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#711
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K7ITM wrote:
OK, so the difference in "FORWARD" current from the bottom to the top is: fwd.bottom.current - fwd.top.current = 1A at 0 degrees - 1 amp at -45 degrees = 1+j0 - sqrt(.5)-j*sqrt(.5) = 1-sqrt(.5) + j*sqrt(.5) (about 0.765 at 67.5 degrees) That is truly magic. Someone must have slept through class that day. Good grief! You can't subtract two currents that are a foot apart from each other. Currents superpose at a point. Currents from each end of the coil a foot apart don't superpose. They don't even know each other exist. Good Grief! Ifor=1A at 0 deg Ifor=1A at -45 deg -----------------X-/////////-Y------------------ Iref=1A at 0 deg Iref=1A at +45 deg The forward current superposes with the reflected current at the bottom of the coil to get 2 amps at zero degrees. The forward current superposes with the reflected current at the top of the coil to get 1.4 amps at zero degrees. The delay through the coil is 45 degrees. Neglecting losses: The energy in the forward wave is the same at the top and bottom of the coil. The energy in the reflected wave is the same at the top and bottom of the coil. There is zero net steady-state energy storage between the top and bottom of the coil. There's no RF battery there. -- 73, Cecil http://www.qsl.net/w5dxp |
#712
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On Sun, 26 Mar 2006 23:46:00 GMT, Cecil Moore
wrote: Trying to add those phases shows a lot of ignorance. Ah! Leading with your chin again. If you are really into adding up phase angles, then add them up every inch. Still leading with your chin? Amazing how you dismiss the "important" stuff with ±59% but want to add every inch. Why would ANYONE do what you suggest in the face of your outright sloppy work? |
#713
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John Popelish wrote:
I would have to graph this on a log frequency plot to see the frequency breakpoints, but I think this looks a lot like a short piece of transmission line below about 6 MHz and like a resonator above that. I expect the delay to start to fall at higher frequencies as the turn-to-turn capacitance takes over. What do you see? I see something that resembles part of a sine wave with a point of inflection (resembling a zero crossing) around 10 MHz. The phase shift around 10 MHz is 60 degrees per MHz. The phase shift above and below 10 Mhz is lower. I sure can see why the lumped circuit model is a total and complete failure when applied at 10 MHz. I also can see why Dr. Corum chose 15 degrees as his cutoff point. -- 73, Cecil http://www.qsl.net/w5dxp |
#714
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On Mon, 27 Mar 2006 01:04:43 GMT, Cecil Moore
wrote: Columbus is famous for missing by 10,000 miles appeal to antiquity to grant 4 orders of magnitude slop, hmmm? Columbus was an Italian huckster who was pitching sloppy math to make himself look authoritative. At least we've found a convergence there. My 60% accuracy is a heck of a lot more accurate than An error of 50, 59 now 60% is not 60% accuracy and given: On Sun, 26 Mar 2006 19:14:36 GMT, Cecil Moore wrote: I've said it befo The delay through the coil is what it is and we don't know exactly what it is. To say the delay is unknown, but you are 60% accurate is one for warranting a dope slap from Lord Kelvinator. |
#715
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Sorry you've missed the point, Cecil. I can only hope the lurkers get
it. (Aside: I'm not exactly sure what you mean by "no net steady-state energy storage." If that's true, then there's never ANY current in the inductor, because the energy stored in an inductor's magnetic field is i^2*L/2, and that's always positive for non-zero i.) Cheers, Tom |
#716
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You are leading yourselves astray again.
Anything which produces a velocity factor which varies significantly with frequency is INCORRECT. The propagation delay (in nano-seconds) along a coil is a constant and is independent of frequency. It depends only on the physical dimensions of the coil, ie., on L and C, which are fixed in a given situation. This is just the same as on an ordinary transmission line. ---- Reg. |
#717
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A bit more on this...
I trust it's an accurate summary to say that Cecil gave us the "forward" and "reflected" currents at both ends of a coil, and correctly deduced the standing-wave currents at each end from those. But given that information, Cecil is unable (and believes it is impossible) to determine the net charge in the volume containing the coil as a function of time (to within a constant, at least), even though the the wires in which we know the currents are the only way for charge to get in and out of that volume. I do hope we can at least agree that current is the rate at which charge passes a point... And I do hope most folk tuned in here don't have so much trouble with it. Farewell, goodbye, auf wiedersehen, adieu... Tom Cecil wrote: "K7ITM wrote: OK, so the difference in "FORWARD" current from the bottom to the top is: fwd.bottom.current - fwd.top.current = 1A at 0 degrees - 1 amp at -45 degrees = 1+j0 - sqrt(.5)-j*sqrt(.5) = 1-sqrt(.5) + j*sqrt(.5) (about 0.765 at 67.5 degrees) That is truly magic. Someone must have slept through class that day. Good grief! You can't subtract two currents that are a foot apart from each other. Currents superpose at a point. Currents from each end of the coil a foot apart don't superpose. They don't even know each other exist. Good Grief! Ifor=1A at 0 deg Ifor=1A at -45 deg -----------------X-/////////-Y------------------ Iref=1A at 0 deg Iref=1A at +45 deg The forward current superposes with the reflected current at the bottom of the coil to get 2 amps at zero degrees. The forward current superposes with the reflected current at the top of the coil to get 1.4 amps at zero degrees. The delay through the coil is 45 degrees. Neglecting losses: The energy in the forward wave is the same at the top and bottom of the coil. The energy in the reflected wave is the same at the top and bottom of the coil. There is zero net steady-state energy storage between the top and bottom of the coil. There's no RF battery there. -- 73, Cecil http://www.qsl.net/w5dxp " |
#718
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Reg Edwards wrote:
The propagation delay (in nano-seconds) along a coil is a constant and is independent of frequency. MOM seems to disagree. -- 73, Cecil http://www.qsl.net/w5dxp |
#719
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K7ITM wrote:
Sorry you've missed the point, Cecil. I can only hope the lurkers get it. If the lurkers think one can add or subtract the forward current at both ends of the coils, as you did, I feel sorry for them. -- 73, Cecil http://www.qsl.net/w5dxp |
#720
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K7ITM wrote:
Cecil is unable (and believes it is impossible) to determine the net charge in the volume containing the coil as a function of time (to within a constant, at least), even though the the wires in which we know the currents are the only way for charge to get in and out of that volume. THERE IS NO RF BATTERY STORING ENERGY! THERE IS ZERO LONG TERM ACCUMULATION OF CHARGE! Neglecting losses, energy in exactly equals energy out over the long term. The fact that 2 amps of standing wave current exists at the bottom of the coil and 1.4 amps of standing wave current exists at the top of the coil doesn't imply any long term accumulation of charge. Long term accumulation of charge in a coil is impossible. -- 73, Cecil http://www.qsl.net/w5dxp |
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