Talk:Yagi–Uda antenna

message: Nice article! Possibly a bit too deep too quickly. Remember, we are not all wireless communications experts ;-)
Can you please provide a key for the energy flow diagram on this page? What is electric field, what is magnetic filed, what is physical antenna etc...
Perhaps we could also provide a link from here back to Tesla's experiments with wireless transmission of electrical energy.
darkside2010 00:26, 2 January 2006 (UTC)
replies: text: As you say, not everyone is a wireless communication expert, but one would be even less of one if one believed much of what is written here. I've no idea what that is supposed to be showing. Since you raised this point more than 3 years ago, and nobody has substantiated it, I think I'll remove it. Drkirkby (talk) 09:21, 18 October 2009 (UTC)
thread_title: Energy Flow Diagram

message: The statement about spacing between elements being "approximately 1/4 of a wavelength" is wrong.  While spacing varies depending on design, the normal spacing is about 1/8 of a wavelength.
A good source we should footnote is http://www.cebik.com.  Mr. Cebik has written a large number of articles on antenna design, many of which cover details of Yagis in far more detail than is appropriate for an encyclopedia.
Off2Explore 19:16, 27 April 2006 (UTC)
replies: text: This article appears to contradict itself; the text has the elements on quarter-wavelength spacing (which is plausible) but the illustration :image:Antena yagiuda500.png denotes one-tenth wavelength spacing. I'm presuming these aren't both correct? --66.102.80.212 (talk) 20:22, 19 March 2009 (UTC)

text: theoretically all spacings will work :) however, because spacing changes the impedance at the feed point of the driven element(dipole), and in the real world we only have the choice of a few cable impedances with which to connect our antenna you will see 1/10 to 1/8 wavelength typicallyBazzaar (talk) 23:36, 2 September 2009 (UTC)
replies: text: Can you provide any professional reference (not amateur site) that theoretically all spacings will work? Of course you can not, since it is simply not true. Even among radio hams I have never herd that one. Drkirkby (talk) 09:17, 18 October 2009 (UTC)
replies: text: I was taught that the reflector should be about half a wavelength behind the active element and that the director(s) are typically separated from each other and the active element by about a quater of a wavelength each but that there's more scope for variation with the directors. BrianDGregory (talk) 15:14, 18 November 2010 (UTC)

text: The diagram that shows the same one tenth wavelength between the reflector and active element as between the active element and director must surely be regarded as totally wrong. Simply making an element a little longer will not change it from a director into a reflector, it's mainly the spacing that does that. BrianDGregory (talk) 15:14, 18 November 2010 (UTC)
thread_title: Element Spacing & Design

message: The diagram needs to be revised.  The text suggests that the reflector and director are 105% and 95% of the driven element length, yet the artist has rendered .55 lambda and .45 lambda.  
:This article appears to contradict itself; the text has the elements on quarter-wavelength spacing (which is plausible) but the illustration :image:Antena yagiuda500.png denotes one-tenth wavelength spacing. I'm presuming these aren't both correct? --66.102.80.212 (talk) 20:22, 19 March 2009 (UTC)
replies: text: theoretically all spacings will work :) however, because spacing changes the impedance at the feed point of the driven element(dipole), and in the real world we only have the choice of a few cable impedances with which to connect our antenna you will see 1/10 to 1/8 wavelength typicallyBazzaar (talk) 23:36, 2 September 2009 (UTC)
replies: text: Can you provide any professional reference (not amateur site) that theoretically all spacings will work? Of course you can not, since it is simply not true. Even among radio hams I have never herd that one. Drkirkby (talk) 09:17, 18 October 2009 (UTC)
replies: text: I was taught that the reflector should be about half a wavelength behind the active element and that the director(s) are typically separated from each other and the active element by about a quater of a wavelength each but that there's more scope for variation with the directors. BrianDGregory (talk) 15:14, 18 November 2010 (UTC)

text: The diagram that shows the same one tenth wavelength between the reflector and active element as between the active element and director must surely be regarded as totally wrong. Simply making an element a little longer will not change it from a director into a reflector, it's mainly the spacing that does that. BrianDGregory (talk) 15:14, 18 November 2010 (UTC)
thread_title:  Diagram Inaccuracies 

message: "If one holds out one's arms to form a dipole and has the reflector behind oneself, one would receive signals with maximum gain from in front of oneself"
...Um, no, one cannot receive signals with one's arms. Not even if one wears a tinfoil hat.
Why not just say that the antenna receives signals with maximum gain from the direction of the director (or smaller element)?  —Preceding unsigned comment added by 99.231.124.188 (talk) 05:58, 16 June 2008 (UTC)
thread_title:  Wording 

message: Why exactly is Cardioid listed as a related article? The word shows up nowhere else in the entire article. Was it used in a previous version of the article? 67.82.99.84 (talk) 02:38, 26 October 2008 (UTC)
replies: text: It's not clear to me any relevance either. It has been removed Drkirkby (talk) 09:33, 18 October 2009 (UTC)
thread_title:  Cardioid? 

message: description of this antenna type is confused with that of the log periodic type;
"directors progressively shorter than a half wavelength to couple signals of increasingly higher frequencies onto the dipole"
no, the elements in a Yagi are progressively shorter so that the phase angle of the signal in each director is changed in such a way that only in the desired direction do they combine in phase and cancel in all other directions, this is the fundamental property of the Yagi which is missing from this article
the log periodic has progressively shorter elements to allow it to cover a greater frequency range, but it has no "the dipole" the whole array is driven
excepting the use of traps, the Yagi is a narrowband antenna(a few percent of design frequency) and the log periodic a broadband antenna(octave frequency coverage)Bazzaar (talk) 23:27, 2 September 2009 (UTC)
thread_title:  Description 

message: Clearly most if not all of this article was written by amateur radio operator (a ham). I have nothing against them (I am one myself). But I know that a lot of this is very poor by the standards of Wikipedia. It is clearly within the scope of amateur radio, but I do not believe that the article should be written with only radio hams in mind. Specific issues I see:
* Terms like good match are not appropriate. 
* I'm not sure what that energy flow diagram is supposed to say.
* The sentence Typically, all elements are arranged at approximately a one-quarter-wavelength mutual spacing, with directors progressively shorter than a half wavelength to couple signals of increasingly higher frequencies onto the dipole. is total rubbish. The directors need to be shorter even for use at only a single frequency. 
* The sentence says a quarter wave spacing, the diagram a tenth of a wavelength. 
* Talk of 15 and 20 meter bands is not professional.
* Many of the references are to poor sources. ham-shack.com and what-is-what.com are not in my opinion sensible references. There are plenty of good books written about this subject. One fairly good one was published by the ARRL, but was a lot more technical than most of the rubbish in ham journals. 
* No mention is made of the fact that the physical length of the elements must be shorter than the electrical lengths. 
The article is flawed in too may ways to list really. If this was a device not used by amateurs, then it would have been written in a completely different way. The fact it used by amateur radio operators (hams) means it is obviously attracts edits from hams, and some of the content needs to be understandable by them. 
I'd personally like to see the name changed to Yagi-Uda, as it is known professionally. Yagi has taken almost all of the credit for this in the eyes of the public, yet Uda done more of the work. The reasons for it often being known as a Yagi are stated, but I believe personally it should be renamed. 
:: My understanding is that the correct terminology is 'Yagi-Uda array', not antenna. Can't find a ref, though. Was in a radio-engineering text book. 2001:44B8:3102:BB00:18C:A1DE:545B:36AC (talk) 20:18, 2 November 2017 (UTC)
thread_title:  Article is far too amateurish 

message: It is easy to locate online DL6WU ARRL k7mem javascript yagi calculators, and downloadable programs and spreadsheets.  But they all seem to just generate numbers.  Are there any custom generators of yagi layout scale drawings, html pdf jpg etc?  For smaller indoor antennas 1:1 scale plots would be very useful, since anyone could just cut pieces of coat hangers and tape them to cardboard to assemble most of the antenna! -71.174.188.137 (talk) 20:02, 12 May 2010 (UTC)
thread_title:  scale drawings 

message: In the diagram it says the reflector is .55 x wavelength longer while in the first paragraph it says 5% longer and shorter. Those are different by a little. Later, in the next paragraph, it says "all elements are typically placed a quarter of a wavelength apart" while the diagram shows them as being a tenth of a wavelength apart. Those are different by a lot. Daniel Christensen (talk) 09:08, 29 September 2010 (UTC)
thread_title: This article contradicts itself in too many ways

message: Nowadays, Wikipedia is synonymous with quality information on the web. The article about Yagi-Uda antenna is not self explanatory. An average reader like me had to branch out to several other pages to understand the working completely. I find the "for dummies" books really enjoyable. If only the articles her were written in that way, life would be a lot easier.  — Preceding unsigned comment added by N sanjay n (talk • contribs) 08:44, 28 August 2011 (UTC)
thread_title:  The article is not comprehensive enough. 

message: In the 2nd paragraph (as of Jul 16, 2014) of the Analysis section, the parasitic element (director) and the driven element are taken "for now" to be the same length.  In the next paragraph, it is claimed that the director is shorter than the driven element and this 'explains' certain features of the Yagi.  You can't have it both ways. You can't explain the theory by assuming equal lengths, then explain other features assuming different lengths...at least not without a clear explanation of why you can hold two contradictory models at once (before breakfast?).Abitslow (talk) 22:05, 16 July 2014 (UTC)
thread_title:  Analysis - confusion - edit needed 

message: Chapter 11 in the ARRL Antenna Book (copyright 2003) confirms this article's statement that Uda "did much of the development work." But it states that Yagi introduced the array to the world outside Japan through his writings in English. It may be referring, at least in part, to a patent, but this isn't stated.
:Pretty much everybody calls them Yagi antennas. "Yagi-Uda" may be better at crediting Uda's work, but it's not the name people actually use. Geoffrey.landis (talk) 18:59, 20 July 2020 (UTC)
thread_title:  Names Yagi and Uda 

message: This is to explain the editing of September/October 2021. I did some intense research in the older literature trying to find a clear and consistent explanation of the passive radiator under far-field conditions. I am currently working on a paper on an antenna that uses passive radiators at some distance and wanted to find a clear conceptual explanation (before introducing mutual impedances), but this seems to be difficult to find. The best reference I found is the RWP King book (one has to interpret the formulas given on the cited page) or H.Zuhrt, Elektromagnetische Strahlungsfelder (1953, in German). 
I found the previous "Theory of Operation" section mostly incomprehensible, as it was physicaly wrong due to its implicit assumption of excitation of the passive radiator without taking any electromagnetic propagation between driven and passive elements into account. In addition, the argument was based on a voltage excitation of the passive antenna, but half-wavelength dipoles are excited by a current.  Therefore I deleted this and replaced it with a correct explanation (which took some time, because the problem is really quite difficult). To make sure that I was not missing any signs, I checked all the explanations with 3D simulations in HFSS. Sometimes the formulas are easy to misinterpret, as in the usual cartesian and spherical coordinate systems Ez and Etheta point in opposite directions in the xy plane, so a minus sign may easily be missed (which would change a 90° lagging phase to a 90° leading phase). Zuhrt and King clearly show that the current on the passive element (when it is at resonance, so that its self-impedance is real) is in phase with the incident electric field and the simulations support this! This shows that most of the explanations that I deleted were indeed wrong.
Now we have to understand where the phase differences between incident radiation and reradiation come from. Here, the diagrams in the "Analysis" section may be easily misleading. We have to distinguish between the near field amplitude (which is never shown) and the far field amplitude, which is drawn also in the diagrams in the "Analysis" section. The far-field amplitude is given as 
\begin{align}
E_\theta &= \zeta_0  \, H_\phi  =  i\frac{\zeta_0 \,I_h\,L \, k}{4\pi\,r} e^{i\,\left(\omega\,t\,-\,k\,r\right)}\,\sin(\theta)
\end{align} 
(see dipole antenna - short dipole). As Etheta points into the opposite direction as the current, we have to add a minus sign when comparing the phase of emitted field (in z direction) and exciting current (in z direction). The exponential describes the propagation delay between current and field and, in effect, we have an additional 90° lagging phase offset due to the factor -j. So the theory shows clearly: there is no phase offset between the incident electric field and the current in the passive element excited exactly at resonance. The 90° lagging phase that we observe in the reemitted field is a result of the excitation of the radiation field at the dipole. 
If the dipole is shorter or longer that the resonant length, the current will receive a phase shift with respect to the incident field (or with respect to the open-circuit terminal voltage of the dipole)- either a leading phase shift for the shorter capacitive director element or a lagging phase shift for the longer inductive reflector element. The two-step explanation using transmission line theory and reflection at a short termination seems ok (except that it ignored the direction of the current of the reverse wave, which I corrected), so I left it. However, King and Zuhrt also give formulas for the open-circuit termial voltage of a receiving dipole as well as for the current of a loaded receiving dipole, so strictly the explanation could be further shortened by just using the formula for the current with a zero load impedance - but both explanations lead to the same result.
Unfortunately, the diagram for the explanation of the Yagi using a single director is partially wrong. The field emitted by the director is never more than 90° out of phase with the incident field (in the diagram it is 110° out of phase). I tweaked the numbers a bit so that we have physically correct numbers in the text, which are also roughly consistent with the diagram. Maybe someone who is more involved with wikipedia could create a better diagram. In this case I would recommend also to improve the numbers: the current numbers don't actually produce a very pronounced directional effect.
The analysis part discussing mutual impedances is correct. This can be found in many books. As the Yagi-Uda antenna cannot be fully understood without taking mutual coupling into account, most books omit a simplified explanation of the passive radiator under far-field conditions and only discuss the passive radiator on the basis of mutual impedances (e.g. Balanis or Kark).
I am full professor of microwave engineering at a university in northern Germany. I spent a few days in understanding the issue. I also double-checked that everything is correct with 3D simulations and some simple modeling (the results will become part of a lecture on electromagnetic wave theory) - so please consider this before editing or reverting the changes I made.  — Preceding unsigned comment added by 90.187.42.73 (talk) 15:26, 7 October 2021 (UTC)
thread_title:  A physically consistent model of the passive radiator - changes of September/October 2021 

message: Kudos to whoever added the correct origin of the Sunderlands "Flying Porcupine" nickname. One of the very few places where I have seen that, and not the universal "because it was so heavily armed" nonsense (in spite of it not being much more heavily armed than numerous other aircraft of the period). Even though someone had to reference that myth as well, just out of tradition.  Idumea47b (talk) 00:01, 19 September 2023 (UTC)
thread_title:  Sunderland