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#11
April 20th 06, 04:01 PM
posted to rec.radio.amateur.antenna
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Current across the antenna loading coil - from scratch
Cecil Moore wrote:
wrote: I can't believe you are still trying to get Cecil to actually read the paper he is misquoting. Unfortunately for your lumped circuit religion, I am not misquoting anything. Page 4 contains a test to see if a coil falls within the limitations of the velocity factor equation. A 75m bugcatcher coil is less than half the upper limit. Here's the calculation: 5*N*D^2/lamda 1 N is turns per unit length and D is the diameter. Cecil, Selective quoting can have the same effect as misquoting. If one goes back a few words in the same long sentence it can be observed that the more complete limitation is stated as: "... an approximation for M has been determined by Kandoian and Sichak which is *appropriate for quarter-wave resonance* and is valid for helices with 5*N*D^2/lambda 1 ..." [emphasis was in the original] You apparently choose to accept the second half of the condition while ignoring the first half. In most cases the "AND" construction means both parts apply. Do you really think the Vf is dependent only on the turn density and not the number of turns? Corum never says such a thing, since the number of turns is dictated by the resonance requirement. How far down does your magic extend? To half the turns needed for resonance? To one turn? To less than one turn? Where is the transition in Vf from the ~1 for zero turns to ~0.02 for a resonant coil? For anyone still reading who is bored (everyone) or confused by this topic (perhaps) the importance to the subject at hand is that Cecil has mis-used this reference paper to "prove" that the 75 meter loading coil replaces approximately 45 degrees of the original unloaded quarter wave antenna. After his long struggle to prove his point with modeling, and achieving only 10 degrees of phase replacement, he abandoned that approach for this latest futile attempt. The "missing" portion of the test antenna is about 75 degrees, so 45 degrees would barely squeak in under the 59% precision rule. 73, Gene W4SZ |
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