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Richard Harrison wrote:
Ian, G3SEK wrote: "Hopefully you will agree that an IDEAL INDUCTANCE does not ever have different currents at its two terminals and does not radiate either." Sorry to disappoint you, but adequate demonstration has already shown different currents in and out of a loading coil. I won`t claim it was an ideal inductor. In that case you have nothing to discuss with me. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Tom Donaly, KA6RUH wrote:
": how do you take the gradient of the current at a point on a transmission line?" Not sure I understand the question. Gradient is the rate of change and that`s the derivative of the current at a given point. Over a certain path it is the difference between the path ends and can be averaged for the path. For convenience, Kraus has collected transmission line formulas. I`m not a typist so I`ll just say they are near the end of the new edition, page 890. In the 1950 edition they can be fornd on pages 506 and 507, also near the end of the book. Work out your own example. Best regards, Richard Harrison, KB5WZI |
Ian
Would you please describe for me the physical arrangement of an IDEAL inductance. I cannot visulise such a thing as I only have seen 'coiled ' inductors ,where each coil has a scientific and analytical relationship to its adjacent coils which thus CREATE an inductance and without which an 'inductance' cannot occur. I don't want to enter the augument that is ensuing on this thread but just want to be sure that there is not an inductance available that is not generated by proximity to other items including its own content (wire length) Using chemical terms, is it an element or a compound if you get my drift , since you later mention that 'inductance.' has a "fundamental physical property................." that does not change regardles of a proximity situation. i.e. Self sufficient.? TIA Art "Ian White, G3SEK" wrote in message ... Cecil Moore wrote: I want you to stop and think a moment, about how an IDEAL INDUCTANCE behaves in an antenna. (Sorry to shout, but every time I type "ideal inductance" quietly, you seem to read something else :-) Ian, please take your own advice. It's pretty obvious that you are thinking about an IDEAL INDUCTANCE in terms of a lumped circuit analysis which is invalid when analyzing a STANDING-WAVE ANTENNA. It makes life easier to compartmentalize your scientific world-view in that way.... but it is deeply, fundamentally wrong. In reality, all true scientific knowledge joins up seamlessly - that's how we *know* it's true! If we can't see how it joins up, that means we still have work to do. Dividing it into compartments that don't join up is lazy and will always lead you false. A fundamental physical property like inductance doesn't change its behaviour depending on the situation it finds itself in. If you cut the antenna wire and insert an ideal, lumped inductance, that inductance will behave in exactly the same way as it does in any other circuit. If you really looked hard at the math of antennas considered as transmission lines, you would find there is no problem whatever about inserting an ideal inductance, with no difference in current between its two terminals. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Tom Donaly wrote:
Cecil Moore wrote: Heh, heh, so you don't believe there is a current drop between the current maximum point and current minimum point on a transmission line with reflections? Seems to me going from 2 amps at a current maximum to 0.1 amps at a current minimum is a measurable drop in total current. Next, Cecil, you're going to be talking about a "current gradient" and a "scalar current field." Here's a question for you, Cecil, and Richard Harrison, and Yuri, too: how do you take the gradient of the current at a point on a transmission line, and, if were possible to do so, what is the physical significance of the result? A total current gradient obviously exists on a transmission line with current minimums and maximums. You can locate those points with a simple pickup loop. The current gradient is caused by the superposition of forward and reflected current waves as described in any transmission line textbook. "Taking the gradient" seems to me to be unnecessary and just a logical diversion away from the qualitative conceptual discussion. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Ian White, G3SEK wrote:
Cecil Moore wrote: Ian, please take your own advice. It's pretty obvious that you are thinking about an IDEAL INDUCTANCE in terms of a lumped circuit analysis which is invalid when analyzing a STANDING-WAVE ANTENNA. It makes life easier to compartmentalize your scientific world-view in that way.... but it is deeply, fundamentally wrong. Would you mind providing some real-world proof of your argument or are you satisfied just to play games in your mind? In reality, all true scientific knowledge joins up seamlessly - that's how we *know* it's true! If we can't see how it joins up, that means we still have work to do. Dividing it into compartments that don't join up is lazy and will always lead you false. Most of our models involve shortcuts. For instance, the shortcut equations for small loops do NOT work for large loops. Your lumped circuit shortcuts don't work for distributed networks. When anything in the circuit is an appreciable percentage of a wavelength, the lumped circuit model doesn't work. That's why the distributed network model was invented. A fundamental physical property like inductance doesn't change its behaviour depending on the situation it finds itself in. If you cut the antenna wire and insert an ideal, lumped inductance, that inductance will behave in exactly the same way as it does in any other circuit. It won't behave at all in reality because an ideal, lumped inductance exists only in the human mind, not in reality. If you want to play mind games, be my guest, but please don't try to pass your mental musings off as reality. The question is not whether your mental current changes through an ideal, lumped inductance existing only in your mind. The question is whether the current changes through a real-world bugcatcher coil that exists in reality. If you really looked hard at the math of antennas considered as transmission lines, you would find there is no problem whatever about inserting an ideal inductance, with no difference in current between its two terminals. An ideal inductance doesn't exist in reality so you are just playing games in your mind. Every real-world coil has a phase shift, i.e. a delay. A phase shift is all that is required for the superposed currents at each end of the coil to be different from each other. You seem to be saying that the phases of the forward and reflected currents don't change through a one-foot diameter, one-foot long bugcatcher coil made from 60 feet of wire? All I can say is, "Get real!" -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Richard Harrison wrote:
Jimmie wrote: "Coiling the wire has nothing to do with how it does or does not radiate,---." Good. Just leave your antenna rolled up. Best regards, Richard Harrison, KB5WZI That's exactly what's done in some "frequency independant" antennas. You can do it with logarithmic spirals or the Archimedean kind, take your pick. 73, Tom Donaly, KA6RUH |
Richard Harrison wrote:
Tom Donaly, KA6RUH wrote: ": how do you take the gradient of the current at a point on a transmission line?" Not sure I understand the question. Gradient is the rate of change and that`s the derivative of the current at a given point. Over a certain path it is the difference between the path ends and can be averaged for the path. For convenience, Kraus has collected transmission line formulas. I`m not a typist so I`ll just say they are near the end of the new edition, page 890. In the 1950 edition they can be fornd on pages 506 and 507, also near the end of the book. Work out your own example. Best regards, Richard Harrison, KB5WZI Thank you, Richard, you just made my point. 73, Tom Donaly, KA6RUH |
wrote:
Ian Would you please describe for me the physical arrangement of an IDEAL inductance. I cannot visulise such a thing as I only have seen 'coiled ' inductors ,where each coil has a scientific and analytical relationship to its adjacent coils which thus CREATE an inductance and without which an 'inductance' cannot occur. I don't want to enter the augument that is ensuing on this thread but just want to be sure that there is not an inductance available that is not generated by proximity to other items including its own content (wire length) Using chemical terms, is it an element or a compound if you get my drift , since you later mention that 'inductance.' has a "fundamental physical property................." that does not change regardles of a proximity situation. i.e. Self sufficient.? TIA Art "Ian White, G3SEK" wrote in message ... Cecil Moore wrote: I want you to stop and think a moment, about how an IDEAL INDUCTANCE behaves in an antenna. (Sorry to shout, but every time I type "ideal inductance" quietly, you seem to read something else :-) Ian, please take your own advice. It's pretty obvious that you are thinking about an IDEAL INDUCTANCE in terms of a lumped circuit analysis which is invalid when analyzing a STANDING-WAVE ANTENNA. It makes life easier to compartmentalize your scientific world-view in that way.... but it is deeply, fundamentally wrong. In reality, all true scientific knowledge joins up seamlessly - that's how we *know* it's true! If we can't see how it joins up, that means we still have work to do. Dividing it into compartments that don't join up is lazy and will always lead you false. A fundamental physical property like inductance doesn't change its behaviour depending on the situation it finds itself in. If you cut the antenna wire and insert an ideal, lumped inductance, that inductance will behave in exactly the same way as it does in any other circuit. If you really looked hard at the math of antennas considered as transmission lines, you would find there is no problem whatever about inserting an ideal inductance, with no difference in current between its two terminals. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek Can you visualize a point mass, Art? An ideal inductance isn't a point mass, but according to the textbooks, one is the mathematical analogue of the other. 73, Tom Donaly, KA6RUH |
Cecil Moore wrote:
Tom Donaly wrote: Cecil Moore wrote: Heh, heh, so you don't believe there is a current drop between the current maximum point and current minimum point on a transmission line with reflections? Seems to me going from 2 amps at a current maximum to 0.1 amps at a current minimum is a measurable drop in total current. Next, Cecil, you're going to be talking about a "current gradient" and a "scalar current field." Here's a question for you, Cecil, and Richard Harrison, and Yuri, too: how do you take the gradient of the current at a point on a transmission line, and, if were possible to do so, what is the physical significance of the result? A total current gradient obviously exists on a transmission line with current minimums and maximums. You can locate those points with a simple pickup loop. The current gradient is caused by the superposition of forward and reflected current waves as described in any transmission line textbook. "Taking the gradient" seems to me to be unnecessary and just a logical diversion away from the qualitative conceptual discussion. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- You and Richard need a refresher course in electromagnetics. I hope Yuri doesn't fall into the same trap. 73, Tom Donaly, KA6RUH |
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