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From: Alan
Date: 14 Apr 2003
Time: 04:18:33
Remote Name: 20.138.254.2
Stefano - if I read your message correctly the 3dB bandwidth of the antenna at 7MHz is 400Hz so this is an "actual" Q of 7000/400 i.e. 17.5 as you said. The measured input resistance is 35 ohms but we do not yet know how this is divided between radiation resistance and loss resistance . . . But if the antenna is .01 wavelength long, its radiation resistance should be about 0.08 ohms from basic theory, because an rf current of 1 ampere flowing in an element .01 wavelengths long should radiate a field which corresponds to a radiated power of 80 milliwatts, and this can be proved from basic theory. If this is true, the efficiency according to the measurements should be .08/35 i.e. 0.2%. . . 73s, Alan