Talk:Antenna (radio)

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Contents

[edit] Staggering Length of this Article

This article has grown by each of us throwing in a nugget until it is overwhelming textbook. Check out this TOC! I have seen some of this addressed better in other articles anyway. Someone please help list the mainstream stereotype antenna ideas that need to be put in front of someone who looks up the word "Antenna." Can we move or merge the esoteric issues that antenna experts want to know about into specialized articles? If we do this will everyone be hurt if we don't each get our favorite topic covered well enough? I propose the following outline; can anyone help make it 'good'?

-.-

Lead Sect (Layman’s view of ‘antenna’)

Historical Origins (Hertz dipoles, loop, monopoles...)

Properties of Antennas (Briefly! "survey" level)

  • Resonance (length and loading)
  • Gain
  • Bandwidth
  • Impedance
  • Radiation pattern and reflectors
  • Polarization
  • Efficiency
  • Transmit & Receive Reciprocity

Kinds of Antennas

  • Imaginary Ideal Isotropic Radiator
  • Monopole (Distinction between ground and counterpoise, -Vertical, -Long Wire, -Beverege, -Helical)
  • Dipole (-Basic Dipole; -Quad; -Yagi; -HF Curtain)
  • Inductive Loop
  • Waveguide horn and orfice


John 07:05, 23 November 2006 (UTC)

[edit] Nature of the EMF

What is the amplitude of the EMF that is applied to a transmitting antenna to provide a signal?

The amplitude depends on the desired power output. Family Radio Service is limited to 500 miliwatts. 5 watts is considered to be the maximum safe power output for a handheld radio. 50 watts is considered to be the maximum safe power output for a radio with the antenna on a car roof. Commercial radio stations use power on the order of 20 kilowatts. See also Effective radiated power. --ssd 05:37, 9 January 2006 (UTC)

[edit] needs disambiguation and expansion

I came by here to add some material about arthropod antenna. But I noted in passing that the discussion of radio antenna focuses pretty much entirely on low-medium-high frequency resonant wire antennae. It seems to me that some additional material on the isomorphy between lenses, reflecting antenna and wire antenna might be appropriate as well as some mention of non-resonant travelling wave antennae like the Beverage and resonant magnetic field antennae like the ubiquitous medium wave tuned loop.

I might come back sometime and do the loop part which I understand. I'm not the right person to do the rest -- DJK

[edit] POV links

The line: "For computers, it's used the de facto standard Mcx cable." is not just bad english, but also probably very POV as there are lots of different cables used for antennas (The link points to a company called MCX Inc!).

[edit] Electrically Short Antenna

The electrically short antenna is far less than 1/4 wavelength in length. Unlike nearly all other antennas in this list, this antenna detects the electric field of the wave instead of the electromagnetic field.

I don't understand this statement. I'm fairly certain the distinction made between "electric field" and "electromagnetic field" doesn't make any sense, but could somebody please confirm?--Jfbolus 07:11, 29 Mar 2005 (UTC)

There is a difference since you can receive more or less completley only the electric component of the electromagnetic field. There are also antennas for the magnetic component for ex.: coil antennas, loop antennas, ferrite antennas. --Xnor 17:55, 18 May 2005 (UTC)

If you're trying to say that a short antenna is excited only by the electric field of a propogating wave, then you're correct, but the quoted statement still doesn't make sense. The electric field is part of the electromagnetic field. The whole "electrically short antennas" bullet point should probably be removed anyway, since its already covered in the Dipole antenna page. --Jfbolus 12:57, 18 November 2005 (UTC)

[edit] Stuff to add to this article

I'd add this stuff but I either don't understand it yet or am too (tired | busy | distracted) to do it just now. If you know something, feel free to add it yourself.

  • More antenna models:
  • antenna like things that aren't antennas
    • dish (and variations)-- reflector that still needs an antenna at the focus
Added this (paragraph about Parabolic antennas)
and a link to the parabolic antennas page OH3GPJ --Miikka Raninen 23:59, 14 April 2006 (UTC)
    • lens -- practical at >10ghz(?) negative refractive index! wave guide construction, diameter <4 ft?
  • incorporate as many of Glossary of antenna terms as reasonable

(Is it possible to have too many antennas listed here? Is order important? They're already listed more or less in order of complexity I think.) --ssd 07:25, 17 Apr 2004 (UTC)

Actually, I now think this article is long enough. Additional antennas that have their own page should just be added to Category:Radio frequency antenna types. They should only be added to this article if they are really common antennas or are too short to have their own article. --ssd 13:50, 31 Jul 2004 (UTC)

[edit] Plural of Antenna

What should the plural of antenna (in the sense of a radio antenna) be? Several sources give it as 'antennas' and the insect variety of antenna as 'antennae'. I have always used the latter for radio antennae. Are both correct, or, as I suspect, the 'American' spelling the one that prevails?

People who know latin or greek use antennae. People who know english use antennas. I suppose both are correct in context. --ssd 13:50, 31 Jul 2004 (UTC)
Isn't antennae used when referring to more than one insect antenna, while antennas is used for radio antennas/aerials? --/ɛvɪs/ /tɑːk/ /kɑntɹɪbjuʃ(ə)nz/ 18:02, July 20, 2005 (UTC)
The plural of antenna is aerials--Dumbo1 22:49, 11 August 2005 (UTC)
That's like saying the plural of pig is porks. --ssd 05:34, 8 January 2006 (UTC)
The correct plural of antenna is, in the radio sense, antennas. The correct plural of antenna, in the biological sense of what insects have on their head, antennae. They are not interchangable, and antennae is wrong for radio usages (though still occasionally used within the industry by people who think they know better). DWaterson 11:33, 28 February 2006 (UTC)

That sounds consistent with what I have heard. Also, Latin bases are very important in biology, but precise engineering and physics are in mathematics, so there is less need for classical languages. David R. Ingham 07:18, 2 March 2006 (UTC)

[edit] transmitting vs. receiving antennas

Someone added a comment that an antenna can't be designed for both transmitting and receiving. This is a false statement. It's something I do every time I make an antenna.

Transmitting antennas are really a subset of receiving antennas. If you design it to transmit well on a specific frequency range, it will also receive well on that range, and with the same radiation pattern. Designing and testing for optimal transmission also insures optimal reception.

The biggest difference between the two is that transmission antennas work best if impedance matched. With a receiving antenna, the receiver(radio) needs to be optimally impedance matched. (It helps if the radio and antenna are matched to each other, but the load is more critical--as already stated in the article.)

Also, most antennas desgined for receiving only are tuned for broadcast frequencies, where the transmitter uses extremely high power (KW typically), and so can be smaller and still get enough input power to be effective.

This type of info would be more appropriate for a real antenna theory article that would go into depth in theory, rather than just glossing over it as I have in this article.

It's not quite true that transmit antennas are a subset of receive antennas (I give an example in the article, now) - a receive antenna may be designed to lose efficiency in favor of noise rejection. Such designs are common in amateur low-band setups. In fact, I've used one: we had a big delta loop and a 120ft tower, and the best configuration was to transmit into the tower and receive using the loop.
That said, I think an antenna theory article would be excellent - of course, it can't cover the whole subject, but a good introduction would be wonderful. I don't know nearly enough about it. --Andrew 03:44, May 10, 2004 (UTC)


Good point, and I've also desgined antennas specifically for receiving. I may tweak the emphasis a bit. Good job on adding polarization--I forgot about that. I may expand on it a bit, at least link it in right. --ssd 04:10, 10 May 2004 (UTC)


Oh, btw, all components in an antenna (including wire!) are important for maximum power. I generalized your otherwise excellent wording. Note that even coax feedline is susceptible to diaelectric breakdown, but that kinda detail is probably too much here.
I heard a rumor that some transmitting antennas use cryogenic superconductors for something, presumably to allow increased power with lower resistance. I've not actually seen any literature on this, or I'd add something about it. --ssd 04:43, 10 May 2004 (UTC)
I read it is used for sharp filters and sensitive recievers in cell phone basis stations--Arnero 21:37, 30 December 2005 (UTC)

[edit] Antenna Theory Section

We need to work on an antenna theory article, or severly work on this article. As you say, a lot is glossed over and said to be difficult to do. More explanation is needed for everything! I am very interested in working on this topic with you. Please reach me via email at brandon.irwin <at]gmail dotcom Brandon.irwin 21:46, 9 Jul 2004 (UTC)

I think I'd rather leave this article for the practical parts of antennas (with just the minimum theory to make sense) and start a fresh article on the theory, otherwise it'll jsut get too long. I'm even leaning towards not adding more antenna models here, especially since the category is now there to collect them all. Unfortunately, all my antenna experience is practical, with very little theory, so I am not really qualified to write the theory part. --ssd 01:07, 10 Jul 2004 (UTC)


[edit] Canadian Flag

I like Canada as much as the next man, but a flag on the antenna? C'mon guys. We all know how the reaction would be if it were a US flag up there. --195.195.244.6 15:34, 9 Mar 2005 (UTC)

Feel free to supply a better antenna picture (this one is duplicated on the Yagi page anyway) but the flag was actually up there, and it is a common tradition to fly flags on antenna towers... --Andrew 17:18, Mar 9, 2005 (UTC)
I'm rather offended that a yagi antenna image was used instead of a dipole! In fact, I'm so outraged that I refuse to change the picture. --Hobophobic 21:26, 14 Mar 2005 (UTC)
LOL. You are jusy a yagiophobe! Stop trying to keep the yagi down. Rob 12:00, 10 March 2006 (UTC)
HF dipoles are very difficult to take pictures of. Sometimes all you get is a picture of a tower with invisible guy wires (which are really the antenna, not the tower). It might be fun to get pictures of more interesting antennas, but meanwhile, the yagi with the canadian flag does fine IMHO. It's more typical than some of the more scary antennas in some of the antenna articles here, and less boring than a dipole. I too refuse (for now anyway) to replace the picture. :) --ssd 12:38, 15 Mar 2005 (UTC)
Now, now, there are other interesting-looking antennas. Some UHF or microwave stuff is really interesting-looking. I'd be happier if we had a separate picture for here and for Yagi antenna. Somewhere I have a picture my parents took of a 42-element 2-meter quagi they built; I can ask them for permission to use it next time they see it. In any case, until we come up with a picture to replace it with, talk about replacing this picture is rather silly (even more so than otherwise, I mean).
Hey, I wonder if there's a picture (or article) for Armstrong rotator? I think you can see it hanging from one end of this yagi... --Andrew 17:53, Mar 15, 2005 (UTC)

[edit] Impedance? Electrically short?

Is there any references to the discussion in the article about impedances for recieving antennas? This RF-engineer does not understand the text... And is there any reference to the electric field vs. electromagnetic field part in the description of short antennas? I dont follow that explanation at all...

Hey! Feel free to improve it more! I believe the text I added is accurate, but others have added things I can't verify, and I'm only an amateur, so I could be wrong too. All my text is refenced from one of the ARRL books, probably either the Antenna book or the Handbook. --ssd 06:28, 29 Mar 2005 (UTC)

[edit] Gain and how does it work

I don't clearly understand yet how Gain works. Imagine I have 1 Watt for my isotropic antenna. No i use a gain antenna. Logically, this new antenna won't have more than the 1 Watt provided by the circuit. So, how does the gain antenna get more power to send? Is the antenna amplified? That would need the antenna to be powered by another energy source additionally. Actually, are there antennas that can amplify a signal by using an additional energy source connected to the antenna? Thanks, --Abdull 09:48, 5 Apr 2005 (UTC)

Well, there are setups where you put an amplifier on the output of your radio; sometimes it lives on the antenna. The opposite situation is actually more common: many antennas (especially for radio telescopes) have a receive amplifier as close to the antenna as possible to reduce the thermal noise.
But this is not what is meant by the gain of an antenna. In your example, the antenna still radiates only one watt. But there is normally only one (or a few) direction you care about - toward the receiver. So if the antenna is pointed towards the receiver and puts out all its power in a hemisphere (instead of a sphere) it will have a gain of 2 (3 dB). In practice, antenna radiation patterns are complicated, but a Yagi antenna (for example) puts out most of its power in one direction, so that the signal strength in that direction is increased compared to an isotropic antenna (at the cost of other directions).
This is complicated by the existence of "omnidirectional" antennas with gain. In fact such antennas are not omnidirectional; normally there are directions that are almost certain not to be useful to send signals to: stright up and down. For HF antennas, radiating at a low angle results in long skips and better communications over long distance, so (for example) a 5/8th wave vertical has gain because it suppresses radiation stright up. --Andrew 10:19, Apr 5, 2005 (UTC)
There is still only 1 watt radiated but it's concentrated like a searchlight in one direction, which makes it as powerful as say 5 watts spread in all directions. --Joe VK4TU

[edit] patents

I find it surprising that there's less than thirty patents on antennas. I'd think there'd be thousands. Are these patents being added just the significant ones, or just the recent ones, or just random ones? If this is only a few recent ones (as I suspect is the case), is it really appropriate to add these at all? --ssd 8 July 2005 04:39 (UTC)

I can't see that they belong here without any accompanying or descriptive information. I will remove them until they can be described or put into some contextual purpose for the article. Wiki is not a raw datadump... --Blainster 17:04, 14 July 2005 (UTC)

[edit] Gain, what is it?

Under the definition of gain seen here http://en.wikipedia.org/wiki/Gain

"In electronics, gain is usually taken to mean the ratio of the signal output of a system to the signal input of the system. A gain of 10 would imply that a property of the signal (usually voltage or power) had increased by a factor of 10."

Which sounds an awful lot like amplification http://en.wikipedia.org/wiki/Amplifier

"An amplifier can be considered to be any device that uses a small amount of energy to control a larger amount, although the term today usually refers to an electronic amplifier. The relationship of the input to the output of an amplifier--usually expressed as a function of the input frequency--is called the transfer function of the amplifier, and the magnitude of the transfer function is termed the gain."

And http://en.wikipedia.org/wiki/Electronic_amplifier

"An idealized amplifier can be said to be "a piece of wire with gain", as the output is an exact replica of the input, but larger."

Which sound like what the term "gain" should be.

Now this page is saying something completely different.

"An antenna has gain if it radiates more strongly in one direction than in another. Gain is measured by comparing an antenna to a model antenna, typically the isotropic antenna which radiates equally in all directions."

Here we are defining gain as the difference in signal strength in one area vrs another area for an output signal only. It considers nothing to do with an amplification procedure.

Correct. So there are two meanings of "gain" as used in electronics. --Heron 18:27, 11 August 2005 (UTC)

Since an antenna has only one pair of terminals, a supplementary reference is needed for the generalization. This is usually taken as the gain of a perfectly efficient isotropic radiator. --David R. Ingham 19:34, 11 August 2005 (UTC)

An important point to note with amplifiers is that we are not creating energy out of nothing.. that is not possible. We will be having a DC supply which supplies the energy for amplification. A crude definition of antenna is it's a passive device which radiates energy.So the gain here is not the relation between the output and input but it tells us about the directivity of an antenna. that is maximum power transferred.

[edit] Contradiction, what's correct??

One of the two (bolded) statements below must be false. Which one? If you know, please correct it :)

  • The small loop antenna, also called the magnetic loop antenna is less than a wavelength in circumference. (Typically less than 1/10 for a receiving loop, less than 1/4 for a transmitting loop.) Unlike nearly all other antennas in this list, this antenna detects the magnetic field of the wave instead of the electric field. As such, it is less sensitive to near field electric noise when properly shielded. The receiving aperture can be greatly increased by bringing the loop into resonance with a tuning capacitor. Due to the small size of the loop, the radiation pattern is 90 degrees from that of the large loop. The radiation pattern is perpendicular to the plane of the loop, with sharp nulls in the plane of the loop.
  • The electrically short antenna is far less than 1/4 wavelength in length. Unlike nearly all other antennas in this list, this antenna detects the electric field of the wave instead of the electromagnetic field. Its receiving aperture can be greatly increased by increasing the voltage; by adding an inductor or resonator tuned to resonance with the signals of interest. Electrically short antennas are typically used where operating wavelength is large and space is limited, e.g. for mobile transceivers operating at long wavelengths.

TH 12:43, 13 October 2005 (UTC)

There is no contradiction. The loop antenna is just that - a closed loop of wire. The short antenna is NOT a closed loop - it is a wire with one end connected to the radio and the other in free space. They are two different things. N0YKG 13:46, 13 October 2005 (UTC)

Surely there is a contradiction, if there isn't it's not explained well enough for normal people (like me) to understand. Both paragraphs claim that "unlike nearly all other antennas in this list", they detect respectively the electric field rather than the magnetic field of the radio wave. So "Unlike nearly all other" must be wrong since that could only possibly be true for one of them.

TH 13:56, 14 October 2005 (UTC)

The difference may not be clear, but that does NOT make this a contradiction. However, see the rewrite, and see if that helps. N0YKG 16:00, 14 October 2005 (UTC)

The rewrite helped me understand the facts, and the new explanation about the electrically short antenna is much clearer. But I still see a blaring contradiction: The section about the small loop antenna claims that "unlike nearly all other antennas in this list, this antenna detects the magnetic component of the electromagnetic wave instead of the electrical component" while the section about the electrically short antenna claims that "unlike nearly all other antennas in this list, this antenna detects the electric field of the wave instead of the electromagnetic field". It follows from simple logic that either the majority of the antennas detect the magnetic fields, and the first statement is right and the second wrong, or the majority detect the electric field and the first statement is right and the second wrong. I think that the electrically short antenna is the exception here and that makes its description correct, while the description of the small loop antenna should be corrected. But I leave it to you or someone else with expertise in the field to actually do the change. TH 15:18, 22 October 2005 (UTC)

OK, what I will do is change the loop to read "detect the magnetic component of the signal only" and the short antenna to be "The electrical component only" - the other types detect both aspects of the field. Better? N0YKG 00:55, 23 October 2005 (UTC)

Excellent, thanks a lot. I missed the idea that the others detected both types, I thought the majority only detected the magnetic. It is much clearer now. TH 22:32, 23 October 2005 (UTC)

[edit] Antenna / Ariel

What is this US / British English thing ? Never heard of the difference in terms of variants of English. From my British education the difference is that an ariel is only designed for reception, whilst an antenna is designed also (or solely) for transmission.

Do others agree ? --jrleighton 15:01, 17 October 2005 (UTC)

According to the article, most antenna designs work equally well for reception and transmission of the wavelenghts they support, so that distinction doesn't seem to me to make much sense. TH 15:20, 22 October 2005 (UTC)

[edit] Antenna / Ariel

Do you mean Antenna / Ariel or should it rather be Antenna / Aerial? AA2HT

The term 'antenna' (pl. 'antennas') is used throughout the microwave and RF industry in the UK. 'Aerial[s]' is now only used colloquially (i.e. outside the industry). I've got two UK written and published books infront of me now 'ANTENNAS': F. R. Connor 1972-79, and 'Short Wave Wireless Communication including Ultra-Short Waves': A. W. Ladner 1932-50, which contains 'Chap. VIII Aerials' and 'Chap. IX Aerial Arrays' - so usage probably changed between 1950 and 1972. --catslash 14:37, 28 July 2006 (UTC)

[edit] Loop antenna

Loop antenna is currently a redirect to this article; it should be replaced with an expanded article. --ssd 23:42, 28 December 2005 (UTC)

Just to say. The chapter on the large loop is wrong. Read the Balanis, it is the best book ever on antenna,actual and both practical and academic (It is not spam, it is true). A small loop has its maximum gain on the plane of the loop, but when you increase the size of the loop, this maximum shift until the circumference have reached the same size as the wavelength where the maximum gain is perpendicular to the plane of the loop (on the axe).--85.218.2.215 19:52, 2 August 2006 (UTC)

OK Balanis is pretty good, but if you don't want to go out and buy it, a good text/reference book available online in about 20 separate PDF chapters is Orfanidis. I've added a link to it in 'External articles and further reading'.--catslash 10:23, 3 August 2006 (UTC)

[edit] Overview section

IMHO the overview section is a bit rambling and unclear. I'm not sure it really adds any information. What do you think? (I wish someone would either delete it or rewrite it. Or maybe just trim it down a bit?) --ssd 05:46, 8 January 2006 (UTC)

Can the article be structured like this:?

  • time
    • frequency, impedance, bandwidth
      • tuned narrowband (Noise rejecting) antenna examples
      • broadband examples
      • multiband antenna examples
  • space
    • gain
    • radiation pattern
      • omnidirectinal
        • Multipole moments
          • monopole
            • omnidirectional radiator
          • electric dipole
          • magnetic dipole
            • loop antenna
            • ferrite core antenna
          • zero elevation, but all azimuth angles
      • directional
        • aperture
        • polarization
          • linear
            • Yagi
          • circular
            • helical antenna
        • combination antennas, detecting singals from from multiple directions
          • Phased array
          • dish mirror
          • luneberg lens
  • practical antennas
    • efficiency
      • resistors

--Arnero 12:15, 8 January 2006 (UTC)

I can't say I care for that. Time vs. Space is not really a valid separtaion of concepts, and I'm not sure that separation is needed. Also, mixing antenna models with theoretical discussion is not a good idea at all. Also, you have miscategorized the directional vs. omnidirectional antennas, which is just further proof that this heirarchial structure is inappropriate. (ex: loop can be omnidirectional, but is usually directional. The reverse is true for dipole.) Perhaps I'm missing the point of this reorganization?
Also, looking at the current list of antennas, I would object to any structural change that did not keep the isotropic and dipole antennas first. The yagi should probably be next, but I could be convinced that one of the others is more common. --ssd 06:16, 9 January 2006 (UTC)

Time is what every electrician understands (as it is 1 dimensional) and were many wiki links are possible. Space is very poorly understood by most readers and hard to show as I have not seen any 2d radiation pattern in wiki, yet. (small loops are omnidirectional, big ones are not. Same with electric dipole antenna, if you omit the coil and instead tune it to high frequency by a capacitor, it will not radiate a dipole pattern).--Arnero 01:38, 13 January 2006 (UTC)

dipole antenna has a nice 2d radiation pattern diagram. Small loops are very directional. They are one of the classic direction finding antenans. Large loops can be omnidirectional if they are oriented horizontally. Any antenna, when used out of its rated frequency, will act differently, and is pretty much not the same antenna. --ssd 07:06, 13 January 2006 (UTC)
  • Ideal dipole (to show in introduction). electric, magnetic.
  • Praktikal dipole (to show in a separate article) electric. magnetic
  • 2d radiation pattern diagram. What is more demonstrative: Radiation pattern or [1].
  • What is simpler: radiation pattern or [2]
  • "omnidirectional if they are oriented horizontally". Maybe we should stop thinking in terms of ground based antennas. The overview article should also hold for cell phones, satellites, and airplanes and there "omnidirectional" does not mean "along the horizon"
  • "out of its rated frequency"> But the coil is ok, I hope: [3]

--Arnero 14:26, 13 January 2006 (UTC)

[edit] Ordering of Ideas

In the Antenna parameters section you have an overview of antenna parameters subsection. This makes sense, but it's put in the middle of the other subsections, this does not flow right. Either put it first or put it last, but not in the middle.

One of the problems with this article is it's very hard to read. The concepts are very jumbled as it's layed out in general. Someone needs to go at this article with an axe and chop out 1/3 to 2/3 of the content... some of which could be farmed out to other articles on those particular concepts. Remember this is an encyclopedia, not a scientific text. The article needs to be clear and to the point, crossreferenced with supporting material. The article should not contain enough information to make anyone an expert on this subject, rather give a fair working concept of it. As it stands now, I have a hard time understanding the article while already knowing the subject.

The A few basic antenna models is anything but. I don't have an exact definition of the word few, but this ain't it. As it stands now it's just a list, it doesn't really support any content and is confusing in its layout. I would think a few antenna models would be more like: Those that detect the electro-magnetic field, those that detect the electric field and those that detect the magnetic field. -That's a few. I wouldn't call the section a few types of anything at all, it isn't very encyclopedic. But whatever it's called, it ought to be shorter! Shove the details to articles in Category:Radio frequency antenna types. Anonym1ty 22:46, 11 January 2006 (UTC)

I can't fairly address the antenna parameter section, but I still don't think time vs. space is relevant here; frequency is not really time. Bandwidth is not time at all. Impedance has nothing to do with time. Polarization is not space (it's shape or direction). None of the antennas should be categorized as "time" or "space" as they are both or neither. Organization is needed, but I don't think time/space is the right concept to organize on.
The basic antenna model section has run away with itself (I think we totally agree here), and most of the content there should be moved to individual articles. I think specific radiation pattern and methods of combining elements are much more important than E or M field. Perhaps, rather than this huge list, it should just list isotropic, dipole FAMILY, loop FAMILY, yagi, phased array (very different), and maybe synthetic aperture. Each of these should be very short; Yagi I think is perfect. Isotropic is long, but good for its significance. Dipole should be two sentences. The rest should probably be one sentence. All the removed material for the rest should go to individual articles. As they are removed, a mention is needed in the parent article for the family (some of the dipoles are already there), and make sure (as you say) it is in category:radio frequency antenna types. The antennas that are redlinked need articles. Perhaps what is here would be a good stub start? --ssd 07:26, 13 January 2006 (UTC)

[edit] Introduction

Some antennas have dielectric or magnetic material. This may not be needed in the first paragraph, but to me it sounds funny to say they are composed of conductors. Less basically, there are structural materials and ray domes.

Now that Si can be used for LEDs and soon lasers, chips may have optical frequency dielectric antennas soon. (With lenses [or mirrors] to focus to and from the plane of another chip.)

When I was a kid, AM radio antennas had iron cores. Maybe some still do. For RAM coatings, and I think also for antennas, magnetic materials give better band widths to thin coatings or small antennas than can (theoretically) be obtained with only conductors and dielectrics. David R. Ingham 02:42, 13 January 2006 (UTC)

Conventional antennas generally avoid dielectrics (as opposed to outright insulators) as they tend to introduce loss, but you are right anyway. The AM broadcast bands use a large wavelength, and so the loopstick is the most popular AM antenna. The "stick" in loopstick is a ferrite powder core (note quite the same as iron). Many commercial quality colinear antennas (very long stick) have a copper core for lightning conduction purposes. -ssd 19:05, 16 January 2006 (UTC)

[edit] slow revisions, other ways to reduce size

The practical antenna section is (I think we all agree) too long. I'm going to slowly review each one that has its own article, make sure everything listed here is in the main article, and then cut what is here to the bare essentials. My goal is to make all but the first two practical antennas (with their own articles) about two sentences long, but I may not get it that tight. --ssd 06:58, 13 February 2006 (UTC)

well unfortunately added to your work by adding a paragraph about parabolic antennas OH3GPJ --Miikka Raninen 23:59, 14 April 2006 (UTC)
The loop and electriclly short antennas need their own pages so those sections can be shortened. --ssd 14:39, 14 March 2006 (UTC)

Everyone want their antenna to be electrically small, but still broad band and high efficiency, so it does seem there should be a page on that subject. There are theoretical limits that could be explained. "Super-gain" antennas could be a sub-heading. David R. Ingham 06:02, 15 March 2006 (UTC)

I like the idea, but what would you put on a page that just lists antennas that is not already in Category:Radio frequency antenna types? --ssd 17:10, 10 May 2006 (UTC)

[edit] Origin of word "antenna"

Added origin of word antenna to the introduction, as this is something I never knew until recently, despite working with antennas for over 35 years. Yaf 16:31, 31 March 2006 (UTC)

[edit] Polarization secton

The section on polarization has become wordy and redundant. I think I spotted the same phrase in there several times. Also, I think the loss due to mismatched polarization is overstated. I seem to remember (i.e., without references) that horizontal vs. vertical polarization is only a 7dB loss. Circular polarizations of opposite circularities is about 14dB loss. Neither of these could be described as "tens of dB"... --ssd 13:34, 10 May 2006 (UTC)

[edit] Direct link for Schmitt reference

The reference "Understanding electromagnetic fields and antenna radiation takes (almost) no math", by Ron Schmitt, EDN Magazine, March 2 2000 is linked to a host that is not related to the publisher (very useful article, by the way). Since the article is freely available on the EDN website, shouldn't the link be made to that page? Here is a direct link: http://www.edn.com/article/CA82250.html That page contains a link to the PDF version, which is the same as the one currently linked.

[edit] Marconi and term "Antenna"

Did something change? pole in Italian is "palo" OR is translate.google wrong? 204.56.7.1 16:20, 27 June 2006 (UTC)

[edit] What is and isn't an antenna

The paragraph beginning with The use of "antenna" usually excludes non-communication applications needs to be sourced (to the patent class description?) and clarified a bit.

-- JP 70.150.177.5 16:10, 17 July 2006 (UTC)

Antennas are certainly called 'antennas' when used in radar, navigation, meteorology and EMC testing - and possibly in some other areas, such as radio astronomy. The whole Terminology section might benefit from radical pruning? --catslash 15:43, 28 July 2006 (UTC)

[edit] Headings name the article title

Wikipedia:Manual of Style (headings) includes mention that headings should not repeat the article title, if possible. It can be assumed that we are talking about antennas. --Charles Gaudette 23:52, 16 August 2006 (UTC)

[edit] angle of incidence

I'm pretty much confused by this "angle of incidence". As illustrated in the picture, the angle (phi) is the angle between the horisontal axis and the direction of the reflected wave. However, in it's own article, the angle of incidence is defined different, so it actually comes as 90-(phi). Which is correct? Did I miss anything ?

No, you are right. The angle \scriptstyle{\theta} (theta) in the drawing is not the angle of incidence. I will correct my mistake. LPFR 06:26, 5 September 2006 (UTC)

[edit] Some clean-up

I erased two paragraphs in "Terminology". The first one, beginning "The use of antenna... ", used to many incorrect terms and mixes. I did not found how to rearrange it. The definition of antenna at the beginning of the page is complete. The second paragraph, redefined the term "radio waves". This definition is not as good as the one given in radio waves, linked in the first line of the page. LPFR 08:56, 8 September 2006 (UTC)

Good work! - this clean-up was long overdue (see above). --catslash 14:53, 8 September 2006 (UTC)

[edit] Physical background

As some wikipedians seem to ask for a more theoretical basis, I changed two descriptive paragraphs about "how the antenna work" for a more "academic" version. LPFR 14:09, 8 September 2006 (UTC)

[edit] A Query..

Does anybody hv the idea about why an antenna length should be a multiple of the wavelength?? This is a question for which i hv not found an answer in any book ( as far as i hv seen).. Can anybody suggest an answer or a book..

The reasons is that the impedance of the antenna is resistive (with no reactive part) when the total length is near (but not exactly) a multiple of half wavelength. Adaptation to the feeder cable is easier as there is no capacitive or inductive part to compensate. This is a good condition but it is not necessary for an antenna to emit or receive. LPFR 12:28, 9 September 2006 (UTC)

Thank you very much. But i hv another query. Can we have a similar resitive antenna at some other lengths larger than half the wavelengths, say 1000 times the wavelength of the signal.

An alternating voltage applied at one end of a wire creates a traveling wave in the wire. This traveling wave is formed by an alternating current in the wire plus a tension on the wire. In an infinite wire, the wave travels down the wire and radiates power in the form of an emitted radio wave. Therefore, the current and the voltage attenuate as the wave progresses.
When the wave arrives to the end of the wire, a new wave is created. This wave travels backward and, added with the forward traveling wave gives a zero current at the extremity of the wire. The reflected wave also radiates power and attenuates. When the reflected wave arrives at the feeder cable, some of it enters the cable and the rest reflects and goes back in the forward direction. And so on. The phase of the sum of all the reflected waves, at the feeder cable, gives the impedance of the antenna. If the phase is 0° o 180° the impedance of the antenna will be resistive (no reactive part). If not, it will be more or less capacitive or inductive.
This is the reason why the impedance of an antenna depends on its length. However, when the wire length is too long, the amplitude of the reflected wave becomes negligible, and the impedance of the wire does not change with the length. In the Smith chart, as the length of the dipole increases, the impedance of the antenna describes a spiral line closing to the point corresponding to twice the impedance of an infinite wire. This impedance depends on the diameter of the wire, but it is of the order of the impedance of free space (the wikipedia page on this subject is bad), about 377 ohms. Your almost infinite dipole, which is no more a dipole or a resonant antenna, will have an impedance of about 800 ohms (resistive), and a gain of 15-20 dBi (but this is just my guess). LPFR 08:02, 14 September 2006 (UTC)

[edit] Reordering the article

I wish to know what you think about reordering this article in this way:

Definition: unchanged.

Terminology: Shortened to origin of the word and included in the definition on antenna.

  • Antenna parameters (definitions stuffed and completed if necessary)
    • Working frequency / bandwidth.
    • Directive gain (definition, etc.)
    • Impedance.
    • Radiation patterns (different possible drawings). Half power lobe width.
    • Polarization
    • Efficiency
    • Cost. Say that cost is also an important parameter and that there are cheap antennas and very expensive ones (phased arrays).
  • Receiving antennas. Reciprocity: same parameters as in transmission. Equivalent circuit. Effective length. Capture area. Maximum available power.
  • Physical background. Unchanged.
  • Practical antennas. To be rewritten, including problems of adaptation and SWR that are now in "overview of antenna parameters".
  • Effect of ground. Unchanged.

I suggest putting a link to a new page "antenna models" containing a list with a brief description of several antenna types with links to pages dedicated to each antenna (if there is enough stuff). The idea is to keep in the Antenna page only the properties and aspects common to all antennas and send each type or family to a specialized page.

I do not think feasible to give a classification or an order for antennas. There are too many possible criteria: resonant/non-resonant, electric/magnetic, simple/composite, professional/amateur, linear/circular polarized, etc. I suggest using just alphabetical order.

Let me know your opinion. LPFR 13:54, 12 September 2006 (UTC)

Agreed, that would be an improvement. (but "Antenna types" rather than "Antenna models" ?) --catslash 14:08, 12 September 2006 (UTC)
I like wiki for aiming higher than most amateur stuff I have read in that it is written and ordered according to physical principles and not to the price anno 2006 or filled with gibberish of clueless marketing guys. For example WiFi is just moving to phased arrays. And some people need to understand that directivity gain has more in common with radiation pattern than with impedance. Arnero 17:15, 12 September 2006 (UTC)
It is positive to talk of all types of antenna form simple whip to phased arrays. My suggestion is not to give the actual prices but just to tell if an antenna is of low or high cost (independent of time). After all the cost criteria is important for most of the people. LPFR 07:20, 13 September 2006 (UTC)
I'm not convinced any discussion of cost (relative or actual) is appropriate here, as cost is more a factor of who made it than what kind it is. --ssd 14:58, 19 October 2006 (UTC)

[edit] 120π or Z0?

Most (all?) of the formulae on this page use 120π for the impedance of free space Z0. This is a very common convention to be sure but...

  • It's not numerically exact. It comes from Z_{0} = \sqrt{\frac{\mu_{0}}{\varepsilon_{0}}} = \mu_{0} c, where μ0 is the permeability of free space, and by the definition of the SI Amp μ0 = 4π10 − 7H/m (exactly). Then putting the speed of light c = 300000000m/s (approximately), so Z0 = 120π (approximately). But c = 299793000m/s is closer, so Z0=119.917π is better.
  • The units are wrong. 120π is a pure number, whereas Z0 has units of Ω, so the units of the various formulae don't come out right.
  • It obscures the fact that the formulae relate to what (at least in the SI view of things), is a universal constant of nature.

So, if nobody objects in the next couple of weeks, then I may go through and change 120π to Z0 --catslash 14:19, 14 September 2006 (UTC)

You are right. The exactitude argument is not very important for antennas but the units argument is a killer. I will correct the formulas. LPFR 16:53, 14 September 2006 (UTC)

[edit] Unfairly

I wrote Those elements are called – unfairly - parasitic elements. I wrote "unfairly" because their usefulness does not deserve the pejorative name of "parasitic". If the name had been chosen in a recent past, they would have probably been christened "slave" instead of "parasitic". User Heron erased "unfairly". Although I appreciate his (or hers) English corrections, I think that this time it was a wrong correction. If the word "unjustly" is better than "unfairly", I agree to the replacement. For the time being, I reset "unfairly". LPFR 12:07, 16 September 2006 (UTC)

I don't think parasitic is a pejorative here. Adding a parenthetical "unfairly" or "unjustly" breaks the flow of the sentence and obscures the important meanings with irrelevant minor details. I don't think the feelings of those poor parasitic elements will be greatly hurt much by ignoring this issue. --ssd 15:01, 19 October 2006 (UTC)
In this phrase, "unfairly" had a physical (or electrical) meaning. As neither Heron nor ssd seem to understood this. I put this meaning in a separate sentence. LPFR 08:03, 20 October 2006 (UTC)

[edit] Human body as antenna

I would very much like someone to add why when I touch an antenna with my hand the signal gets much louder and clearer on a VHF radio. Can that be put in the article about how/why this happens and why the body is so go and being an antenna etc. Thanks JulianHensey 21:00, 2 December 2006 (UTC)

Your body is an electrical conductor (not a good one, in fact). When you touch the antenna, the result is the same as to lengthen the antenna with a length of wire. In MW, all antennas are always too short and a long antenna works better than a short one. Your body is not an antenna, but it can be used as an antenna, a conductor and even as a heating resistance (but this last utilization is not recommended). LPFR —The preceding unsigned comment was added by 90.2.204.70 (talk • contribs) 07:58, 3 December 2006 (UTC).
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