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Original W8JI post:
"The only thing that prevents people from shooting themselves in the foot with the wire below the Beverage is the wire couples to the lossy media below it so well it becomes very lossy, and of course that means it doesn't help with stability or termination." Yuri, K3BU wrote: "If anybody cares to discuss the subject, or explain how the conductor laid on the ground can lose its conductivity, bring it on." "Lose its conductivity" is likely a mischaracterization. "Becomes very lossy" or paraphrased "lose its conductivity" to make the point? Conductivity of a wire at a particular temperature and frequency is a function of the form, size, and material the wire is made of. QSL. Proximity of the earth should not affect conductivity directly. QSL Loss from an R-F carrying conductor can come from energy coupled into the surroundings. Obvious source is the R-F in the conductor. Closer the conductor comes to the earth, the higher its capacitive coupling, and the more current flows in the lossy earth, especially in the case of an unbalanced conductor. I can see conductor (assuming insulated wire) having its electrical length affected by the capacitance between wire and earth, but wouldn't current stay close to same along the length? So, like if we have a coax, which has quite a capacitive coupling between the center conductor and shield, we would lose (significant) RF current at the other end? The fact that a conductor laid on the ground can lose R-F does not mean it lost conductivity. It means the conductor has induced loss in the ground upon which it is laid. (or improved conductivity?) Isn't it really case of two (resistive) conductors in parallel? Wire and dirt, with less resistance wire taking over? Why do we use radials if the conductors become lossy? Why does the Beverage laid on the ground work? I can see conductor as a (resonant) RF circuit becoming "detuned" and affected by earth proximity, but saying that it "becomes very lossy" is not very descriptive. With two wire Beverage I can see the interference between two "antennas" having same physical length, but different electrical lengths causing deterioration of pattern (which is observed). Cecil help? :-) Best regards, Richard Harrison, KB5WZI Yuri, K3BU |
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