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Gene Fuller wrote:
As for the E- and H-fields, this just gets more amusing by the minute. The second paragraph is even more curious. Do you have a reference for this migration of energy from the H-field to supply the suffering E-field? Here's the reference: From "Fields and Waves" by Ramo and Whinnery. Take a close look at the exponential transmission line equations for flat lines (no reflections): V = Vmax(e^-az)(e^wt-bz) (1) I = Vmax(e^-az)(e^wt-bz)/Z0 (2) 'a' (alpha) is the attenuation factor. The two equations are identical except for the Z0 term. If you divide equation (1) by equation (2), you get Z0. In a flat transmission line (no reflections) the current is ALWAYS equal to the voltage divided by the characteristic impedance of the transmission line. The voltage and current are attenuated by EXACTLY the same factor. If the voltage drops because of I^2*R losses, the current must decrease by exactly the same percentage. (I have avoided calling it a current drop so it wouldn't upset you.) Since the attenuation factor is R/2*Z0 + G*Z0/2 and since, for most transmission lines used on HF, R/2*Z0 G*Z0/2, the current attenuation is caused by the series I^2*R drop in the voltage and the V/I=Z0 ratio that must be maintained - pretty simple logic. I must have missed that day in class. Yep, you must have. But it's not too late to learn what you missed that day. :-) -- 73, Cecil, W5DXP |
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