Talk:Coaxial cable

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Contents 1 questions 2 COAX IS WAVEGUIDE?? 3 Coax use in Amateur radio 4 Text flow 5 Differences in coaxial cables 6 Coaxial v.s. Component/SVideo/Composite 7 Perspective needed? 8 LMR standard? 9 vertical and horizontal 10 10Base5 is not RG-anything 11 RG 12 Balun 13 Typo in specs table 14 Leakage section is difficult to read 15 History? 16 Patent 514,167 17 Article is still not accessible to novices

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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).

[edit] 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)

[edit] 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).

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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 electtrical 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)