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On Tue, 27 Nov 2007 07:55:57 -0800 (PST), James barrett
wrote: Why is the twin lead consideres less lossy than coax? Hi Jim, All loss is in the bulk of the conductor. When comparing the two, twin lead usually has more bulk = less loss. I had thought that higher ohms meant higher impedance and I thought higher impedance means higher loss. Obviously I have not read the chapter on transmission lines yet ;-), so I may have that all wrong. You do. Impedance restricts energy, it doesn't consume it (loss). Also, in the article, I liked the part about before 1950, no one even heard about swr, and that antennas with high swr were working just fine. This is much the same illusion of climbing into a car with the speedometer exclusive marked in kM/h and thinking it has great 0-60 acceleration. Everything is just fine (ignorance is bliss). But I make 2 assumptions: 1) I'm thinking, even if they didn't know or care about swr, they still had to cut their dipoles for the band they were transmitting on. You don't even have to do that now, much less before 1950. Resonance merely simplifies things and gives you a benchmark for performance. If you don't have resonance, you accommodate to re-achieve that benchmark for performance (this is how it is done now, and how it was done before 1950). 2) I still would not want to use a 10m dipole and transmit 100 watts on 80 without at least using a tuner. Am I correct in these assumptions? That would be a pretty good intuition to proceed along. In this specific case, you may even stand to lose power with the best of tuners. Further correspondence will reveal those pitfalls. 73's Richard Clark, KB7QHC |
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