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Coils and Transmission Lines.
Yuri Blanarovich wrote: More astonishing than that, Until the "gurus" put their finger on the coil, or aquarium thermometer, or RF ammeter, or infrared scope and see that the loading coil (in a typical quarter wave resonant whip) is heating up at the bottom, being the reality that defies their "scientwific theories why it shouldn't" - they will keep committing the same mental blunders over and over. Yuri, No one I have seen has every said one tuern can't get hotter than another turn in a loading coil. For example, I can take a piece of airdux and short a single turn anywhere in the coil. That turn and the turns around it will get very hot, often even melting the form and discoloring the wire, even with modest power applied in a resoant circuit. I had my 75 watt Novice rig melt miniductor in certain spots way back in the very early 60's. The problem is wild theories are created from small grains of truth or factoids. It is the wild theories that people question. In an effort to support the wild claims, there seems to be an effort to dismiss anything but the wild theories. Here is how it goes: 1.) My Hustler antenna loading coil (known to be a poor electrical design) melted the heatshrink at the bottom 2.) This must be becuase there is only high current at the bottom of every loading coil. 3.) This must be because the standing waves on the antenna all wind up in the loading coil. 4.) This must mean all loading coils act just like they are the x degrees of antenna they replace. 5.) This is why, no matter what we do with loading coil Q, efficiency doesn't change much. 6.) We will write a IEEE paper about this astounding fact, since all the texbooks about loading coils or inductors in general must be wrong 7.) Anyone who point out it is imperfections in the design of the system that cause this must be wrong, since I saw the coil get hot 8.) Anyone who disagrees with me must think himself a guru, and be incapable of learning or understanding how things work 9.) I know all this because the bottom of the coil gets hot in my antenna What's next? There is less current in a wire (coil) where wire (coil) gets hotter? Thermometers don't lie, meters don't lie, even EZNEC shows it! So wasaaaaap? It's all been explained over and over again. If the termination impedance of the coil is very high compared to shunting impedances inside the coil to the outside world, a coil can have phase shift in current at each terminal and it can have uneven current distribution. This is not caused by standing waves or "electrical degrees" the coil replaces, but rather by the displacement currents which can provide a path for the through currents. Reg actually explained this very well, as has Roy, Tom D, Gene, Tom ITM, Ian, and a half dozen others. The reason you keep beating your head against the wall is you want to think the conclusions you formed were correct. If I wanted to design a loading coil that has virtually 100% current taper, I could. If I wanted to design one with virtually no taper, I could. I could actually have an antenna of a fixed height and by making various styles of loading coils go anywhere from nearly uniform distribution at each end of the coil to some significant taper. The problem is Cecil attributes it all to standing waves, and not to the inductor's design. You seem to be doing the same. Since we won't agree with your wrong theories, you then conclude we are saying step one is wrong and you never saw what you saw. Step one is fine. Step two is where everything you say falls apart. 73 Tom |
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