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back on topic,..
i still ponder if i put power into a superconducting antenna if their is no resistance, and a given about of power would therefore 'stay' in the antanna longer ie no resistance and a sorta flywheel effect exists the fields would have to exist longer for fixed-given power , .. seems that all adds up to more than a trival gain Not really, no, at least not in the commoner cases. Let's assume that you could find a superconductor which would be truly superconducting even at RF frequencies (which today's superconductors are not, I gather). So, you could cut the loss resistance of the antenna to precisely zero, in this hypothetical case. According to a note Reg posted some time ago, "At 3.75 MHz the resistance of 20 awg copper wire is 0.206 ohms per metre. Overall end-to-end dipole resistance 8.24 ohms." Using the hypothetical perfect superconductor (which may be impossible) you might reduce this dipole resistance to zero. Great reduction in loss, right? Less than you'd think. Remember, the loss resistance of 8.24 ohms appears in series with the antenna's radiation resistance (which is due to the RF energy being radiated) which will be around 70 ohms for an antenna in free space. With the loss resistance present, just under 90% of the energy is radiated ("dissipated" in the "radiation resistance"), and 10% turns into heat in the loss resistance. Getting rid of the loss resistance entirely will thus increase your radiated power by only about 10% - a small fraction of one dB. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
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