|
Thanks for the correction regarding proximity effect. In that case,
Reg's program should report the loss more accurately than EZNEC when the turns are very closely spaced. Yes, indeed, EZNEC does account for the capacitance -- it comes about from the coupling of fields between turns, which is at the heart of the fundamental NEC-2 electromagnetic field calculations. As I said, the self-resonant frequency reported by EZNEC is pretty close to that calculated by your program. Roy Lewallen, W7EL Reg Edwards wrote: EZNEC doesn't model proximity effect (significant only when the turns are pretty closely spaced) but I don't think Reg's program includes proximity effect, either. Roy Lewallen, W7EL ====================================== Yes it does! But you can forget it. It doesn't matter except when calculating efficiency. It has no affect on how the thing works which is what you are all so-aggressively fighting about. You'll soon be using assault weapons. Program "Loadcoil" also includes the ALL-IMPORTANT COIL CAPACITANCE (which I suspect Eznec does not - I never use it) - the existence of which the whole set of you block-heads, so-called electrical engineers, appear to be entirely ignorant. We ARE dealing with alternating currents. Oh Boy - I enjoyed typing that! ;o) ---- Reg, G4FGQ |
Jim Kelley wrote:
Tom Donaly wrote: Jim Kelley wrote: Tom Donaly wrote: 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? 73, Tom Donaly, KA6RUH The standing wave current profile along, for example, a quarter wave radiator is a cosine function. The gradient then would be the derivative of the cosine function which is a -sine function. 73, ac6xg Jim, current, in a wire, is the total current density integrated across a cross section of the wire. It's a vector, as is the current density. Now tell me, how do you take the gradient of a vector? David K. Cheng, in his book Field and Wave Electromagnetics, defines the gradient operation this way: "We define the vector that represents both the magnitude and the direction of the maximum space rate of increase of a scalar as the gradient of that scalar." He wrote "scalar," not "vector," Jim. You and the rest of the boys are acting as if current had magnitude but no direction, whereas it has both. 73, Tom Donaly, KA6RUH Not sure why you don't like gradients, Tom. I'm sure Mr. Cheng is undoubtedly correct, but I'm just as sure he didn't intend that sentence as any sort of definition of the term "gradient". Actually, he did. It's the accepted definition of the term in electromagnetics. You and Cecil are using the term in a more general fashion which you've made up for the purpose. It doesn't make much sense in an elecromagnetic setting. Similarly, Yuri, Richard and Cecil made up a very loose term "current drop" for a change in current at two ends of a coil. That was misleading and wrong if they were trying to convey something about the electromagnetics of a coil, which they were. I've seen you fellows pick each other to death over trivia time and again. It's time you paid attention to what you write. That's something you have apparently read into it. The gradient in our case (since you proposed the question) would be expressed as the superposition of forward and reverse currents, with magnitude and phase (or direction if you prefer) written as a function of either position or angle *along* the radiator. It's nothing fancy. Honest. It's simply the rate of change of current as a function of position. The gradient across the radiator at any given point along the radiator could then be determined using some additional parameters - if someone were really that interested in it (which I'm not). 73, ac6xg How could the gradient be in your case if I proposed the question? 73, Tom Donaly, KA6RUH |
Tom Donaly wrote:
However, the term "current drop" as used by Yuri was wrong. There is no place for it in electromagnetic theory, and if you had known enough theory to understand that, you wouldn't have answered as you did. I've been in Las Vegas for ten days and didn't see Yuri's posting. All I know is there is a "current drop" from the current maximum point to the current minimum point on a transmission line with reflections. So exactly how did Yuri use "current drop"? If it is through a mobile loading coil, I explain exactly how that happens on my web page through the superposition of the forward and reflected currents. For the typical base-loaded or center-loaded shortened mobile antenna, If+Ir at one end of the coil is NOT equal to If+Ir at the other end of the coil even if the two currents through the coil are of constant magnitudes. I have explained that multiple times here with no disagreement. For typical standing-wave antennas with loading coils: The forward current through a loading coil is reasonably constant. The reflected current through a loading coil is reasonably constant. The two above facts are obeying Kirchhoff's laws. The total current is the sum of the forward current and the reflected current and results in a cosine function standing wave on the antenna. The differing phases of forward current and reflected current is what causes the variation in the total current, i.e. the current drop. The current drop in a standing wave antenna is similar to the current drop in a section of transmission line with reflections. The governing equations can be found in any EM textbook and for lossless situations are of the form: Itot = If*e^-yz - Ir*e^+yz Losses to radiation or I^2*R add another couple of e^-2ad (attenuation) terms. -- 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 =--- |
Tom Donaly wrote:
Besides, you missed the point again. Sorry, I've been out of town for 10 days and haven't read all the postings. So please bring me up to date. Exactly what is "the point"? -- 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 =--- |
Tom Donaly wrote:
you've hit the nail squarely on the head. The validity of the whole argument boils down to whether or not you can safely neglect the effects of the physical dimensions of the inductor on the behavior of the antenna. It looks to me as if you can, but some of the other fellows on this newsgroup seem to be as much interested in characterizing Tom Rauch as a rat as they are in verifying some antenna effects due to the properties of real loading coils. You guys have completely missed the point. The argument is not about the behavior of the antenna. The original argument is/was about the current in a real-world antenna loading coil. The behavior of the antenna is irrelevant to that original argument. -- 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 =--- |
Tom Donaly wrote:
I don't agree with the term "current drop" because, even in a transmission line, current, or more properly, current density, doesn't act like a potential of any sort to which you could ascribe a "drop." Webster defines "drop" as "to become less". Seems to me, the current "becomes less" as one moves the measurement point from a current loop to a current node on a standing-wave antenna. -- 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 =--- |
Tom Donaly wrote:
current, in a wire, is the total current density integrated across a cross section of the wire. It's a vector, ... From "Fields and Waves in Communications Electronics", by Ramo, Whinnery, & Van Duzer, page 239: "It must be recognized that the symbols in the equations of this article have a *different* meaning from the same symbols used in Art. 4.06. There they represented the instantaneous values of the indicated *vector* and scalar quantities. Here they represent the complex multipliers of e^jwt, giving the in-phase and out-of-phase parts with respect to the chosen reference. The complex scalar quantities are commonly referred to as *phasors*, ..." From the IEEE Dictionary: "The phase angle of a phasor should not be confused with the space angle of a vector." You are obviously confusing vectors and phasors. -- 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 Clark wrote:
There is no such Kirchoff law of two separate points of current, that is Kirchoff's voltage law. A point (singular, the only component of Kirchhoff's current law) has no dimension, any departure from this necessarily excludes itself from strict Kirchhoffian analysis. Yes, you are starting to get it. Point inductances don't exist in reality. -- 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 =--- |
On Thu, 21 Oct 2004 00:18:59 -0500, Cecil Moore
wrote: starting to get it took you a long time too. |
On Wed, 20 Oct 2004 23:44:01 -0500, Cecil Moore
wrote: behavior of the antenna is irrelevant sour grapes :-) |
Cecil Moore wrote:
Tom Donaly wrote: current, in a wire, is the total current density integrated across a cross section of the wire. It's a vector, ... From "Fields and Waves in Communications Electronics", by Ramo, Whinnery, & Van Duzer, page 239: "It must be recognized that the symbols in the equations of this article have a *different* meaning from the same symbols used in Art. 4.06. There they represented the instantaneous values of the indicated *vector* and scalar quantities. Here they represent the complex multipliers of e^jwt, giving the in-phase and out-of-phase parts with respect to the chosen reference. The complex scalar quantities are commonly referred to as *phasors*, ..." From the IEEE Dictionary: "The phase angle of a phasor should not be confused with the space angle of a vector." You are obviously confusing vectors and phasors. -- 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're just digging the hole deeper, Cecil. I know you think you can use the simplifications of transmission line theory to explain everything in electromagnetics. Reg seems to think that's a valid way of doing things, too. If it were true, it would certainly make life easier for those poor souls who have to study Maxwell's equations in colleges throughout the world. Just think, no more vector calculus for engineers! From what I've read on this group the past few days, many engineers don't learn it anyway, so why not just dumb things down to your level? Maybe you should write a letter to Texas A&M telling them they don't have to teach it any more. (If they still do, that is. Some colleges have dumbed themselves down considerably in the past 20 years.) 73, Tom Donaly, KA6RUH |
Richard Clark wrote:
Cecil Moore wrote: behavior of the antenna is irrelevant sour grapes :-) Yes, from you guys. "OK, I admit I was wrong, but that original argument didn't matter anyway." :-) ----== 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 =--- |
Tom Donaly wrote:
You're just digging the hole deeper, Cecil. I know you think you can use the simplifications of transmission line theory to explain everything in electromagnetics. The transmission line model is more complicated than the circuit model and works for transmission lines, including antennas, which are single-wire transmission lines. Your overly simplified circuit model doesn't work for transmission lines or for antennas. That's what got you (and others) into trouble. All you guys can do now to try to save face is sandbag and divert the issue. -- 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 =--- |
Tom Donaly wrote:
"I know you think you can use the simplification of transmission line theory to explain everything in electromagnetics. Reg seems to think that`s a valid way of doing things, too." I had a graduate course in Maxwell`s equations, but had a long rewarding career without using Maxwell directly. Reg is an advocate of Oliver Heaviside`s work based on Maxwell. Nothing wrong with that. In his 1950 work "Antennas", Kraus has this to say about Maxwell`s equations: "Maxwell`s equations are summarized in the tables. The first table gives Maxwell`s equations in differential form and the second table in intergral form. The equations are stated for the general case, free-space case, harmonic-variation case, steady case (static fields but with conduction currents), and static case (static fields with no currents). In the table giving the integral form, the equivalence is also indicated between the various equations and the electrical potential or emf, the magnetic potential or mmf, the electric current, the electric flux, and then magnetic flux. Many texts do very well with no mention of Maxwell despite his contributions to electromagnetics. That`s too bad, but that`s the way it is. Best regards, Richard Harrison, KB5WZI |
Tom Donaly wrote: Jim Kelley wrote: Not sure why you don't like gradients, Tom. I'm sure Mr. Cheng is undoubtedly correct, but I'm just as sure he didn't intend that sentence as any sort of definition of the term "gradient". Actually, he did. It's the accepted definition of the term in electromagnetics. You and Cecil are using the term in a more general fashion which you've made up for the purpose. It doesn't make much sense in an elecromagnetic setting. Similarly, Yuri, Richard and Cecil made up a very loose term "current drop" for a change in current at two ends of a coil. That was misleading and wrong if they were trying to convey something about the electromagnetics of a coil, which they were. I've seen you fellows pick each other to death over trivia time and again. It's time you paid attention to what you write. That's something you have apparently read into it. The gradient in our case (since you proposed the question) would be expressed as the superposition of forward and reverse currents, with magnitude and phase (or direction if you prefer) written as a function of either position or angle *along* the radiator. It's nothing fancy. Honest. It's simply the rate of change of current as a function of position. The gradient across the radiator at any given point along the radiator could then be determined using some additional parameters - if someone were really that interested in it (which I'm not). 73, ac6xg How could the gradient be in your case if I proposed the question? 73, Tom Donaly, KA6RUH Are you trying to make some point? If so, I'd sure like to know what it is. It appears you're trying to pretend that the gradient (a mathematical term) in the standing wave current along the length of a radiator doesn't exist. Why? It's a very simple and straightforward notion. 73, Jim AC6XG |
Jim Kelley wrote:
Tom Donaly wrote: Jim Kelley wrote: Not sure why you don't like gradients, Tom. I'm sure Mr. Cheng is undoubtedly correct, but I'm just as sure he didn't intend that sentence as any sort of definition of the term "gradient". Actually, he did. It's the accepted definition of the term in electromagnetics. You and Cecil are using the term in a more general fashion which you've made up for the purpose. It doesn't make much sense in an elecromagnetic setting. Similarly, Yuri, Richard and Cecil made up a very loose term "current drop" for a change in current at two ends of a coil. That was misleading and wrong if they were trying to convey something about the electromagnetics of a coil, which they were. I've seen you fellows pick each other to death over trivia time and again. It's time you paid attention to what you write. That's something you have apparently read into it. The gradient in our case (since you proposed the question) would be expressed as the superposition of forward and reverse currents, with magnitude and phase (or direction if you prefer) written as a function of either position or angle *along* the radiator. It's nothing fancy. Honest. It's simply the rate of change of current as a function of position. The gradient across the radiator at any given point along the radiator could then be determined using some additional parameters - if someone were really that interested in it (which I'm not). 73, ac6xg How could the gradient be in your case if I proposed the question? 73, Tom Donaly, KA6RUH Are you trying to make some point? If so, I'd sure like to know what it is. It appears you're trying to pretend that the gradient (a mathematical term) in the standing wave current along the length of a radiator doesn't exist. Why? It's a very simple and straightforward notion. 73, Jim AC6XG Keep trying, Jim. 73, Tom Donaly, KA6RUH |
Cecil Moore wrote:
Tom Donaly wrote: You're just digging the hole deeper, Cecil. I know you think you can use the simplifications of transmission line theory to explain everything in electromagnetics. The transmission line model is more complicated than the circuit model and works for transmission lines, including antennas, which are single-wire transmission lines. Your overly simplified circuit model doesn't work for transmission lines or for antennas. That's what got you (and others) into trouble. All you guys can do now to try to save face is sandbag and divert the issue. -- 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 =--- Who said anything about a circuit model? 73, Tom Donaly, KA6RUH |
Tom Donaly wrote: Jim Kelley wrote: Keep trying, Jim. 73, Tom Donaly, KA6RUH To what end? It's not a controversial issue. 73, Jim AC6XG |
Tom Donaly wrote:
Who said anything about a circuit model? I'm going to present an example, step by step. Please contribute something technical in response. It's a simple lossless quarter-wave matching section example. ------50 ohm feedline---+---1/4WL 600 ohm feedline---7200 ohm load Pfor1=100w-- Pfor2=352w-- 100w --Pref1=0w --Pref2=252w Vfor1=70.7v-- Vfor2=460v-- Vload=849v --Vref1=0v --Vref2=389v Ifor1=1.414A-- Ifor2=0.766A-- Iload=0.118A --Iref1=0A --Iref2=0.648A Vref2 is 180 degrees out of phase with Vfor2 and thus they subtract. Iref2 is in phase with Ifor2 and thus they add. The impedance at '+' is (Vfor2-Vref2)/(Ifor2+Ifor1) The impedance at '+' is (460v-389v)/(0.766A+0.648A) = 70.7V/1.414A = 50 ohms Note that the impedance seen at the match point is: Vfor1/Ifor1 = (Vfor2-Vref2)/(Ifor2+Iref2) So Tom, do you find anything wrong with this network analysis? If so, please be technically specific. (Sorry, your feelings don't matter.) -- 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 =--- |
Cecil Moore wrote:
Tom Donaly wrote: Who said anything about a circuit model? I'm going to present an example, step by step. Please contribute something technical in response. It's a simple lossless quarter-wave matching section example. ------50 ohm feedline---+---1/4WL 600 ohm feedline---7200 ohm load Pfor1=100w-- Pfor2=352w-- 100w --Pref1=0w --Pref2=252w Vfor1=70.7v-- Vfor2=460v-- Vload=849v --Vref1=0v --Vref2=389v Ifor1=1.414A-- Ifor2=0.766A-- Iload=0.118A --Iref1=0A --Iref2=0.648A Vref2 is 180 degrees out of phase with Vfor2 and thus they subtract. Iref2 is in phase with Ifor2 and thus they add. The impedance at '+' is (Vfor2-Vref2)/(Ifor2+Ifor1) The impedance at '+' is (460v-389v)/(0.766A+0.648A) = 70.7V/1.414A = 50 ohms Note that the impedance seen at the match point is: Vfor1/Ifor1 = (Vfor2-Vref2)/(Ifor2+Iref2) So Tom, do you find anything wrong with this network analysis? If so, please be technically specific. (Sorry, your feelings don't matter.) -- 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 =--- Cecil, if I had a dollar for every time you challenged someone to solve a quarter wavelength transmission line transformer problem I could eat a meal in the best restaurant in San Francisco and still have change left over to pay a 20% tip. The question is not whether or not the theory you made up in your head is right or not, but whether the length, shape, volume, whatever of a loading coil on a short antenna makes any substantial difference in the efficiency of the antenna. The problem of increasing the total current on a short antenna was solved so many years ago the fellows who solved it are old enough to be Richard Harrison's grandparents. If Yuri would spend more time researching his subject and less time with his fish thermometers and his diatribes against Tom Rauch he would learn that. 73, Tom Donaly, KA6RUH |
"Tom Donaly" wrote in message m... Cecil Moore wrote: Tom Donaly wrote: Who said anything about a circuit model? I'm going to present an example, step by step. Please contribute something technical in response. It's a simple lossless quarter-wave matching section example. ------50 ohm feedline---+---1/4WL 600 ohm feedline---7200 ohm load Pfor1=100w-- Pfor2=352w-- 100w --Pref1=0w --Pref2=252w Vfor1=70.7v-- Vfor2=460v-- Vload=849v --Vref1=0v --Vref2=389v Ifor1=1.414A-- Ifor2=0.766A-- Iload=0.118A --Iref1=0A --Iref2=0.648A Vref2 is 180 degrees out of phase with Vfor2 and thus they subtract. Iref2 is in phase with Ifor2 and thus they add. The impedance at '+' is (Vfor2-Vref2)/(Ifor2+Ifor1) The impedance at '+' is (460v-389v)/(0.766A+0.648A) = 70.7V/1.414A = 50 ohms Note that the impedance seen at the match point is: Vfor1/Ifor1 = (Vfor2-Vref2)/(Ifor2+Iref2) So Tom, do you find anything wrong with this network analysis? If so, please be technically specific. (Sorry, your feelings don't matter.) -- 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 =--- Cecil, if I had a dollar for every time you challenged someone to solve a quarter wavelength transmission line transformer problem I could eat a meal in the best restaurant in San Francisco and still have change left over to pay a 20% tip. The question is not whether or not the theory you made up in your head is right or not, but whether the length, shape, volume, whatever of a loading coil on a short antenna makes any substantial difference in the efficiency of the antenna. The problem of increasing the total current on a short antenna was solved so many years ago the fellows who solved it are old enough to be Richard Harrison's grandparents. If Yuri would spend more time researching his subject and less time with his fish thermometers and his diatribes against Tom Rauch he would learn that. 73, Tom Donaly, KA6RUH Tom You would have enough money to own the restaurant. sigh Here goes--- Any difference in current between the ends of a compact loading coil in the center of a short whip is due to radiation from the coil. The same people have been making the same arguments here for years. sheesh! OTOH is has been entertaining. 73 H. |
Tom Donaly wrote:
The question is not whether or not the theory you made up in your head is right or not, but whether the length, shape, volume, whatever of a loading coil on a short antenna makes any substantial difference in the efficiency of the antenna. No, that's not the question at all. You have diverted the issue from current through the coil to efficiency. The question is whether the current at each end of a real-world loading coil is the same or not the same. Efficiency is irrelevant. Diverting the issue is an obvious tactic employed by someone who is losing the argument. If one doesn't understand standing waves on a transmission line, one cannot understand standing-wave antennas. The ignorance of how standing- wave antennas work is the basic problem. I am attempting to alleviate that ignorance. -- 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 =--- |
H. Adam Stevens, NQ5H wrote:
Any difference in current between the ends of a compact loading coil in the center of a short whip is due to radiation from the coil. That's an old wives' tale. But don't feel bad. Kurt N. Sterba made essentially that same mistake in his Nov. 2004 article in "Worldradio". Anyone who believes that the current is zero at the tip end of a standing-wave antenna because it has been radiated needs a refresher course in standing waves. ************************************************** ******************* * Any difference in forward current between the ends of a loading * coil is due to radiation from the coil. * * Any difference in reflected current between the ends of a loading * coil is due to radiation from the coil. ************************************************** ******************* Please read those two statements until they soak in because they agree with you about component currents but disagree with you about superposed currents. The main difference between the net superposed current at each end of the coil is caused by the phase shift through the coil acting on each of those current components in opposite phase-rotation since they are traveling in opposite directions. Is any difference in current between the ends of a section of transmission line due to radiation from the transmission line? Yes, but most of the difference is due to phase shifts between the forward and reflected waves. Exactly the same concepts apply both to a transmission line with standing waves and a standing-wave antenna. In fact, a horizontal wire antenna is nothing more than a "lossy" transmission line losing energy to radiation. A mobile antenna is a standing-wave antenna possessing a Z0, just like a transmission line. There's a forward current and a reflected current. The superposition of those two component currents causes the main difference in the magnitude of the net current at each end of the coil. When Roy, W7EL, measured the phase of the current at each end of the coil, he measured the phase of the NET superposed current, not the phase of the forward current or reflected current. The phase shift of the NET superposed current is only a couple of degrees max from feedpoint to end as asserted by Kraus in "Antennas for all Applications", page 464. In the ARRL Antenna Book is an equation for the characteristic impedance of a single wire over ground. It is 138*log(4h/d) where 'h' is the height of the antenna and 'd' is the diameter of the wire. The Z0 for a piece of #16 wire positioned 24 feet above ground is about 600 ohms. A quarter wavelength of that wire used as an antenna responds essentially the same as a quarter wavelength of lossy transmission line. There is a large reflected current component at the tip of a mobile (standing-wave) antenna. In fact, my earlier quarter-wavelength matching section plus its 100w load acts similar to a quarter-wavelength antenna radiating 100w. -- 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 =--- |
Cecil Moore wrote:
Tom Donaly wrote: The question is not whether or not the theory you made up in your head is right or not, but whether the length, shape, volume, whatever of a loading coil on a short antenna makes any substantial difference in the efficiency of the antenna. No, that's not the question at all. You have diverted the issue from current through the coil to efficiency. The question is whether the current at each end of a real-world loading coil is the same or not the same. Efficiency is irrelevant. Diverting the issue is an obvious tactic employed by someone who is losing the argument. If one doesn't understand standing waves on a transmission line, one cannot understand standing-wave antennas. The ignorance of how standing- wave antennas work is the basic problem. I am attempting to alleviate that ignorance. -- 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 =--- Cecil, I'll believe you know something about loading coils when you go back to school and learn something about basic classical electromagnetic theory. As it stands, all you can do is make one unsupported statement after another and hope someone is gullible enough to believe you. 73, Tom Donaly, KA6RUH (P.S. How do you know what the subject was? You didn't read all the posts.) |
Tom Donaly wrote:
Cecil, I'll believe you know something about loading coils when you go back to school and learn something about basic classical electromagnetic theory. Been there - done that - even got the T-shirt with Maxwell's equations on it. I suspect that your university never taught the real thing. As it stands, all you can do is make one unsupported statement after another and hope someone is gullible enough to believe you. I supported my statements with examples. Strangely enough, you haven't posted any technical disagreement with my examples. All you do is take potshots based on nothing except your feelings. It's impossible to argue with you on a technical basis because you have not posted anything technical. Do you disagree that the Z0 of a single #16 wire located 24 ft. above ground is ~600 ohms? Do you disagree that such a wire can support standing waves whether used as a transmission line or as an antenna? Please post what you find technically wrong with my examples (all based on valid distributed network reflection models) which I learned in the 50's from "Field and Waves in Modern Radio" by Ramo and Whinnery and a later edition of the same book in graduate school. -- 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 =--- |
"Cecil Moore" wrote in message ... Jimmie wrote: What, Coililng the wire has nothing to do with how well it does or does not radiate, only with how the radiation is summed into the total field. The current distribution in a loading coil should be very similar to the current distribution in the secton of antenna it is replacing. Actually, coiling the wire tends to reduce the far-field radiation because much of the near-field(s) cancel each other. The currents on each side of the coil are traveling the opposite direction in much the same way they do in a transmission line. However, that doesn't mean the currents at the bottom and top of the coil are identical. The magnitude of the total current at the bottom and top of the coil depends in large amount on the phase shift through the coil. -- 73, Cecil http://www.qsl.net/w5dxp Just because it is canceld in the far field does not mean the coil did not radiate. I would not even say it is canceled in the far field although this is a convenent way of looking at radiation. All you can really say for sure is that the out of phase voltages in the receiving antenna combine destructively. ----== 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 in message ... 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 And it will radiate, assuming no other changes but the geometry of the antenna.. When the out of phase componts of the radiation reach a receiving antenna they will destructivly combine. |
Cecil Moore wrote:
Tom Donaly wrote: Cecil, I'll believe you know something about loading coils when you go back to school and learn something about basic classical electromagnetic theory. Been there - done that - even got the T-shirt with Maxwell's equations on it. I suspect that your university never taught the real thing. As it stands, all you can do is make one unsupported statement after another and hope someone is gullible enough to believe you. I supported my statements with examples. Strangely enough, you haven't posted any technical disagreement with my examples. All you do is take potshots based on nothing except your feelings. It's impossible to argue with you on a technical basis because you have not posted anything technical. Do you disagree that the Z0 of a single #16 wire located 24 ft. above ground is ~600 ohms? Do you disagree that such a wire can support standing waves whether used as a transmission line or as an antenna? Please post what you find technically wrong with my examples (all based on valid distributed network reflection models) which I learned in the 50's from "Field and Waves in Modern Radio" by Ramo and Whinnery and a later edition of the same book in graduate school. -- 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 =--- I'm not going to waste my time arguing with you , Cecil; as you say, been there, done that. I know there are people in the past who have attempted to characterize antennas as transmission lines. It's an old, hoary method. You have a copy of Balanis. He has references you can look up to see how close your ideas are to the truth. Nope, I don't need to argue. I have a wife who is always willing and ready to provide arguing services whenever I need them. I don't need you. 73, Tom Donaly, KA6RUH |
Jimmie wrote:
Just because it is canceld in the far field does not mean the coil did not radiate. It is generally accepted that if RF energy doesn't escape to the far- field, that energy is not "radiated". Energy can appear in the near- field around a wire without being "radiated". I would not even say it is canceled in the far field although this is a convenent way of looking at radiation. All you can really say for sure is that the out of phase voltages in the receiving antenna combine destructively. If the fields combine destructively in the near-field, that field energy is returned to the system and never reaches the receiving antenna in the far field. That's how transmission lines are supposed to work and why the spacing between the two conductors needs to be negligible compared to a wavelength. The near-balanced currents on each side of a coil, traveling in opposite directions, cause destructive interference in the near field, thus limiting the amount of energy radiated by the coil. An electrical 1/4WL helical antenna radiates slightly less RF than does a 1/4WL straight wire. That implies the amount of radiation from an air-core coil is slightly less than from a wire the same overall length as the coil. -- 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 =--- |
Jimmie wrote:
And it will radiate, assuming no other changes but the geometry of the antenna.. When the out of phase componts of the radiation reach a receiving antenna they will destructivly combine. If it actually radiates and if that radiation destructively combines at one receiving antenna, then radiation must constructively combine at another (potential) receiving antenna, or else the conservation of energy principle would be violated. Any far-field destructive interference event must be exactly balanced by an equal magnitude constructive interference event at some other location in the far-field. If there is a receiving antenna there, it will experience gain over the first location. And a coiled up antenna is likely to experience a lot of I^2*R losses. -- 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 =--- |
Tom Donaly wrote:
I'm not going to waste my time arguing with you , Cecil; as you say, been there, done that. Don't want to argue, Tom. I just want you to make a posting that contains some iota of technical content. My ten-year-old grand-neice could easily have thought up your last dozen (mostly ad-hominem) postings. I know there are people in the past who have attempted to characterize antennas as transmission lines. It's an old, hoary method. You have a copy of Balanis. He has references you can look up to see how close your ideas are to the truth. Since you brought up Balanis, here are some quotes from Chapter 10 of his book that should impress you: "The sinusoidal current distribution of long open-ended linear antennas is a standing wave constructed by two waves of equal amplitude and 180 deg phase difference at the open-end TRAVELING IN OPPOSITE DIRECTIONS along its length" page 488 (emphasis mine) "THE CURRENT AND VOLTAGE DISTRIBUTIONS ON OPEN-ENDED WIRE ANTENNAS ARE SIMILAR TO THE STANDING WAVE PATTERNS ON OPEN-ENDED TRANSMISSION LINES." Page 488 (emphasis mine) "Standing wave antennas, such as the dipole, can be analyzed as traveling wave antennas with waves propagating in opposite directions (forward and backward) and represented by traveling wave currents If and Ib." page 489 Uhhhhh Tom, following Balanis' direction is EXACTLY what I have been doing. Since you disagree with Balanis, it appears that you have never cracked open his book. I, OTOH, have attended Balanis' antenna classes at ASU and worked hand in hand with him on a joint Intel-ASU project. -- 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 =--- |
Nope, I don't need to argue. I have a wife who is always willing
and ready to provide arguing services whenever I need them. I don't need you. 73, Tom Donaly, KA6RUH Cecil, fuggetaboutit, don't waste your time, looks like this is one of those smart alec trollers. Who cares what they "know". Thanks for your contribution to the subject. Looks like I should put the article together, looks like misguided "experts" are confusing the issue. I hope to find some time now, WX is getting about right, time to get out the gadgets and some real life measurements and modeling helixes in EZNEC. 73 Yuri, K3BU |
Yuri Blanarovich wrote:
Cecil, fuggetaboutit, don't waste your time, looks like this is one of those smart alec trollers. Who cares what they "know". Looks like Tom would rather argue with his wife than with Balanis or me. (I don't blame him for that.) I had relatively long discussions with Balanis and he personally agreed with everything I have posted although he didn't go to such lengths in his book. Thanks for your contribution to the subject. Looks like I should put the article together, looks like misguided "experts" are confusing the issue. I hope to find some time now, WX is getting about right, time to get out the gadgets and some real life measurements and modeling helixes in EZNEC. Who's going to publish it? I spent a lot of time preparing an article on what happens at a match point and QEX refused to consider publishing anything that disagreed in the slightest with Dr. Best who denied there is such a thing as interference at a match point. (Hint: Without interference, a match is impossible in a system with reflections.) There's a good-old-boys network in amateur radio. If you are politically incorrect within the ARRL political power structure, you are black-balled from publishing. It doesn't matter if you are technically correct. The current through a loading coil is constant by definition in that good-old-boys network. Forget reality. -- 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 =--- |
Who's going to publish it? I spent a lot of time preparing an article on
what happens at a match point and QEX refused to consider publishing anything that disagreed in the slightest with Dr. Best who denied there is such a thing as interference at a match point. (Hint: Without interference, a match is impossible in a system with reflections.) There's a good-old-boys network in amateur radio. If you are politically incorrect within the ARRL political power structure, you are black-balled from publishing. It doesn't matter if you are technically correct. The current through a loading coil is constant by definition in that good-old-boys network. Forget reality. -- 73, Cecil http://www.qsl.net/w5dxp 100% QSL we can give it a try, there is always internet and e-Books. It is amusing to see two versions of current in loading coil in ARRL published books, one version in Antenna Book, Compendia and Handbook vs. other in ON4UN Low Band DXing. 73 Yuri, K3BU.us |
Yuri Blanarovich wrote:
It is amusing to see two versions of current in loading coil in ARRL published books, one version in Antenna Book, ... Correction: Two versions in the ARRL Antenna Book. The first illustration, Fig 7 on 16-4 in my 15th edition shows the current taper across the coil. Fig 10 on 16-6 shows no current taper across the coil. :-) -- 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 =--- |
Cecil Moore wrote:
Yuri Blanarovich wrote: Cecil, fuggetaboutit, don't waste your time, looks like this is one of those smart alec trollers. Who cares what they "know". Looks like Tom would rather argue with his wife than with Balanis or me. (I don't blame him for that.) I had relatively long discussions with Balanis and he personally agreed with everything I have posted although he didn't go to such lengths in his book. Suuuurrrre he did. Thanks for your contribution to the subject. Looks like I should put the article together, looks like misguided "experts" are confusing the issue. I hope to find some time now, WX is getting about right, time to get out the gadgets and some real life measurements and modeling helixes in EZNEC. Who's going to publish it? I spent a lot of time preparing an article on what happens at a match point and QEX refused to consider publishing anything that disagreed in the slightest with Dr. Best who denied there is such a thing as interference at a match point. (Hint: Without interference, a match is impossible in a system with reflections.) There's a good-old-boys network in amateur radio. If you are politically incorrect within the ARRL political power structure, you are black-balled from publishing. It doesn't matter if you are technically correct. The current through a loading coil is constant by definition in that good-old-boys network. Forget reality. And now there's a cabal of old boys conspiring against you and Yuri. This just keeps getting better and better. For those who really want to know the truth, go to Tom Rauch's web site and read about loading coils. (He doesn't use the term "current drop" once." 73, Tom Donaly, KA6RUH |
Correction: Two versions in the ARRL Antenna Book. The first illustration, Fig 7 on 16-4 in my 15th edition shows the current taper across the coil. Fig 10 on 16-6 shows no current taper across the coil. :-) -- 73, Cecil http://www.qsl.net/w5dxp You are right, also my "lucky" thirteenth edition (1974) has picture 15-6 showing current drop across the coil. Back in those days they were some smart and knowledgeable editors at ARRL. Cecil, you are merciles protector of the truth :-) Yuri, K3BU.us |
Tom Donaly wrote:
For those who really want to know the truth, go to Tom Rauch's web site and read about loading coils. (He doesn't use the term "current drop" once." I'm glad you used "truth" instead of "facts". Tom's truth doesn't agree with scientific fact. You guys have turned your "truth" into a religion. Is there a current drop in a transmission line from the current maximum (loop) to the current minimum (node) when standing waves are present? Is there a current drop from the feedpoint of a helical 1/4WL antenna to the tip of the antenna? If a coil occupies 90 degrees of a standing-wave antenna or an unterminated transmission line with reflections, the current can be maximum at one end of the coil and zero at the other. The electrical 3/4WL antenna below consists of 1/4WL of wire, loading coil, and 1/4WL of wire. The net current at one end of the coil could be one amp while the net current at the other end of the coil is zero. If you don't understand that fact, I feel sorry for you. coil Feedpoint---1/4WL wire---x-///////-y---1/4WL wire--- When the above antenna is made resonant, the net current at 'x' is zero while the net current at 'y' is maximum. How do you explain a coil with zero current at the bottom and one amp at the top? It happens all the time in distributed networks. If a coil occupies 180 degrees of a standing wave antenna or an unterminated transmission line with reflections, the current can be zero at both ends and maximum in the middle. Such a configuration is illustrated in "Antennas for all Applications", by Kraus and Marhefka on page 824. -- 73, Cecil http://www.qsl.net/w5dxp "The current and voltage distributions on open-ended wire antennas are similar to the standing wave patterns on open-ended transmission lines ... Standing wave antennas, such as the dipole, can be analyzed as traveling wave antennas with waves propagating in opposite directions (forward and backward) and represented by traveling wave currents If and Ib ..." _Antenna_Theory_, Balanis, Second Edition, Chapter 10, page 488 & 489 ----== 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 =--- |
Cecil Moore wrote:
Tom Donaly wrote: For those who really want to know the truth, go to Tom Rauch's web site and read about loading coils. (He doesn't use the term "current drop" once." I'm glad you used "truth" instead of "facts". Tom's truth doesn't agree with scientific fact. You guys have turned your "truth" into a religion. Is there a current drop in a transmission line from the current maximum (loop) to the current minimum (node) when standing waves are present? Is there a current drop from the feedpoint of a helical 1/4WL antenna to the tip of the antenna? If a coil occupies 90 degrees of a standing-wave antenna or an unterminated transmission line with reflections, the current can be maximum at one end of the coil and zero at the other. The electrical 3/4WL antenna below consists of 1/4WL of wire, loading coil, and 1/4WL of wire. The net current at one end of the coil could be one amp while the net current at the other end of the coil is zero. If you don't understand that fact, I feel sorry for you. coil Feedpoint---1/4WL wire---x-///////-y---1/4WL wire--- When the above antenna is made resonant, the net current at 'x' is zero while the net current at 'y' is maximum. How do you explain a coil with zero current at the bottom and one amp at the top? It happens all the time in distributed networks. If a coil occupies 180 degrees of a standing wave antenna or an unterminated transmission line with reflections, the current can be zero at both ends and maximum in the middle. Such a configuration is illustrated in "Antennas for all Applications", by Kraus and Marhefka on page 824. Did you have fun writing that, Cecil? What makes you think the variation in current in two seperate places of a coil carrying A.C. is a "current drop?" 73, Tom Donaly, KA6RUH |
Yuri Blanarovich wrote:
Cecil, you are merciless protector of the truth :-) Guess that's why I receive no mercy. :-) -- 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 =--- |
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