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On Tue, 12 May 2009 21:29:31 +0200, Szczepan Bia?ek
wrote: You went to details. Early you wrote: "An antenna radiates in ALL directions from EVERYPOINT of the antenna. " They do. Textbooks say that EM transversial waves are emitted by current (the sparks in Hertz apparatus - not from the ends). That is not the same thing as radiation. Repeating poor quotations does not make it better. I say that from the ends (as electric waves similar to acoustics). Compressional waves or longitudinal waves? In solid or air or in liquid? The answers to these questions lead to very, very different behavior. As I say, these simplicities you use are nonsense. The directional pattern must be different. The directional pattern is a combination of EVERYPOINT radiating in ALL directions. The differences in their position contribute to an unique pattern. This is the whole basis of the "method of moments" application of modeling radiation emitters. The directional patterns of loudspeakers and Herts dipoles are very similar. The are more differences than similarities. So I try to find evidences. Now I do not know if you prefer EM or electric waves. That shouldn't keep you from answering the simple physics of: Let's start with some serious misunderstandings with a few questions to test them. First, let us return to that link you offered with the Hertzian Loop with its spark gap. Let us say that this loop is 1 meter of wire (about the actual size anyway). Let us say there is a current detector at each end of this loop. Let us say we have closed a switch that applies voltage to the loop, and the first meter has indicated current flow. This is our time reference point. Now the questions: 1. For the electron that went through the first current detector, how long does it take for that SAME electron to get to the second detector? 2. How long does it take for the second detector to indicate there is current flow? Hint: the answer for 1. is very, very different for the answer for 2. Now, let us say that before that SAME electron gets to the second current detector, that path is broken open (maybe 1 pico second before the SAME electron arrival). The SAME electron sees an open circuit. What is the amount of energy required for the electron to break out of the metal conductor, and into the air? 73's Richard Clark, KB7QHC |
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