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Cecil Moore wrote:
Ian White, G3SEK wrote: This brings us back to the question of practical loading coils, and how much radiation (and therefore current variation along the length) we can expect. For the feedpoint impedance to be purely resistive in an electrical 1/4WL shortened vertical, the current must undergo a round trip phase shift of 360 degrees and the voltage must undergo a round trip phase shift of 180 degrees. The loading coil must provide the phase shift that the antenna doesn't provide. For a typical 75m 8 ft mobile antenna, the coil must provide approximately 80 degrees of phase shift. I'm sure you'll find the answer in Balanis, if you read it with an open mind instead of trying to force him to agree with you. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) Editor, 'The VHF/UHF DX Book' http://www.ifwtech.co.uk/g3sek |
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