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Velocity Factor and resonant frequency
Roy, W7EL wrote:
"This means that if we put a current into one end of the inductor, it`ll take about 40 ns for current to reach the other end, right? So we should expect a phase delay in current of 180 degrees at 6.15 MHz, from one end to another?" Hopper`s rule is one foot traveled per nanosecond. 40 feet of wire takes 40 nanoseconds. The wavelength of 6.15 MHz is 48,8 or about 160 feet and in that space the phase rotates 360-degrees. 40 feet is 1/4 of 360-degrees or 90-degrees at 6.15 MHz. At 1 MHz, the wavelength is 300 meters. 12,2 meters of wire is about 15-degrees of delay by my $1-dollar Chinese calculator. Best regards, Richard Harrison, KB5WZI |
Velocity Factor and resonant frequency
Roy, you are allowing your imagination to stray.
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Velocity Factor and resonant frequency
Sorry, my mistake. So let me rephrase my question:
This means that if we put a current into one end of the inductor, it'll take about 40 ns for current to reach the other end, right? So we should expect a phase delay in the current of 90 degrees at 6.15 MHz, or about 15 degrees at 1 MHz, from one end to the other? Roy Lewallen, W7EL Richard Harrison wrote: Roy, W7EL wrote: "This means that if we put a current into one end of the inductor, it`ll take about 40 ns for current to reach the other end, right? So we should expect a phase delay in current of 180 degrees at 6.15 MHz, from one end to another?" Hopper`s rule is one foot traveled per nanosecond. 40 feet of wire takes 40 nanoseconds. The wavelength of 6.15 MHz is 48,8 or about 160 feet and in that space the phase rotates 360-degrees. 40 feet is 1/4 of 360-degrees or 90-degrees at 6.15 MHz. At 1 MHz, the wavelength is 300 meters. 12,2 meters of wire is about 15-degrees of delay by my $1-dollar Chinese calculator. Best regards, Richard Harrison, KB5WZI |
Velocity Factor and resonant frequency
Cecil, W5DXP wrote:
"Dr. Corum`s VF equation predicts a VF of approximately double Richard`s----." I wonder why? Dr. Terman wrote that the wave follows the turns in a coil. My recollection of common solid-dielectric coax VF is about 2/3 that of free-space due to the fense plastic. Twice the velocity factor in a coil requires a wave traveling faster than light or taking a short-cut around the turns. I often learn from my mistakes. Where did I err? Best regards, Richard Harrison, KB5WZI |
Velocity Factor and resonant frequency
"Richard Harrison" wrote: Twice the velocity factor in a coil requires a wave traveling faster than light or taking a short-cut around the turns. I often learn from my mistakes. Where did I err? The current does take a short-cut due to adjacent coil coupling. But please note the velocity factor only approximately doubles from the "round and round the coil" calculation. Even though a VF of 0.04 is ~double the "round and round the coil" approximation, it is still 96% away from the VF=1.0 originally asserted by W8JI which assumes that all the coils couple 100% to all the other coils. -- 73, Cecil, W5DXP |
Velocity Factor and resonant frequency
Cecil, W5DXP wrote:
"The current does take a short-cut due to adjacent coil coupling." R.W.P. King wrote on page 81 of Transmission Lines, Antennas, and Wave Guides: "The electromagnetic field in the near zone is characterized by an inverse-square law for amplitude and by quasi-instantaneous action." I still don`t know what to make of King`s assertion regards instantaneous action. Best regards, Richard Harrison, KB5WZI |
Velocity Factor and resonant frequency
Richard Harrison wrote:
Cecil, W5DXP wrote: "The current does take a short-cut due to adjacent coil coupling." R.W.P. King wrote on page 81 of Transmission Lines, Antennas, and Wave Guides: "The electromagnetic field in the near zone is characterized by an inverse-square law for amplitude and by quasi-instantaneous action." I still don`t know what to make of King`s assertion regards instantaneous action. From the IEEE Dictionary: "instantaneous - A qualifying term indicating that no delay is purposely introduced in the action of the device." Does anyone have a formula for the coupling factor between turns in a coil? -- 73, Cecil http://www.qsl.net/w5dxp |
Velocity Factor and resonant frequency
I'm going with Drs. Corum on this one. Solve equation 28 for tau, get
beta from equation 4. The phase velocity along the axis of the coil is omega/beta. The velocity factor in question is that phase velocity over the speed of light in a vacuum. The coil modes are surface waves in a weird coordinate system. Note that the paper is very explicit in saying they're not TEM. Throw equation 28 into Mathematica or Matlab or something and solve for tau. The cases given after equation 28 with all the limitations appear(ed?) to be a point of some contention, but equation 28 seems *only* to have the limitation of circumferential symmetry of the surface waves on the coil. At the junctions between the wire and the coil, there is a transfer of energy between the surface wave modes on the coil and the usual antenna mode (I guess it's TEM?) The coil is like G-line in that it guides surface waves, but the coil modes are modes specific to the helical geometry; the G-line surface waves are specific to the straight-wire geometry. There is a mode on the helix where the waves go round and round the turns, but the example given is a traveling wave tube for microwave amplification, and it seems to me that there are a few turns over a few inches for *microwave* frequencies. I am not one to argue with a solution to Maxwell's equations. -Dan |
Velocity Factor and resonant frequency
I need to proofread more. "At the junctions between the *ANTENNA* wire
and the *LOADING* coil there is a transfer of energy..." would have been a bit clearer. Also very possibly inaccurate. The energy transfer may happen somewhere else in space as the fields around the antenna wire do not have the exponentially decaying radial behavior that the coil surface wave fields have. I expect, though, that the current at the antenna wire/coil junction is what does the exciting of the surface wave modes on the helix. Also should have said "a few turns over a few inches for a *TWT OPERATING* at microwave frequencies". -Dan |
Velocity Factor and resonant frequency
Dan, N3OX wrote:
"Also should have said "a few turns over a few inches for a "TWT OPERATING" at microwave frequencies". That`s interesting. John D. Kraus invented the axial-mode helix antenna after attending a lecture on traveling wave tubes given by a famous scientist visiting Ohio tate University. Kraus asked the visitor if he thought the helix could be used as an antenna. The visitor said no, so Kraus went home, wound seven turns one wavelength in circumference and discovered it made a sharp beam off the open end when he used a ground plane across the driven end. The story appears on page 222 of Hraus` 3rd edition of "Antennas". Lenkurt described operation of the traveling wave tube in its August 1965 edition of the "Demodulator". Here is an excerpt: "The signal to be amplified by the tube is coupled into the gun end of the helix. This RF signal travels as a surface wave around the turns of the helix, toward the collector, at about the velocity of light. The forward or axial velocity of the signal is slower, of course, because of the pitch and diameter of the helix. This forward movement of the wave is analogous to the travel of a finely threaded screw where many turns are required to drive it into position. The signal wave generates an axial electric field which travels with it along the longitudinal axis of the helix. This alternating electric field interacts or velocity modulates the electrons in the beam." Terman`s description in the 1955 edition of "Electronic and Radio Engineering" starts on page 678 and is very similar to Lenkurt`s. i`d bet that it is more than coincidental. Kraus says of his new helical antenna on page 223 of his 3rd edition of "Antennas": "At a low frequency (helix circumference about lambda/2) there was almost a pure standing wave (VSWR goes to infinity) all along the helix (outgoing and reflected waves nearly equal) (Fig. 8-3a)--." Surely an antenna loading coil resembles Kraus` low-frequency helix. It has an open-circuit whip producing a reflection into one end. The circumference is well below 1/2-wavelength, giving a current distribution such as shown in Fig. 8-3a for a frequency below the axial mode of operation. Fig. 8-3c shows uniform outgoing and reflected currents over the middle section of the helix. Kraus` figures were produced from actual measurements. Best regards, Richard Harrison, KB5WZI |
Velocity Factor and resonant frequency
Richard Harrison wrote:
. . . Surely an antenna loading coil resembles Kraus` low-frequency helix. It has an open-circuit whip producing a reflection into one end. The circumference is well below 1/2-wavelength, giving a current distribution such as shown in Fig. 8-3a for a frequency below the axial mode of operation. . . . So does this mean if we put a current into one end of the inductor I described, it'll take about 40 ns for current to reach the other end? So we should expect a phase delay in the current of 90 degrees at 6.15 MHz, or about 15 degrees at 1 MHz, from one end to the other? What good are all these books if the information can't be used to solve a simple problem? Roy Lewallen, W7EL |
Velocity Factor and resonant frequency
Roy Lewallen wrote:
So does this mean if we put a current into one end of the inductor I described, it'll take about 40 ns for current to reach the other end? So we should expect a phase delay in the current of 90 degrees at 6.15 MHz, or about 15 degrees at 1 MHz, from one end to the other? Equation (32) at http://www.ttr.com/TELSIKS2001-MASTER-1.pdf answers that question. The VF is about double the "round and round the coil" calculated value and the VF changes with frequency. -- 73, Cecil http://www.qsl.net/w5dxp |
Velocity Factor and resonant frequency
Cecil Moore wrote:
Roy Lewallen wrote: So does this mean if we put a current into one end of the inductor I described, it'll take about 40 ns for current to reach the other end? So we should expect a phase delay in the current of 90 degrees at 6.15 MHz, or about 15 degrees at 1 MHz, from one end to the other? Equation (32) at http://www.ttr.com/TELSIKS2001-MASTER-1.pdf answers that question. The VF is about double the "round and round the coil" calculated value and the VF changes with frequency. Beware of academics who use phrases such as "anisotropically conducting cylindrical boundary," "helically disposed surface waveguide," and "voltage magnification by standing waves." These are just figures of speech. Some academics - fractenna comes to mind - get so carried away with their ideas, they'll try anything to justify them, including the use of nounspeak and polysyllabic jargon. Real scientists and engineers don't have to use such tactics to make a point. 73, Tom Donaly, KA6RUH |
Velocity Factor and resonant frequency
Roy, W7EL wrote:
"What good are all the books if the information can`t be used to solve a simple problem?" Many problems fit examples in the books. Some don`t. Implications in my case are sometimes slow to sink in. An example is what Kraus writes on page 227 of the 3rd edition of "antennas": "Thus, a helix combines the geometric forms of a straight line, a circle, and a cylinder." Cecil says that RF on a helix may take a short-cut. He may be right. Why would not a wave deviate from the round and round path on a coil and sweep at least in part directly along the cylindrical length? It may be a case for experimentation with a variety of lengths, pitches, and circumferences. Best regards, Richard Harrison, KB5WZI |
Velocity Factor and resonant frequency
If the language in the Corum paper bothers you, check the math.
The Corum paper gives a mathematical solution of Maxwell's equations for a helix that allows you to answer the questions that have been ongoing in this thread. I'm not going to claim that I worked through the solution myself. I did read it and try to understand the process. It looks just like what I've done over and over again in electromagnetic theory courses. You write down the wave equation, the boundary conditions, and you solve. The geometry of the problem leads to lots of bessel functions and the necessity to numerically solve the resulting equations to find the solutions in the middle ground between a lumped circuit coil and a TWT helix. I feel like this is typical of physical problems that have a limiting case at either end. If you go to infinite propagation speed, or a coil that is very very short compared to a wavelength, you get a lumped circuit. If you go to a very long helix with respect to a wavelength, the wave on the helix goes round and round the turns. In the middle, the Corum paper describes the situation in mathematical detail. Both crackpots and respectable scientists can use complicated terms. The former use them to obscure unverifiable claims, the latter use them to try to put a concise name on something that has a complicated mathematical description. Throw all the words out of the Corum paper, if you like. Let's look only at the solution. Is there anything wrong with the mathematical solution to the wave equation on the helix presented there? Is the solution in fact applicable to a GIVEN ham antenna loading coil? Can we use it to predict the difference in current at either end of a loading coil for a given ham antenna loading coil? I was going to write "typical" ham antenna loading coil, but I realized that's a trap. You can't take the solution in the Corum paper, reduce it to a rule of thumb for the "typical" ham loading coil, and then use that rule of thumb to make quantitative predictions about a particular coil in a particular configuration! Does the solution applicable to all helix sizes and pitches (the transcendental equation, equation 28 for the constant tau) and the equation for the velocity of propagation along the axis of the coil (phase velocity = omega/beta) give the correct delay or not? I think equation 28 can be solved in Matlab or Mathematica or something else. I haven't quite figured out if Figure 1 uses approximations or if it is numerical solutions of equation 28. If it's the latter, you can just use the figure. 73, Dan N3OX |
Velocity Factor and resonant frequency
So is that a "yes", or "no"?
Roy Lewallen, W7EL Richard Harrison wrote: Roy, W7EL wrote: "What good are all the books if the information can`t be used to solve a simple problem?" Many problems fit examples in the books. Some don`t. Implications in my case are sometimes slow to sink in. An example is what Kraus writes on page 227 of the 3rd edition of "antennas": "Thus, a helix combines the geometric forms of a straight line, a circle, and a cylinder." Cecil says that RF on a helix may take a short-cut. He may be right. Why would not a wave deviate from the round and round path on a coil and sweep at least in part directly along the cylindrical length? It may be a case for experimentation with a variety of lengths, pitches, and circumferences. Best regards, Richard Harrison, KB5WZI |
Velocity Factor and resonant frequency
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Velocity Factor and resonant frequency
Tom Donaly wrote:
Beware of academics who use phrases such as "anisotropically conducting cylindrical boundary," "helically disposed surface waveguide," and "voltage magnification by standing waves." These are just figures of speech. Some academics - fractenna comes to mind - get so carried away with their ideas, they'll try anything to justify them, including the use of nounspeak and polysyllabic jargon. Real scientists and engineers don't have to use such tactics to make a point. 73, Tom Donaly, KA6RUH Beware of academics who use "real physical based equations" as they may mislead you because they are based in reality. tom K0TAR |
Velocity Factor and resonant frequency
Tom Donaly wrote: Consider your normal mobile antenna with a large loading coil. Now, in your mind's eye, replace the coil with a cylinder. Now, compute the cutoff frequency for that cylinder for either a TE or TM mode and see how close you can get to 3.75 Mhz. Of course, if your waves are slow enough, you should be able to cram something in there, but you have to show experimentally both that you can do it, and how you can do it. Tom Donaly, KA6RUH TE, TM, or TEM a small loading coil cannot behave very much like a transmission line. If you read the Corum paper carefully, you see he clearly states it is an approximation or solution for a coil under the very special condition of being self-resonant. He is working on Tesla coils, not loading coils. He is working with coils that have essentially no termination and that actuallly behave like a series of L networks with high reactance shunt C and high reactance series L. Worse yet, we have one person who is trying to use a large diameter helice with wide turn spacing that is large enough to support TEM waves as a comparison to a tiny fraction of a wavelength dieameter and length inductor that has relatively close turn spacing and tight coupling from turn to adjacent turn. Unless we do something to cause the radial electric field to be very intense and support significant displacement currents, all the standing waves in the world external to the won't make a coil behave like a linear conductor. Notice also how Cecil misquotes to make a point. The Vf I measured on 80 meters for a large bug-catcher style coil was actually .5 compared to spatial length, not 1.0 On the other hand Cecil has measured virtually nothing, Yuri has measured nothing, and Harrison probably hasn't even owned a bug catcher coil being a technician class license holder. It's easy to dismiss measurements when you have not done a thing on your own except talk. 73 Tom |
Velocity Factor and resonant frequency
wrote:
TE, TM, or TEM a small loading coil cannot behave very much like a transmission line. We are not discussing small coils, Tom. We are discussing big honking 75m bugcatcher coils. Why do you guys always retreat from the real world into the area of "small" coils? If you read the Corum paper carefully, you see he clearly states it is an approximation or solution for a coil under the very special condition of being self-resonant. False. He clearly states that the VF and Z0 were established at the self-resonant frequency and that those values hold as long as the coil pitch, coil diameter, and frequency remain unchanged. That's exactly what I have done using EZNEC models. He is working on Tesla coils, not loading coils. The first words in the title are, "RF Coils, ...". Figure 2 looks just like a 75m bugcatcher system with a top hat. A 75m bugcatcher coil is a helical resonator that brings the antenna system into resonance. He has a litmus test for RF coils. If the coil dimensions pass the litmus test, then his VF and Z0 equations are known to be valid within 10%. A 75m bugcatcher coil passes that litmus test by a 100% margin. A self-resonant coil is 90 degrees long. Dr. Corum says the lumped circuit model doesn't work until the coil is trimmed down to 0.167 of that length. Seems you have proven that to be true. Notice also how Cecil misquotes to make a point. The Vf I measured on 80 meters for a large bug-catcher style coil was actually .5 compared to spatial length, not 1.0 Sorry, my memory was faulty on that one but 0.5 is still 1000% different from the value predicted by Dr. Corum's VF equation and flies in the face of known technical facts about coils. On the other hand Cecil has measured virtually nothing, Yuri has measured nothing, ... Which is better, Tom. Valid science or invalid measurements? You still haven't answered my question as to why you don't just assert that a 1/4WL monopole is zero degrees long since there is zero degrees of phase shift in the standing wave current phase from end to end in the antenna. Heck, you can even prove that a 1/2WL thin-wire dipole is zero degrees long using the same measurement techniques that you used on a coil. ... and Harrison probably hasn't even owned a bug catcher coil being a technician class license holder. Instead of belittling his ham license, how about you compare your technical degrees to "Harrison's"? -- 73, Cecil http://www.qsl.net/w5dxp |
Velocity Factor and resonant frequency
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Velocity Factor and resonant frequency
Cecil Moore wrote:
wrote: TE, TM, or TEM a small loading coil cannot behave very much like a transmission line. We are not discussing small coils, Tom. We are discussing big honking 75m bugcatcher coils. Why do you guys always retreat from the real world into the area of "small" coils? If you read the Corum paper carefully, you see he clearly states it is an approximation or solution for a coil under the very special condition of being self-resonant. False. He clearly states that the VF and Z0 were established at the self-resonant frequency and that those values hold as long as the coil pitch, coil diameter, and frequency remain unchanged. That's exactly what I have done using EZNEC models. He is working on Tesla coils, not loading coils. The first words in the title are, "RF Coils, ...". Figure 2 looks just like a 75m bugcatcher system with a top hat. A 75m bugcatcher coil is a helical resonator that brings the antenna system into resonance. He has a litmus test for RF coils. If the coil dimensions pass the litmus test, then his VF and Z0 equations are known to be valid within 10%. A 75m bugcatcher coil passes that litmus test by a 100% margin. A self-resonant coil is 90 degrees long. Dr. Corum says the lumped circuit model doesn't work until the coil is trimmed down to 0.167 of that length. Seems you have proven that to be true. Notice also how Cecil misquotes to make a point. The Vf I measured on 80 meters for a large bug-catcher style coil was actually .5 compared to spatial length, not 1.0 Sorry, my memory was faulty on that one but 0.5 is still 1000% different from the value predicted by Dr. Corum's VF equation and flies in the face of known technical facts about coils. On the other hand Cecil has measured virtually nothing, Yuri has measured nothing, ... Which is better, Tom. Valid science or invalid measurements? You still haven't answered my question as to why you don't just assert that a 1/4WL monopole is zero degrees long since there is zero degrees of phase shift in the standing wave current phase from end to end in the antenna. Heck, you can even prove that a 1/2WL thin-wire dipole is zero degrees long using the same measurement techniques that you used on a coil. ... and Harrison probably hasn't even owned a bug catcher coil being a technician class license holder. Instead of belittling his ham license, how about you compare your technical degrees to "Harrison's"? Tom sure hit the nail on the head this time, didn't he, Cecil. When are you guys going to do your own experiments and measurements. Yuri at least threatens to do them. You just use a fast mouth and a few hick rhetorical techniques to get someone - anyone - to go along with you. A man can justify just about anything with his mouth, including CFA antennas and their kin, but providing repeatable experiments and measurements is something else again... ain't it. 73, Tom Donaly, KA6RUH |
Velocity Factor and resonant frequency
On Sun, 30 Apr 2006 12:20:10 GMT, Cecil Moore
wrote: A 75m bugcatcher coil passes that litmus test by a 100% margin. That would be pretty poor litmus! Acceptable error has increased from ±59% to ±100% So as to conserve thread length, please choose excuse by number: 1. Typing error; 2. Poor eye cite; 3. MENSa decreptis; 4. Xerox copier jam; 5. Rhetorical answer. |
Velocity Factor and resonant frequency
Tom Donaly wrote:
Everyone wants to use the most unreliable instrument they possess, their brain, to measure natural phenomena. The Corum boys wrote an entertaining paper that makes use of what is evidently an old technique for explaining helical behavior in the microwave range to make a point about self-resonant coils being superior to coil-capacitor combinations for producing long sparks in Tesla coils. Taken literally, the paper misses the magic ingredient of validation by experimentation. Drs. Corum have published many papers which include experiments and measurements. The above referenced paper is the technical summation of theory and measurements. The other paper that I quoted contains all the experimental measurements that you could ask for. Enjoy. It is at: http://www.ttr.com/corum/index.htm -- 73, Cecil http://www.qsl.net/w5dxp |
Velocity Factor and resonant frequency
Tom Donaly wrote:
When are you guys going to do your own experiments and measurements. I've already done them and reported them here, Tom. Here's the procedure again. 1. Take a sample coil and measure the 1/4WL self resonant frequency over my GMC pickup ground plane. 2. Keeping everything else the same, cut off half of the above coil. 3. Add enough straight wire as a stinger to bring the antenna system back to resonance at the previous self- resonant frequency. 4. The delay through half the coil at the self resonant frequency of the whole coil, is known to be 45 degrees. The stinger is 11 degrees long. The impedance discontinuity between the coil and the stinger provides the other 34 degrees of phase shift. Both sides of the argument assumed only two phase shifts were involved. Both sides were wrong. The third phase shift is obvious once you know it exists and is perfectly visible on a Smith Chart. When the impedance at Z01 is 1.0 on the Smith Chart and transforms to 9.0 on the Smith Chart for Z02, that's obviously a large phase shift. Two years ago, both sides agreed that the stinger was about 11 degrees of the antenna. 1. Side 1 said that the base loading coil acted as a purely lumped inductance providing 79 degrees of phase shift essentially at a point. 2. Side 2 said that the base loading coil provided a 79 degree delay like the delay in a transmission line, which was the source of the 79 degree phase shift. At that time, both sides were unaware of the phase shift occuring at the impedance discontinuity point. Now we know that both sides were partially right and partially wrong. As side 1 said, there is an abrupt phase shift at a point. As side 2 said, there is a delay through the coil. The truth seems to be just about in the middle of the two previous arguments which should make both sides happy. There are tens of degrees of delay through the coil. There are tens of degrees of abrupt phase shift at the coil to stinger impedance discontinuity. Both sides were equally right and equally wrong. Who won? Both sides. Who lost? Both sides. This is the invariable result when both sides are forced off the rails by reality. -- 73, Cecil http://www.qsl.net/w5dxp |
Velocity Factor and resonant frequency
Tom, W8JI wrote:
"--Harrison probably hasn`t even owned a bug catcher coil being a technician class license holder." You don`t need to own things to understand them. I have a technician class radio amateur license renewed after its initial ten-hear term. My First FCC license was a 1st class radiotelephone license passed on my first attempt at the test in the Houston FCC Office in early 1949. Shortly thereafter I got a call from a Houston broadcaster that resulted in employment at a plant housing two AM atations which shared a common antenna system. From there I went to work in medium-wave and shortwave broadcasting stations for a dozen years, got several college degrees including a BSEE. I took a job with a petrochemical conglomerate which called me in 1960 saying that it intended to "automate" its operations and they thought I might be helpful. In their employment, I installed low-frequency aircraft beacons, 6-GHz microwave, shortwave AM, FM, and SSB. Installed telephones and electric power plants. The conglomerate found, produced, transported, traded, refined. manufactured and marketed oil and gas and products made from them. That was only a start. The company mined materials from the earth and from the sea bottom. It farmed, manufactured tractors and automobile components and tools. It built nuclear submarines, surface ships, natural gas tankers which consumed their own boil off, and it laid pipe across Canada and the U.S.A. It even consulted for other countries on the best ways to install and operate pipelines. I worked with a handfull of others for the subsidiary that did that for awhile. The company sold insurance because insurance companies have mush of the capital, and for a similar reason it bought and operated banks.. We made PVC and other chemical products. I worked in many of the company`s divisions when they asked for my services. We eventually put the pipeline divison under computer control from from Houston dispatcher`s office. Hundred of remotes were involved between Maine and Mexico. I`ve wound plenty of coils and tuned many mobile whips with my own hands. We used HF radios from Ecuador to Tierra del Fuego. I`ve worked on HF and VHF radios in the company`s aircraft. When I retired in 1986, I was manager of telecommunications. Best regards, Richard Harrison, KB5WZI |
Velocity Factor and resonant frequency
Cecil Moore wrote:
Tom Donaly wrote: Everyone wants to use the most unreliable instrument they possess, their brain, to measure natural phenomena. The Corum boys wrote an entertaining paper that makes use of what is evidently an old technique for explaining helical behavior in the microwave range to make a point about self-resonant coils being superior to coil-capacitor combinations for producing long sparks in Tesla coils. Taken literally, the paper misses the magic ingredient of validation by experimentation. Drs. Corum have published many papers which include experiments and measurements. The above referenced paper is the technical summation of theory and measurements. The other paper that I quoted contains all the experimental measurements that you could ask for. Enjoy. It is at: http://www.ttr.com/corum/index.htm That's your idea of careful experimentation is it? First start out with a controversy that doesn't exist, then prove what everyone knows in the first place. So what part of the experimentation addresses the "sheath helix" model of their Tesla coil, Cecil? 73, Tom Donaly, KA6RUH |
Velocity Factor and resonant frequency
Cecil Moore wrote:
Tom Donaly wrote: When are you guys going to do your own experiments and measurements. I've already done them and reported them here, Tom. Here's the procedure again. 1. Take a sample coil and measure the 1/4WL self resonant frequency over my GMC pickup ground plane. 2. Keeping everything else the same, cut off half of the above coil. 3. Add enough straight wire as a stinger to bring the antenna system back to resonance at the previous self- resonant frequency. 4. The delay through half the coil at the self resonant frequency of the whole coil, is known to be 45 degrees. The stinger is 11 degrees long. The impedance discontinuity between the coil and the stinger provides the other 34 degrees of phase shift. Both sides of the argument assumed only two phase shifts were involved. Both sides were wrong. The third phase shift is obvious once you know it exists and is perfectly visible on a Smith Chart. When the impedance at Z01 is 1.0 on the Smith Chart and transforms to 9.0 on the Smith Chart for Z02, that's obviously a large phase shift. Two years ago, both sides agreed that the stinger was about 11 degrees of the antenna. 1. Side 1 said that the base loading coil acted as a purely lumped inductance providing 79 degrees of phase shift essentially at a point. 2. Side 2 said that the base loading coil provided a 79 degree delay like the delay in a transmission line, which was the source of the 79 degree phase shift. At that time, both sides were unaware of the phase shift occuring at the impedance discontinuity point. Now we know that both sides were partially right and partially wrong. As side 1 said, there is an abrupt phase shift at a point. As side 2 said, there is a delay through the coil. The truth seems to be just about in the middle of the two previous arguments which should make both sides happy. There are tens of degrees of delay through the coil. There are tens of degrees of abrupt phase shift at the coil to stinger impedance discontinuity. Both sides were equally right and equally wrong. Who won? Both sides. Who lost? Both sides. This is the invariable result when both sides are forced off the rails by reality. The only problem with that, Cecil, is that in neither the coil nor the inductor do you have a uniform Z0. Since the capacitance per unit length is a variable, so is Z0 which is dependant on it. You've been sucked into Reg's practice of assuming an average Z0 in order to do calculations, but in your case it won't work because you have to posit two distinct Z0s to have your impedance boundary. In actuality, there's a constant change in Z0 up and down both the stinger and the coil so your idea is a bust. By the way, if you or the Corum boys really want a transmission line resonator for your antenna/Teslacoils you should switch to a helical resonator, the kind ensconced in a can. Of course, the sparks will be disappointing, but the theory will work better. 73, Tom Donaly, KA6RUH |
Velocity Factor and resonant frequency
Tom Donaly wrote:
In actuality, there's a constant change in Z0 up and down both the stinger and the coil so your idea is a bust. The gradual change in Z0 really doesn't matter. What matters is the *abrupt* change in Z0's at the coil to stinger impedance discontinuity. That's where the abrupt phase shift occurs. -- 73, Cecil http://www.qsl.net/w5dxp |
Velocity Factor and resonant frequency
Cecil Moore wrote:
Tom Donaly wrote: In actuality, there's a constant change in Z0 up and down both the stinger and the coil so your idea is a bust. The gradual change in Z0 really doesn't matter. What matters is the *abrupt* change in Z0's at the coil to stinger impedance discontinuity. That's where the abrupt phase shift occurs. Yes it does. 73, Tom Donaly, KA6RUH |
Velocity Factor and resonant frequency
Tom Donaly wrote:
Cecil Moore wrote: The gradual change in Z0 really doesn't matter. What matters is the *abrupt* change in Z0's at the coil to stinger impedance discontinuity. That's where the abrupt phase shift occurs. Yes it does. It only matters from a quantitative standpoint and it matters not one iota from a conceptual, qualitative standpoint. We already have real world transmission lines that change Z0 gradually. They obey the laws of physics. -- 73, Cecil http://www.qsl.net/w5dxp |
Velocity Factor and resonant frequency
Hi Richard,
Impressive carreer and background! That should slap another giant egg on the face of the technical imposter and "guru" parading as "know-it-all" riding on a high horse of plagiarized material. When he fails technical arguments, he resorts to name calling and insults. We still have to find out where he got his engineering degree and by what rights he uses "JI Engineering". Comparing your professional career to his "design" career like Dentron Clipperton L amplifier "capable" of producing barely 600W instead of 1200 on 160 due to joke of a final tank design and his digs at people illustrates the pathetic behavior. His modus operandi is to defend his wrong "knowledge", ridiculing and trivializing those who know better, then he realizes he was wrong, then he goes quiet for a while, then he twists and "adjusts" his arguments "showing" he said the same things, few months later he surfaces as a guru on the subject, proclaiming the gospel that he fought in the first place. Been there few times with him. He is incapable to engage in decent technical discussions if he thinks different. Will not admit being wrong, but will resort to personal digs when runs out of ammunition. BTW W9UCW and K8CFU did years of tests and measurements and shared some results pointing to the real behavior of the current in loading coils, but W8JI can make a coil that has the same current at both ends - end of story, because he proclaimed that current is ALWAYS the same and Kirchoff said so, never mind the reality of standing wave current. According to him, the RF chokes should not work either, let's hear some "'splanation". Oh well, there is bad apple in every RF barrel. 73, Yuri da BUm "Richard Harrison" wrote in message ... Tom, W8JI wrote: "--Harrison probably hasn`t even owned a bug catcher coil being a technician class license holder." You don`t need to own things to understand them. I have a technician class radio amateur license renewed after its initial ten-hear term. My First FCC license was a 1st class radiotelephone license passed on my first attempt at the test in the Houston FCC Office in early 1949. Shortly thereafter I got a call from a Houston broadcaster that resulted in employment at a plant housing two AM atations which shared a common antenna system. From there I went to work in medium-wave and shortwave broadcasting stations for a dozen years, got several college degrees including a BSEE. I took a job with a petrochemical conglomerate which called me in 1960 saying that it intended to "automate" its operations and they thought I might be helpful. In their employment, I installed low-frequency aircraft beacons, 6-GHz microwave, shortwave AM, FM, and SSB. Installed telephones and electric power plants. The conglomerate found, produced, transported, traded, refined. manufactured and marketed oil and gas and products made from them. That was only a start. The company mined materials from the earth and from the sea bottom. It farmed, manufactured tractors and automobile components and tools. It built nuclear submarines, surface ships, natural gas tankers which consumed their own boil off, and it laid pipe across Canada and the U.S.A. It even consulted for other countries on the best ways to install and operate pipelines. I worked with a handfull of others for the subsidiary that did that for awhile. The company sold insurance because insurance companies have mush of the capital, and for a similar reason it bought and operated banks.. We made PVC and other chemical products. I worked in many of the company`s divisions when they asked for my services. We eventually put the pipeline divison under computer control from from Houston dispatcher`s office. Hundred of remotes were involved between Maine and Mexico. I`ve wound plenty of coils and tuned many mobile whips with my own hands. We used HF radios from Ecuador to Tierra del Fuego. I`ve worked on HF and VHF radios in the company`s aircraft. When I retired in 1986, I was manager of telecommunications. Best regards, Richard Harrison, KB5WZI |
Velocity Factor and resonant frequency
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Velocity Factor and resonant frequency
Yuri,
Just a fair warning. I'd be very careful what you say in public. At some point your big mouth and very small brain will get you into trouble. Do not be too bold with your personal comments when you do not know what you are saying and your statements are full of errors. False statements if they cause harm will backfire on you, I can promise that. On a similar topic, don't blame others for your lack of self-esteem. When you are and how you feel about yourself isn't anyone's problem but you own. You make your own reputation Yuri. Please don't try to make me look as bad as you. Tom |
Velocity Factor and resonant frequency
There you go again.
What applies to you , you are trying to slap on others. Reputation is judged by others, judging our doings and record. How is your statement "JI Engineering" made in public and publications justified? I will not go into listing my accomplishments and professional background like Richard did (it would be another big egg on your pea brain and big mouth), I don't make living of ham radio and I don't care what you think. Fair warning back to you! You starting to sound like Freaktenna, nice going! 73 Yuri wrote in message ps.com... Yuri, Just a fair warning. I'd be very careful what you say in public. At some point your big mouth and very small brain will get you into trouble. Do not be too bold with your personal comments when you do not know what you are saying and your statements are full of errors. False statements if they cause harm will backfire on you, I can promise that. On a similar topic, don't blame others for your lack of self-esteem. When you are and how you feel about yourself isn't anyone's problem but you own. You make your own reputation Yuri. Please don't try to make me look as bad as you. Tom |
Velocity Factor and resonant frequency
Yuri and Tom,
AD Hominem gains nothing except to raise blood pressure and raise hostility. It certainly does not contribute to the discussion. Reasonable people can and do disagree. Please, in the interest of Harmony and Respect, let's move on. /S/ Deacon Dave (Rev. Mr.), W1MCE |
Velocity Factor and resonant frequency
Dave wrote:
Yuri and Tom, AD Hominem gains nothing except to raise blood pressure and raise hostility. It certainly does not contribute to the discussion. Reasonable people can and do disagree. Please, in the interest of Harmony and Respect, let's move on. /S/ Deacon Dave (Rev. Mr.), W1MCE This is one Christian I can agree with. It's hard to see how anyone can get exercised over a coil of wire. 73, Tom Donaly, KA6RUH |
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