Talk:Air stripline

GA Review

This review is transcluded from Talk:Air stripline/GA1. The edit link for this section can be used to add comments to the review.

Reviewer: Navinsingh133 (talk · contribs) 11:58, 16 October 2017 (UTC)

I am currently reviewing this article as a qualified reviewer.

This article is nicely and neatly written, but may need a little more grammatical work(use of articles, spacing, etc.), layout(# See also) and content expanding. Will fix minor errors my self!

British English is acceptable(such as minimise).

I believe that this article passes GA Criteria 4,5,6 clearly, and 1b,2,3 are almost acceptable. However,1a needs slight work and 2b,2c,2d, and 3a are not verified by me yet(references are not easily accessible). Perhaps it will be better if some online reliable references are added(I will try to do it myself!).

Thank you, Navinsingh133 (talk) 11:58, 16 October 2017 (UTC)

Hi Navingsingh133. Thanks very much for reviewing. Unfortunately, I have reverted most of your last edit. It is not a grammatical requirement that air stripline needs to be preceded by an article. It can be used as a generic term without an article. Compare the coaxial cable, twisted pair, light pipe and microstrip articles. That usage can be found in numerous textbooks and papers, e.g. [1].

Also, please do not remove the sentence double spacings. This is the correct way to type and makes the text easier to read in edit mode. Although most browsers use a proportional font and will not render the double spacers, the readability advantage is still there for anyone who wants to render the text in a proportional font.

I don't think you should be concerned about the references being in print. Print sources are explicitly allowed, even welcomed – because they are generally high quality and reliable. Have you read what Wikipedia:Reviewing good articles has to say on this? I don't think it would be helpful to add additional, possibly poorer quality, online sources when these have not been used to construct the article. In any case, most of the sources in this article can be partially viewed in gbooks or Amazon by following the ISBN number link. If there is any passage you have doubts over the accuracy, I can give you the direct quotes from the source. SpinningSpark 17:28, 16 October 2017 (UTC)

Dear Spinningspark, Thanks for your notification. However you do not need to tell me in person that you have reverted my edit due to some reasons, just a brief summary is sufficient. My apologies for removing the double spacing, where I live it is considered incorrect.

Also, I am not saying that prints sources aren't reliable (or allowed), neither I am concerned, what I am saying is I can't verify them under criteria 2b,2c, and 2d because I don't have access to those prints, so I don't know what they are and can't review the article under those criteria. "Perhaps it will be better if some online reliable references are added(I will try to do it myself!)" means that I will try to find those prints online or other reliable online sources such as eBooks, and I see you have provided some links, thanks!--Navinsingh133 (talk) 20:00, 17 October 2017 (UTC)

This article is reassessed and I believe that This article passes GA criteria 1a, 2a, 2b, 3b, 4, 5, 6 clearly, and rest are acceptable for the GA standard. The article also holds promises of detailed expansion in near future. Therefore I believe it should be a pass. However, Just one person cannot give accurate review(and more time should be given), therefore I am inviting other reviewers to take a look at the article. Till then, I see no problem in keeping it in a good article(or at least B) category. --Navinsingh133 (talk) 09:14, 18 October 2017 (UTC)

Subsequent review

This is still listed as an active review. Given the comparative inexperience of the editor at the time this was opened—about six weeks of Wikipedia editing and fewer than 200 total edits—I have taken the liberty of changing the status from "onreview" to "2ndopinion" in the hopes that a more experienced reviewer can check and see whether the article does indeed meet the GA criteria. As it is a technical article, someone who is good with such prose would be a plus. Many thanks. BlueMoonset (talk) 00:26, 18 November 2017 (UTC)

I have completed my review for this article, and have listed my comments and concerns below. I am willing to work with the editor to bring the article up to standards. (See Analysis and Recommendations and Review table below).  Spintendo  ᔦᔭ  19:09, 27 December 2017 (UTC)

The subsequent review having been completed, and all improvements and/or explanations having been made, the status of Good Article is made on Air Stripline. Congratulations to SpinningSpark for their hard work. Also thanks to catslash and the previous reviewer Navinsingh133. Spintendo ᔦᔭ 15:11, 8 January 2018 (UTC)

Table of Contents

1. GA Review Table
   1. Bhat source
      1. Nominated article
      2. Source
      3. Analysis
   2. Matthaei source
      1. Nominated article
      2. Source
      3. Analysis
   3. Oliner source
      1. Nominated article
      2. Source
      3. Analysis

GA Review Table

Rate	Attribute	Review Comment
1. Well-written:
	1a. the prose is clear, concise, and understandable to an appropriately broad audience; spelling and grammar are correct.	✓ The issues of grammar have been corrected.
	1b. it complies with the Manual of Style guidelines for lead sections, layout, words to watch, fiction, and list incorporation.	✓ The article complies with WP:MOS.
2. Verifiable with no original research:
	2a. it contains a list of all references (sources of information), presented in accordance with the layout style guideline.	✓ The manner with which two of the references are handled in the article are not in accordance with the layout style guidelines for WP:INTEGRITY (See individual Analysis sections I and II below for a description of these.) per WP:BLUE & WP:BUNDLING
	2b. reliable sources are cited inline. All content that could reasonably be challenged, except for plot summaries and that which summarizes cited content elsewhere in the article, must be cited no later than the end of the paragraph (or line if the content is not in prose).	✓ Source was updated.
	2c. it contains no original research.	✓ The nominated article does not contain original research (the mistakenly cited passages mentioned above not included.)
	2d. it contains no copyright violations or plagiarism.	✓ In the sources I personally checked, I encountered no evidence of plagiarism.
3. Broad in its coverage:
	3a. it addresses the main aspects of the topic.	✓The main topic is addressed.
	3b. it stays focused on the topic without going into unnecessary detail (see summary style).	✓The details of air stripline versus other kinds of stripline were delineated. This was remedied by the grammar changes in section 1a, and the source No. III integrity changes in 2a and 2b.
	4. Neutral: it represents viewpoints fairly and without editorial bias, giving due weight to each.	✓ The article does not display any bias.
	5. Stable: it does not change significantly from day to day because of an ongoing edit war or content dispute.	✓ There does not seem to be a problem with reverting.
6. Illustrated, if possible, by media such as images, video, or audio:
	6a. media are tagged with their copyright statuses, and valid non-free use rationales are provided for non-free content.	✓Both images are licensed under the Creative Commons Attribution-ShareAlike 3.0 License. Attribution: Courtesy Spinningspark at Wikipedia. Neither file meets CSD F8.
	6b. media are relevant to the topic, and have suitable captions.	✓Captions appear to be pertinent.
	7. Overall assessment.	✓Improvements have been made and all areas are completed. As the second review opinion, I concur with the previous reviewer's hastily made, yet essentially correct assessment that this article passes GA status.

I. Bhat source

Nominated article findings

• Reference note #5 (citing p. 302) is placed at the end of one sentence: "High end designs may use a crystalline substrate, such as boron nitride or sapphire, as the suspended substrate."
• Reference note #11 (citing pp. 212, 280-287, 302-311) is placed in the last sentence of a paragraph containing 10 sentences. "This also makes mechanical support easier because the lines are more rigid."¹¹

Bhat source findings

• Page 212 is titled "Design Data on Edge Coupled Stripline-like Transmission Lines—Characteristic Impedances and Effective Dielectric Constants." That page delineates coupled line configurations, in particular, the edge-coupled parallel conductor configuration. Bhat discusses how these circuits adopt either the edge-coupled homogeneous stripline or edge-coupled microstrip line and how a few adopt edge-coupled suspended striplines "especially at higher microwave frequencies." Bhat then goes on to describe how Matthaei (the author of the book reviewed below, after this one) has provided complete design curves characterizing the various fringe capacitances and also formulas for determining the structural parameters from "even-and-odd mode impedances."
• On the upper half of page 302 is the passage from which reference note #5 was created for, which reads:"Broadside coupled suspended stripline using uniaxially anisotropic pyrolytic boron nitride or sapphire as the suspended dielectric layer is attractive in the design of filters and high directivity tight couplers demanding highly reproducible characteristics.
• In pages 280-287, Bhat delineates the various ways in which broadside-coupled techniques offer more efficiency in their impedances and dielectric constances, mainly through the illustration of formulas. The first ones described are the unified capacitance formulas for structures with iso/anisotropic substrates (fig 7.1–fig7.3d), followed by the characteristic impedance of broadside-coupled homogeneous stripline-conformal mapping formulas (7.4a–7.7b), followed by explicit expressions for the dimensional parameters of broadside-coupled symmetric homogeneous striplines in terms of coupling (fig 7.8a–7.12). Bhat explains the differences in spacing variations between two broadside-coupled transmission structures with isotropic dielectric substrates (e.g., homogeneous and suspended striplines) by illustrating the design data dimensional parameters expressed in coupling factor degrees (in figures 7.2a, 7.13a, and figures 7.13b and 7.14, respectively).
• The lower half of page 302 through page 311 are figures. One of the figures, on page 303, reads: "Characteristic impedances Z_e and Z_o and phase velocity ratio vo/ve versus w/b and d/b as parameter of broadside coupled homogeneous stripline filled with uniaxially anisotropic dielectric substrate pyrolytic boron nitride."

Analysis and recommendations

1. The "Uses" heading: It's not clear that the paragraph containing the Ref#11 note fits under the "Uses" heading. After looking at the source, it appears what is being described are the variations of transmissive technologies, with the reader being told about the different configurations of different types of couplings, rather than delineating how these variations differ in their "uses". I suspect "Variations in usage" may have been what the editor was thinking with "uses".
   1. The point of the para is that air stripline can get much stronger coupling through the "broadside coupling" technique and indirect coupling can thus be used for a wider range of applications. I've added an opening sentence to clarify this. SpinningSpark 17:10, 7 January 2018 (UTC)
2. Nomenclature used: While the article describes some striplines as "supported", the book chooses to differentiate this further, using "suspended" or "inverted" — distinctions which will be lost to readers of the article.
   1. Inverted stripline is not a form of air stripline and hence is not covered in this article. It is the same as inverted microstrip with the addition of an upper ground plane. The suspended form of air stripline is clearly explained in the "Structure" section. SpinningSpark 17:10, 7 January 2018 (UTC)
3. Reference note #11 (citing pp. 212, 280-287, 302-311) WP:INTEGRITY: Wikipedia's content guidelines for a citation's placement state that "The point of an inline citation is to allow readers and other editors to check that the material is sourced; that point is lost if the citation is not clearly placed." These guidelines clearly leave the final decision on the distance "between material and its source" in the hands of "editorial judgment", advising that editors "exercise caution when rearranging or inserting material to ensure that text–source relationships are maintained." In the nominated article, reference #11's placement is assumed to be meant as reference for the entire paragraph, when considering that the final sentence in which it appears is too particular a statement, and not broad enough, to warrant a reference covering 18 pages of material. The guidelines state: "If a sentence or paragraph is footnoted with a source, adding new material that is not supported by the existing source to the sentence/paragraph, without a source for the new text, is highly misleading if placed to appear that the cited source supports it. When new text is inserted into a paragraph, make sure it is supported by the existing (source) or a new source." Taking that guideline into consideration it is my opinion that the material in this paragraph, and the reference note #11 meant as the source citation for it, does not meet an acceptable threshold for text–source integrity. This many pages of material pressed into one note is odd (pages 212, 280–287, and 302–311) and the fact that other parts of the nominated article easily possess text–source integrity (see analysis no.4, below) makes the inability of reference note #11 in meeting an acceptable threshold for text–source integrity all the more puzzling. 18 pages worth of material should have easily broken down into several different reference notes across 10 sentences, and yet these pages weren't separated. Looking at WP:INTEGRITY, one sees that the standard for text–source integrity is "editor's judgment." An editor who asks for 10 paragraphs in their article to be allowed with only one citation would doubtless be pressing their luck. My question asks where the line should be drawn. At what point does a Good Article nominee begin to press their luck, at 10 paragraphs or 10 sentences? The guidance that citations be bundled into one reference placed at the end of a paragraph (WP:SCICITE) appear to apply in certain cases:

   The verifiability criteria require that such statements be sourced so that in principle anyone can verify them. However, in many articles it is cumbersome to provide an in-line reference for every statement ... therefore, in sections or articles that present well-known and uncontroversial information – information that is readily available in most common and obvious books on the subject – it is acceptable to give an inline citation for one or two authoritative sources in such a way as to indicate that these sources can be checked to verify statements for which no other in-line citation is provided. These inline citations are often inserted either after the first sentence of a paragraph or after the last sentence of the paragraph.

   Which of these two policies WP:INTEGRITY or WP:SCICITE is felt to take precedence here and ought to be implemented should be for the article's nominator to decide.
   1. It's really against my Wikipedia religion to excessively break up citations. It is of no real benefit to either the reader or the reviewer and destroys a lot of the enjoyment for content creators (ask me outside this review to explain why). Wikipedia reviewers have become far too pedantic on this point (probably only because it is an easy point to make). Nowhere else in real life is this a requirement. In this case the paraagraph is cited entirely to only one source (but multiple pages). A gbooks search for the term air stripline strong coupling gets 1,640 hits according to Google's own highly inaccurate count. That shows that the basic claim of this para is well known to those skilled in the art and surely meets the requirement "information that is readily available in most common and obvious books on the subject". SpinningSpark 17:42, 7 January 2018 (UTC)  Works for me Spintendo ᔦᔭ 14:40, 8 January 2018 (UTC)
4. Reference note #5 (citing p. 302) WP:INTEGRITY: Unlike reference note #11, the text–source integrity for reference note #5 is unassailable. It was placed at the end of one sentence and the information contained in that sentence was easily located and verified in the source.
   1. No actionable request. SpinningSpark 17:44, 7 January 2018 (UTC)
5. Sentence change: In addition to the changes above, the sentence For this reason stripline parallel coupled lines are used in directional couplers with a coupling factor no more than −10 dB but power splitters (coupling factor −3 dB) use a direct coupling technique. In air stripline there is another possibility, the lines can be stacked one on top of the other." should be changed to: "For this reason, stripline parallel coupled lines are used in directional couplers with a coupling factor no more than −10 dB. Power splitters, with their coupling factor −3 dB, use a direct coupling technique. Air stripline makes use of an alternative arrangement, with lines stacked one atop of the other."
   1. Has this not already been addressed by Catslash's edit? SpinningSpark 17:44, 7 January 2018 (UTC)  Resolved Disregard the grammar change recommendations in the text. We took care of those, and I changed their status in the review table, this was just redundancy having them written down here. Spintendo ᔦᔭ 14:40, 8 January 2018 (UTC)

II. Matthaei source

Nominated article findings

• Reference note #6 (citing page 173) covers methods of construction and the use of spaced insulators. The sections describes how a certain method is more suitable for high power applications. It remarks upon the conductor cross-section's corners and the fact that they are rounded.
• Reference note #7 (citing pages 422-423) speaks to the disadvantages of insulators, and how the need to avoid insulators has led to the use of grounding points which double as mechanical supports.
• Reference note #10 (citing pages 598-603) talks about filters, power dividers and directional couplers at microwave frequencies, and how air stripline is used to make these components when "air stripline" is the transmission medium.

Matthaei source findings

• Page 173 contains Figure 5.04-5, labeled as "Theoretical Breakdown Power of Air Dielectric Rounded Strip Transmission Line." Matthaei describes (on page 172) the figure (on page 173) as the following: "The average power, P (measured in kw), that can be transmitted along a matched strip line having an inner conductor with rounded corners is plotted in Fig 5.04-5. In this figure, the ground plane spacing b is measured in inches, and the breakdown strength of air is taken as 2.9 x 10⁴ volts/cm."
• Pages 422-423 contain a table summary of "Band Pass and Pseudo High Pass Filters" labeled "Stripline or Coaxial and Semi-Lumped-Element Filters". This table goes on to illustrate typical resonators and filter properties.
• Pages 598-603 feature different tables showing impedances obtained through the use of differing filters. Page 601 for example, shows a diagram of "Details of Transition from Filter to Type-N Connector."

Analysis and recommendations

1. Reference note #6 (citing p. 173): Fixed The article mentions rounded strip transmission lines, which the figure shown on page 173 indeed shows. However, the statement in the article makes claims as to the protections offered by these "rounded" corners, whereas Matthaei speaks only of the "average power P (measured in k/w)" and stops short of labeling this a "protection". What makes this power differential a "protection" ought to be included either in the text or from an additional reference. (Note: If the "protection" offered is that it prevents a transmission line from being damaged or destroyed, then this reference as it's worded is acceptable; in which case the citation should be changed to read "p. 172" or at least "pp. 172-173".)
   1. I've changed the page range as requested. I am puzzled by your putting "protection" in quotes as this word does not appear in the article. It is true that Matthaei does not explicitly give the reason for using rounded corners at high power. However, it is certainly well known that sharp points and edges lead to high field strengths (not just in this application, but throughout electrical engineering - it is a big consideration, for instance, in transformer design on power grids). It's not hard to find sources saying the stripline conductor should be rounded in power applications, but in most of them the author assumes the reader already knows the reason for this. I put the information in here because that is not necessarily true for Wikipedia readers. The only source I can find on a quick search that says this explicitly is this book: "This version of triplate has been devised in order to extend the use of stripline to higher-power operation: the absence of sharp corners on the centre conductor is obviously an essential requirement for such usage, in order to avoid high field-strength areas which could lead to "flash- over" and voltage breakdown." I can put this source in if you like, but there are two problems with it. Firstly, it is not explicitly discussing the air stripline form of stripline. Secondly, I only have this gbooks snippet and am a little uncomfortable using a source I can't read properly. SpinningSpark 18:24, 7 January 2018 (UTC)
2. Reference note #7 (citing pp. 422-423):  ResolvedThe same as with 173 above — while discussing insulators and grounding points shown in the diagrams from the source, the article makes claims which do not appear to be present on the pages indicated (e.g., "...insulators are electrically undesirable..."). (Note: If by "undesirability" it means that the transmission line becomes damaged or destroyed, then this reference as it's worded is acceptable.)
   1. I'm going to go with WP:BLUE on that one. It is patently obvious that a component whose benefits reside in it being composed of air is going to be compromised by anything in it that is not air. It is a waste of everyones time to trawl the internet trying to find a source saying that explicitly. SpinningSpark 18:45, 7 January 2018 (UTC)
3. Reference note #10 (citing pp. 598-603) / The usage of figures and formulas from a source as a reference: Fixed As much of the Matthaei (and Bhat) sources describe pages wherein technical figures or formulas reside, the question becomes this: does Wikipedia policy permit the use of figures and formulas as references themselves? The answer to this is not so clear. The inactive but historically kept WP:MOSDIAG describes guidelines for their usage. These figures should:

• Give an explicit presentation that is directly relevant to the subject of the article(s) in which they appear
• Are fully consistent with, and support, the surrounding text

The second guideline requiring "the surrounding text" to be "consistent" with the figures, and the first guideline that they "give an explicit presentation that is directly relevant to" the article in question, are the main questions here. As far as using the diagrams directly as references, MOS:MATHS gives some guidance, most notably saying that figures should "Provide further reading enabling other editors to verify and to extend the given information, as well as to discuss the quality of a particular source." It should be the case that when the use of figures from a source are required to cite a reference for text in an article, those very same figures ought to be reproduced and included in the article. However, MOS:MATHS warns that "Wikipedia articles cannot be a substitute for a textbook. Also, often one might want to find out more details (like the proof of a theorem stated in the article)." There is also direction from WP:SCICITE which states that formulas or calculations are allowed when they involve:

Converting units, rounding to appropriate levels of precision for the article, describing quantitative relationships in words, and other simple methods that both accurately describe the information from the source(s) and do not tend to advance a novel argument. If a calculation, although routine, takes more than one or two steps, it may be helpful to present the details of the calculation in a note to the text.

In the Matthaei source many of these formulas are used as a reference, although their details are not expounded upon as WP:SCICITE suggests.

I have no idea what I was thinking of when I put the Matthaei source in there. I suspect that it is the right page numbers for a different source, but I no longer can remember. I'll look for something better. SpinningSpark 19:48, 7 January 2018 (UTC)

Ok, I've removed Matthaei from that para and put in a new source. Also reworded more in line with the new source. SpinningSpark 22:09, 7 January 2018 (UTC)

 Resolved Spintendo ᔦᔭ 14:50, 8 January 2018 (UTC)

III. Oliner source

Nominated article findings

• Reference note #2 (citing page 558) covers one simple sentence, describing one of two basic ways in which an "air stripline" is constructed. The way described is the "dielectric supported stripline (also called a suspended stripline or suspended substrip), where the strip conductor is deposited on a thin dielectric substrate, sometimes on both sides and connected together to form a single conductor."
• Reference note #12 (citing pages 557-558) is more complex, covering five sentences. The passage first describes who invented stripline and who first manufactured it. It then goes on to describe how stripline has become a generic term, and what that generic "anadorned" term now signifies. It concludes by suggesting that stripline was an early "planar technology of choice" while claiming that it "has now been superseded bymicrostrip [sic] for most general purpose applications."

Oliner source findings

• Page 557 describes how striplines came about, in that "they removed the side walls altogether and extended the top and bottom walls sideways. The result was called a strip transmission line or stripline. Different methods were used by different companies to support the center strip, but in all cases the region between the two outer plates was filled with only a single medium, either dielectric material or air." Oliner then goes on to describe how a modification that emerged at roughly the same time involved removing the top plate and leaving only the strip and the bottom plate, called a microstrip. Page 557 then goes on to list Robert M. Barret as the inventor of the stripline concept, and how his work went on to inform the work carried out by three organizations, namely, the Polytechnic Institute of Brooklyn, Tufts College, and Airborne Instruments Laboratories (AIL). The bottom of page 557 shows sketches of two commercial microwave printed circuits.
• Page 558 features sketches of three main manufactured circuits: Microstrip® made by Federal Telecommunications Laboratories (ITT); Tri-Plate® manufactured by Sanders Associates; and Hi-Q Stripline® manufactured by AIL. Below the sketches, Oliner describes the essential differences between the three, a description which carries over to page 559.

Analysis and recommendations

1. Reference note #2 (citing pp. 558):  Fixed The nominated article suggests that there are two different ways of constructing an air stripline, and that one of these ways involves a stripline where the strip conductor is deposited on a thin dielectric substrate. However, on p. 557 of the source (and not p. 558, as stated in the nominated article) Oliner states that "in all cases, the region between the two outer plates was filled with only a SINGLE medium, EITHER dielectric material OR air." If this is the case that an air stripline is a stripline where the region between the two outer plates is filled with air and a dielectric substrate stripline is one which is filled with dielectric substrate, then the nominated article's claim that the two basic ways of constructing an air stripline involving one way which does not utilize air (the dielectric substrate) is a spurious claim.
2. Reference note #12 (citing p. 557-558):  Fixed Similar to what was seen with the Bhat source, the nominated article makes several claims in a paragraph and then bundles them under one reference note. Just as with the Bhat reference, this raises problems. Two of the claims made within the bundled reference are not substantiated on the pages indicated by the reference. Firstly, that stripline was the planar technology of choice which has been superseded by microstrip for mass produced items; Secondly, that Stripline® was the first stripline manufactured by AIL. In the first instance, when the nominated article mentions microstrips, it fails to explain the difference between the dielectric filled microstrip and the microstrip that superseded the stripline for mass produced items. The Oliner source explains that the two are different. In the second instance, the nominated article claims that the Airborne Instruments Laboratories "Stripline" (which was in fact called Hi-Q Stripline®) was the first manufactured; the source indicates that the 3 striplines were manufactured roughly at the same time, and that the microstrip was just one of these modifications — and not the superseding one.
3. Sentence change:  Fixed In addition to the other changes listed in this section, the sentence "The unadorned term stripline would now likely be assumed to be stripline with a solid dielectric." should be changed to: "The unadorned term stripline is now likely assumed to be a stripline with a solid dielectric."

References

Spintendo ᔦᔭ 19:09, 27 December 2017 (UTC)

Oliner actually says "Different methods were used by different companies to support the center strip, but in all cases the region between the two outer outer plate was filled (or effectively filled) with only a single medium, either dielectric material or air" and later "...(b) is clearly dielectric filled, whereas that in (c) is essentially air-filled because very little field is present in the thin center sheet that supports the center strip." (my emphasis) --catslash (talk) 22:42, 5 January 2018 (UTC)

The article does sometimes use dielectric to mean any dielectric (including air), and sometimes to mean specifically solid dielectric - could this cause confusion? [fixed] --catslash (talk) 23:18, 5 January 2018 (UTC)

Thanks to user:Catslash for addressing some of these issues. Am I right in thinking that the all the remaining issues are to be found under "analysis and recommendations" for the Bhat and Matthaei sources? SpinningSpark 16:41, 7 January 2018 (UTC)

Minor comment

"make the dielectric essentially air"

So it is air, or not? What is this "essentially"? Maury Markowitz (talk) 17:17, 5 December 2017 (UTC)

It means near enough as makes no difference. Perhaps almost entirely would be clearer, though it's not the relative volumes of the materials that matter so much as the relative magnitudes of their effects. Maybe somebody has a better suggestion? Predominantly? --catslash (talk) 23:26, 2 January 2018 (UTC)

The strip requires some kind of mechanical support, it cannot simply be levitated in air. This may consist of a very thin substrate or periodic pillars. These are made of solid insulating material which has some dielectric effect but they are made as small and insignificant as possible. This is to be compared to a line with a solid dielectric. Here the dielectric itself provides the mechanical support, hence the dielectric is entirely homogenous. SpinningSpark 16:26, 7 January 2018 (UTC)