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Phase Shift through a 75m Texas Bugcatcher Coil
On May 14, 7:44 pm, Cecil Moore wrote:
In order to get a valid measurement of the delay through a coil, the coil needs to be loaded with its characteristic impedance to minimize the reflected current. What if a 3' long stainless steel whip is loading the coil? ac6xg |
Phase Shift through a 75m Texas Bugcatcher Coil
Jim Kelley wrote:
On May 14, 7:44 pm, Cecil Moore wrote: In order to get a valid measurement of the delay through a coil, the coil needs to be loaded with its characteristic impedance to minimize the reflected current. What if a 3' long stainless steel whip is loading the coil? That makes the antenna a standing wave antenna. Here are the characteristics of standing waves vs traveling waves for 1/4WL of wire. The phase of standing wave current is useless for phase measurements because it it fixed very close to zero degrees over the entire antenna. http://www.w5dxp.com/travstnd.gif Standing wave current has a negligible phase shift in the coil or in the whip and therefore cannot be used to measure the delay through a loading coil. To the best of my knowledge, all attempted phase measurements reported on this newsgroup, on current through a loading coil have been made using standing wave current with its fixed phase. No useful coil delay information can come from such measurements. -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
On May 15, 5:42 am, Cecil Moore wrote:
Jim Kelley wrote: On May 14, 7:44 pm, Cecil Moore wrote: In order to get a valid measurement of the delay through a coil, the coil needs to be loaded with its characteristic impedance to minimize the reflected current. What if a 3' long stainless steel whip is loading the coil? That makes the antenna a standing wave antenna. It makes it an antenna. Standing wave current has a negligible phase shift in the coil or in the whip and therefore cannot be used to measure the delay through a loading coil. The delay through the coil depends on inductance and capacitance. To the best of my knowledge, all attempted phase measurements reported on this newsgroup, on current through a loading coil have been made using standing wave current with its fixed phase. No useful coil delay information can come from such measurements. So your claim is that information about Bugcatcher coils with a load resistor attached is more useful? ac6xg |
Phase Shift through a 75m Texas Bugcatcher Coil
Jim Kelley wrote:
Cecil Moore wrote: Jim Kelley wrote: Cecil Moore wrote: That makes the antenna a standing wave antenna. It makes it an antenna. Well, putting a load resistor on a coil is a lot like a T2FD. :-) In fact, the way that a T2FD lowers the 50 ohm SWR is by reducing the reflections from that load resistor. Standing wave current has a negligible phase shift in the coil or in the whip and therefore cannot be used to measure the delay through a loading coil. The delay through the coil depends on inductance and capacitance. Yes, but the delay is not measurable using standing wave current because standing wave current doesn't change phase in a coil or in a wire. So far, all of the phase measurements reported here have been using standing wave current phase. Standing wave current essentially doesn't change phase in a 1/4WL long open-ended antenna. To the best of my knowledge, all attempted phase measurements reported on this newsgroup, on current through a loading coil have been made using standing wave current with its fixed phase. No useful coil delay information can come from such measurements. So your claim is that information about Bugcatcher coils with a load resistor attached is more useful? It is more useful for determining the delay through the coil. If you were trying to measure the phase shift through a 1/4WL stub, would you use the standing wave current with its zero phase shift? Or would you terminate the stub in its characteristic impedance and measure the phase shift in the subsequent traveling wave? Here are some recently generated graphics around which I am going to put some words. Hopefully, they will provide some stand alone information. Given: http://www.w5dxp.com/openstus.GIF How would you determine the phase shift at any point in the open stub? Given: http://www.w5dxp.com/openstus.GIF How would you determine the phase shift at any point in the terminated stub? Note that the two stubs are identical except for one being open and one being terminated so they have identical traveling-wave phase shifts. -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
I made a posting with a mistake, canceled it, and
am reposting. If the earlier posting got through, please ignore it. Jim Kelley wrote: Cecil Moore wrote: Jim Kelley wrote: Cecil Moore wrote: That makes the antenna a standing wave antenna. It makes it an antenna. Well, putting a load resistor on a coil is a lot like a T2FD. :-) In fact, the way that a T2FD lowers the 50 ohm SWR is by reducing the reflections from that load resistor. Standing wave current has a negligible phase shift in the coil or in the whip and therefore cannot be used to measure the delay through a loading coil. The delay through the coil depends on inductance and capacitance. Yes, but the delay is not measurable using standing wave current because standing wave current doesn't change phase in a coil or in a wire. So far, all of the phase measurements reported here have been using standing wave current phase. Standing wave current essentially doesn't change phase in a 1/4WL long open-ended antenna. To the best of my knowledge, all attempted phase measurements reported on this newsgroup, on current through a loading coil have been made using standing wave current with its fixed phase. No useful coil delay information can come from such measurements. So your claim is that information about Bugcatcher coils with a load resistor attached is more useful? It is more useful for determining the delay through the coil. If you were trying to measure the phase shift through a 1/4WL stub, would you use the standing wave current with its zero phase shift? Or would you terminate the stub in its characteristic impedance and measure the phase shift in the subsequent traveling wave? Here are some recently generated graphics around which I am going to put some words. Hopefully, they will provide some stand alone information. Given: http://www.w5dxp.com/openstus.GIF How would you determine the phase shift at any point in the open stub? Given: http://www.w5dxp.com/termstus.GIF How would you determine the phase shift at any point in the terminated stub? Note that the two stubs are identical except for one being open and one being terminated so they have identical traveling-wave phase shifts. -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Cecil doesnt seem to worry about this error, but just saying it
doesn't actually mean anything without differences. What is different about his claim and Wests'? On May 13, 3:52 pm, Richard Clark wrote: On Sun, 13 May 2007 18:17:29 GMT, Cecil Moore wrote: Tedious Xerography snipped as being obviously unread by Xerographer. Exactly what did I miss? If you have to be taken by the hand to have it pointed out to you, you shouldn't be doing these kind of things without adult supervision. A I have taken Wes's helical coil from: http://www.k6mhe.com/n7ws/Loaded%20antennas.htm B and modeled it with EZNEC. ... That coil512.EZ file can be downloaded from: is distinctly false. A B Does a symbolic reply nail it down? |
Phase Shift through a 75m Texas Bugcatcher Coil
Cecil Moore wrote:
The delay through the coil depends on inductance and capacitance. Yes, but the delay is not measurable using standing wave current because standing wave current doesn't change phase in a coil or in a wire. But you aren't measuring it. The point is, it's calculable. So your claim is that information about Bugcatcher coils with a load resistor attached is more useful? It is more useful for determining the delay through the coil. The fact that it doesn't give you an answer that agrees with any other method notwithstanding. If you were trying to measure the phase shift through a 1/4WL stub, would you use the standing wave current with its zero phase shift? If I were trying to measure delay I would use pulses. Or would you terminate the stub in its characteristic impedance and measure the phase shift in the subsequent traveling wave? I would want the system to be configured in exactly the same way as I intended for it to be used. Given: http://www.w5dxp.com/openstus.GIF How would you determine the phase shift at any point in the open stub? Given: http://www.w5dxp.com/termstus.GIF How would you determine the phase shift at any point in the terminated stub? The phase shift of what, with respect to what? ac6xg |
Phase Shift through a 75m Texas Bugcatcher Coil
Jim Kelley wrote:
Cecil Moore wrote: Yes, but the delay is not measurable using standing wave current because standing wave current doesn't change phase in a coil or in a wire. But you aren't measuring it. The point is, it's calculable. But w8ji and w7el *are* measuring it and getting something different from those calculations. They are reporting their flawed measurements as technical fact. That's what the whole argument is about. There is no way in heck to get a 3 nS delay out of a 100 turn, 10", 2" diameter coil. It is more useful for determining the delay through the coil. The fact that it doesn't give you an answer that agrees with any other method notwithstanding. It means that the existing posted methods are invalid. And that doesn't extend just to the side that asserts the delay through the coil is close to zero. It also extends to the other side who accepts the use of standing-wave current as a valid measurement technique. *All* of the measurements made using standing-wave current are bogus. If I were trying to measure delay I would use pulses. How do you know the pulsed delay is the same as the steady-state delay? Has anyone published a delay using pulses? I'm not saying a pulsed delay won't yield valid results - I just don't know. If it is a DC pulse, there would be known problems. I would want the system to be configured in exactly the same way as I intended for it to be used. Then you will find it is impossible to measure the delay through the coil during steady-state. -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
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