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On Mar 23, 1:10*pm, JIMMIE wrote:
On Mar 23, 1:56*pm, Art Unwin wrote: On Mar 23, 12:13*pm, Tim Shoppa wrote: On Mar 22, 9:24*pm, "Joel Koltner" wrote: I know that many people think G3LHZ is a little bit off his rocker, but out of curiosity... what he suggests on slide 15 hehttp://frrl.files.wordpress.com/2009...ts-of-small-an... - is that a valid approach to measuring antenna efficiency? -- Use a thermal camera to note how much an antenna heats up with a given input power, find out how much DC power it required to heat it to the same temperature (the antenna's loss), and -- poof! -- antenna efficiency = (input power-loss)/input power? What are the significant loss mechanisms that he's not accounting for? *(He claims his matching network isn't getting at all hot.) With some feedlines and frequencies, feedline radiation can become an issue. For example, using 4" ladder line at UHF. I think his method, especially for physically compact antennas and feed systems which tend to have very low radiation resistance at HF frequencies, is a great check on theoretical calculations. There has to be a meeting point between mathematical models/NEC and reality and he is working at one such point. There are of course other points too (e.g. near field and far field measurements). Tim. I can't see how the external fields come into it! * That would automatically be within the two vectors that supply acceleration, this would be measure by the skin depth created by the displacement current. The accelleration of charge is a constant dependent on the conductor used. Where the particle goes when acceleration stops i.e. after leaving the boundary is of no consequence.This would be seen in the oscillation losses of the radiator in the same way as with a pendulum If you dont understand external fields then you dont understand Maxwell's equations at all. Maxwell is all about fields. This pretty much means you havent had a clue about anything you have ever said about antennas. Jimmie Jimmy I am referring to the boundary laws which is energy in versus energy out. Maxwells laws finish with the completion of acceleration of charge. The boundary laws are covered by this action and reaction per Newton. The particle that is accellerated is the smallest known with respect to mass and we know that it is accellerated to the speed of light which is known for any particular medium. Thus knowing the energy supplied we must equate it to the ejection vector applied to the particles and the reaction force applied to the radiating member. NEC computer programs do just this and for such equations produce arrays where each element is resonant and tipped to oppose the two vectors of gravity and the rotation of the Earth by supplying the array only where it is in a state of equilibrium and all elements are resonant as a result of the initial two vectors. The NEC computer programs do just this when applying Newton's laws which are not mismanaged to reflect planar forms. Again I state that Newtons equations account for all vectors involved in radiation and does not in any way reflect the fields that are generated beyond acceleration and how the particles are dispersed beyond this point. This way it represents all types of radiation that the radiator is capable of and likewise makes it sensitive to all that is thrown at the receiving end ie H,V, cw, ccw signals e.t.c. and all the rest that is thrown at it which it converts to a useable current signal for the radio.Now if you are still in a state of flux as to the use of equilibrium in all the laws of the Universe then you are still spitting into the wind. Art Unwin KB9MZ....xg |
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