Talk:Near and far field

message: It seems that this article could do with some improvement, is anyone active here at present? Martin Hogbin (talk) 11:01, 25 August 2008 (UTC)
thread_title:  Any active discusion still? 

message: For anyone looking for the mathematical concept of Near Field it is easy to overlook the small link at the top of the article; it seems to me that a disambiguation page would be more helpful. It is likely that the electromagnetic meaning is more common, but it is not clearly a primary meaning. For the word "rice" the primary meaning is the foodstuff, not simply in the sense that it is most common, but in the sense that it is clearly the meaning normally understood in the absense of reason to the contrary. By contrast, there is no normally understood meaning of "Near field": to a physicist working in electromagnetic field theory one meaning will appear normal, to a mathematician working in algebra the other will. I therefore propose to replace the redirect with a disambiguation page if no one argues a countercase.
JamesBWatson (talk) 16:47, 8 November 2008 (UTC)
thread_title:  Disambiguation Page? 

message: Could someone PLEASE re-write this entire article. It requires extensive simplification, verification and citation. It also suffers severely from 'look at my big brain' verbiage instead of being genuinely informative and descriptive.  —Preceding unsigned comment added by 70.26.38.207 (talk) 01:54, 17 November 2010 (UTC)
replies: text: Some work could be done to expand the lede to make it accessable to your average high school grad. However, electric, magnetic, and electromagnetic fields and the way they change in time and space, are not inherently "simple" concepts that can just be explained easily to anybody, because they aren't LIKE anything in everyday experience. So what prompted you to come to this article, what did you know already, what did you want to learn (but didn't), and what is your background? You can't just complain-- you need to supply specifics. You're the unhappy "audience" so tell us about your education, a bit. SBHarris 04:37, 17 November 2010 (UTC)
thread_title:  Absolutely TERRIBLE article 

message: At the start of the article it says "The "far-field", which extends from about two wavelengths distance from the antenna to infinity,". Then there's a diagram showing this too. It it totally wrong. According to that theory, for the 305 m diameter dish at the Arecibo Observatory, operating at 2380 MHz, the far field would start 252 mm from the dish. According to the usual theory of 2 D^2/lambda, it would be 1.5 million metres! 
It seems some people just love writing about things they don't have a clue about.  — Preceding unsigned comment added by 193.93.38.6 (talk) 10:14, 10 November 2011 (UTC)
replies: text: Clearly the thing needs to be qualified for conditions like dish antenna like Arecibo (or any radar dish) whose diameter D is much larger than lambda. In that case, you must use units of R = 2D^2/lambda and the near and far field roughly begin where this R is about lambda. However, for an antenna which is smaller than the wavelength (as often happens with whip antennas) then the approximation given at the beginning of the article, that near and far field start at roughly R = lambda, is correct. These are two different situations and you are correct that the article doesn't make that clear. I'll see what I can do in the short term to insert qualifiers that the simple "lamba approximation" only works with "short" antennas WRT wavelength. SBHarris 19:31, 10 November 2011 (UTC)
replies: text: Thank you. I see you (or someone else) has edited this to make this a bit clearer, but there are no references given. I know about the 2 D^2/lamda case, but are unsure if that is a sufficient or even necessary condition at all times. It seems hard to find any hard evidence on this - I've looked at a number of antennas books, and can't seem to find a definitave answer. Drkirkby (talk) 15:08, 1 December 2011 (UTC)
thread_title:  Contains numerous factual errors.  

message: The article now says: 
A "short" antenna is defined in this context as one that is shorter than the wavelength of the radiation it emits"
I don't think anyone would consider a half-wave dipole a short antenna, but that's 0.5 lambda. I've seen some references to "short" antennas being less than lambda/10. Drkirkby (talk) 15:22, 1 December 2011 (UTC)
replies: text: See above. D = Lambda/2 is right at the boundary where things start to go wrong. Right there you still get near field effects where you don't need to worry about D/lamba ratios, but with any antenna larger than half a wavelength, you do. The antennas of lamba/10 are "short" only in the sense of being very capacitative, meaning that to match impedience they need some type of inductive load. SBHarris 05:03, 2 December 2011 (UTC)
thread_title:  Short antenna 

message: I feel this article needs editing by an expert. It's a complex topic, but it does not appear to me that anyone editing this is really very knowledgeable on the topic. I don't claim I am. I have an MSc in Microwaves and Optoelectronics and design antennas for a living, but don't feel I know enough about this topic to make it a decent article. (I've also got a Ph.D., but not in this area). It really needs someone who is an expert on the topic. Drkirkby (talk) 15:36, 1 December 2011 (UTC)
thread_title:  I've added the "expert" tag 

message: In the section "Electromagnetically long antenas" the notation d_f (d subscript f) appears to be used to represent two separate things.  First it is used to represent the Fraunhofer distance, and then to represent a "far-field region distance".  One of these should be changed to a different symbol to avoid confusion.-- Tim314 (talk) 20:17, 9 May 2013 (UTC)
thread_title:  Inconsistent notation

message: The introduction says "Near-field strength decreases with distance, whereas far-field strength decreases with the inverse square of the distance", but elsewhere in the article it seems to be the opposite, which makes more sense.  — Preceding unsigned comment added by 88.96.79.118 (talk) 21:58, 12 January 2015 (UTC)
thread_title:  Contradiction 

message: Noting that you are talking about field strength, the sentence should read:
 "Near-field strength decreases with the square of the distance,whereas far-field strength decreases with distance."
For a discussion of this, see page 21:
 "Foundations of Antenna Theory and Techniques" by Vincent F. Fusco, 2005 Pearson Education Limited, .
And thanks for writing the Wikipedia entry!  — Preceding unsigned comment added by 68.47.85.67 (talk) 23:52, 12 July 2015 (UTC)
thread_title:  Last sentence of first paragraph has "decreases with distance" transposed with "decreases with the square of the distance"