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Current across the antenna loading coil - from scratch
Tom Donaly wrote:
Here's a more general equation for you Cecil: (A1-A2)*Cos(wt-kx) + 2*A2*Cos(kx+d/2)*Cos(wt+d/2). Yes, it is more general, Tom, but since the subject is standing waves and not traveling waves, it is overly general. Why would you post an equation containing a traveling wave term when the subject is the equation for standing waves? This is the total equation for the condition where power is being delivered to a load in the presence of standing waves. The first term makes it to the load. The second term doesn't. The first term is a traveling wave and indeed does contain phase information. There's no argument about whether a traveling wave contains phase information. The argument is whether the second term, the standing wave term, contains phase information. Gene Fuller says it doesn't, Eugene Hecht says it doesn't, and I'm inclined to agree. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
wrote:
When you show a track record of being honest and you stop those attacks and your constant distortions of what other people say, I'm sure people will start talking to you again. Of course, you never attack anyone. Pot, Kettle - Kettle, Pot. Here's a smattering of what you have said to me during the past month: W8JI wrote: 3/5/06 "Cecil, You are a horse's ass." 3/10/06 "If you weren't so pig-headed ... Until you stop, put the beer away,..." 3/11/06 "I'm also a victim of Cecil's twicted reality now." 3/11/06 "It would be comical to watch Cecil twist reality if it wasn't sad." 3/11/06 "Cecil's normal tactic is to change what other people say." 3/27/06 "how much will you pay me for putting up with you?" 3/27/06 "I feel sorry for anyone who has to deal with you on a daily basis. No wonder your wife split." -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Richard Fry wrote:
But clearly these lengths in degrees do not define the self-resonant length of that radiator. Could it be that the resonant 80 degrees of physical length is 90 degrees of electrical length? -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
wrote in message
ups.com... but we can not use electrical degrees to 'splain the behavior of coiled antenna wire? I can see how problems could arise going by the length of coil wire length in degrees only. Lets say you run a coil 1 foot from the base. Lets say that coil uses 25 turns to tune a particular frequency. Now, move the coil up 2 ft higher, and see if that same 25 turns will tune the same frequency. It won't. You will have to add a few more turns. So just going by the total mast plus coil wire length in degrees could vary all over the map just by changing the position of the coil. As you raise the coil, you will have to add more and more of "degrees" of wire to tune the same frequency. :/ Dunno...There may well be some variation of current from the bottom vs the top of the coil, but overall, I still view the operation of a loading coil as a "lumped" mechanism overall. Even if you all decide that the current changes, or it doesn't , it ain't gonna make a hoot's worth of difference in the design of mobile whips. I think it's an argument that has no real value to me as far as mobile whips go. The performance of all the various coil heights, and configs have been well known for years. Coil current taper or not. I just don't see the facination with arguing about something that even if decided one way or the other, still won't make any difference in the final antenna design. Oh well...Continue the tail chasing excercise.... I'm outa this one... One post is all I will waste on this subject.. I couldn't mount my coil much higher if I wanted to... Current taper or not. :/ MK MK, that is the whole point, that you portray missing or not appreciating. It might not matter to you if you lose $100, but it might matter to someone else. Same with loading coil. What you are describing, the effect where the coil is located, being known, is the result of the phenomena we are trying to straighten out, explain and apply properly in modeling and design exercises. The position of coil within the antenna has significant effect. The worst is at the base, fewer turns required. The best is somewhere about 2/3 up the radiator, more turns required. You stick it on the top, no stinger or hat, you get it almost invisible. With what we are discussing and defending here is the proper understanding of the current flow in the loading coil and its drop across and its effect on the efficiency of the loaded antenna. Efficiency is proportional to the area under the current curve distribution along the radiator. If you properly model the coil as solenoid or loading stub to see the real drop of current across the coil and its effect in various positions along the radiator, the all is clear and is with agreement with practical experience, antenna shootout results, measurements. As I mentioned numerous times, its effect on design and modeling loaded antenna systems will be even more pronounced, because effect gets magnified when you start adding elements. This is especially important when you try to design super receiving antennas for low bands where F/B and clean pattern is very desirable and is the most critical aspect of antenna design or modeling. It is harder to obtain the max F/B or least rear lobes than to maximize the design for max gain. It might not matter to you, but I am sure many would benefit from knowing more precisely what is REALLY going on and then use or correct their design methodology. I think it is fine for you to ignore this and poh-poh it. But I know how huge difference it made in my 160m mobile antenna when I extended the whip to the front bumper with wire. We are not saying that piece of wire that coil is wound with, has so many electrical degrees. If we carefully consider and understand the phenomena, you would realize that the radiator has same electrical length (say 15 deg) and when you move the coil and ADJUST THE TURNS to bring the antenna back to resonance (90 deg) that coil would "replace, take care of" 75 degrees. The turns have to be adjusted in order to "participate" in the current replacement game. The lesson is, the higher you place the coil on the radiator, the more turns you need to reresonate the radiator, the high current portion of the antenna current distribution curve gets "stretched up", better efficiency (larger area under the overall curve). Then the coil DROPS the current across itself to some lower value, which then continues to drop across the tip and that area, quite smaller adds to the one from the bottom part of the radiator. This all is supported by reality, except "gurus" who insist that the current is (about) the same across the coil and they make (theoretically) antenna current to be higher across the tip and "more" efficient than it is. Again, you stick 6 of those in the 3 el loaded Yagi design and you get GI-GO. It is known how profound effect had replacement of loading stubs by coils in the KLM 3 el. 80 m loaded Yagi. Better gain, huge improvement in the F/B and pattern. Has been done and described. And this is just replacing the same inductance value stub with coil, where delta current from stub wires was enough to throw monkey wrench in the Yagi performance. Now consider larger error from the wrong assumption or calculation caused by wrong current magnitudes and distribution. Again you might not give a hoot about this "trivial" exercise, but if I want to design 4 el loaded quad or Yagi for 80 or 160, it matters a lot. So it just amazes me that some of the smarter heads resist so much in trying to find out reality and develop better consideration of the effect for design and modeling. No technical answers to Cecil's questions and my "from scratch" thread deteriorated into pink electrons and dead end in electrical degrees. So far what we have is the reality, few who are trying to legitimize it and few who got off on the wrong foot, in effort to preserve their (wrong) face they cling to it with scientwific "proofs" why it can't be so, when IT IS. When I tried to go step by technical step through the case, the "gurus" are not there. Cases that Cecil showed in EZNEC model and demonstrating that current across the loading coil (not one in the box) in the antenna can have anything from equal to "nothing" at the other end, depending on its position in the standing wave picture. It all jives with our original argument. We spotted the "problem", we dissected it, thanks to fierce flat earthers, and now have better understanding of the phenomena and can use to design better antennas. I care about antennas, this is the last frontier where we can still improve thing, now with modeling tools. I still operate contests and go for ultimate - beating the all time records, and that's where the edge can be obtained. Heloooo guys! Measure, feel, whatever, the frickin' current across the loading coil and then come back and tell the world why it IS different, but IT CAN'T be so, because you said so in the beginning and you just can't admit being wrong. Reality can't be twisted, just like Earth is not going back to flat! Saying now that is no big deal, not important, will not exonerate the "wrongoes". It is significant not to be ignored. If I was in "their" shoes, I would say: "gee guys, interesting, thanks for bringing it up, explaining it, I guess we were wrong, now we can design better antennas". Stay tuned..... Thanks again Cecil, Richard and others for putting up with and shedding more and more light on the phenomena. It must go down in history as big as Galileo's fight :-) I am glad that, hopefully, nobody will burn us. 73 Yuri, K3BU.us |
Current across the antenna loading coil - from scratch
On Tue, 4 Apr 2006 10:32:08 -0400, "Yuri Blanarovich"
wrote: Now consider larger error from the wrong assumption or calculation caused by wrong current magnitudes and distribution. Hi Yuri, Why is it that you can say this so often, and yet never put a number to it? What is the error? You also speak of efficiency. What is the efficiency? Very simple questions. Technically based. Selected because they seem to be of supreme importance to you, and yet you don't seem to have a handle on the situation. 73's Richard Clark, KB7QHC |
Current across the antenna loading coil - from scratch
"Cecil Moore" wrote ...
Richard Fry wrote: But clearly these lengths in degrees do not define the self-resonant length of that radiator. Could it be that the resonant 80 degrees of physical length is 90 degrees of electrical length? __________ That a self-resonant, unloaded broadcast radiator length is shorter than the 90 degree conventional "electrical length" defined by the FCC is a given. But this reality sometimes is not recognized. RF |
Current across the antenna loading coil - from scratch
Cecil Moore wrote:
John Popelish wrote: Cecil Moore wrote: Compared to zero amps of standing wave current when the forward current phasor and the reflected current phasor are 180 degrees out of phase, just how much effect can capacitance have? A standing wave voltage passes exactly as much (AC RMS) current through a capacitance as a traveling wave voltage does. But the two waves are different as can be seen from their equations. That difference is a difference in the pattern (distribution) of voltage and current along the line, as well as a possible difference in amplitude and phase at any given point. But at any point that is not a node in the standing wave pattern, there will be an ordinary AC voltage or current at some amplitude between double the traveling wave amplitude and zero amplitude, and one of two phases (that switch each time you pass a node). A traveling wave transfers net energy along a transmission line or antenna wire. A standing wave transfers zero net energy along a transmission line or antenna wire. No argument. But a standing wave still represents storage of energy in the line, as with any resonant structure, and that stored energy shows up as magnetic fields and electric fields along the line. The big difference is that the magnetic fields bob up and down at some areas and the electric fields bob up and down half way in between those areas. At any given moment, there is a fixed total energy in the combination of all the magnetic and electric fields. In the areas where the electric field is bobbing up and down, there must be capacitive current caused by that variation in electric field. From "Fields and Waves in Modern Radio", by Ramo & Whinnery, 2nd edition, page 43: "The total energy in any length of line a multiple of a quarterwavelength long is constant, merely interchanging between energy in the electric field of the voltages and energy in the magnetic field of the currents." Exactly. How can you write this, but deny the capacitive current that delivers this electric field energy twice every cycle to all capacitance feeling this voltage swing? Hecht says it best in "Optics" concerning standing waves: "The composite disturbance is then: E = Eo[sin(kx+wt) + sin(kx-wt)] Applying the identity: sin A + sin B = 2 sin 1/2(A+B)*cos 1/2(A-B) yields: E(x,t) = 2*Eo*sin(kx)*cos(wt)" cos(wt) is the AC swing that drives the capacitive current. sin(kx) is the positional variation of that AC voltage along the line. I have absolutely no argument with the expression, only with your understanding of what it says. "This is the equation for a STANDING or STATIONARY WAVE, as opposed to a traveling wave. Its profile does not move through space; it is clearly not of the form Func(x +/- vt)." Profiles do not charge capacitance, instantaneous rate of change of voltage drives current through capacitance. cos(wt) describes a sinusoidal variation of voltage over time (you couldn't have an RMS value of voltage at a point or an RMS value of current past a point, without it. [Standing wave phase] "doesn't rotate at all, and the resultant wave it represents doesn't progress through space - its a standing wave." I suggest you drop talking about phasors, till you understand what cos(wt). Speaking of "... net transfer of energy, for the pure standing wave there is none." But it does represent net storage of energy. The total stored energy is the sum of energies in the two traveling waves over the length. A standing wave does not violate conservation of energy. Storage that must continuously be swapping back and forth from magnetic field energy to electric field energy. When the energy storage is all electric, that implies charges capacitance. Don't give up, the light may be just about to come on. |
Current across the antenna loading coil - from scratch
Cecil Moore wrote:
Tom Donaly wrote: Here's a more general equation for you Cecil: (A1-A2)*Cos(wt-kx) + 2*A2*Cos(kx+d/2)*Cos(wt+d/2). Yes, it is more general, Tom, but since the subject is standing waves and not traveling waves, it is overly general. Why would you post an equation containing a traveling wave term when the subject is the equation for standing waves? This is the total equation for the condition where power is being delivered to a load in the presence of standing waves. The first term makes it to the load. The second term doesn't. The first term is a traveling wave and indeed does contain phase information. There's no argument about whether a traveling wave contains phase information. The argument is whether the second term, the standing wave term, contains phase information. Gene Fuller says it doesn't, Eugene Hecht says it doesn't, and I'm inclined to agree. Cecil, I won't try to educate you because it's a waste of time, but for everyone else, consider that in an antenna, there is energy going into, and being radiated out of, the antenna in the form of an electromagnetic wave. Since Cecil says standing waves can't transfer energy from one place to another (he didn't always say this) that means that the only way energy can be radiated is through the traveling wave component of the electromagnetic wave. You would think that this would be important to him in his search for a dumbed down theory of reflection mechanics, but evidently he is more interested in his arguing point concerning Tom R. and Roy measuring current in a standing wave environment than he is in reaching an understanding of what he's talking about. No wonder no one's communicating with him. 73, Tom Donaly, KA6RUH |
Current across the antenna loading coil - from scratch
John Popelish wrote:
But at any point that is not a node in the standing wave pattern, there will be an ordinary AC voltage or current at some amplitude between double the traveling wave amplitude and zero amplitude, and one of two phases (that switch each time you pass a node). Please give us the equation for "ordinary AC voltage or current". No argument. But a standing wave still represents storage of energy in the line, as with any resonant structure, and that stored energy shows up as magnetic fields and electric fields along the line. The big difference is that the magnetic fields bob up and down at some areas and the electric fields bob up and down half way in between those areas. At any given moment, there is a fixed total energy in the combination of all the magnetic and electric fields. No argument, and therefore no need for the "But" in your statement. I agree with you but it doesn't change a thing about the real argument. Exactly. How can you write this, but deny the capacitive current that delivers this electric field energy twice every cycle to all capacitance feeling this voltage swing? I don't deny it - never have - never will. Please stop trying to set up straw men. The discussion has *NEVER* be about what happens during one cycle. The current measured by W8JI and W7EL and reported by EZNEC is RMS current. Instantaneous values are just another straw man diversion. Profiles do not charge capacitance, ... I'm glad you agree. Profiles are maximum RMS envelope values and that is what EZNEC reports. [Standing wave phase] "doesn't rotate at all, and the resultant wave it represents doesn't progress through space - its a standing wave." I suggest you drop talking about phasors, till you understand what cos(wt). Hecht and I have been a little lose with words while assuming the readers have a certain knowledge level. For the uninitiated, When Hecht (or I) say the phasor doesn't rotate at all, we mean the phasor doesn't rotate at all with respect to the source phasor. Any initiated person would know that. The phase of the standing waves doesn't change with respect to the phase of the source signal. Hecht assumed you would know what he meant by that statement. Speaking of "... net transfer of energy, for the pure standing wave there is none." A standing wave does not violate conservation of energy. Exactly my point! Nothing violates conservation of energy. If the RMS forward current in the coil is the same magnitude at both ends and the RMS reflected current in the coil is the same at both ends, the conservation of energy principle is satisfied NO MATTER WHAT THE STANDING WAVE CURRENT TURNS OUT TO BE. What is it about that statement that you don't understand? Storage that must continuously be swapping back and forth from magnetic field energy to electric field energy. When the energy storage is all electric, that implies charges capacitance. Again, nobody has ever been discussing what happens within a partial cycle. Discussion of such is obviously a diversionary straw man. Feel free to find someone else willing to discuss it. It is completely irrelevant to this discussion of RMS envelope values. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Cecil,
You dismissed my honest, straightforward accounting of the charge transport implied directly by the scenarios you set up. In no way was it a "logical diversion." It was very much to the point of explaining just WHY there is in fact a time delay through your bugcatcher coil. Then you have the unmitigated gaul to say it's time to stop the attacks, and then refuse yourself to get into a serious technical discussion. Away with you, evil spirit. And be very happy that this is a polite forum. |
Current across the antenna loading coil - from scratch
Richard Fry wrote:
"Cecil Moore" wrote ... Could it be that the resonant 80 degrees of physical length is 90 degrees of electrical length? That a self-resonant, unloaded broadcast radiator length is shorter than the 90 degree conventional "electrical length" defined by the FCC is a given. But this reality sometimes is not recognized. For instance, EZNEC says a 33 ft. vertical made of #30 wire is resonant on 7.265 MHz while a one foot diameter pipe is resonant on 6.9 MHz. Does the FCC define physical lengths or electrical lengths? -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
"Cecil Moore"
Does the FCC define physical lengths or electrical lengths? ____________ They call it an electrical length, but calculate it as the number of free-space electrical degrees contained in the physical length of the radiating structure, at the carrier frequency. So really, FCC "electrical length" is a measure of a physical length, not of an effective electrical length. The effective electrical length of a MW monople radiator determines its resonant frequencies, and that must include the velocity of propagation along the structure -- which is a function of the height AND width of the radiator (mainly), and the operating frequency. RF |
Current across the antenna loading coil - from scratch
On Tue, 04 Apr 2006 16:38:48 GMT, "Tom Donaly"
wrote: No wonder no one's communicating with him. Hi Tom, To him, from him, at him. OK, this is not going to be a grammar exercise. No, more that complaints should be registered at the box office where you bought the ticket to this comedy when you expected a technical presentation. Myself, on the other hand, I read the program notes and seeing all the credits and roles played like: "Occam the magnificent" or "Cecileo the ball juggler" performances of "My Contacts with the Aliens" plus dramatic readings "Sleepless with Kraus" all that remains is to saunter back for some popcorn during this between-acts filler routine, or to wait for the strippers when the real show begins. -OH- yeah.... I guess now we know what killed vaudeville. 73's Richard Clark, KB7QHC PS So seeing that "from scratch" is beginning to show why, flea bites, it's time to add some real entertainment value that befits the gravitas of this opera: "Pal-yat-chee" [H&J] When we was in the city, we was a-wonderin' where to go. The sign spelled out "Pagliacci" up in lights above the show. We thought 'twould be a Western, 'til the stage lit up with light, And ninety-seven people sung, without a horse in sight! We couldn't unnerstand 'em 'cause they spoke a furrin tongue, But we can give you some idear of what we think they sung--- [tenor] Ridi, Pagliaccio, Sul tuo amore infranto! [H&J] All at once, there's a fat guy in a clown suit. 'Tain't Hallerween, that's for shore! Then this here feller, This Punchy-neller, Begins to beller, Like we all was deef! [tenor] Ah, hahahahahahahaha.... [H&J] That was Pal-yat-chee, and he sung: Invest in a tuba, and somethin' or other 'bout Cuba, He sung about a lady, who weighed two-hunnerd-and-eighty. When she takes a powder, he just starts chirpin' louder, An' he don't mean a gol-durned thing, 'cept to stand up there and sing. When we listen to Pal-yat-chee, we get itchy and scratchy. This shore is top corn, so we go an' buy some popcorn. We hate to go back, but we cain't get our dough back; Ain't no use complainin', 'cause outside it's a-rainin. [Slicker chorus] Seven hours later, we're still in the durned thee-aye-ter, Takin' turns a-nappin, a-waitin' fer somethin' to happen. Pal-yat-chee, he ain't worryin', And the folks on stage are flurryin', And it sounds like Kat-che-turian's "Sabre Dance". [to the melody of "Sabre Dance"] Then ole Pal-yat-chee finds the guy he's seekin' cheek-to-cheekin' With his wife, he grabs a knife And stabs the louse who stole his spouse And then he stabs the lady and him self, 'Tain't very sa-ni-ta-ry. They all collapse, But then Pal-yat-chee sets up and he gets up singin' "I am dyin', I am dyin', I am dyin'", we start cryin' 'Cause to tell the truth, we're dyin', too. [end "Sabre Dance"] As the footlights fade out, we see Pal-yat-chee laid out, But the dagger never caused it: Pal-yat-chee was plumb ex-haus-ted! [tenor] Ridi, Pagliaccio, Sul tuo amore in-- [loud belch] [vaudeville stinger: da-dut dahhhh da-dut DAT! DAAAAAAAHHH! cymbal crash] *Rich* |
Current across the antenna loading coil - from scratch
Tom Donaly wrote:
Cecil, I won't try to educate you because it's a waste of time, but for everyone else, consider that in an antenna, there is energy going into, and being radiated out of, the antenna in the form of an electromagnetic wave. That's true, but compared to the standing waves, it is pretty small. In fact, when Kraus talks about a 1/2WL thin-wire dipole, he completely ignores the traveling wave and energy "lost" as radiation and assumes the forward wave and reflected wave have the same magnitude. If you want to argue that trivial point, take it up with Kraus. Here's what he says: "It is generally assumed that the current distribution of an infinitesimally thin antenna is sinusoidal, and that the phase is constaant over a 1/2WL interval, changing abruptly by 180 degrees between intervals. That would only be true if the reflected wave was equal in magnitude to the forward wave, i.e. no loss due to radiation or I^2*R losses. If Kraus gives us permission to ignore the traveling wave for purposes of discussion, who are you to argue? I have calculated that there is only a 10% drop between forward voltage or current and the reflected voltage or current arriving back at the feedpoint for a 1/2WL dipole. For the sake of discussion of standing waves in standing wave antennas, with an accuracy within 10%, the loss due to radiation can be ignored according to Kraus. It's akin to ignoring the losses in a transmission line for the sake of discussion. Since Cecil says standing waves can't transfer energy from one place to another ... sthat means that the only way energy can be radiated is through the traveling wave component of the electromagnetic wave. Yes, that's true and since I have never said otherwise, this seems to be just another straw man. With an accuracy of about 10%, Kraus gives us permission to ignore the traveling wave in standing wave antennas for the purposes of discussion. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
K7ITM wrote:
You dismissed my honest, straightforward accounting of the charge transport implied directly by the scenarios you set up. In no way was it a "logical diversion." It was very much to the point of explaining just WHY there is in fact a time delay through your bugcatcher coil. The biggest clue that you are not arguing in good faith is that you trimmed out all the technical content and didn't quote anything I said. This posting of yours is disembodied from reality so you can demonize me and emote your angry gut feelings. Responses with no technical content and no quotes are an obvious attempt to obfuscate - so obfuscate away. It is possible I misunderstood what you were trying to say but unless you quote something of technical value, I will have no idea what my misunderstanding, if any, was all about. John P. seems to want to discuss instantaneous movement of energy. Why don't you two keep that discussion going? -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Cecil Moore wrote:
John Popelish wrote: But at any point that is not a node in the standing wave pattern, there will be an ordinary AC voltage or current at some amplitude between double the traveling wave amplitude and zero amplitude, and one of two phases (that switch each time you pass a node). Please give us the equation for "ordinary AC voltage or current". The simplest (without a reference phase) would be cos(wt). The standing wave function contains this term, with a modifier to tell you how amplitude varies with position. But at any point, cos(wt) times some amplitude describes the ordinary AC voltage or current swing. No argument. But a standing wave still represents storage of energy in the line, as with any resonant structure, and that stored energy shows up as magnetic fields and electric fields along the line. The big difference is that the magnetic fields bob up and down at some areas and the electric fields bob up and down half way in between those areas. At any given moment, there is a fixed total energy in the combination of all the magnetic and electric fields. No argument, and therefore no need for the "But" in your statement. I agree with you but it doesn't change a thing about the real argument. Exactly. How can you write this, but deny the capacitive current that delivers this electric field energy twice every cycle to all capacitance feeling this voltage swing? I don't deny it - never have - never will. Please stop trying to set up straw men. The discussion has *NEVER* be about what happens during one cycle. The current measured by W8JI and W7EL and reported by EZNEC is RMS current. Instantaneous values are just another straw man diversion. EZNEC must take those within a cycle currents and voltages into account to come up with the amplitude values. The RMS value is just the amplitude value for a cycle. Profiles do not charge capacitance, ... I'm glad you agree. Profiles are maximum RMS envelope values and that is what EZNEC reports. See? We agree on lots of stuff. [Standing wave phase] "doesn't rotate at all, and the resultant wave it represents doesn't progress through space - its a standing wave." At a given point the traveling wave phasor doesn't rotate, either. Phasor rotation only applies to the phase change over length for a traveling wave. The phase for standing waves has a discontinuous jump as you pass through a node, instead of a continuous rotation over length. I guess one might call that a form of jumpy rotation. Who doesn't recognize these facts? I suggest you drop talking about phasors, till you understand what cos(wt). Hecht and I have been a little lose with words while assuming the readers have a certain knowledge level. For the uninitiated, When Hecht (or I) say the phasor doesn't rotate at all, we mean the phasor doesn't rotate at all with respect to the source phasor. ....and within a half cycle of propagation length. Any initiated person would know that. The phase of the standing waves doesn't change with respect to the phase of the source signal. Hecht assumed you would know what he meant by that statement. Still, it is worth saying well, once in a while. Speaking of "... net transfer of energy, for the pure standing wave there is none." A standing wave does not violate conservation of energy. Exactly my point! I missed that point. Sorry. Nothing violates conservation of energy. If the RMS forward current in the coil is the same magnitude at both ends and the RMS reflected current in the coil is the same at both ends, the conservation of energy principle is satisfied NO MATTER WHAT THE STANDING WAVE CURRENT TURNS OUT TO BE. What is it about that statement that you don't understand? You don't add superposed RMS values to get the resultant RMS value. You have to add instantaneous values over a cycle (so that the relative phases of the two wave cycles are taken into account), and take the RMS of the resultant cycle. See? We have to get inside an individual cycle to understand what is going on. You cannot just deal with RMS (while cycle amplitude values) and get the same answer. This is why I (and others) keep coming back to what is happening inside a cycle, instead of discussing RMS values, only. One cannot understand either traveling wave mechanisms or the super position to a pair of traveling waves (a standing wave) if you think only in RMS values. They display the result of the process, but hide the way the process produces that result. Storage that must continuously be swapping back and forth from magnetic field energy to electric field energy. When the energy storage is all electric, that implies charges capacitance. Again, nobody has ever been discussing what happens within a partial cycle. I have. You may not be, but that is your lack. Discussion of such is obviously a diversionary straw man. Feel free to find someone else willing to discuss it. It is completely irrelevant to this discussion of RMS envelope values. There is no discussion of RMS envelope values. There is just you repeating the same thought, over and over, while the rest of us discuss the mechanisms that produce that resultant envelope. You obviously understand how a phase measurement is useless to measure phase shift within a half cycle of a purely standing wave process. I am waiting for you to realize that you can measure the phase shift of each of the traveling waves that superpose in a standing wave process that includes a coil (or any other network) by using only the RMS amplitude envelope, with no reference to phase, in an EZNEC simulation or a real experiment. That was the whole point that began this discussion, wasn't it? You keep showing how the current into and out of a particular coil does not have the same RMS value. We get it. Now, measure the phase shift of that coil (for each of the equal amplitude waves traveling through it) without having to change its environment to put it into a pure traveling wave process. And don't use a phase measurement to do it (which you know is impossible). Use the amplitude envelope. You should be able to measure its phase shift to within a degree or so. And you can then see how that phase shift changes (or if it does) when you move the coil to different places in the standing wave system. |
Current across the antenna loading coil - from scratch
On Tue, 4 Apr 2006 12:11:20 -0500, "Richard Fry"
wrote: The effective electrical length of a MW monople radiator determines its resonant frequencies, and that must include the velocity of propagation along the structure -- which is a function of the height AND width of the radiator (mainly), and the operating frequency. WGOP 80.00° tall 125.2 meters tall 540 kHz WWCS 63.50° tall 98.8 meters tall 540 kHz WFTD 79.00° tall 64.0 meters tall 1080 kHz KYMN 118.60° tall 92.3 meters tall 1080 kHz WWLV 90.00° tall 47.2 meters tall 1620 kHz WTAW 204.00° tall 106.7 meters tall 1620 kHz http://www.fcc.gov/mb/audio/amq.html The FCC provides BOTH measurements. The correlation is obvious. Any association between resonance, velocity of propagation, height, width, etc. and something like our 118.60° tall antenna needs a heap more explaining than resonance, velocity of propagation, height, width, etc. - but such explaining is a specialty occupation here in this group. 73's Richard Clark, KB7QHC |
Current across the antenna loading coil - from scratch
K7ITM wrote:
You dismissed my honest, straightforward accounting of the charge transport implied directly by the scenarios you set up. In no way was it a "logical diversion." It was very much to the point of explaining just WHY there is in fact a time delay through your bugcatcher coil. Cecil Moore wrote: The biggest clue that you are not arguing in good faith is that you trimmed out all the technical content and didn't quote anything I said. This posting of yours is disembodied from reality so you can demonize me and emote your angry gut feelings. Grow up Cecil. Everyone sees what you are doing. |
Current across the antenna loading coil - from scratch
I see that Cecil's latest fetish is that EZNEC reports RMS values of
voltage and current. Because we know that the voltages and currents are purely sinusoidal, the RMS value and phase angle (also reported by EZNEC) are adequate to define the time waveform. That is, when we know the RMS amplitude and the phase angle, we know the value of the waveform at every instant in time. No additional information is necessary. Roy Lewallen, W7EL |
Current across the antenna loading coil - from scratch
John Popelish wrote:
Cecil Moore wrote: Please give us the equation for "ordinary AC voltage or current". The simplest (without a reference phase) would be cos(wt). The standing wave function contains this term, with a modifier to tell you how amplitude varies with position. But at any point, cos(wt) times some amplitude describes the ordinary AC voltage or current swing. But please notice that cos(kx+wt) is different from that term. The only time they are the same is if 'x' = 0. Is 'x' always equal zero? No. All your equation tells us is that whatever current it represents, it is always in phase with the reference source at 'x' = 0. So your equation is too simple to be useful. Please try again. EZNEC must take those within a cycle currents and voltages into account to come up with the amplitude values. "Must" or "does". I have no idea. At a given point the traveling wave phasor doesn't rotate, either. On the contrary - at any given point 'x', the traveling wave phasor is rotating with respect to the source phasor. That's what makes it different from a standing wave phasor which doesn't rotate with respect to the source phasor. Phasor rotation only applies to the phase change over length for a traveling wave. No, that's wrong. Take another look at cos(kx+wt). Holding 'x' at a constant value, the phase keeps on changing. The traveling wave phasor is rotating with respect to the source. The standing wave phasor is not rotating with respect to the source, just as Hecht says speaking of standing waves: "The resultant phasor is E1 + E2 = E ... Keeping the two [traveling wave] phasors tip-to-tail and having E1 rotate counterclockwise as E2 rotates (at the same rate) clockwise, generates E [total] as a function of 't'. ... It doesn't rotate at all, and the resultant wave it represents doesn't progress through space - it's a standing wave." You really need to get you a copy of Hecht's "Optics". It the best treatment of standing waves that I have ever seen - also best at superposition and interference explanations. You don't add superposed RMS values to get the resultant RMS value. Sure you do. Current #1 is an RMS value at angle 1. Current #2 is an RMS value at angle 2. The superposition is: RMS#1*cos(A1) + RMS#2*cos(A2) = RMS(total) There is no discussion of RMS envelope values. Where have you been? The currents displayed by EZNEC are RMS envelope values. The antenna currents plotted in Kraus and Terman are RMS envelope values. The currents measured at the top and bottom of the coils by W8JI and W7EK are RMS envelope values. I am waiting for you to realize that you can measure the phase shift of each of the traveling waves that superpose in a standing wave process that includes a coil (or any other network) by using only the RMS amplitude envelope, with no reference to phase, in an EZNEC simulation or a real experiment. That was the whole point that began this discussion, wasn't it? Yes, I said that months ago but nobody would buy the argument. Over those months, I have given countless examples proving that to be true. Everyone just ignored those technical facts as they have ignored 95% of the technical content of my postings only to concentrate on the 5% containing feelings or bad humor. Now, measure the phase shift of that coil ... Sorry, the coil is obviously not the problem. Everyone understands how a coil works. What everyone doesn't understand is how standing waves in a wire work. That will be my topic of discussion from now on. But feel free to continue the coil topic with anyone else. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
wrote:
Grow up Cecil. Everyone sees what you are doing. Everyone should see that I am trying to discuss technical issues while the rest of you object to the 5% of my postings that are bad humor or complaints about how I am being unfairly treated. Why do you refuse to discuss technical issues? For instance, you have avoided responding to my black box question. Are you afraid everyone will see just how wrong you are? Here is it again assuming a lossless transmission line: Source-----------a-BB-b-------------c-BB-d-----------open The current measured at 'a' is one amp. The current measured at 'b' is zero amps. The current measured at 'c' is zero amps. The current measured at 'd' is one amp. What are the possibilities for what could be in the black boxes? There could be 90 degrees of transmission line in each box. Or there could be 90 degree coils in each box. Or one box could contain 90 degrees of transmission line and the other contain 90 degrees of coil. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Roy Lewallen wrote:
I see that Cecil's latest fetish is that EZNEC reports RMS values of voltage and current. Because we know that the voltages and currents are purely sinusoidal, the RMS value and phase angle (also reported by EZNEC) are adequate to define the time waveform. That is, when we know the RMS amplitude and the phase angle, we know the value of the waveform at every instant in time. No additional information is necessary. Since you agree with me, what's with the fetish remark? You seem to feel obliged to take an ad hominem pot shot every time you mention my name. I assure you, it is hurting your reputation more than it is hurting mine. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Ok, I'll bite once more since you have put so much work into
that post.... :/ MK, that is the whole point, that you portray missing or not appreciating. Yes. It is quite true. I don't really appreciate the importance of knowing if the current tapers across a coil or not. Even if I did, what could I do about it? But you can consider this a personal problem... It might not matter to you, but I am sure many would benefit from knowing more precisely what is REALLY going on and then use or correct their design methodology. How are you going to to fix what is not broke? There is nothing wrong with the current state of mobile whip design. I don't see how it can be improved without going to unpractical measures. Deciding whether or not there is current taper across the coil is not going to help you improve a mobile antenna one whit. Now, I'll agree there might be other app's where it could be useful to be aware of this, but not for mobile whips. I think it is fine for you to ignore this and poh-poh it. But I know how huge difference it made in my 160m mobile antenna when I extended the whip to the front bumper with wire. No kidding.... I've never heard of adding a longer whip to improve a mobile antenna. :/ What does coil current taper have to do with this? I could have told you about adding longer whips way before you even thought about current taper. I've never needed current taper technology to know that adding a longer top whip to a short mobile antenna will generally improve performance. Have you ever tried Reg's "vertload"? You can play "what if" till the cows come home... I often have... The lesson is, the higher you place the coil on the radiator, the more turns you need to reresonate the radiator, the high current portion of the antenna current distribution curve gets "stretched up", better efficiency (larger area under the overall curve). And this lesson is new? Get a grip...I've been aware of this for years. And I think most others have been too... This all is supported by reality, except "gurus" who insist that the current is (about) the same across the coil and they make (theoretically) antenna current to be higher across the tip and "more" efficient than it is. You can't fool a field strength meter. It makes no difference whether one believes there is a taper or not, the antenna is still going to perform the same for a given coil height on a given height mast. It is known how profound effect had replacement of loading stubs by coils in the KLM 3 el. 80 m loaded Yagi. Better gain, huge improvement in the F/B and pattern. Has been done and described. And this is just replacing the same inductance value stub with coil, where delta current from stub wires was enough to throw monkey wrench in the Yagi performance. Now consider larger error from the wrong assumption or calculation caused by wrong current magnitudes and distribution. Not a very good example. Sure, replacing inferior stubs, or whatever methods of linear loading are usually going to be improved by changing to coil loading. No big surprise. If doing this makes a large improvement in f/b, pattern, etc, sounds like it was a poor design from the git go... I still don't follow how knowing about current taper is going to help you much here. How will you apply this knowledge? Will this "improved coil taper technology" improve performance more than 1 db? At this point, I won't be holding my breath. Heloooo guys! Measure, feel, whatever, the frickin' current across the loading coil and then come back and tell the world why it IS different, but IT CAN'T be so, because you said so in the beginning and you just can't admit being wrong. Dunno...I think you have me confused with someone who really gives a hoot. I could care less if you are right or wrong. What I want to know is how is this "knowledge" going to improve a mobile whip. ? I'll grant you that there may well be cases where knowledge of this could be useful. Mainly when modeling very complex antennas. But as far as the basic mobile whip, knowing about current taper across the coil is not going to help you improve the antenna one bit. Trying to say that it showed you that you need to add a longer capacitive whip to a 160m antenna is silly. You can run "vertload" and see the appx best place for the coil very quickly. No current taper technology will be used, yet it will be quite accurate for most all uses. This coil taper effect you have spent months trying to prove may seem very important to you, but to me it's fairly ho-hum..."snore" It's been shown that the possible errors in modeling are going to be generally small and usually under 1 db in most cases. There may be something useful to come out of all this, but it ain't going to be an improvement of mobile antenna design. I think it's safe to say you can take that to the bank. The optimum location of a coil on a short whip is already well known and etched in fairly hard material. Deciding there is current taper across the coil is not going to change this. MK |
Current across the antenna loading coil - from scratch
Since EZNEC has been mentioned so much lately, it's appropriate to point
out that it's able to calculate the current at all points along a helically modeled loading inductor with what I believe to be very good accuracy. And it does it without any use or knowledge of presumed traveling voltage or current waves. It deals only with the total current. Perhaps Cecil would benefit from investigating how this is done. EZNEC uses NEC-2 for calculations, and the NEC-2 manual is available on line at no cost. A detailed description of its methodology is presented in Part I. For those who want just a general overview of the method (the method of moments) in a more easily understood format, one can be found in the second and later editions of Kraus' _Antennas_. I notice that most newer antenna texts also include a description of the moment method, and it should be available in the web as well. Roy Lewallen, W7EL |
Current across the antenna loading coil - from scratch
Cecil wrote, in reply to John P.,
"Of course, *everyone* except you and Tom Donaly are talking about charge stored over a whole cycle." Excuse me??? Note Cecil's emphasis on "everyone". Note that this was posted AFTER I had repeatedly told him that _I_ was not talking about 'charge stored over a whole cycle'. I'm offended that Cecil would fail to acknowledge me as not being in the "everyone" group. I'll let others speak for themselves, but I'd put pretty good odds that several others will be crystal clear about not being included in that "everyone." |
Current across the antenna loading coil - from scratch
Roy Lewallen wrote:
And it does it without any use or knowledge of presumed traveling voltage or current waves. Thanks for the reference, Roy, I'll take a look at it. One wonders how EZNEC tells the difference between a standing wave antenna and a traveling wave antenna "without any use or knowledge of presumed traveling voltage or current waves". I'm willing to bet it doesn't use lumped circuit theory. :-) I'm also willing to bet that forward and reflected waves are taken care of in the equations used by NEC. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
K7ITM wrote:
I beg your pardon? Excuse me? I "trimmed out all the technical content and didn't quote anything you said"??? Yes, and you are doing it again. I'm quoting your entire posting and there is not one quote from me. As a matter of fact, I took exactly the numbers you gave us, ALL of them, and used them and ONLY them in my accounting. If THAT's "disembodied from reality," then I'd point out that it's YOUR numbers that are disembodied from reality. In fact, I didn't argue with YOUR numbers at all. I just took them at face value. You were the one that discarded what I carefully developed from them without out so much as an ounce of reasoning or explanation. After that I went on to FURTHER EXPLAIN why I had done what I did in the first place, and you dismissed that again without any technical explanation. It's all there for everyone to see, Cecil. If there's a quote from me in this posting, Tom, I am unable to find it. Go ahead, dig yourself deeper into it. Since you didn't quote anything I said, I have no idea what you are talking about. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
You really think so, Cecil?? I saw through it the first time you
posted it. As an EZNEC and NEC2 user, I know that not only the current magnitude, but also its phase, is reported. I knew that what you posted about it was incorrect. I don't see Roy's comment as agreeing with you at all, but completely disagreeing. You said that it only gave amplitude information, when in fact it gives phase and amplitude. |
Current across the antenna loading coil - from scratch
K7ITM wrote:
Cecil wrote, in reply to John P., "Of course, *everyone* except you and Tom Donaly are talking about charge stored over a whole cycle." It sure would be nice if you made your attributions conform to netnews guidelines. I cannot tell what you are responding to since your attributions are all screwed up. Excuse me??? Note Cecil's emphasis on "everyone". Note that this was posted AFTER I had repeatedly told him that _I_ was not talking about 'charge stored over a whole cycle'. I'm offended that Cecil would fail to acknowledge me as not being in the "everyone" group. I'll let others speak for themselves, but I'd put pretty good odds that several others will be crystal clear about not being included in that "everyone." I obviously got my "Tom's" mixed up. There's three of you here and it's likely a common mistake. I profusely apologize and don't know what else I can do to rectify my mistake. If there were two Cecil's here and you got us mixed up, I wouldn't get my panties bunched into a wedgie because of that. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
"Richard Clark" wrote in message ... On Tue, 4 Apr 2006 10:32:08 -0400, "Yuri Blanarovich" wrote: Now consider larger error from the wrong assumption or calculation caused by wrong current magnitudes and distribution. Hi Yuri, Why is it that you can say this so often, and yet never put a number to it? Experience, my dear, experience. If I am capabl;e of writing to you, I don't have to put number on it, how many letters of alphabet I master. What is the error? You also speak of efficiency. What is the efficiency? Stick in the EZNEC and find out if you can't sleep without numbers. Anyone who looks at current distribution curves can see that there is a difference. No need for lawyers and precise numbers. If only this was the problem, then I would give you answer to 4 decimal places. You have greater problem with "gurus" not getting the big picture (or pretending to). Very simple questions. Technically based. Selected because they seem to be of supreme importance to you, and yet you don't seem to have a handle on the situation. I have the handle on it, appreciate the magnitude and with time there will be some numbers. Cecil posted files, anyone who is hang up on numbers can get them from the EZNEC if properly defined, instead of poking needles. We are having problem with people admitting there could be difference in the current across loading coils, and here the "problems" is what is the error? So lets stick to the big problem and fuggettabout detours and nitpicking. Yuri, K3BU 73's Richard Clark, KB7QHC |
Current across the antenna loading coil - from scratch
K7ITM wrote:
You really think so, Cecil?? I saw through it the first time you posted it. As an EZNEC and NEC2 user, I know that not only the current magnitude, but also its phase, is reported. I knew that what you posted about it was incorrect. I don't see Roy's comment as agreeing with you at all, but completely disagreeing. You said that it only gave amplitude information, when in fact it gives phase and amplitude. Again, no quote from me. I have no idea to what you are responding or even if you are responding to something I said today or last year. I didn't say EZNEC doesn't give phase information. I said there is no phase information in the phase information that EXNEC gives. What is it about Gene's posting that you don't understand? Regarding the cos(kz)*cos(wt) term in a standing wave: Gene Fuller, W4SZ wrote: In a standing wave antenna problem, such as the one you describe, there is no remaining phase information. Any specific phase characteristics of the traveling waves died out when the startup transients died out. Phase is gone. Kaput. Vanished. Cannot be recovered. Never to be seen again. The only "phase" remaining is the cos (kz) term, which is really an amplitude description, not a phase. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Yuri Blanarovich wrote:
We are having problem with people admitting there could be difference in the current across loading coils, and here the "problems" is what is the error? Actually, the problem is more elementary than coils. Everyone seems to understand coils installed in circuits. The ignorance seems to be of the nature of the physics involved in standing waves, whether on a wire or on a coil or in free space. So I have switched the discussion to where it belongs, to a discussion of standing waves, with or without coils, with or without wires. I offered the following example which the gurus refuse to touch with a ten foot pole. One wonders why. The transmission line is lossless and BB is a black box. Source-------a-BB-b-----------c-BB-d---------open circuit The current at 'a' is measured at one amp. The current at 'b' is measured at zero amps. The current at 'c' is measured at zero amps. The current at 'd' is measured at one amp. What's in the black boxes? Would you believe ZERO responses from the gurus? -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Yuri Blanarovich wrote: We are having problem with people admitting there could be difference in the current across loading coils, and here the "problems" is what is the error? So lets stick to the big problem and fuggettabout detours and nitpicking. Yuri, K3BU Yuri, Rather than playing like Cecil and making words for others, please post the dates and statements made by people who say current cannot be uneven at each end of a coil. Show us where that is said with an exact in context quote, don't pull a Cecil and invent something that you expect us to blindly accept as the truth. It would help if we knew what you were talking about. 73 Tom |
Current across the antenna loading coil - from scratch
Cecil Moore wrote:
Yuri Blanarovich wrote: We are having problem with people admitting there could be difference in the current across loading coils, and here the "problems" is what is the error? Actually, the problem is more elementary than coils. Everyone seems to understand coils installed in circuits. The ignorance seems to be of the nature of the physics involved in standing waves, whether on a wire or on a coil or in free space. So I have switched the discussion to where it belongs, to a discussion of standing waves, with or without coils, with or without wires. I offered the following example which the gurus refuse to touch with a ten foot pole. One wonders why. The transmission line is lossless and BB is a black box. Source-------a-BB-b-----------c-BB-d---------open circuit The current at 'a' is measured at one amp. The current at 'b' is measured at zero amps. The current at 'c' is measured at zero amps. The current at 'd' is measured at one amp. What's in the black boxes? Would you believe ZERO responses from the gurus? In an Internet discussion, everybody has the right to attempt to switch the discussion away from the point. Everybody else has the inalienable right not to follow them. -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Current across the antenna loading coil - from scratch
On Tue, 4 Apr 2006 16:47:05 -0400, "Yuri Blanarovich"
wrote: Very simple questions. Technically based. Selected because they seem to be of supreme importance to you, and yet you don't seem to have a handle on the situation. I have the handle on it, appreciate the magnitude and with time there will be some numbers. Hi Yuri, So, after all these years, you have more grief than numbers. You cannot give us the accuracy necessary to resolve this, and you haven't got a number to call efficiency. The solution has long been offered, so this must be more a matter of personality than technicality. So lets stick to the big problem and fuggettabout detours and nitpicking. You haven't told us how "big" problem is, and with more tears than numbers, "big" seems to be an emotional measure. You would get more traction hiring professional mourners for this wake. At least we could count them to see how important the corpse was. To this point there seems to be only one mourner, and a Texas cowboy spitting in his face and calling it the refreshing dew of early spring. 73's Richard Clark, KB7QHC |
Current across the antenna loading coil - from scratch
Cecil Moore wrote:
John Popelish wrote: Cecil Moore wrote: Please give us the equation for "ordinary AC voltage or current". The simplest (without a reference phase) would be cos(wt). The standing wave function contains this term, with a modifier to tell you how amplitude varies with position. But at any point, cos(wt) times some amplitude describes the ordinary AC voltage or current swing. But please notice that cos(kx+wt) is different from that term. The only time they are the same is if 'x' = 0. Is 'x' always equal zero? No. All your equation tells us is that whatever current it represents, it is always in phase with the reference source at 'x' = 0. So your equation is too simple to be useful. Please try again. Thanks for agreeing with me. I said every bit of this in words added as modifiers to cos(wt). EZNEC must take those within a cycle currents and voltages into account to come up with the amplitude values. "Must" or "does". I have no idea. At a given point the traveling wave phasor doesn't rotate, either. On the contrary - at any given point 'x', the traveling wave phasor is rotating with respect to the source phasor. That is not what the formula says. Pick and X and you get a constant phase angle with respect to the zero degree reference. Pick a point on a standing wave, and you get a constant phase angle (one of two, 180 degrees apart). If one rotates, so does the other. of one does not rotate, neither does the other, at that point. That's what makes it different from a standing wave phasor which doesn't rotate with respect to the source phasor. I disagree. There are differences, but that is not one of them. Phasor rotation only applies to the phase change over length for a traveling wave. No, that's wrong. Take another look at cos(kx+wt). Holding 'x' at a constant value, the phase keeps on changing. No. the kx term is the phase term. Pick and X and the phase (with respect to the zero phase reference freezes. The wave continues to unfold in time, but with that fixed phase relationship to the phasor reference. The traveling wave phasor is rotating with respect to the source. Not at a point. at any point, there is a fixed phase relationship withe the phasor zero degree reference. The standing wave phasor is not rotating with respect to the source, just as Hecht says speaking of standing waves: "The resultant phasor is E1 + E2 = E ... Keeping the two [traveling wave] phasors tip-to-tail and having E1 rotate counterclockwise as E2 rotates (at the same rate) clockwise, generates E [total] as a function of 't'. ... It doesn't rotate at all, and the resultant wave it represents doesn't progress through space - it's a standing wave." The standing wave is a mathematical concept that represents the super position of a pair of waves that are going someplace. It represents a case where two equal energys are being delivered in two opposite directions, so no net energy moves. But waves continue to travel. You really need to get you a copy of Hecht's "Optics". It the best treatment of standing waves that I have ever seen - also best at superposition and interference explanations. I don't need this reference. I have a form grasp of traveling waves and their superposition. You don't add superposed RMS values to get the resultant RMS value. Sure you do. Current #1 is an RMS value at angle 1. Current #2 is an RMS value at angle 2. The superposition is: RMS#1*cos(A1) + RMS#2*cos(A2) = RMS(total) That is not adding, that is scaled adding (with a possibility that one or both scaling factors are negative). Do you get negative total RMS current, if both cos(A) terms are negative? There is no discussion of RMS envelope values. Where have you been? The currents displayed by EZNEC are RMS envelope values. The antenna currents plotted in Kraus and Terman are RMS envelope values. The currents measured at the top and bottom of the coils by W8JI and W7EK are RMS envelope values. I didn't mean that no one is dealing with RMS values, I meant that no one disagrees (is discussing) RMS values. It is not a point of contention. I am waiting for you to realize that you can measure the phase shift of each of the traveling waves that superpose in a standing wave process that includes a coil (or any other network) by using only the RMS amplitude envelope, with no reference to phase, in an EZNEC simulation or a real experiment. That was the whole point that began this discussion, wasn't it? Yes, I said that months ago but nobody would buy the argument. Over those months, I have given countless examples proving that to be true. Everyone just ignored those technical facts as they have ignored 95% of the technical content of my postings only to concentrate on the 5% containing feelings or bad humor. Now, measure the phase shift of that coil ... Sorry, the coil is obviously not the problem. Everyone understands how a coil works. When did everyone agree on that? Last time I looked, you were claiming that one could use the self resonant frequency as a way to predict the phase shift through a coil at other frequencies (to some rather open tolerance) with the assumption of constant time delay. And then you tested (with EZNEC) a coil in a one way wave situation and demonstrated a 5 to 1 change in time delay over a rather small frequency range, then you dropped the subject of coils and claim we are all talking about some mystery of standing waves. It is hard to keep up. What everyone doesn't understand is how standing waves in a wire work. That is a pretty broad claim, unless you are really speaking for yourself. That will be my topic of discussion from now on. But feel free to continue the coil topic with anyone else. Okay. I won't mention "bug catchers" any more in posts responding to you. Glad that's over. ;-) |
Current across the antenna loading coil - from scratch
On Tue, 04 Apr 2006 18:31:53 -0400, John Popelish
wrote: Glad that's over. ;-) "The triumph of hope over experience" |
Current across the antenna loading coil - from scratch
John Popelish wrote:
Cecil Moore wrote: So your equation is too simple to be useful. Thanks for agreeing with me. No - thank you for agreeing with me that your equation is too simple to be useful. :-) That is not what the formula says. Pick and X and you get a constant phase angle with respect to the zero degree reference. But that phase angle is not zero as it is for standing waves. You seem to be talking in circles. How can the phase shift between the traveling wave and the source reference ever be zero at a point 90 degrees away from the source? If it cannot, then you have evidence that the traveling wave is NOT identical to the standing wave as evidenced by their different equations. Last time I looked, you were claiming that one could use the self resonant frequency as a way to predict the phase shift through a coil at other frequencies (to some rather open tolerance) with the assumption of constant time delay. Where have you been? I gave up on that idea long ago. I even posted a Dr. Corum quote to that effect. You obviously need to look more often. Let's cut to the bottom line. You seem to believe that standing wave current is identical to traveling wave current. If that's your point, just say so. Otherwise, please tell us the difference between the standing wave current and the traveling wave current which seems obvious to me from the equations. -- 73, Cecil http://www.qsl.net/w5dxp |
Current across the antenna loading coil - from scratch
Roy Lewallen wrote:
Since EZNEC has been mentioned so much lately, it's appropriate to point out that it's able to calculate the current at all points along a helically modeled loading inductor with what I believe to be very good accuracy. And it does it without any use or knowledge of presumed traveling voltage or current waves. Yet, EZNEC reports the difference in standing wave current and traveling wave current better than you do. EZNEC correctly reports the phase of the standing wave current to be essentially zero all up and down a 1/2WL dipole using small wire. EZNEC correctly reports the phase of the traveling wave current to be the number of degrees away from the source in a traveling wave antenna. EZNEC clearly recognizes the difference between standing wave current and traveling wave current. Yet you tried to use standing wave current with its unchanging phase to measure the phase shift through a coil. Standing wave current doesn't even change phase through 45 degrees of wire. Why would you expect it to change phase through 45 degrees of coil? -- 73, Cecil http://www.qsl.net/w5dxp |
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