Talk:Isotropic radiator

message: If an Isotropic antenna cannot exist, then what is the device shown in the image? I'm guessing is as some antenna designed as a very close approximation to a isotropic antenna, but if that is the case, it really ought to be mentioned. 74.5.162.102 (talk) 23:34, 22 October 2009 (UTC)
replies: text: It seems to be three dipoles (or loops) with three receivers, one for each axis. The sum of the three received powers will independent of the polarization and direction of illumination. However any linear combination of the signals from the three loops/dipoles would be zero for some particular illumination, and so no electrical connection of the three would constitute a single isotropic antenna which could be connected to a just one receiver. --catslash (talk) 14:32, 23 October 2009 (UTC)
thread_title:  The antenna shown in the image 

message: Is there some reason (tradition, definition, ...) why an isotropic radiator must be a point source?  Is it so that the radiation can travel an unbounded distance?  If not, then why can't it be either of the following?
:# The inside surface of a closed cavity (of any shape) at a uniform temperature.
:# An infinite volume of CO2 at a uniform pressure and temperature equal to that at say the surface of Venus, with nothing else in the universe.
The latter has in common with a point source that it is ideal and physically unrealizable, but the former is easily realized and is the basis for constructing excellent approximations to a black body when a small hole is drilled in it.  At the center of a spherical cavity the radiation is uniform in all directions, meeting that condition, and unlike a point source  there is nothing unphysical about the center of a spherical source.  
In the latter, every photon travels a finite distance before being absorbed by a CO2 molecule, and the uniformity of the gas ensures uniformity of the radiation at each frequency.  (There is no frequency at which the probability of absorption by a nearby CO2 molecule is exactly zero.)  The gas is supercritical and pressure broadening is extreme, with photons whose wavenumber is in the vicinity of 650 cm−1 having mean free paths on the order of millimeters or less.
A spherical parcel of Venusian atmosphere of radius 1 m and altitude 1 km would be an extremely good approximation.
While the latter seems likely to be OR, the former obviously isn't, but the reason for excluding it is not obvious to me, though presumably it's a reasonable reason.  --Vaughan Pratt (talk) 00:33, 13 November 2011 (UTC)
thread_title:  Why a point source? 

message: The editing history of this important page goes back to 2005 making this twelve years of editing yielding just one reference to back up a point... Really? Claims without "inline" references are on the chopping block. Let's see if we can't do better. I will help where I can, but come on folks, you know the Wikipedia rules.crcwiki (talk) 18:51, 5 September 2017 (UTC)
replies: text: There are plenty of references. The things missing are citations. The claims made here are verified, they're just not linked to make it obvious. Congratulations though on your undoubtedly effective motivational technique for encouraging other editors to contribute. Andy Dingley (talk) 15:39, 6 September 2017 (UTC)
replies: text: No doubt the work to date contains good material, but in the wikipedia world references=annotated-citations. It's clear more attention needs to be paid to the various antenna articles by antenna professionals for the good of Wikipedia. I am one so will do my part. crcwiki (talk) 17:16, 6 September 2017 (UTC)
thread_title:  One reference in twelve years?!?!?! 

message: you've inserted a surprising caveat: https://en.wikipedia.org/w/index.php?title=Isotropic_radiator&diff=prev&oldid=798961436. Can you source it, please? Currently it seems to contradict the first sentence in the lead:
: An isotropic radiator ... radiates the same intensity of radiation in all directions. (...) The unrelated term "isotropic radiation refers to radiation which has the same intensity in all directions; thus an isotropic radiator does not produce isotropic radiation.
Thanks. fgnievinski (talk) 01:14, 28 February 2024 (UTC)
replies: text: Yeah, that's not very clear and I should have sourced it.  Thanks for catching that.  I'm sure you understand what I was referring to; in thermodynamics "isotropic radiation" is the radiation field you would find in a thermal cavity at equilibrium, the power density is the same in every direction and at each point in the cavity. --ChetvornoTALK 22:56, 29 February 2024 (UTC)
thread_title:  Isotropy