Talk:Traveling-wave tube

Article name and spelling

First, a spelling nit: while "travelling" (two Ls) is acceptable, the more common spelling of this word is "traveling". (It's listed first in most dictionaries, and is the spelling used by all major TWT manufacturers.)

Since this article is almost exclusively dedicated to a discussion of the traveling wave tube (and not the amplifiers designed around them), I'd have preferred to see it titled "Traveling Wave Tube" without the appended "Amplifier". At least one other editor would seem to agree with me; refer to the usage note added earlier.

Anyone else care to weigh in? Engineer Bob 05:27, 21 August 2005 (UTC)

• I agree. This article should be "Traveling Wave Tube". miterdale 14:34, 21 August 2005 (UTC)

• Since there were no objections, the article has been moved as suggested; and the amplifier information has been moved to Traveling wave tube amplifier. I'm also cleaning up all of the redirects. Engineer Bob 23:08, 12 November 2005 (UTC)

"travelling" (two Ls) is acceptable is the original UK spelling. The original UK spelling is usually used by UK manufacturers.

Rudy and John both spelled it with one L on their books, so let's leave it alone. Dicklyon (talk) 17:40, 30 October 2009 (UTC)

Merge or not?

The merged article as it existed before today (covering both TWT and TWTA) had a major weakness. As we all know, a TWTA is a complex piece of electronic equipment while a TWT is the equally complex microwave tube used inside. The previous article had the TWTA title but was almost exclusively focused on TWTs. I moved the TWTA information to a separate article, allowing people to expand that article to address the finer points of EPCs and linearizers while keeping this article focused on the tube itself. Half an hour later, it's been nominated for a merge. I'm obviously not in favor; it makes about as much sense as merging the automobile and internal combustion engine articles. However, if a merge is deemed appropriate by the majority, then I believe the primary article should remain "Traveling wave tube" with a section on TWTAs. Other opinions? Engineer Bob 23:57, 12 November 2005 (UTC)

Or merging magnetron with microwave oven. Unless someone (perhaps User:The Anome) can explain why they think they should be merged, I think the merge banner can be removed. If there is a real desire for a merge then I agree that the page should be primarily about the TWT with a section on TWTA (as for the other high power vacume tubes). miterdale 13:36, 24 November 2005 (UTC)

Since no further discussion or rationale has been offered, I have removed the merge tag. Engineer Bob 06:50, 2 January 2006 (UTC)

Picture

Does the diagram actually show a TWT with a 4 stage depressed collector? Do such TWT's exist - most I came across was two stage. Suppose we could do with a paragraph on why depressed collectors are used too (might get round to it :-). miterdale 14:40, 21 August 2005 (UTC)

Hard to tell for sure -- but yes, the diagram does appear to show a 4-stage collector. I've seen as many as five collector stages in some space TWTs (where the small increase in efficiency is worth it), but radar TWTs tend to be designed with not more than 2 stages. Engineer Bob 18:29, 21 August 2005 (UTC)

The diagram shows a 4-stage collector, which is used, as Engineer Bob pointed out, when efficiency is at a premium, e.g. in space helix TWTs. --Willus 12:58, 7 July 2007 (UTC)

Bandwidth

What do we actually mean by wide bandwidth wrt TWTs? I've used pulsed coupled cavity TWTs with 50kW peak power, and 500MHz bandwidth at 9.75GHz - in my option pretty good bandwidth :-) miterdale 14:34, 21 August 2005 (UTC)

Helix TWTs have an inherently wideband structure and can easily achieve up to an octave of bandwidth (especially CW communications tubes). Coupled cavity tubes are more typically limited to 5-10% of the center frequency. Engineer Bob 18:29, 21 August 2005 (UTC)

How come the word "octave" is used to describe the bandwidth? Octaves are logaritmic units (like dB), do that doesn't really say anything about the BW, or am I just being stupid here? /Alkanen, 9 February 2007 (UTC)

The word octave actually originates in music, and corresponds to a doubling in frequency (on a musical scale it's a span of eight notes, hence the root 'oct'). For bandwidth, an octave is a range of frequencies where the upper limit is double the lower limit. For example, 4-8 GHz is an octave of bandwidth. Engineer Bob 21:04, 9 February 2007 (UTC)

Uses

I've worked on several TWT based systems (airborne surveilance, ground based surveilance/fire control, naval ECM), so don't think we should make the 'particularly in airborne fire-control radar systems' statement. Maybe a statement of why high bandwidth is useful for radar/ECM (frequency agility, narrow pulses/chirped pulses, etc.)? miterdale 14:34, 21 August 2005 (UTC)

Yes, TWTs are used in many types of radars (although many of the higher-power systems use a TWT preamp driving a crossed-field amplifier ... another article waiting to be written?) I added the 'airborne fire-control radar' note as an initial attempt to expand the 'radar' one-liner; that obviously reflects my own background, and I'd welcome additional edits in this paragraph. As for ECM applications, that probably deserves an additional paragraph of its own. Engineer Bob 18:29, 21 August 2005 (UTC)

Backward waves

Is it possible to replace the attenuation by a ferrite that acts like an isolator (circulator) ? --Arnero 06:40, 16 July 2006 (UTC)

I suppose anything is possible, but putting magnetics near the electron beam is generally a bad idea and would complicate the focusing structure. The attenuation material is commonly made of some form of RF-absorbing graphite, and many helix TWTs have a physical sever between sections so that the isolation is excellent (well over 100 dB). --Willus 12:55, 7 July 2007 (UTC)

The never-mentioned acronym: TWAT

Early in my career I learned this was once referred to as a TWAT (convencient pronunciation of TWT, but also for Traveling Wave Amplifier Tube), and I confirmed this with older engineers who had been employed in the 1950s. Older microwave engineers I have talked to all seem to know this term, but one never sees it in print for obvious reasons, especially in these modern times when the engineering profession isn't almost exclusively male. I think this historical tidbit deserves a mention. -Axlq 05:51, 14 December 2006 (UTC)

It might deserve a mention if you could find it in print. In the 33 years that I knew John Pierce, he only used TWT and TWTA. I never heard TWAT (or not in that context, I mean). It's probably just a way to pronounce TWT. Dicklyon 05:57, 14 December 2006 (UTC)

That's the problem, it's one of those terms that occur in conversation and informal reports, but generally not in print. In the 22 years I've been in the radar cross section measurement business, I've seen and heard it called TWAT (in informal contexts) as well as TWT. It's like the mnemonic to remember the resistor color code; the really memorable version doesn't appear in any textbook.

However, after some searching, I actually did find a few references for TWAT:

• Definition in thefreedictionary acronyms
• Federation of American Scientists acronyms - I might add that fas.org is considered a respectable source in military circles
• Here's even a patent that uses the term!

I think it's valid to include. -Axlq 06:19, 14 December 2006 (UTC)

I'd support including the alternate acronym, but only a quick mention -- for example:

"The device has also occasionally been referred to as a traveling wave amplifier tube, or TWAT."

-- Engineer Bob 09:16, 14 December 2006 (UTC)

That'd be fine if you cite a source. Dicklyon 17:08, 14 December 2006 (UTC)

The acronym definition on fas.org or the patent I cited above aren't enough? =Axlq 03:36, 15 December 2006 (UTC)

Seems OK. Cite one or both. Dicklyon 04:37, 15 December 2006 (UTC)

Axlq, thanks for finally just putting the acronym instead of beating around the bush. Dicklyon 07:54, 19 December 2006 (UTC)

I think all of us who were contributing to that sentence were beating around the bush. I finally realized something I read in a policy somewhere, "Wikipedia is not censored." So be it. -Axlq 15:28, 19 December 2006 (UTC)

(Responding to recent edit from Dicklyon) gentlemen, I realize there seems to be this compelling need to bring up the TWIT and TWAT stuff, but can we keep this towards the end of the article? As far as I'm concerned, both are archaic and basically unused today, and both make the device sound, for lack of a better term, stupid. I don't feel we should lead the article with them and get people using them again. I've been involved with TWTs for 15 years. I've been to five of nine international vacuum electronics conferences since 2000, where the TWT is front and center, and 400 participants come from around the globe. I've done a search on the IEEE journal database. I have never heard either of these uses, except on Wikipedia. The only term I regularly hear is "tweetuh" for a TWTA or "El-tweetuh" for a linearized TWTA. Willus (talk) 13:30, 11 July 2008 (UTC)

BTW, this has also been discussed on Axlq's talk page. Willus (talk) 14:33, 11 July 2008 (UTC)

I would be happy to omit them entirely; we know of only a single document that says TWAT stands for traveling-wave amplifier tube, and it's probably just wrong (the other one that was listed used TWAT for traveling wave tube, and it was in a patent, so was probably just an attorney's typo). Feel free to fix it. Dicklyon (talk) 15:47, 11 July 2008 (UTC)

I'll think about what I'd like to do. I don't think TWAT is "wrong" since Axlq remembers it and claims that older engineers he's talked to remember it, so I'm fine (and Axlq was, too) keeping it and giving it a less prominent position and also making it clear that it's outdated. Do you have any suggestions for an alternate place for it? Willus (talk) 19:13, 11 July 2008 (UTC)

I don't mind putting it elsewhere in the article. but I think it deserves mention somewhere. I listed three sources near the top of this discussion that mention it. We were using it in the 1980s but the term was falling out of favor - I surmise that may be due to more women becoming engineers. A Vietnam-era radar operator and other engineers from the 1950s told me their use of the term was routine. The term has historical interest but I agree it isn't something you see in use nowadays, except in older documents. =Axlq 04:59, 12 July 2008 (UTC)

I agreed before that it should be mentioned if we have a reliable source. At this point, however, I'm not convinced that any of the sources are reliable. We have it listed in two (or more) acronym dictionaries, but no actual uses in books or papers; the patent use of "TWAT" was for "traveling wave tube", so not very convincing there. The recollection of people who used it informally is not very relevant. Five books that include it all have "acronyms" in their title; they seem to copy from each other irrespective of whether the acronym is ever actually used. Google scholar find nothing. Dicklyon (talk) 06:12, 12 July 2008 (UTC)

Look at it this way: I challenge you to find a source for the resistor color code mnemonic that everyone knows and uses ("bad boys rape our young girls but Violet gives willingly"), but isn't published anywhere you would consider relevant. Yet, there's something notable about an oral tradition that propagates without ever being written down by the practitioners in the field. As such, it deserves mention in an encyclopedia, even if the only sources that can be found aren't textbooks or technical papers.

Just look at the citations in electronic color code#Mnemonics — a book about literature, and a book of fiction! Naturally less-memorable versions will appear in textbooks. For obvious reasons, that mnemonic as well as the acronym TWAT aren't going to be found easily in technical sources. The fact that I found better sources for TWAT than for the resistor color mnemonic surprises me, frankly. =Axlq 15:31, 12 July 2008 (UTC)

Many versions of the color code has been published, and are referenced in wikipedia. Wikipedia is NOT about oral tradition; it's about reliable secondary and tertiary sources. Dicklyon (talk) 15:42, 12 July 2008 (UTC)

You missed my point. The version passed on most by oral tradition isn't to be found in a source you would consider valid, but we do the best we can. Same with TWAT. The acronym was used, I'd say widely at one point, and there are references for it, better references than what editors managed to find for the resistor color code. =Axlq 16:50, 12 July 2008 (UTC)

I think I got your point, but disagreed with it. The resistor color code and mnemonics for it are well sourced in books (e.g. these 21 with "...our young girls, but...", most of which include "rape" and "gives willingly", and some with "black boys" which makes the most mnemonic sense since it disambiguates black from brown). The use of "TWAT" for traveling wave amplifier tube appears nowhere exception in acronym compilations, the majority of which share an editor. No actual uses or discussions of it have been found, and oral history is not what we should be reporting here and unless we find a source about the oral history. Dicklyon (talk) 18:07, 12 July 2008 (UTC)

My feeling is that for something that was mostly an oral tradition, any reference is reasonable, even if it is debatable, since references for oral traditions can be hard to find. How about a "Historical Notes" section at the end of the article where this could be mentioned? Willus (talk) 18:22, 12 July 2008 (UTC)

You're saying that for things were reliable sources are hard to come by, we don't need them? Dicklyon (talk) 04:19, 13 July 2008 (UTC)

The term I used was "debatable," not "reliable." I got tired of waiting and implemented my suggestion, along with some slight wording changes. If you guys decide to remove this altogether, I'm fine with it. It's between the two of you now. Just please don't put it back near the top of the article. Willus (talk) 14:54, 13 July 2008 (UTC)

Looks fine to me. If that's all you wanted to do, we shouldn't have gotten sidetracked by this debate. =Axlq 13:40, 15 July 2008 (UTC)

Just wanted to say as a third-person that I think the historical notes section is an adequate solution. I have not been in that business by more than 4 years, but I have never heard other terms than TWT (pronounced as the individual letters) used where I am. -- Slaunger (talk) 22:52, 20 July 2008 (UTC)

The difference between a klystron and a TWT

I just read this article after eading the klystron article because I would like to familiarize my-self with those two types of RF amplifiers. I sit back with some open questions are reading them

1. I have the impression that if you take a klystron and add a helix wire you have (conceptually) a TWT. Is that correct understood from a birds eye perspective?
2. The concept of the klystron (1939) was developed before the TWT (WWII). Would it be fair to consider a TWT as a refinement of the klystron?
3. The helix wire makes thwe RF signal propagate with the same speed as the electron beam along the tube. Is this what makes the TWT so widebanded?

I do not know what the answers of these questions are, but I think it could be helpfull to add some comparative remarks to klystron (and possibly other types of RF amplifiers that I have yet to learn about) in this article as it helps the reader to navigate and relate the different kinds of amplifiers to each other. -- Slaunger 13:25, 30 October 2007 (UTC)

In all fairness I should mention that reference is made to the klystron, but I think the some comparative remarks should be moved up in the more introductory text and perhaps be elaborated a little. -- Slaunger 07:41, 31 October 2007 (UTC)

Solenoid coil or permenant magnet

64.209.156.12 substantially removed the following:

"A solenoid coil wrapped around the tube creates a magnetic field which focuses the electrons into a beam, which then passes down the middle of a wire helix that stretches the length of the tube, finally striking a collector at the other end. (In lower-power devices, the solenoid coil can be replaced by permanent magnets.)"

This was substantially replaced with:

A magnetic containment field around the tube focuses the electrons into a beam, which then passes down the middle of a wire helix that stretches from the RF input to the RF output, The electron beam finally striking a collector at the other end. (rem, lower power is not an absolute value and is therefore meaningless)

I think the original was appropriate in the article. Nevertheless, the comment about low power being meaningless is a comment about the article which should have been put on the discussion page, not in the article itself. I removed it. Rsduhamel 21:00, 4 December 2007 (UTC)

I think the original was appropriate, too. The new version removes important information about typical focusing structures in TWTs in favor of something more generic. "Lower power" was not meaningless, as most PPM-focused TWTs (tens to hundreds of watts, but largely dependent on frequency) are indeed "lower power" than most solenoid-focused TWTs (multi-kilowatt, again with lots of wiggle room). Because solenoids require a power source, are heavy, and frequently require cooling, they are typically used only when the beam cannot be adequately focused by a PPM stack, and that typically occurs as beam current (and hence beam power and RF power) increases. At some point, this should be reverted--maybe not exactly to what it was, but with information about solenoids vs. PPM again. I can do it at some point. Willus (talk) 18:52, 8 May 2008 (UTC)

Merge from TWTA into TWT

In Nov. 2005, when there was a consensus to change title from traveling wave tube amplifier to traveling wave tube, Engineer Bob did that, but then also, without any prior suggestion or comment, took out the TWTA bits and made a new article that has remained unreferenced and nearly orphan. I propose we merge it back in as a section or two. Dicklyon (talk) 21:33, 6 January 2008 (UTC)

Done; improvements are invited. Dicklyon (talk) 07:45, 15 January 2008 (UTC)

Sorry for the delay; I haven't logged in here in several weeks. The re-merge was nicely done, and I concur with the end result. -- Engineer Bob (talk) 03:43, 29 January 2008 (UTC)

Book Spam

Why the removal of the Gilmour reference and the removal of the reference to the IEEE journal search engine from the TWT article on July 3, 2008? The Gilmour reference is not spam. It is very likely the best selling TWT book of the last 20 years (for what that's worth, though I cannot verify that--I suppose I could contact the author and ask how many he has sold). It is on the shelf of a significant number of TWT engineers (though I can only really vouch for U.S. engineers). As for the IEEE, it is the publisher of the proceedings of the annual International Vacuum Electronics Conference (IVEC), which is where most members of the TWT community publish their latest research, so it should be mentioned as the leading repository of modern TWT journal articles. By putting these references with Pierce and Kompfner, I'm trying to give the key modern references for TWTs to contrast to the 50-year old works of the inventors. Willus (talk) 14:14, 3 July 2008 (UTC)

It said "In 1994, A.S. Gilmour wrote a modern TWT book[5] which is widely used by U.S. TWT engineers today, and research publications about TWTs are frequently published by the IEEE." The book and author were being promoted, not used as a ref; it work be great to say something supported by the book, and cite it. As for the IEEE search engine citation, that is basis of the "original research" claim which is probably not otherwise supportable. Dicklyon (talk) 15:08, 3 July 2008 (UTC)

I'll come up with something to reference Gilmour. I don't understand your statement about the IEEE search engine. Please clarify. I would like to acknowledge the IEEE as a good source for modern TWT journal papers. How do you think I should do this? Willus (talk) 17:34, 3 July 2008 (UTC)

Using a search result to back up an interpretation is WP:Original research. If you find an actually WP:RS that says that there are still lots of TWT pubs, you could say that, but to search the IEEE and infer it, you can't do. They're well known as a good source for electronics articles already, so don't worry about; reference a paper or two if you find some interesting content there. Dicklyon (talk) 18:54, 3 July 2008 (UTC)

Reference Style

(moved from my talk page July 9, 2008) Discussion of using just "References" footnoting (status quo) or changing to reference style where books are separated out.

I reverted your major edit because it completely changed the reference style to a more awkward style. Dicklyon (talk) 05:58, 9 July 2008 (UTC)

You know, Dick, I really tried this time, and you keep killing my edits. More awkward is your opinion. Two of the most recent featured articles I looked at (e.g. atom), used exactly the same style. Show me the best way to do multiple book references pointing to different pages in the book. Show me an official Wikipedia guideline that says the style I went to is not preferred. As the TWT articles expands (which I hope to help with, if you'll let me!), there will be more book and journal article references. The other advantage is that moving the books to the end makes the editing area easier to follow. Willus (talk) 12:57, 9 July 2008 (UTC)

Yes, more awkward in my opinion; but in general, you don't change an existing ref style (see Wikipedia:CITE#Citation_styles). If you really need to point to different pages specifically you can list a book more than once. Or just list the book without pages, or with a range of pages. Dicklyon (talk) 15:24, 9 July 2008 (UTC)

So I reverted it again. Make you content improvements, but respect the exisiting citation style. Dicklyon (talk) 15:26, 9 July 2008 (UTC)

So if the initial author's referencing scheme isn't a good fit as the article evolves, we're stuck with it? I can understand the sentiment of that rule, but as I look through featured Wikipedia articles, the ones that have evolved to a lot of references tend to follow the format of, e.g. the atom article. I would like to establish this format now, particularly since I can envision several references to different pages of large books on TWTs (and there are many good ones to choose from) and do not wish to have the same book reference repeated again and again in the edited draft, and it is very helpful to have page numbers for large book references. The more sensible format for multiple book references with different pages is the one I chose. I tried the link to the user who posted the first draft of the TWT article and established the references format, but that user doesn't even seem to exist anymore. Does anybody else feel strongly about this issue? Willus (talk) 20:10, 9 July 2008 (UTC)

I can't see what problem you're trying to solve. Is it just that one of the books is cited on two different pages? Dicklyon (talk) 20:22, 9 July 2008 (UTC)

I'm thinking long-term here. The TWT article could end up being much more extensive, with several references to the same books, but yes, different pages. It seems like articles with lots of references (that I've looked at) tend towards the reference style in atom. The current reference style in the TWT article doesn't seem to lend itself well to citing different pages out of the same book at different places in the article. Or am I missing something? Willus (talk) 23:16, 9 July 2008 (UTC)

I'd say it's not broke; so don't fix it. Dicklyon (talk) 23:27, 9 July 2008 (UTC)

It is broken to me. I changed it because I want to make it easier to edit this article. Putting the exact same citation information in the edited text several times for any given book is tedious, more mistake prone, and harder to edit, which is exactly why articles like atom use the style they do. If you can't offer me a better alternative, then why not leave my edits in and see if other people might actually appreciate them before undoing them so hastily. With the atom reference style which I tried to implement, it is easier for me and for others to reference other parts of a book which is already cited. Willus (talk) 01:21, 10 July 2008 (UTC)

I prefer the style that we have, and the general policy is to not change it. You don't have to put a ref in twice to use it twice; just use a name as in <ref name=x>. Dicklyon (talk) 01:26, 10 July 2008 (UTC)

<ref name=x> does not allow specifying unique page numbers for the same book in different references. In the book by Pond for example, which is an excellent new book about TWTs which I can foresee citing in numerous places, the index is very poor and page numbers are critical to checking the citations. I'm offering a way to improve the article in terms of looking up citations and for future editing. Do you plan on having this article grow and improve, or do you prefer that it stagnate? Willus (talk) 03:10, 10 July 2008 (UTC)

Template:Rp allows unique page numbers. — Athaenara ✉ 10:55, 10 July 2008 (UTC)

It's not my impression that the reference style will prevent growth. If you run into problems with citations, propose a change at that time and see if others agree. Dicklyon (talk) 03:35, 10 July 2008 (UTC)

Thank you, Athaenara. I hadn't caught your comment initially. I will use your suggestion. Willus (talk) 11:02, 10 July 2008 (UTC)

"The bandwidth of a broadband TWT can be as high as three/one octaves"?

Near the beginning of the article is stated "The bandwidth of a broadband TWT can be as high as three octaves". Near the end is stated "The bandwidth of a broadband TWTA can be as high as one octave". Which is it? --Dan Griscom (talk) 00:11, 21 October 2009 (UTC)

Inventor of TWT

Rudolf Kompfner or "Nils Lindenblad of the Radio Corporation of America", re this edit. Is there any controversy about this? I reverted as no new reference was given.-☢-220.101 talk^\Contribs 14:24, 28 September 2010 (UTC)

Fire Direct Website

This reference has been in the article since at least July 2008, but seems largely promotional ie. lots of contact info, but only one line is relevant as a reference to when TWTs were manufactured by English Electric Valve Company Ltd (now E2V).-☢-220.101 talk^\Contribs 14:24, 28 September 2010 (UTC)

That one line is the point. The company was listed as an early producer of TWTs, and this source seems like it provides reasonable support for that, no? Dicklyon (talk) 15:14, 28 September 2010 (UTC)

Surely there is something better around? (I tried looking but for some reason I am having trouble with accessing Google at the moment!) What about the previous question about the inventor of the TWT. Is there real debate about who was 'first' ie. Nils Lindenblad not Rudolf Kompfner as the editor I reverted suggested? - 220.101 talk^\Contribs 17:07, 28 September 2010 (UTC)

I think the main reason Lindenblad isn't credited for inventing the TWT is that his patent didn't use the term "traveling-wave tube." That's essentially what it was, but Lindenblad called it an "Electron Discharge Device System." It was amazingly advanced for a TWT--it had periodic magnetic focusing, a multi-stage collector, and a tapered helix--all features of modern day versions. But Kompfner, I believe, coined the term TWT, hence he gets most of the credit. I'd have to check this in some of Kompfner's original work to be sure. Willus (talk) 14:22, 9 October 2010 (UTC)