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WikiProject Electronics (Rated C-class, Mid-importance)
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Are there any diagrams/photos of valve tetrodes on WP?--Light current 03:39, 20 January 2006 (UTC)

Merge Screen grid into Tetrode[edit]

Agree Pol098 (talk) 23:20, 16 March 2009 (UTC)

plate characteristic curves[edit]

I enjoyed reading the the article. I think it gives an excellent understanding of the purpose and uses of the extra grids. The only thing I thought was missing was a set of typical plate characteristic curves. The triode article does include one. The tetrode and pentode plate characteristic is very different from that for the triode, and I think the comparison is illuminating. I believe that most designers working with electronic amplifiers rely on these graphs. As many readers may know, this sort of graph is useful enough that there is actually an instrument called a curve tracer designed specifically to create them (although these are not generally sold for vacuum tubes). --AJim (talk) 14:53, 12 May 2009 (UTC)

Peer review request[edit]

Just a note that the request seemed to have been archived, and not the review itself. Opencooper (talk) 04:52, 13 December 2015 (UTC)

Merge Beam Tetrode into Tetrode ?[edit]

No real consensus either way in over a year.
The following discussion is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion. (talk) 17:15, 13 February 2016 (UTC)

Opinions ? G4oep (talk) — Preceding undated comment added 10:24, 6 January 2015 (UTC)

  • Support. Beam tetrode is no more than a large stub. Expanding it into an adequate article would require a great deal of duplication of content in this article. The two tubes should be treated in the same article. --ChetvornoTALK 11:14, 6 January 2015 (UTC)
  • Support, I guess Meh Slightly oppose - this article (tetrode) is already 25 K, beam tetrode is 7 k - on the other hand, some of the content that would be brought over is already duplicated here, so perhaps the merge won't make the result too long. Oh, go ahead, if some keener writes 65000 bytes of brilliant referenced prose on the history and economic effect of the beam tetrode, we can always split it off later. I'll put the tags on, must follow sacred procedures. --Wtshymanski (talk) 14:45, 6 January 2015 (UTC)
  • Strongly Oppose. A beam tetrode and a tetrode are not the same thing and have very different characteristics. If a merge was on the cards, then it would be more appropriate to merge beam tetrode with pentode as it has a much closer affinity. The article even compares it with a pentode. It should be remebered that the beam tetrode was developed by MOV solely to side step Philips's patent on the pentode (though having been developed has many desireable characteristic - so much so that many valves officially described by their manufacturers as pentodes are, in reality, beam tetrodes)). On the other hand no tetrode valve would ever be built as a beam tetrode because they are so completely different. (talk) 16:47, 6 January 2015 (UTC)
  • Oppose. Like the IP above. --Wosch21149 (talk) 22:24, 6 January 2015 (UTC)
  • Re the points made by, I have added some material to the present page relating to beam tetrodes with pure tetrode structure and no beam plates. As indicated in the text, these tetrodes were built as beam tetrodes, and explicitly named as such by the manufacturer. This type of beam tetrode is very familiar to HF & VHF power amplifier users, though valve audio buffs might not be aware of it. I can sympathise with the point of view that beam tetrodes with beam plates could (maybe should) be classified as pentodes, since the beam plates definitely form a fifth electrode system, and their function is identical to that of the suppressor grid, although their mode of action is quite distinct. On the other hand, beam tetrodes without beam plates cannot be classified as a type of pentode if the etymology of these terms is to retain any significance (4 vs 5 electrodes). So perhaps, in addition to the established naming system, the question hangs on whether beam tetrodes with beam plates have enough in common with pure tetrode beam tetrodes for them to be classified together. The similarity between them, and the common distinction from pentodes lies in the use of a space-charge electron beam to prevent secondary electrons from reaching the screen grid at low anode voltage. Pentodes achieve this result with a completely different technique. (talk) 15:11, 7 January 2015 (UTC)G4oep (talk) 17:38, 7 January 2015 (UTC)
For those who want to merge beam tetrode into pentode, I would like to point out that this is against WP:COMMONNAME. In WP, in general, topics are covered in articles based on their common names, not on what they "act like". --ChetvornoTALK 22:03, 12 January 2015 (UTC)
  • Support: Since the tetrode article already includes three different types of devices (space charge, bi-grid and screen grid) with very different purposes and characteristics, there doesn't seem to be an issue with introducing a fourth. However, if beam tetrode is merged into tetrode, then the pentode article should include mention that beam tetrodes are occasionally referred to as pentodes in some circles (e.g. audio) because the two device types have similar characteristics and applications. --Theodore Kloba (talk) 15:40, 9 July 2015 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.


Tetrode Assessment[edit]

The following was posted to my talk page. I think it best to respond here. ~KvnG 22:34, 10 January 2015 (UTC)

Thank you for looking at the Tetrode article and responding to my request for a reassessment. One of the reasons for my request was to gain some experience in the way in which the criteria for assessment are applied, and what you have done has helped. I do not like to presume too much on your time and effort, but it would help me further if you were to give some comments on the deficiencies in the article. Do they lie in the referencing (largely historical, and difficult to access), the inclusion of irrelevant material (such as my explanation of the superhet), omission of needed relevant material (if so what new material should be included), general organisation & presentation - I have aimed at the Class B criterion of avoidance or explanation of technical language; does this detract from the required style, or augment it ? I would like to become more proficient as a Wiki editor, and if you could help me to focus on what is required, using this article as an example for honing my skills, it would be a great help. If you are sufficiently interested in this topic to provide detailed criticism, we could, perhaps co-operate in raising the quality further; I would do the necessary research and editing, of course unless you want to contribute to that as well. The history of thermionic tubes is of considerable interest to me, so I would be quite happy to research this further - I have already learned a lot. G4oep (talk) 10:47, 10 January 2015 (UTC)

I've given the article a c-class rating. As far as what can be done to reach b-class, see Wikipedia:Version_1.0_Editorial_Team/Assessment/B-Class_criteria. The article, as it stands, is weak on structure, writing and accessibility. We need to fully resolve the Beam tetrode merge issue. The prose needs to be tightened up. We need to get feedback from non-technical readers as to sections that are difficult to understand without sufficient electronics background; Start with the lead here. Have a look at Vacuum tube as an example of something closer to a b-class article (technically, a true b-class article should not have any maintenance tags). Achieving b-class is actually a fairly big deal for any article. ~KvnG 22:46, 10 January 2015 (UTC)

Thank you for your comments. I appreciate the trouble you have taken. I have changed the title of the anode characteristics section to make it clear that this is not a digression, but is an essential link between the screen-grid & beam tetrode sections. In other respects I feel the structure is sound - I introduce the 3 types then describe them in historical order. However you have not commented on the inclusion of the superhet material. Re "accessibility" are you referring to the references, many of which are historical ? Many of these (for example the references to early C20 patents), are important when questions of priority are considered, and are also important primary sources. However, many of them are referred to in Thrower, which I believe is still in print. Do you feel that it is better to quote modern secondary sources rather than rare and difficult primary ones ? Since valve technology is now only of historical interest modern textbooks covering this topic (for example an alternative to Terman) simply don't exist. Finally, would you like to comment on the merger question ? Presumably, if it is to be answered, the more fors or againsts the better. — Preceding unsigned comment added by G4oep (talkG4oep (talk) 17:37, 11 January 2015 (UTC)

I don't have enough expertise to weigh in the merge proposal. There doesn't seem to be consensus or consistency on how to represent the relationship between tetrode, pentode and beam tetrode. I have made some improvements to the lead to improve accessibility. ~KvnG 19:27, 11 January 2015 (UTC)

The relationships between pentodes, tetrodes & beam tetrodes[edit]

This is how I see it, and I would like to invite the comments of others.

1) Tetrodes are best defined as valves having 4 electrodes. Examples are those I have given, including beam tetrodes which do not have beam plates. Exclude beam tetrodes with beam plates for the time being. With that exclusion, I don't expect this point to be contentious.

2) Pentodes could be defined as: (a) valves having 5 electrodes, or (b) valves having 3 mesh grids, an anode and a cathode. I prefer the former definition.

3) That leaves beam tetrodes with beam plates (BTWBP). My view is that logically these should be classed as a type of pentode, since this would fit my preferred definition of a pentode. However, historical usage is against this; "beam tetrode" is an established term which has been used to refer to these types since their invention, and the term is still current. It is no use for me, or anyone else in the modern world, to try to change this - we are stuck with it, however illogical it might seem. Historically it is easy to see why BTWBPs were not classified as pentodes. At the time of the invention of the BTWBP, the name 'pentode' had already been claimed and the device patented; it was a valve with 3 grids (definition 2b). The BTWBP was a separate invention with its own patent, and the manufacturers established a legal right for it to be distinguished from a "pentode" as a consequence of its separate patent, and distinctly different mode of operation. To my mind, this explains why a BTWBP is not a "pentode"; the point was argued and settled definitively and legally about 75 years ago, and there is no point in re-opening the argument.

4) The term "beam pentode" would seem appropriate for BTWBPs, but it is rarely used. The only example I have found is this:

I therefore propose that in agreement with generations of valve users before us, we accept the historical terminology, and continue to discuss BTWBPs under the heading "Tetrode", and not "Pentode". G4oep (talk) 19:37, 12 January 2015 (UTC)

I agree. In compliance with WP:COMMONNAME this article should cover tubes that are commonly called "tetrodes". It should either have a section on "beam tetrodes" or a link to a separate article. If there is a question, the usage found in the largest number of reliable engineering sources should decide. We want people to be able to find the correct article with a minimum of clicking. --ChetvornoTALK 21:48, 12 January 2015 (UTC)

Peer review[edit]

This is a review of the current state of the article by Chetvorno. I have education in electronics but no special knowledge or experience with vacuum tubes.

I think the article has been improved greatly over the last few months by the distinction of the different types of tetrodes used over the years: space-charge grid tube, bi-grid valve, beam tetrode in addition to the screen grid tube, and the addition of valuable historical material on their development and use. I had no idea that the space charge grid tube had wide use! The narrative of the development of the tubes is excellent. The detailed information on characteristics and applications of the tubes is very useful. The graphs of anode curves of the triode and tetrode are a great visual aid; comparing them clearly shows the improvement in anode resistance discussed in the text.

Although the article is really much better, since G4oep asked for specific ways to improve it I will devote most of the review to that. These are just my personal opinions:

  • I feel a deficiency in the article is a lack of distinction between historical and modern tubes. It's not made clear (at least in the Introduction and Overview) which types are obsolete and which are still used, and which were most important and widely used (WP:ROC). As fascinating as the historical tubes are, I think most readers will be interested in modern uses of the tetrode, as in: "Dude, how do the tetrodes in my tube-type guitar amplifier work?" or "How do the tetrodes in my amateur radio transmitter work?". I think that (besides the beam tetrode) the screen-grid tube is clearly the most important if not the most used, and is what most sources mean by the term "tetrode": [1], [2], [3], [4], [5], [6], [7], [8]. Are the space-charge and bi-grid tubes largely obsolete? If so, I think the introductory sections should concentrate on the screen-grid tube and avoid giving WP:UNDUE WEIGHT to the less-used obsolete types. Rather than covering the tubes chronologically, maybe the screen-grid tube description could be moved to the top, and the space-charge grid tube and bi-grid valve possibly put under a "History" or "Historical tubes" section?
    • Perhaps a "Types" section could be added, consisting of a bulleted list of the different types of tetrode discussed in the article, with a summary of its differences from other tetrodes and what made it notable. Something like:
      • Screen-grid tube (developed 1919-1926, Ando, Hull, Tellegen) - Second grid added between control grid and anode to prevent parasitic oscillation. Most well-known type and type most commonly meant by the term "tetrode". Largely superseded by the pentode in 1940s because of secondary emission, although still in use in legacy equipment.
      • Beam tetrode (1933, Bull and Rodda) - In addition to screen grid had beam-forming electrodes. Probably most widely used. Commonly used as power amplifiers into the 1960, and still used in power applications.
      • Space charge grid tube (1913, Langmuir) - Second grid added between control grid and cathode to allow tube to operate on lower anode voltage and increase gain. Earliest type of "tetrode". Had limited use in battery-powered equipment until 1950s.
      • Bi-grid tube - etc.
  • I agree with Kvng above that the text should be more accessible for general readers. See WP:TECHNICAL, MOS:ACCESSIBILITY, and WP:Make technical articles understandable. Although the writing is clear to a person with an electronics background, a lot of the readers may be totally nontechnically-educated (think English majors). So at least the first parts of the article should be written for a more elementary level, say secondary-school students (WP:UPFRONT). Although the article of a complicated device like this can't be totally understandable to everyone, the lead and "Overview" section should be (WP:EXPLAINLEAD), and the rest should be as much as possible. Another issue is each WP article is supposed to stand on its own as much as possible, and not require the reader to read another article (such as vacuum tube) to understand it. Below are some points that could be improved - again these are just my opinion:
    • The introduction describes the order of the electrodes but not the tube construction. There should be a brief but complete physical description of the tetrode in the Overview. For example: "The screen grid type tetrode consists of a sealed evacuated glass envelope containing four concentric metal electrodes; cathode, control grid, screen grid, and anode. The thermionic cathode is a narrow metal tube down the center heated red-hot by an internal heater wire, the two grids are cylindrical screens or helixes of wire surrounding the cathode, and the anode is a sheet metal cylinder or box surrounding the grids." Since the screen grid tube is the one most commonly meant by the term "tetrode", I think it should be described up front, and then the sections on the other tubes can describe how they differ from it.
    • The current and past applications of tetrodes should be listed up front. Many readers may not know that, along with other vacuum tubes, tetrodes were used in consumer electronic devices, TVs and radios, until the 1970s when they were largely replaced by transistors. Now they are mostly used in power applications (I think?) like radio transmitters and industrial heating (I think?).
    • In the "How it works" section, rather than the technical word "gain" maybe use "amplification", nontechnical readers need to know the purpose of the tetrode is to amplify. I think that word should be in the Intro too; the tetrode is an amplifying vacuum tube.
    • In the "Screen grid valve" section, the instability of the triode that led to the invention of the screen grid could be explained in more elementary detail; the interelectrode capacitance caused energy to be fed back from the plate circuit into the grid circuit to be amplified again; this positive feedback loop caused unwanted oscillation, parasitic oscillations. In 1920s triode TRF radio receivers these caused annoying shrieks and whistles from the speaker.
    • Similarly the process of secondary emission could be explained in greater detail for general readers: how electrons from the cathode, accelerated by the anode voltage, "knock" secondary electrons out of the anode surface. Perhaps a separate subsection could be devoted to it, before its effects on anode characteristics are described.
    • Most of the sections have large blocks of dense text which are kind of hard to read. It would improve readability, especially in the important sections relating to the screen grid tube, to add structure by breaking them up into subsections or bullet points where possible. For example, the two benefits of adding the screen grid, (1) preventing feedback and (2) increasing output impedance, could be listed in bullet points.
    • An alternative solution to the accessibility problem is to add a second brief, simplified, nontechnical discussion of the important points of the screen grid tube to the "How it works" section for general readers: the feedback of the triode, how the screen grid prevents this, how in the screen grid tube secondary electrons "knocked out" of the anode go to the screen, causing negative resistance, which was solved by the invention of the pentode. Then your more technical discussion of these points in "Screen grid valve" and "Anode characteristics of screen grid valve" can be left as it is, for the more experienced readers.
    • The pictures are great, but it would be nice to find a cutaway diagram of a tetrode tube. A simple circuit diagram of a "generic" tetrode stage would be useful too, showing how the screen grid is biased from the plate supply and bypassed to ground.
  • As Kvng mentioned, I feel the text is a little wordy and could be tightened up.

Other issues:

  • The labels on the triode graph are not legible. Maybe they could be given in the caption: "Horizontal axis - plate voltage, Vertical axis - plate current, branches represent increasing control grid voltage"
  • I read in some sources [9] that later screen-grid tetrodes (post WW2) had a coating on the anode which suppressed secondary emission, reducing the negative resistance "kink"?
  • On your question to Kvng about sources, theoretically primary sources should be backed up by secondary ones (WP:PSTS). A lot of old out-of-print vacuum tube textbooks are available for free download at
  • A general guide to improving articles is WP:Writing better articles. For examples of the best technical articles, see the articles on technical subjects in WP:Featured articles.

In summary, although more could be done to make it easily comprehensible, a great deal of important information has been added, and it has the basics of an excellent article. --ChetvornoTALK 05:16, 15 January 2015 (UTC)

Thanks a lot for that - I appreciate your comments greatly. This has been an interesting experience, and I have enjoyed doing the research. The subject matter interests me, but conforming to the bureaucratic requirements is tedious and unrewarding; I am happy to delegate that to someone else with the right mindset. I will continue to work on this for my own purposes and in my own way, but I shall make no further changes to the article. I might add a page to my own website in order to make my work available to others. G4oep (talk) 10:32, 18 January 2015 (UTC)

I hope you will stick around and contribute improvements to other articles. You might want to consider joining WP:ELECTRONICS. ~KvnG 20:50, 20 January 2015 (UTC)


I consider the removal of the circuit symbol of the tetrode to be an act of vandalism. I downloaded the original diagram, made a minor edit, then uploaded the edited version, with the explanation that the edit was my own work, for which I made no copyright claim. There can be no reason for not accepting this. Whoever made the deletion is clearly more interested in the minutiae of wikki bureaucracy and mindless form-filling than in improving the content of the pages. I find this kind of pettiness a real deterrent to creative input. I have made several attepmts to improving this and other pages, and have been continuously hampered by opposition from others who are just plain ignorant. g4oep — Preceding unsigned comment added by (talk) 11:39, 3 April 2015 (UTC)

You're referring to this one, right? It looks like it was done automatically by a Commons bot, due to some technical problem with the licensing. --ChetvornoTALK 12:42, 3 April 2015 (UTC)