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Reg Edwards wrote:
Thank you Roy. I don't doubt that your answer conforms to the learned text books on the subject. But I am suspicious the text books may be wrong. I will do some calculations related to radiation resistance and power available to a matched receiver. If I think my suspicions are correct then I will come back to you. ---- Reg. To tell the truth, I got the result for a wire over ground from an NEC-2 model, after first checking to make sure I got the theoretical 0.5 volt for the center of a dipole in free space. (NEC-2 has provision for applying a plane wave to the model.) In the process of confirming the 0.5 volt value, I found an error in a popular text, Balanis, _Antenna Theory, Analysis and Design_. On p. 61, he incorrectly states that the current along a short dipole "can be assumed to be constant", which isn't true, and from that concludes that the "induced voltage" would be 1 volt when the dipole feedpoint is short circuited. How he defines "induced voltage" with a shorted feepoint isn't clear, but the uniform current assumption he used to get it is incorrect. Kraus, in _Antennas_, and others get it right, and modeling confirms it. Roy Lewallen, W7EL |
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