc - c.f. connecting an antenna to a transmitter). It's not immediately obvious why ethernet traffic should be carried over coax. In it's current state, I think EoC would slightly overwhelm this page, confusing the main topic. But adding a link is definitely a good idea. GyroMagician (talk) 20:59, 10 June 2009 (UTC)

Illustrations

I changed the main illustration in the introduction to the photograph of a piece of RG59 (previously located further down the article). I think it is much clearer to see a photo of a real piece of coax than a computer model. I also didn't really see the need for the URL on cable master's picture. GyroMagician (talk) 18:02, 14 June 2009 (UTC)

I have removed the CG coax cable illustration again. It adds nothing to the page except promoting a URL. I assume this is Cable master again - I notice he tried the same thing on the Optical fibre page. GyroMagician (talk) 19:19, 16 June 2009 (UTC)

Reverted spam image again. If the image adds something to the article, please explain what it adds here. If the URL was removed, the case to include it would be stronger. GyroMagician (talk) 11:31, 22 June 2009 (UTC)

COAX IS WAVEGUIDE??

I didnt know that all coaxial cables were waveguides. If they were they would have almost zero loss and they dont! Light current 04:34, 12 August 2005 (UTC)

Coaxial cables are not waveguides, although not for the reason that you give. The Penguin Dictionary of Electronics says that waveguides can be filled with dielectric, which presumably will make them lossy. You can also have air-filled coax, which is almost as lossless as a waveguide.

The true difference between coax and waveguides is that, in coax, the E and M fields are both perpendicular to the direction of propagation (called the transverse electric and magnetic or TEM mode), while in a waveguide only one of the fields is perpendicular to the d.o.p. while the other has a component which is tangential to it (called the TE or TM modes, depending on which field is transverse). The practical difference between the two types of transmission line is that coax can transmit DC, whereas waveguides are useless below their cutoff frequency. See this reference. --Heron 19:35, 12 August 2005 (UTC)

No, the point I was trying to make is that above a certain frequency a coax cable will become a waveguide with very low losses, but below the waveguide cutoff freq., it will revert to lossy old coax again. Is this correct??Light current 21:01, 12 August 2005 (UTC)

"...above a certain frequency a coax will become a waveguide" - true. I added this statement to the article yesterday. "...with very low losses" - not sure about this. This article (search for "screw up your loss") says that engineers usually try to avoid inducing high-order modes in coax because this makes the losses higher, not lower. However, I can't find much information about the relative losses in TEM and waveguide modes. --Heron 16:15, 13 August 2005 (UTC)

This is actually true; above a certain frequency, a coax will become a waveguide. But Heron's second point is also true; no engineer ever wants to operate a coax in this mode because what you likely have are several modes propagating together, and they may not have the same velocity of propagation, leading to interesting distortions of the signal. But it is for this reason (the coax shifting to being a waveguide as the frequency increases) that high frequencies demand coaxial cables with extremely small diameters; you want the cable to be a waveguide far "beyond cutoff" so waveguided modes won't propagate in your coax.

Atlant 12:22, 23 May 2006 (UTC)

This is a semantic issue. By the most general definition, a coaxial (or triaxial, etc.) transmission line is a waveguide. See Waveguide (electromagnetism). But it seems to be more common to talk about waveguides as hollow structures. Technically, as Heron says above, coaxial cable is a waveguide that supports the TEM00 mode of propagation, which has no critical frequency -- it works at DC. Obviously, coax is not hollow, so if that's your definition, coax is not a waveguide. It is important to note that hollow waveguide is not loss-free. The same factors that give loss in coax, do so in waveguide: resistivity of the conductors and dielectric loss. Waveguide generally has lower loss per foot because you can use higher order TE or TM modes that are somewhat more "efficient". Based on the foregoing, I think it is worth making a small change in the article.--Albany45 (talk) 22:53, 4 August 2010 (UTC)

RG8x diameter incorrect in chart

I'd rather not attempt to edit someone's nice handiwork in the spec chart, but RG8x is incorrectly listed as having an OD of .27". I believe this should actually be .24". The OD seems to be very close to that of RG-59. Someone is going to be buying the wrong connectors based upon this and be most unhappy! http://www.therfc.com/coax.htm de AF6IT69.225.4.177 (talk) 04:02, 17 October 2010 (UTC)

Changed OD to 0.242. Glrx (talk) 16:48, 17 October 2010 (UTC)

"Hard Line"

Hard line seems to mean different things to different people. Broadcast engineers seem to use this term mainly for rigid coax, whereas CATV OSP folks use it for semi-flexible smooth solid-shielded aluminum coax hung from power poles. 184.41.138.97 (talk) 20:34, 11 March 2011 (UTC)

How it Works & Description

I am going to try to combine these two sections and upgrade the "how it works" part and add an actual reference. We need to try to trim down and restructure the whole article, but one step at a time! --Albany45 (talk) 15:24, 11 July 2011 (UTC)

This is an excellent idea, and long overdue (I never really found time to do it myself) - thanks! Maybe you could also fold in the following section (propagation)? I'll try to at least comment on your rewrite. GyroMagician (talk) 15:41, 11 July 2011 (UTC)

Albany45, your rewrite describes shielded cables in general, not coax specifically. The feature that distinguishes coaxial cables from other shielded cable is the uniform conductor spacing and construction that creates a constant characteristic impedance along the cable and through connectors, preventing RF reflections. Coax is used for RF transmission lines, NOT for audio. Are you sure you understand this subject well enough to edit the article? I think the original version was better. --Chetvorno^TALK 04:48, 13 July 2011 (UTC)

The previous version made it sound very much as if coax does not carry DC, which is of course not true. Coax is like any shielded cable, with the exception - as you point out - that it has a well defined impedance. We should find a way to express that in the article. We can then go on to describe TEM propagation, etc. I find transmission over coax surprisingly subtle, but the article, as it stands, does not communicate that. Chetvorno - you sound familiar with the topic - between the three of us we could improve it. GyroMagician (talk) 10:06, 13 July 2011 (UTC)

This is a semantic issue. What does "coax" mean? FWIW I'd say it's a matter of geometry, to begin with. That's the etymology. The current wording is not saying anything incorrect, but a sentence emphasizing higher frequencies and impedance control is possible. (Shielded audio cable also uses TEM00 transmission! As a matter of physics, there's no difference from "coax". It's labeling and design intent.) And note, the contrast of coax vs "shielded cable" is already stated in the article's 3rd para and then impedance is discussed at length further down. The relationship of the lead-in and "General Description" could be harmonized some more.--Albany45 (talk) 15:48, 13 July 2011 (UTC)

Do not wish to start an edit war, but the Belden reference states: "Specialty coaxial cables include low-noise and musical interconnects cables. These are specially designed to minimize piezoelectric and triboelectric noise in cables and are not for RF use. The cables may be loosely based upon RG type designs, but utilize semi-conductive material layers within the cable." On this basis, I am restoring the audio application for "coax". Coax really has many applications beyond RF signaling! If someone has a better reference, let's have it, but personal opinion shouldn't enter into it.--Albany45 (talk) 00:52, 16 July 2011 (UTC)

Specialty cable sounds like WP:UNDUE. Coaxial cable at audio frequencies is not constant impedance. Typical audio applications only need shielded cable. Yes, one can use coaxial cable at audio frequencies, but I would not give it prominence. Glrx (talk) 01:15, 16 July 2011 (UTC)

Also, it's not a common application (Common applications of coaxial cable include video and CATV distribution, RF and microwave transmission, low-level audio connections, and computer and instrumentation data connections.[3]). Besides that, what does low-level mean? --catslash (talk) 01:43, 16 July 2011 (UTC)

I agree with the above comments - while audio signals certainly can be carried over coax, it's not the primary use. I use coax to carry DC power and TTL triggers sometimes, but it's not what coax is designed for, and so does not need to be described here. This page should describe the primary use, which is to carry signals where constant impedance matters - i.e. RF. GyroMagician (talk) 16:56, 16 July 2011 (UTC)

RFE Top/Introduction

IMO the second paragraph should describe the (electrical) properties resulting from the design before describing the uses/applications. Thanks. 79.180.217.149 (talk) 18:43, 9 October 2011 (UTC)

If you reckon you know how to improve article, then just do it (and remember to give an edit summary) --catslash (talk) 21:56, 9 October 2011 (UTC)

Outer diamater of braid would be useful in the table

I don't know if there is any standard, but the outer diameter of the braid is not given. I admit for most things this does not matter, but it does for some. Some antenna designs, such as the coaxila colinear (CoCo) use coax in an odd way. If you want to make a computer model of it, you need to know the dimensions of the braid. For RG213 I just measured 8.1 mm OD. Drkirkby (talk) 09:35, 18 November 2011 (UTC)

Sheath

In the first paragraph, the description of the various layers comprising the cable does not include all the layers since it ended at 'conducting shield', therefore I suggest that the 'outer plastic sheath' be appended to the discription. 71.139.177.218 (talk) 02:20, 28 November 2012 (UTC)

It's not required for coaxial cable, and not all coax has it (semi-rigid springs to mind) - but most does, so I guess it deserves a mention. GyroMagician (talk) 18:40, 28 November 2012 (UTC)

Quick check: RG-56/U is shown as over 1/2" outer diameter in table

That seems a tad :) thick. Was this mixed up with RG-8x? It also lists RG-56/U as 48 Ohms. Isn't it the same impedance as RG-6/U (75 Ohms) ? This is not my direct bailiwick, so if someone here could verify that for me I'd appreciate it. Thanks! — Preceding unsigned comment added by Tgm1024 (talk • contribs) 13:06, 28 August 2012 (UTC)

I don't see any spec for RG-56/U in my old Ref Data for Radio Eng. Searching on the web leaves me confused and believing that common usage of RG-56/U refers to video cable and may be confusion/error/typo for RG-6/U or RG-59/U. I'm tempted to delete the entire entry because it doesn't have much data anyway. Glrx (talk) 05:47, 11 December 2012 (UTC)

According to an Anixter catalog (Anixter Canada 1996), an RG 56/U is 0.308 inches OD with rubber (!) dielectric, two braided shields, PVC jacket, with 48 ohms (!) nominal impedance and rated for 8000 volts. It weights .243 lbs/foot. The innter conductor is stranded 0.0585 inches diameter (not an AWG size, close to #15 AWG) with 19 strands 0.0117 inches bare copper. The catalog says the RG designations are for reference only since they aren't part of the current standard. Just because it's in the (old) catalog doesn't mean it's being made any more. --Wtshymanski (talk) 14:36, 11 December 2012 (UTC)

RG59 cable illustration

The cable in this illustration has clearly been stripped by an amateur. The screen has been cut around the cable and a few of the remaining strands brought out to the soldered end. No professional would prepare a cable end this way. For the intended illustation purposes it is probably acceptable for the screen to be completely cut shorter than the inner dielectric. DieSwartzPunkt (talk) 17:14, 11 December 2012 (UTC)

And as an absolute professional, you will be providing a replacement image? GyroMagician (talk) 20:07, 11 December 2012 (UTC)

Fringing capacitance of an open coaxial cable

The article gives the capacitance per length of infinitely long coax.

When coax is open at the ends, there is a fringing capacitance. Does anyone have a formula for this? I understand that the fringing capacitance increases with frequency. An open circuit coax is often uses as a sensor, for measuring things like the electrical properties of dielectrics. There is for example a paper "Improvement in dielectric measurement technique of open-ended coaxial line resonator method " Electronics Letters Volume: 22 , Issue: 7, pp 373-375 That references a book "Maucutive, N.: 'Waveguide handbook' (McGraw-Hill, New York, 1951), pp. 213-216" but I doubt that is an original paper - more likely a collection of formula in a book. I'd like to find a formual, and if possible a derrivation, if anyone is aware of this. ¬¬ — Preceding unsigned comment added by Drkirkby (talk • contribs) 16:00, 22 December 2012 (UTC)

RG 402 & RG 405

These are semi-flex tinned coated cables, and they should be added to the chart. I do not know how to do this. Jimaginator (talk) 16:44, 28 October 2011 (UTC)

I added the specs for RG402/RG405 using datasheets supplied with cables I have purchased. Table need different header because dB/100 feet at 750MHz is not what you find in most of datasheets. Should it be metric like dB/m and allow multiple frequencies? ---Alexei (talk) 03:59, 5 January 2014 (UTC)

History?

This article needs a history section. J. D. Redding 20:38, 23 January 2008 (UTC)

Agreed - this article needs a history section. I propose that it start with a paragraph describing Espenschied's work and Tesla's work. Those are the two inventors I've found have made the breakthroughs. There is useful informtion in their respective patents. Progress in coaxial cable seems to follow closely the development of plastics - dielectrics and jackets. 70.129.18.100 (talk) 08:25, 11 May 2008 (UTC)

I've started the history section, all those interested please expand it. —IncidentFlux ^{[ TalkBack | Contributions ]} 10:21, 18 April 2009 (UTC)

Thanks for the new section. I'm sure coax is much older than AT&T would have you believe. I've briefly looked around - the best I have so far is (1929) "C.S. Franklin patented the coaxial cable in England to be used as an antenna feeder", taken from "History of Wireless" by Sarkar et al, Wiley, 2006. The same book also describes Kirchhoff deriving the telegraphers equation for coaxial cable in 1857, which sounds closer to the mark. GyroMagician (talk) 21:16, 19 April 2009 (UTC)

Here's a better ref: IEEE Microwave Symposium Digest, 1988, 'Heinrich Hertz at work in Karlsruhe', Helmut Friedburg. The paper describes Hertz's work in 1887/8, experimentally proving Maxwell's theory. While investigating skin effect (in the 1880's!), Hertz appears to have invented the coaxial transmission line. I'll try and chase the Kirchhoff reference, but until then I think the prize goes the Hertz. GyroMagician (talk) 21:55, 19 April 2009 (UTC)

Hi MMuzammils - well found with Heaviside! I wouldn't have guessed he was the inventor. I Googled around for some details about Heaviside and came to the simple English wiki, where curiously there was far more detail than here, so I've copied across. I can't decide which format would be better for this section - a list as it is currently, or in prose. Any thoughts? GyroMagician (talk) 15:05, 3 May 2009 (UTC)

Hi GyroMagician, well I can't take credit for finding Heaviside. Anon user with IP 129.31.69.137 added that. I merely did a fact check, and came across the source book at Google Books. The list seems more interesting, since it looks like a timeline, but if we add a short paragraph before that list about the history. That'd improve the overall look of the section, challenge is adding that para without duplicating too much info from the list. —IncidentFlux ^{[ TalkBack | Contributions ]} 17:21, 3 May 2009 (UTC)

Was the Tasmanian cable really the first undersea coax? http://atlantic-cable.com/CableCos/KeyWest/index2.htm describes four cables between Key West and Havana. Three were laid in 1921, and a fourth in 1930. The first three were described in http://atlantic-cable.com/Cables/1921KeyWestHavana/aiee.htm They appear to have been coaxial in construction and operation, although perhaps unintentionally so. Telegraph cables conventionally used sea-earths to provide a return path, but a copper sheath was required around the gutta-percha insulation of the cable to protect it from the teredo worm. By 1921 engineers had obviously realised that this outer sheath could be used as a return conductor. In one of the 1936 articles about the Tasmanian cable, it is described as being "essentially the same as the one laid between Key West and Havana five years ago...", so it would seem that the 1930 cable was definitely coaxial. GusTheTheatreCat (talk) 10:53, 11 May 2010 (UTC)

Coax was a vital part of the radar battles during WWII. While the Nazis had VHF radars, they never thought centimetric radar possible because they lacked both magnetrons and solid {not airgap} coax. They had invented polyethylene years before but never tested its RF qualities... (per http://www.amazon.com/Radar-History-World-War-Imperatives/dp/0750306599/ref=sr_1_2?ie=UTF8&qid=1325114878&sr=8-2)166.84.1.5 (talk) 23:33, 28 December 2011 (UTC)

A modern looking co-axial RF cable in a 1943 'Tenaplas' advertisement in Flight here: [2] — Preceding unsigned comment added by 80.7.147.13 (talk) 20:31, 18 March 2014 (UTC)

"Significance of Impedance"

The "Significance of impedance" section currently states "The best coaxial cable impedances to use in high-power, high-voltage, and low-attenuation applications were experimentally determined in 1929 at Bell Laboratories to be 30, 60, and 77 Ω respectively". It is fairly easy to derive at least the first two of these numbers analytically, which leads me to suspect that these aren't necessarily experimental results. To derive them, pick a constant outer cable diameter, and find the maximum voltage (or minimum power dissipated) for an ideal (lossless) air-filled cable. —Preceding unsigned comment added by 131.215.171.212 (talk) 07:29, 10 February 2009 (UTC)

So you have to wonder why 50 or 52 ohms became standard in many uses, as it is optimum for precisely nothing! Reference to the half wave dipole is incorrect, and I am about to remove that, and clarify the circumstances under which a 1/4 wave antenna approximates to 50 ohms. Tiger99 (talk) 09:04, 11 October 2014 (UTC)

Superscreened

After some failed edit attempts which are logged (don't know what went wrong) I have made mention of superscreened cables in the section on signal leakage, because they do provide a truly massive reduction in leakage. Naturally, they are expensive! I have provided one URL, unfortunately it is the company that I work for, who inherited the rights to make these cables indirectly from UKAEA, who I think invented them in the 1950s. We don't actually have a cable factory, and I am not sure who actually makes them for us. But all of that is irrelevant, as it seems to be inappropriate for me to write much more about something my employer does, as it could be thought of as advertising, and we don't want that here. I am thinking that the subject of superscreened cables deserves an article of its own, or at least a larger section here, if someone independent comes forward to write it. I welcome constructive suggestions on how best to proceed. Tiger99 (talk) 08:48, 11 October 2014 (UTC)

You could describe the construction, or mention TEMPEST. --catslash (talk) 14:57, 11 October 2014 (UTC)

Good idea, and I will describe them, but next week. Right now I am in the middle of a rush job involving those pesky superscreened cables. And yes, I suppose I could mention the T word, which would be an ideal application. I should let my sales people know about that! (Although we do advertsise the cables publicly anyway.) Found out where they are made too, but as I said, next week's job...

Tiger99 (talk) 15:33, 13 October 2014 (UTC)

RF Pre-Amp & ground loops

Many commercial/residential antenna systems include an RF Pre-Amplifier, especially if it is expected that the signal will be split to several receivers. Often the Pre-Amp is mounted near the antenna, and powered by a DC voltage on the center conductor, rather than a separate DC conductor. The 'Ground Loop' section of the coaxial cable article should at least mention the complications of this configuration.
--Wikidity (talk) 18:21, 23 November 2013 (UTC)

That topic is more about antennas and feed lines rather than an article about coaxial cables. Glrx (talk) 00:31, 27 November 2013 (UTC)

You're saying that the coaxial cable powers the pre-amplifier? Does it power anything else? If so, then that should be part of the lead.--Wyn.junior (talk) 15:58, 8 March 2014 (UTC)

This is worthy of mention in the Feed line or Antenna feed articles, but not really relevant to the topic of coaxial cables. --catslash (talk) 16:23, 8 March 2014 (UTC)

If coaxial cables can be used as a power cord is important information.--Wyn.junior (talk) 00:04, 9 March 2014 (UTC)

Any pair of conductors can be used as a power cord. None of the interesting properties of coax are related to its use at DC. I would agree with Glrx that this information doesn't really fit here. GyroMagician (talk) 14:28, 9 March 2014 (UTC)

I don't agree. Coax is used specifically at DC when the voltage is hazardous, and the user must be protected by the earthed (grounded) screen in the event of insulation breakdown. It is commonly used in this way on radiation detectors (hundreds to thousands of volts, but negligible current), test equipment, etc, and I think you will find that the undersea DC links between the UK power grid and mainland Europe are in effect DC coaxial cables. It is also often necessary to pass DC through an electrically noisy environment without corrupting it, or generating a magnetic field external to the cable. So we should be very clear that coax is used at DC for transmitting power, in a wide variety of circumstances. The article should deal with that, but I will leave it to others to decide where it should be put. Maybe write a new section? Tiger99 (talk) 08:56, 11 October 2014 (UTC)

We have separate articles for high-voltage cable and also for shielded cable. --catslash (talk) 14:46, 11 October 2014 (UTC)

OK, will have a look about improving that, or not, when I do the superscreened stuff, hopefully next week. There are other bits needing some attention too. A Wikipedia contributor's work is never done...... Tiger99 (talk) 15:36, 13 October 2014 (UTC)

Specs table needs

Hi, it would be great if you could add additional information in the specs table section that would include the following types of information: 1. Cable groups (for instance G7 cables would include the following cable types: RG-316/U; RG-174/U; RG-188A/U; LMR-100A; LMR-100A-UF) this means that a connector designed for a G7 cable would be interchangeable between those cable types. (However, I am not sure whether this information would infringe on the copyright laws? One could perhaps get permission from the connector manufacturer if need be.) 2. Attenuation ( dB / 100 m ) at different frequencies e.g. 100 MHz / 150 MHz / 200 MHz / 400 MHz / 450 MHz / 500 MHz / 900 MHz / 1.5 GHz / 2 GHz / 2.5 GHz / 5 GHz / 10 GHz / 18 GHz / 20 GHz. 3. Recommended frequency (Hz). 4. Recommended power (W). 5. Shielding (dB). 6. Temperature - min & max. 7. Minimum Bend Radius for 1 x cable and/or for multiple repetitive cables.

(I have been working on a table similar to Wikipedia's one and have it available in a different publishing software program, but I'm not too sure how to edit it into Wikipedia's table.) — Preceding unsigned comment added by Eternelini (talk • contribs) 08:00, 22 April 2015 (UTC)

Triaxial cable?

I'm inclined to add that this term - though common - is a misnomer when used to describe three-conductor coaxial cable. "Tri-axial" implies three axes (similar to "twin-axial"), and would be better applied to three core mains lead or similar.

Anyone have any strong feelings about this?

InelegantSolution (talk) 08:59, 1 July 2015 (UTC)

Do you have a source for the claim? Glrx (talk) 17:33, 4 July 2015 (UTC)

Not so much a claim - it's what the word means. First four dictionaries found on line (Dictionary.com, thefreedictionary.com, merriam-webster.com and oxforddictionaries.com) all have themes for "triaxial" based on having (or involving) three axes. Three-conductor coaxial cable has one axis. See also the section on "twin-axial" in this article and the linked one - looks like we're being inconsistent here, though if there's a legitimate source for "tri-axial" meaning "three things about one axis", I'll go along with it as an alternative. InelegantSolution (talk) 10:45, 10 August 2015 (UTC)

Wikipedia is not being inconsistent but rather using the WP:COMMONNAME. Twin-ax is different from triax. Triax is three conductors sharing the same axis. Glrx (talk) 23:46, 13 August 2015 (UTC)

LMR standard?

The list of LMR cables that Jnavas just added looks to me more like a list of product designations from one particular manufacturer than like a system of vendor-independent standard cable types. Markus Kuhn 20:10, 4 March 2007 (UTC)

While LMR is proprietary to a single company (Times Microwave Systems, a subsidiary of Smith Group plc), it has become a de facto standard for low-loss communications coaxial cable, as you will see if you check design guides for radio systems, cable suppliers, and the emergence of LMR equivalents (HDF, CFD). That said, I would have no objection to moving the LMR material to (say) a new separate De Facto Standard section. It certainly wouldn't serve Wikipedia to simply ignore it. --John Navas 08:33, 5 March 2007 (UTC)

Table splitting done. De Facto or not we can't call it a standard unless the makers publish the specs for others to build. Meggar 19:37, 12 March 2007 (UTC)

Update and some suggested additional text:

LMR is registered trademark of Times Microwave Systems, an Amphenol company. LMR cables are high performance broadband, flexible, low loss 50 Ohm coaxial communication cables designed for use in wireless applications. Theyhave RF performance comparable to traditional corrugated copper cables, but unlike corrugated cables they are highly flexible, non-kinking, and offer ease and speed of connector installation. Compared to RG type braided cables, LMR cables offer much lower loss and better RF shielding. These features make LMR cables a good choice for many wireless application.Lou Caruso (talk) 14:17, 1 February 2016 (UTC)

Sounds like an advertisement. . . Mean as custard (talk) 14:29, 1 February 2016 (UTC)

Missing part names

Could/would someone with knowledge of coax cables provide the names of the numbered parts in this image? Thanks. — Ineuw talk 00:47, 14 February 2016 (UTC)

I've nominated the file for deletion as apparent copyvio of http://www.exirbroadcasting.com/Portals/5/docs/Kataloger/Rigid%20Line.pdf. Glrx (talk) 03:09, 16 February 2016 (UTC)

I don't particularly care if it's deleted. Out of curiosity, what happens if the manufacturer was the uploader? — Ineuw talk 05:42, 16 February 2016 (UTC)

The uploader must prove he is the copyright holder and is releasing the image. If he does that, then there's a OTRS ticket system that indicates the proof has been supplied. Glrx (talk) 20:34, 19 February 2016 (UTC)

Units

The use of units in this article is a mess. Wikipedia should consistently use SI units. Why give the attenuation in dB per 100 feet? That's odd even in Narnia* units. (*=Narnia units should be the official name for the used-to-be-imperial/US system ;-) since it's not an empire anymore and not exclusively used by the US.) — Preceding unsigned comment added by 2003:87:4F46:6301:1877:64C1:2A88:54AC (talk) 19:55, 20 March 2017 (UTC)

Finally

I remember promising someone some information on standards for superscreened cables a very long time ago. Well I finally found the information that was lost so it is now done. If anyone can add to it, please feel free. — Preceding unsigned comment added by Tiger99 (talk • contribs) 16:36, 3 June 2017 (UTC)

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What does a shield do????

I had difficulty in reading the article. What is the shielding good for? That should be in the first paragraph. — Preceding unsigned comment added by Rstevaux (talk • contribs) 00:40, 24 August 2016 (UTC)

The shield keeps the signal inside the cable. That is, shields it from the outside, and the outside from the signal. Gah4 (talk) 23:05, 26 October 2018 (UTC)

Inductance of Coaxial Cable

The formula in the present article is only correct at infinitely high frequencies when the skin depth is infinitely small. At low frequencies the internal inductance inside the conductor has to be taken into consideration. At medium frequencies it becomes much more complicated since the skin depth will be somewhere in the middle. These assumptions should at least be mentioned in the formula. EV1TE (talk) 14:21, 27 March 2017 (UTC)

You know what to do. Cite it and write it. But I've never seen a textbook derivation of this formula worry about finite skin depth. You should also point out that the equations are only true for an infinite coaxial line - practical cables have finite length and there will be end effects. Also finite resistivity of the conductors, and finite resistivity of the dieelectric. Oh, and it assumes there's no relativistic effects - the whole derivation is predicated on a Newtonian approximation of space time. It's amazing the formula has any relevance to the real world at all.--Wtshymanski (talk) 23:38, 25 June 2017 (UTC)

Which formula don't you like? All the given ones are plenty close enough for the usual uses. They are the ones used to give cables the characteristic impedance that they are rated for. For unusual uses, especially at the highest frequencies, one has to understand that the cables are not rated for that use, and adjust accordingly. Note that as skin-depth decreases, the resistance increases, so that has to be taken into account. Many cables use copper plated steel for the inner conductor, as the skin depth is small enough already. Only put copper where actual current flows. Gah4 (talk) 23:22, 26 October 2018 (UTC)

rigid line table

The rigid line section indicates different inner conductor diameter for different impedance, but then the table doesn't indicate this. At minimum the table should indicate the impedance used, but better would be for columns for different impedance. Gah4 (talk) 23:23, 26 October 2018 (UTC)

Use if the term "dielectric constant". Change to "relative permittivity"?

I know the term "dielectric constant" is often used, but I received a paper from the National Physical Laboratory (NPL), where it is considered best practice not to use the word "constant", since there is nothing constant about it. It varies both with temperature, frequency, and to a lesser extent some other things. "A guide to the characterisation of dielectric materials at RF and microwave frequencies", published in 2013 by NPL. http://www.npl.co.uk/publications/a-guide-to-the-characterisation-of-dielectric-materials-at-rf-and-microwave-frequencies To quote from there "Don't use the term Dielectric Constant. It encourages the wrong attitude towards the dielectric properties of materials! The relative permittivity of materials is not constant. It can vary significantly with temperature, humidity, concentration, preparation method, level of contamination, polarisation, etc. See the Glossary, Chapter 10, and Section 2.1 for preferred usage." Drkirkby (talk) 15:32, 28 October 2018 (UTC)

I put in a request for the NPL report, so haven't read it yet. While I agree that dielectric constant isn't so constant, it seems that is the WP:COMMONNAME for it. (Not that I always agree with WP:COMMONNAME, though.). While it can vary with the parameters listed, for the good ones used in cables, it doesn't vary so much. Also, for the desired frequency range, it usually doesn't vary so much, either. To paraphrase a famous saying: some constants are more constant than others. Maybe I will change after I read the article, but for now I believe that the world goes with dielectric constant, constant or not. Gah4 (talk) 19:11, 29 October 2018 (UTC)

But relative permittivity (Epsilon_r) is also commonly used. I think relative permittivity is more common in professional journals and dielectric constant more common in amateur radio publications. If you look at the wikipedi page on relative permittivity you will see it is sometimes called dielectric constant, which it says is a depreciated term, and provides reference to the IEEE and also some chemical reference. So it is not just NPL saying the term should not be used but the IEEE as well.

You say that it does not vary much. I assume from that you are not a microwave engineer that pays a lot of money for phase stable cables.

I think it would be better to change to relative permittivity, but mention it is sometimes referred to by the depreciated name of dielectric constant.

The physics books I remember all called it dielectric constant, so I looked up in a more recent physics book, that my son used just a few years ago. It seems that newer ones still call it dielectric constant. In Gaussian units, there is no discussion of permittivity, so relative permittivity would not be needed. Most books now are SI, though. Yes I am not a microwave engineer, but I do know some about microwave engineering. Hollow waveguides don't have dielectric, but the frequencies of more ordinary electronics keep increasing. One then tries to use better dielectrics, though teflon tends to be expensive. For relatively narrow bandwidth it is constant enough, just different from that of lower frequencies. Otherwise, it is just a name; as above it might be a WP:COMMONNAME, right or not. I don't know if I have enough new engineering books to see what they do. Gah4 (talk) 01:50, 31 October 2018 (UTC)

Missing table information

The table only lists attenuation at 750 MHz and a complete description would certainly take too much space but some type of intended frequency range (albeit this depends on cable lenghth and requirements) would be good to include. Maximum voltage is also of interest, coaxial lines are often used for e.g. detectors requiring high DC voltages and small or modest power. 150.227.15.253 (talk) 12:18, 6 March 2020 (UTC)

WP:NOTCATALOG. Constant314 (talk) 20:03, 6 March 2020 (UTC)

A low relative permittivity allows for higher-frequency usage

The article says: A low relative permittivity allows for higher-frequency usage. High frequency mostly needs low dielectric loss (attenuation), which doesn't have a lot to do with permittivity. Many materials with high relative permittivity (dielectric constant, or index of refraction) are transparent, and low loss, at optical frequencies. There are some complications with impedance, attenuation, resistance, and such, but mostly permittivity is down on the list. Gah4 (talk) 16:37, 11 June 2020 (UTC)

There is merit to what you suggest, however, I would not support changing the article without a reliable source. If you do not have a reliable source, then perhaps mark the passage with a citation needed template. There are at least two effects that complicate very high frequency usage: loss and the onset of waveguide modes. For a given geometry, lower permittivity increases the cutoff frequency of the lowest waveguide mode. It is not obvious to me whether loss or waveguide modes are the dominating effect with the low-loss materials we have now, hence the need for a reliable source. It may be that fat cables are limited by waveguide modes and thin cables by loss.Constant314 (talk) 17:29, 11 June 2020 (UTC)

You mean when other than TEM00 modes propagate? As far as I know, usual sized cables are way too far from that. I am suspecting that someone tried to connect dielectric loss to permittivity. I suppose vacuum and air have lower loss and lower permittivity, but you can't just generalize from that. Well, also, foam dielectrics are used to reduce loss but again, it is the air (or other gas) that is the reason. Gah4 (talk) 19:02, 11 June 2020 (UTC)

Wrong picture of the coaxial cable x2

Hello, I am an R&D engineer for in the cable industry. The two pictures having the label "Section of a coaxial cable" are wrong. It is not a coaxial cable but a High voltage cable (minimum 320 kiloVolt). You can recognize it at the Milliken copper conductor, and at the two thin black layers which are semi conductive layers for being sure that the insulation interface is smooth. Besides the screen is a copper screen and not a braid.

So it is definitly not a coaxial cable... — Preceding unsigned comment added by 178.225.57.204 (talk) 11:53, 19 May 2020 (UTC)

The cable shown in the pictures is literally a coaxial cable, but clearly a high voltage cable and not an r.f. transmission line. Furthermore, in the second picture, the conductor radii are labelled d and D, which is potentially confusing. The pictures are therefore best removed. catslash (talk) 22:14, 11 June 2020 (UTC)

unbalanced line

The article mentions the impedance of a center-fed dipole, but you need a balanced line to drive one. That needs a transformer which reduces the reason for impedance matching. The usual case is a 75 to 300 ohm balun driving a folded dipole. Gah4 (talk) 16:01, 19 October 2020 (UTC)

permeability

There is a recent addition regarding materials with relative permittivity and permeability not one. Coaxial cables with dielectric are common, and so the capacitance increases. I know of no coaxial cables with high permeability materials. There are coaxial cables with a helical center conductor to increase the inductance, and decrease the velocity of propagation. (Used for delay lines.) I suspect one could make one with a center conductor helical wound around a core with ferrite in it. I suppose also with ferrite in the dielectric. I suspect that the article on inductance doesn't cover those cases. Gah4 (talk) 02:49, 17 June 2021 (UTC)

I’m just punching in the dark here, but I think Heaviside proposed increasing the inductance by including iron filings in the dielectric. The early trans-oceanic telegraph cables included permalloy that was wound around the center conductor, adding effective inductance to the dielectric. It doesn’t seem like an egregious generalization. Constant314 (talk) 03:36, 17 June 2021 (UTC)

Also, the recent edit did not change the formula or the symbol, it just pointed out the meaning of μ without a subscript. Constant314 (talk) 05:17, 17 June 2021 (UTC)

Yes, but it did remind me of things I knew years ago. I was remembering a physics lab where we measured the impedance, velocity of propagation, and attenuation of some cables. One was ordinary lamp cord, some were common coaxial cables, but one was the delay line mentioned above. It also reminds me of a physics homework problem, which I don't know that I ever knew the right answer to, which is an inductor (coil) made with iron wire. Note that the propagation on a high-inductance helix is an important part of the Traveling-wave tube. An EM wave propagates at close to the same speed as an electron beam, and extracts power from the beam. It turns out the the velocity based on inductance is close enough to the velocity you get assuming that the wave follows the helical wire. (Including correction for dielectric constant.) Fun with physics! Gah4 (talk) 07:34, 18 June 2021 (UTC)