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Loading coils: was Dish reflector
Roy Lewallen wrote:
If you look at the transmission line properties of a vertical, you see that the two conductors (the antenna and ground plane) get farther and farther apart as the distance from the feedpoint increases. This behaves like a transmission line whose impedance increases with distance from the feedpoint and, in fact, a TDR response shows just this characteristic. So what? An ever increasing Z0 does not change the basic characteristics of a standing wave antenna, one characteristic of which is: The phase of the current relative to the feedpoint current phase changes by a minuscule amount. So exactly how did you use that current to measure and calculate delay??? I've never seen an attempt at simulating it with distributed resistance, ... Then, just as I suspected, you have never looked at my web pages. Radiation "loss" can easily be simulated by resistance wire. Please download http://www.w5dxp.com/stub_dip.EZ and alleviate your ignorance. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
Loading coils: was Dish reflector
On Apr 22, 11:58*am, Cecil Moore wrote:
Roy Lewallen wrote: If you look at the transmission line properties of a vertical, you see that the two conductors (the antenna and ground plane) get farther and farther apart as the distance from the feedpoint increases. This behaves like a transmission line whose impedance increases with distance from the feedpoint and, in fact, a TDR response shows just this characteristic. So what? An ever increasing Z0 does not change the basic characteristics of a standing wave antenna, one characteristic of which is: The phase of the current relative to the feedpoint current phase changes by a minuscule amount. So exactly how did you use that current to measure and calculate delay??? I've never seen an attempt at simulating it with distributed resistance, ... Then, just as I suspected, you have never looked at my web pages. Radiation "loss" can easily be simulated by resistance wire. Please download http://www.w5dxp.com/stub_dip.EZ and alleviate your ignorance. -- 73, Cecil, IEEE, OOTC, *http://www.w5dxp.com Anybody got a copy of the two articles that Roy alluded too I would really like to read them Regards Art |
Dish reflector
On Apr 20, 8:43*pm, Art Unwin wrote:
On Apr 20, 7:28*pm, Jim Lux wrote: Art Unwin wrote: I made a helical end fed antenna that is inside a cone shaped reflector The reflector is made from 1/2" mesh steel with an aluminum foil liner and connected to the braid of the feed coax. No baluns are used, just direct connections. *I was surprised to hear signals from the rear! *I thought that a dish reflector prevented such signals getting to the receiver. So what can be wrong with the reflector or can signals get reflected back from the frontal area? Antenna is at a 40 foot height Any ideas as to what the fault could be? Regards Art I have no experience with dishes thus the question Note, the helical antenna does not protrude beyond the dish envelope. Art What's the relative size of "reflector" and helix? *(i.e. is the reflector in the near field of the helix, in which case, you could easily have waves propagating along the surface of the reflector) The helix is four foot long and a foot diameter. The base *of the reflector is 1.5 feet with a 45 degree angle. I have had the helix 0.5 feet shorter and 0.5 feet longer with similar results.On re examination of the antenn I now see that the ground lead of the radiator is connected to the inside of the reflector at a half way point and the coax ground is connected at the base of the reflector. I think I will change that ground connection to a common point. Regards Art Changing the ground point did not clear up the reception from the rear! Have made a smaller antenna ( not for top band) and mounted on a framework on the ground. Same thing happening but band does seem squirrily! Have put a tilt mechanism on it and I am working on putting a rotator on it so that I can get a better feel on things. I was going to do this anyway as I want to see what this arrangement has on TOA. If radiation is a matter of charged particles then penetration of dish would change the direction of gain.....food for thought The group can now go back to the subject of change Regards Art |
Loading coils: was Dish reflector
Cecil Moore wrote:
Jim Kelley wrote: I have the same recollection as Tom. If you do, it was from many years ago when I was young and foolish. :-) Evidently some things never change. :-) ac6xg |
Loading coils: was Dish reflector
Jim Kelley wrote:
Evidently some things never change. :-) The thing that never changes is that you always remember to dredge up the worst about someone even if it happened 10 years ago. Have you always been perfect? -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
Dish reflector
Art Unwin wrote:
The helix is four foot long and a foot diameter. The base of the reflector is 1.5 feet snip Art A 1 foot diameter helix would be a design for the 1 meter band, not 160. You need to scale it up just a bit. The diameter should be about 50 meters. The reflector should be maybe 150 meters in diameter. This is not going to fit in your back yard. tom K0TAR |
Dish reflector
On Apr 22, 8:46*pm, Tom Ring wrote:
Art Unwin wrote: The helix is four foot long and a foot diameter. The base *of the reflector is 1.5 feet snip Art A 1 foot diameter helix would be a design for the 1 meter band, not 160. * You need to scale it up just a bit. The diameter should be about 50 meters. *The reflector should be maybe 150 meters in diameter. *This is not going to fit in your back yard. tom K0TAR Tom What you say it should be is guided by conventional teachings and my designs are not conventional. Per conventional teachings it would be very large indeed which is why my design has to be different Actually I want to see if I can lower the conventional take of angle with the use of tipping mechanism plus the rotator addition. With CP I may lose a bit of S meter readings but if I can lower the TOA with the antenna on the ground that will be a big step forward. Any way the antenna doesn't know that it should not work and despite your comments it works OK, but as yet I have not been able to establish the radiation patterns. So I have a antenna at around 30 feet and the other on the ground with a tipping device so the up coming tests should be interesting. Both antennas will cover top band and of course will have gain, but at the moment it is TOA that I am concentrating on, after that it is patterns It is the journey not the destination. Regards Art |
Dish reflector
Art Unwin wrote:
On Apr 22, 8:46 pm, Tom Ring wrote: Art Unwin wrote: The helix is four foot long and a foot diameter. The base of the reflector is 1.5 feet snip Art A 1 foot diameter helix would be a design for the 1 meter band, not 160. You need to scale it up just a bit. The diameter should be about 50 meters. The reflector should be maybe 150 meters in diameter. This is not going to fit in your back yard. tom K0TAR Tom What you say it should be is guided by conventional teachings and my designs are not conventional. Per conventional teachings it would be snip Art Ok. So what have you changed from a standard helical design that makes it "not conventional" ? Your original description sounded pretty much like a stock 1m band helical, so if you've done something to pull it down 160:1 in frequency, I'd love to hear what it is. It must be simple and obvious, because you didn't mention it in your post. tom K0TAR |
Dish reflector
Tom Ring wrote:snip
Tom What you say it should be is guided by conventional teachings and my designs are not conventional. Per conventional teachings it would be snip Art Ok. So what have you changed from a standard helical design that makes it "not conventional" ? Your original description sounded pretty much like a stock 1m band helical, so if you've done something to pull it down 160:1 in frequency, I'd love to hear what it is. It must be simple and obvious, because you didn't mention it in your post. tom K0TAR Oh, I forgot. Art, you need to google for "axial mode". tom K0TAR |
Dish reflector
On Apr 22, 10:59*pm, Tom Ring wrote:
Tom Ring wrote:snip Tom *What you say it should be is guided by conventional teachings and my designs are not conventional. Per conventional teachings it would be snip Art Ok. *So what have you changed from a standard helical design that makes it "not conventional" ? Your original description sounded pretty much like a stock 1m band helical, so if you've done something to pull it down 160:1 in frequency, I'd love to hear what it is. *It must be simple and obvious, because you didn't mention it in your post. tom K0TAR Oh, I forgot. Art, you need to google for "axial mode". tom K0TAR- Hide quoted text - - Show quoted text - I tried to tell Art this but he just told me Krauus was wrong. Jimmie |
Dish reflector
On Apr 22, 9:59*pm, Tom Ring wrote:
Tom Ring wrote:snip Tom *What you say it should be is guided by conventional teachings and my designs are not conventional. Per conventional teachings it would be snip Art Ok. *So what have you changed from a standard helical design that makes it "not conventional" ? Your original description sounded pretty much like a stock 1m band helical, so if you've done something to pull it down 160:1 in frequency, I'd love to hear what it is. *It must be simple and obvious, because you didn't mention it in your post. tom K0TAR Oh, I forgot. Art, you need to google for "axial mode". tom K0TAR Tom I tried to share and I started with Gauss's law of statics. I never really got into it hard because of the reaction to the first step. Without an understanding of that first step it becomes impossible to move further. Yes, I have made comments beyond that point but I also left out certain factors because my work is not complete. The bottom line is that the new antennas have been made and meet my expectations up to this point but I have more to do. This group is not for antenna debate it is for gottchas by those who perceive themselves as experts and beyond the point of debate. Now I accept the group for what they are while enjoying my achievements on the side. As for you telling me what I need to do with respect to axial mode, I know my own needs better than you.I think you will be better off listening instead of posting starting with what Cecil has to say and the difficulties that you are having in digesting. Regards Art |
Dish reflector
Art Unwin wrote:
On Apr 22, 8:46Â*pm, Tom Ring wrote: Art Unwin wrote: The helix is four foot long and a foot diameter. The base Â*of the reflector is 1.5 feet snip Art A 1 foot diameter helix would be a design for the 1 meter band, not 160. Â* You need to scale it up just a bit. The diameter should be about 50 meters. Â*The reflector should be maybe 150 meters in diameter. Â*This is not going to fit in your back yard. tom K0TAR Tom What you say it should be is guided by conventional teachings and my designs are not conventional. To say the least... -- Jim Pennino Remove .spam.sux to reply. |
Loading coils: was Dish reflector
Roy Lewallen wrote:
If you look at the transmission line properties of a vertical, you see that the two conductors (the antenna and ground plane) get farther and farther apart as the distance from the feedpoint increases. This behaves like a transmission line whose impedance increases with distance from the feedpoint and, in fact, a TDR response shows just this characteristic. It's open circuited at the end, so it behaves pretty much like an open circuited transmission line, resulting in the same reflections and resulting standing waves you see on a real antenna. The Z0 characteristic impedance that matters is the one that exists at the coil-stinger junction which can be estimated from the single-wire transmission line Z0 equation. It's usually in the neighborhood of a few hundred ohms. For instance, a #14 horizontal wire at 30 feet has a Z0 very close to 600 ohms according to the formula. One difficulty is accounting for the radiation, which adds resistance to the feedpoint. I've never seen an attempt at simulating it with distributed resistance, which I don't think would work except over a narrow frequency range. I have simulated such using EZNEC's wire resistivity option. The resistance wire simulates the radiation "loss" from the antenna. But for a standing wave antenna, the "loss" to radiation is only about 20% of the total energy stored on the standing wave antenna. Therefore, a qualitative conceptual analysis can be done assuming lossless conditions just as it can be done with transmission lines. But one shortcoming of many antenna transmission line analogies is the attempt to assign a single "average" or "effective" characteristic impedance to the antenna, rather than the actual varying value. This is where a lot of care has to be taken to assure that the model is valid in the regime where it's being used. Seems EZNEC automatically compensates for the varying Z0 so all we need to estimate is the single effective Z0 at the coil to stinger impedance discontinuity. There's no reason you can't also include a loading coil in the transmission line model, and Boyer devotes much of the second part of his article to doing just that. A solenoidal coil raises the characteristic impedance of the length of "line" it occupies, because of the increase in L/C ratio in that section. The traveling wave delay in that section of the transmission line also increases due to the increased LC product. Are you saying the physics of the delay through a loading coil changes between a traveling wave and a standing wave??? The standing wave is composed of a forward traveling wave and a reflected traveling wave. They would experience the same delay that you are talking about above. So why didn't you use a traveling wave to measure the delay through a loading coil??? Exactly how can the following antenna current (from EZNEC) be used to calculate delay? The current changes phase by 2.71 degrees in 90 degrees of antenna. If the antenna was lossless, i.e. no radiation, that current would not change phase at all. EZNEC+ ver. 4.0 thin-wire 1/4WL vertical 4/23/2009 6:52:13 AM --------------- CURRENT DATA --------------- Frequency = 7.29 MHz Wire No. 1: Segment Conn Magnitude (A.) Phase (Deg.) 1 Ground 1 0.00 2 .97651 -0.42 3 .93005 -0.83 4 .86159 -1.19 5 .77258 -1.50 6 .66485 -1.78 7 .54059 -2.04 8 .40213 -2.28 9 .25161 -2.50 10 Open .08883 -2.71 -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
Loading coils: was Dish reflector
On Apr 23, 7:06*am, Cecil Moore wrote:
Roy Lewallen wrote: If you look at the transmission line properties of a vertical, you see that the two conductors (the antenna and ground plane) get farther and farther apart as the distance from the feedpoint increases. This behaves like a transmission line whose impedance increases with distance from the feedpoint and, in fact, a TDR response shows just this characteristic. It's open circuited at the end, so it behaves pretty much like an open circuited transmission line, resulting in the same reflections and resulting standing waves you see on a real antenna. The Z0 characteristic impedance that matters is the one that exists at the coil-stinger junction which can be estimated from the single-wire transmission line Z0 equation. It's usually in the neighborhood of a few hundred ohms. For instance, a #14 horizontal wire at 30 feet has a Z0 very close to 600 ohms according to the formula. One difficulty is accounting for the radiation, which adds resistance to the feedpoint. I've never seen an attempt at simulating it with distributed resistance, which I don't think would work except over a narrow frequency range. I have simulated such using EZNEC's wire resistivity option. The resistance wire simulates the radiation "loss" from the antenna. But for a standing wave antenna, the "loss" to radiation is only about 20% of the total energy stored on the standing wave antenna. Therefore, a qualitative conceptual analysis can be done assuming lossless conditions just as it can be done with transmission lines. But one shortcoming of many antenna transmission line analogies is the attempt to assign a single "average" or "effective" characteristic impedance to the antenna, rather than the actual varying value. This is where a lot of care has to be taken to assure that the model is valid in the regime where it's being used. Seems EZNEC automatically compensates for the varying Z0 so all we need to estimate is the single effective Z0 at the coil to stinger impedance discontinuity. There's no reason you can't also include a loading coil in the transmission line model, and Boyer devotes much of the second part of his article to doing just that. A solenoidal coil raises the characteristic impedance of the length of "line" it occupies, because of the increase in L/C ratio in that section. The traveling wave delay in that section of the transmission line also increases due to the increased LC product. Are you saying the physics of the delay through a loading coil changes between a traveling wave and a standing wave??? The standing wave is composed of a forward traveling wave and a reflected traveling wave. They would experience the same delay that you are talking about above. So why didn't you use a traveling wave to measure the delay through a loading coil??? Exactly how can the following antenna current (from EZNEC) be used to calculate delay? The current changes phase by 2.71 degrees in 90 degrees of antenna. If the antenna was lossless, i.e. no radiation, that current would not change phase at all. * * * * * * * * * * * *EZNEC+ ver. 4.0 thin-wire 1/4WL vertical * * 4/23/2009 * * 6:52:13 AM * * * * * --------------- CURRENT DATA --------------- Frequency = 7.29 MHz Wire No. 1: Segment *Conn * * *Magnitude (A.) *Phase (Deg.) 1 * * * *Ground * * 1 * * * * * * * *0.00 2 * * * * * * * * * .97651 * * * * *-0.42 3 * * * * * * * * * .93005 * * * * *-0.83 4 * * * * * * * * * .86159 * * * * *-1.19 5 * * * * * * * * * .77258 * * * * *-1.50 6 * * * * * * * * * .66485 * * * * *-1.78 7 * * * * * * * * * .54059 * * * * *-2.04 8 * * * * * * * * * .40213 * * * * *-2.28 9 * * * * * * * * * .25161 * * * * *-2.50 10 * * * Open * * * .08883 * * * * *-2.71 -- 73, Cecil, IEEE, OOTC, *http://www.w5dxp.com Cecil The problem in this debate is that others are concentrating on resonance where as you are thinking in terms of anti resonance which portends to a higher impedance and also the condition of equilibrium. When considering the boundary law one must recognise that momentum increases and decreases twice per period. Thus when considering the boundary laws the negative area of the sine wave must be placed underneath the positive area such that momentum is taken account of. When the diagram provided by Best on this thread was shown what it described was the period was extended by the containment within the boundary and where that containment extended the period which is now longer than the period of non containment.In one case you have accelleration and deaccelleration which is depicted as the emmission of energy or flux. Consevation of energy laws demands that for balance we must take into account the energy or flux that enters the boundary to maintain equilibrium which is depicted by the negative area of the sine wave period such that this area is placed directly under the positive area while still remaining within the arbritrary boundary. Thus we have effectively changed the period when looking at a coil where the slow wave is now half of the original wave as is theresonant point is half of the anti resonant point which in terms of Newton and Maxwell represents the point of equilibrium. When using the resonant point in terms of relativity ie Maxwell you are seeing movement of a charge from "a" to "b" which when repeated is repetitive movement in a single direction. When using the anti resonant point the charge returns to the starting point and if time is regarded as /dt then the charge only moves in the vertical direction. Thus in terms of Earth mass consists of energy movement in the ":z" plan and with respect to the Universe the energy movement is solely in the "x" or "y": direction until this action is equated with an action from the opposite direction as per the law of Newton. Thus like Einstein viewing the same action of Newton this thread is viewing the same problem where one is static and one is relative but never the less the same problem but relatively different. Pure physics my dear Watson viewed fron different vantage points., one takes equilibrium into account where as the other doesn't. Not "babble"' David just an explanation per classical physics which is the sole and only root of both mechanical and electrical engineering Best regards Art Unwin KB9MZ xg(uk) |
Loading coils: was Dish reflector
Art Unwin wrote:
The problem in this debate is that others are concentrating on resonance where as you are thinking in terms of anti resonance which portends to a higher impedance and also the condition of equilibrium. I apologize if I gave you that idea, Art. I am talking about a physically short (38 degrees), electrically 1/4WL (90 degrees) *resonant* antenna over mininec ground. The feedpoint impedance is low and resistive. In the example given, the stinger supplies 19 degrees of phase shift, the base-loading coil supplies 19 degrees of phase shift, and the impedance discontinuity between the coil and the stinger provides a point phase shift that makes up the difference between 38 degrees and 90 degrees. As I hammer away at this concept, I am wondering if a loaded mobile antenna can be optimized if only the correct model is adopted. Is a high-Q loading-coil always better than a loading-coil with a lower Q? Are fat/short loading- coils always better than skinny/long loading-coils? Some field measurements have cast doubt on some long-held concepts. But obviously the question cannot be answered as long as some people insist on using the lumped circuit model for the loading coil, e.g. virtually zero delay through the coil. I have measured the delay through a 75m bugcatcher coil. It was approximately 25 nS, a magnitude greater than w8ji's "measurements". It doesn't matter if my measurements were off by 20%. The magnitude difference between my measurements and w8ji's "measurements" is too significant to be ignored. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
Loading coils: was Dish reflector
Roy Lewallen wrote:
A single conductor doesn't have a characteristic impedance -- it's the impedance between the two conductors of a transmission line. You can measure a characteristic impedance between, say, a coil and ground, but its value depends on the spacing between the two. If the coil is tilted with respect to the ground, the impedance of this two-conductor system will change with the position along the coil. Roy: I understand what you are saying. But the derivation of Characteristic Impedance in the Corum Bros. paper depends only on the coil dimensions and number of turns; it is independent of any relationship to other conductors or groundplanes. I also note that ON4AA's inductance calculator predicts the "Characteristic impedance of n=0 sheath helix waveguide mode at design frequency" based purely on the coil geometry. The maths is a bit beyond me (trying to solve Maxwell's equations for a solenoidal helix), but seems to bear analogy to the derivation of the characteristic impedance of a waveguide. I'm inclined to try to understand it better, because it's this derived Characteristic Impedance, along with the axial Velocity Factor, that generates the reactance values which seem such a good match to experimental and modelled results. Regards, Steve G3TXQ |
Loading coils: was Dish reflector
steveeh131047 wrote:
I'm inclined to try to understand it better, because it's this derived Characteristic Impedance, along with the axial Velocity Factor, that generates the reactance values which seem such a good match to experimental and modeled results. Steve, you will find some old-fashioned concepts here based on the lumped-circuit model rather than the distributed network EM wave reflection model. One can easily disprove the assertion that a single wire in free space doesn't have a characteristic impedance by asking the question: Does a single electromagnetic wave traveling through free space (without a wire) encounter a characteristic impedance? If so, why doesn't a single wave traveling through a wire in free space encounter a characteristic impedance? Of course, the ratio of the electric field to the magnetic field, whatever that turns out to be, is the characteristic impedance of a single wire in free space. It, like the characteristic impedance of free space, seems to be a few hundred ohms. There are lots of old wives tales asserted by the gurus on this newsgroup. One must be careful what one accepts as technical fact. "A single conductor doesn't have a characteristic impedance." is a preposterous assertion. If free space itself has a characteristic impedance, what are the chances that a single wire in free space would not have a characteristic impedance??? Zero, at best??? :-) Some will say: "Where is the return path for the current?" I will respond: Where is the return path for the "current" arriving from the Sun that can be captured by a solar panel? Good Grief! -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
Loading coils: was Dish reflector
On Apr 23, 3:21*pm, Cecil Moore wrote:
I have measured the delay through a 75m bugcatcher coil. It was approximately 25 nS, a magnitude greater than w8ji's "measurements". It doesn't matter if my measurements were off by 20%. The magnitude difference between my measurements and w8ji's "measurements" is too significant to be ignored. Cecil: that's a very significant result. If I feed the dimensions of W8JI's coil into Equation 32 in the Corum Bros. paper it predicts an axial Velocity Factor of 0.33. That would equate to a delay across the 10" long coil of 24.7nS !!!!! Regards, Steve G3TXQ |
Loading coils: was Dish reflector
On Apr 23, 3:21*pm, Cecil Moore wrote:
I have measured the delay through a 75m bugcatcher coil. It was approximately 25 nS, a magnitude greater than w8ji's "measurements". It doesn't matter if my measurements were off by 20%. The magnitude difference between my measurements and w8ji's "measurements" is too significant to be ignored. Cecil: that's a VERY significant result. If I feed the dimensions of W8JI's coil into Equation 32 in the Corum Bros paper it predicts an axial Velocity Factor of 0.033. That would equate to a time delay of 24.7nS across the 10" long coil !!!! Regards, Steve G3TXQ |
Loading coils: was Dish reflector
steveeh131047 wrote:
On Apr 23, 3:21 pm, Cecil Moore wrote: I have measured the delay through a 75m bugcatcher coil. It was approximately 25 nS, a magnitude greater than w8ji's "measurements". It doesn't matter if my measurements were off by 20%. The magnitude difference between my measurements and w8ji's "measurements" is too significant to be ignored. Cecil: that's a very significant result. If I feed the dimensions of W8JI's coil into Equation 32 in the Corum Bros. paper it predicts an axial Velocity Factor of 0.33. That would equate to a delay across the 10" long coil of 24.7nS !!!!! Of course, you mean *0.033* for the VF of w8ji's coil which was 10tpi, 100turn, 2" dia. 10"/12/0.033 = 25 feet equivalent to straight wire. The VF of my Texas Bugcatcher coil is 0.02. It has 4tpi, 26turn, 6" dia. 6"/12/0.02 = 25 feet equivalent to straight wire. These two coils have essentially equal delays at 4 MHz. They are each very close to 0.1WL, i.e. 36 degrees. The delay for one wavelength at 4 MHz is 250.5 nS so each coil would have a delay of 1/10 that value or 25 nS. Everything fits the model. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
Loading coils: was Dish reflector
steveeh131047 wrote:
Cecil: that's a VERY significant result. If I feed the dimensions of W8JI's coil into Equation 32 in the Corum Bros paper it predicts an axial Velocity Factor of 0.033. That would equate to a time delay of 24.7nS across the 10" long coil !!!! One of the problems with this newsgroup is that one cannot edit one's posting like one can over on QRZ.com. I see you have corrected your earlier typo. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
Loading coils: was Dish reflector
steveeh131047 wrote:
I've read various web pages and postings which argue qualitatively that things like "distributed capacitance" might explain some of the observations, but as yet I've seen no quantitative analysis which attempts to predict the numbers. Hi Steve, For a more quantitative illustration of how distributed reactance in transmission lines causes delay see http://www.rhombus-ind.com/dlcat/app1_pas.pdf 73, ac6xg |
Loading coils: was Dish reflector
On Apr 23, 9:21*am, Cecil Moore wrote:
Art Unwin wrote: The problem *in this debate is that others are concentrating on resonance where as you are thinking in terms of anti resonance which portends to a higher impedance and also the condition of equilibrium. I apologize if I gave you that idea, Art. I am talking about a physically short (38 degrees), electrically 1/4WL (90 degrees) *resonant* antenna over mininec ground. The feedpoint impedance is low and resistive. In the example given, the stinger supplies 19 degrees of phase shift, the base-loading coil supplies 19 degrees of phase shift, and the impedance discontinuity between the coil and the stinger provides a point phase shift that makes up the difference between 38 degrees and 90 degrees. As I hammer away at this concept, I am wondering if a loaded mobile antenna can be optimized if only the correct model is adopted. Is a high-Q loading-coil always better than a loading-coil with a lower Q? Are fat/short loading- coils always better than skinny/long loading-coils? Some field measurements have cast doubt on some long-held concepts. But obviously the question cannot be answered as long as some people insist on using the lumped circuit model for the loading coil, e.g. virtually zero delay through the coil. I have measured the delay through a 75m bugcatcher coil. It was approximately 25 nS, a magnitude greater than w8ji's "measurements". It doesn't matter if my measurements were off by 20%. The magnitude difference between my measurements and w8ji's "measurements" is too significant to be ignored. -- 73, Cecil, IEEE, OOTC, *http://www.w5dxp.com Exactly. !/4WL is not in equilibrium,a full wave length is and that is where you are argueing past each other. Radiation is the accelleration of a charge or a particle of energy. A half wave accelerates a charge and the second half replaces the static particle that created the facilities for the next radiation or application of charge. If you only use a portion of the period then you are messing with the speed of light. The speed of light is the time it takes for a magnetic field to be produced and the time it takes for a magnetic field to decay which also equals the time that it takes for an electric field to be formed and decay the sum time of both being a period or the speed of time. Thus a WL is equal to equilibrium and less than that is not. Maxwells laws are valid ONLY when equilibrium is present, thus the quarrelling between the two parties. Embroiled in the middle of that is the misconception of standing waves. A charged particle changes direction and then returns to the starting point to constitute a full period. If you have a 1/4 wave the charge continues its direction until half a period has passed and only then can particles be collected for sunsequent acceleration and radiation. So for half the time or 1/4 of the time for a 1/4 WL is the radiating at an angle i.e the addition of two vectors,forward and displacement current, the rest of the time the remaining charge is the accelleration of the charge continuing off of the end of the radiator ( not bouncing back) where the energy is seen as a spark or straight line radiation. So Cecil the debate in fact is over a series of misconceptions resulting from the omission of equilibrium which makes both sides of the debate invalid. Regards Art |
Loading coils: was Dish reflector
steveeh131047 wrote:
Cecil: that's a VERY significant result. If I feed the dimensions of W8JI's coil into Equation 32 in the Corum Bros paper it predicts an axial Velocity Factor of 0.033. That would equate to a time delay of 24.7nS across the 10" long coil !!!! Regards, Steve G3TXQ Hi Steve, You're right. The numbers are amazingly close - almost as if his 'experimental apparatus' had calculated the result rather than measure it. 73, ac6xg |
Loading coils: was Dish reflector
On Apr 23, 10:07*am, Cecil Moore wrote:
steveeh131047 wrote: I'm inclined to try to understand it better, because it's this derived Characteristic Impedance, along with the axial Velocity Factor, that generates the reactance values which seem such a good match to experimental and modeled results. Steve, you will find some old-fashioned concepts here based on the lumped-circuit model rather than the distributed network EM wave reflection model. One can easily disprove the assertion that a single wire in free space doesn't have a characteristic impedance by asking the question: Does a single electromagnetic wave traveling through free space (without a wire) encounter a characteristic impedance? If so, why doesn't a single wave traveling through a wire in free space encounter a characteristic impedance? Of course, the ratio of the electric field to the magnetic field, whatever that turns out to be, is the characteristic impedance of a single wire in free space. It, like the characteristic impedance of free space, seems to be a few hundred ohms. There are lots of old wives tales asserted by the gurus on this newsgroup. One must be careful what one accepts as technical fact. "A single conductor doesn't have a characteristic impedance." is a preposterous assertion. If free space itself has a characteristic impedance, what are the chances that a single wire in free space would not have a characteristic impedance??? Zero, at best??? :-) Some will say: "Where is the return path for the current?" I will respond: Where is the return path for the "current" arriving from the Sun that can be captured by a solar panel? Good Grief! -- 73, Cecil, IEEE, OOTC, *http://www.w5dxp.com Cecil, reference you comment that a straight wire does NOT have a characteristic impedance, this is one place where you misunderstanding things. A charge rests on the surface and when it is radiating it instantly is removed from the surface by the displacement current in coordination with the applied current. If the radiator is not a full wave length there is no surface for a displacement current to exist thus the direction of charge is not elevated away from the surface but continuing the parallel to the surface direction which is the observed as "end effect" If the concept of a bounce back of charge was maintained then the amount of charge must also change as time revolves around a full period where eventually the charge totally reaches the scource when the bouncing around coincided with a period. Thus if the charge is in "standing wave" form the impedance changes during every circuit of the charge back to the source and that can never be. Characteristic impedance is that seen only with a closed anti resonant point or in other words at the point of equilibrium which is represented by a period. Looking at things from a different angle, when the time varying field becomes a constant which is then the application of DC then you have a tesla coil where the spark or energy and thus radiation is parallel to the conductor and where the period covered by over shoot, a one time event, where radio radiation is shown by the area of the curve during the time of that event. Best regards Art |
Loading coils: was Dish reflector
On Apr 23, 4:42*pm, Jim Kelley wrote:
For a more quantitative illustration of how distributed reactance in transmission lines causes delay seehttp://www.rhombus-ind.com/dlcat/app1_pas.pdf 73, ac6xg Jim, thanks for the reference. Perhaps I should have expressed myself more clearly. What I've not seen, for example, is a lumped-element analysis which takes just the coil dimensions as input, and predicts theoretically - without a lot of empirical "tweaking" - the reactance at a particular frequency; particularly a frequency close to self-resonance. There may be one out there, but I've not yet found it! In contrast, the ON4AA calculator - based on Corums' transmission-line analysis - does just that, and produces results which seem to match well the EZNEC modelling results. Regards, Steve G3TXQ |
Loading coils: was Dish reflector
On Apr 23, 11:16*am, Art Unwin wrote:
On Apr 23, 10:07*am, Cecil Moore wrote: steveeh131047 wrote: I'm inclined to try to understand it better, because it's this derived Characteristic Impedance, along with the axial Velocity Factor, that generates the reactance values which seem such a good match to experimental and modeled results. Steve, you will find some old-fashioned concepts here based on the lumped-circuit model rather than the distributed network EM wave reflection model. One can easily disprove the assertion that a single wire in free space doesn't have a characteristic impedance by asking the question: Does a single electromagnetic wave traveling through free space (without a wire) encounter a characteristic impedance? If so, why doesn't a single wave traveling through a wire in free space encounter a characteristic impedance? Of course, the ratio of the electric field to the magnetic field, whatever that turns out to be, is the characteristic impedance of a single wire in free space. It, like the characteristic impedance of free space, seems to be a few hundred ohms. There are lots of old wives tales asserted by the gurus on this newsgroup. One must be careful what one accepts as technical fact. "A single conductor doesn't have a characteristic impedance." is a preposterous assertion. If free space itself has a characteristic impedance, what are the chances that a single wire in free space would not have a characteristic impedance??? Zero, at best??? :-) Some will say: "Where is the return path for the current?" I will respond: Where is the return path for the "current" arriving from the Sun that can be captured by a solar panel? Good Grief! -- 73, Cecil, IEEE, OOTC, *http://www.w5dxp.com Cecil, reference you comment that a straight wire does NOT have a characteristic impedance, this is one place where you misunderstanding things. A charge rests on the surface and when it is radiating it instantly is removed from the surface by the displacement current in coordination with the applied current. If the radiator is not a full wave length there is no surface for a displacement current to exist thus the direction of charge is not elevated away from the surface but continuing the parallel to the surface direction which is the observed as "end effect" If the concept of a bounce back of charge was maintained then the amount of charge must also change as time revolves around a full period where eventually the charge totally reaches the scource when the bouncing around coincided with a period. Thus if the charge is in "standing wave" form the impedance changes during every circuit of the charge back to the source and that can never be. Characteristic impedance is that seen only with a closed anti resonant point or in other words at the point of equilibrium which is represented by a period. Looking at things from a different angle, when the time varying field becomes a constant which is then the application of DC then you have a tesla coil where the spark or energy and thus radiation is parallel to the conductor and where the period covered by over shoot, a one time event, where radio radiation is shown by the area of the curve during the time of that event. Best regards Art Cecil, You based your proof of a magnetic wave in a vacuum but it is an accelerating charge which obviously must have mass, that is radiation ala the particle. If you have a Tesla set up in a vacuum the speed of the particle/spark/ light is the approximation of the speed of light.( I say approximation since I am using the metric of Earth's vacuum and not that of the Universe) The velocity factor is the true ratio of the mismatch with the travel of a electric current on Earth with all its relavent factors and comparing it to the speed of light in the average metric of vacuum of the Universe. Bottom line is particles are part of radiation as is light, "waves" are not involved other than a bevy of particles separated by a fraction of a period. Art |
Loading coils: was Dish reflector
On Apr 23, 11:26*am, steveeh131047 wrote:
On Apr 23, 4:42*pm, Jim Kelley wrote: For a more quantitative illustration of how distributed reactance in transmission lines causes delay seehttp://www.rhombus-ind.com/dlcat/app1_pas.pdf 73, ac6xg Jim, thanks for the reference. Perhaps I should have expressed myself more clearly. What I've not seen, for example, is a lumped-element analysis which takes just the coil dimensions as input, and predicts theoretically - without a lot of empirical "tweaking" - the reactance at a particular frequency; particularly a frequency close to self-resonance. There may be one out there, but I've not yet found it! In contrast, the ON4AA calculator - based on Corums' transmission-line analysis - does just that, and produces results which seem to match well the EZNEC modelling results. Regards, Steve G3TXQ That is because the transmission line is considered to be within a arbitrary boundary where all applicable forces equals zero, ie in equilibrium. Eznec is also based on the condition of equilibrium as applied by Maxwell in concert with Newton. This group is using the conditions accounted on this Earth where as scientific laws are based upon a Universe within a boundary and not just the Earth. TRhat is equivalent to saying weight is the same metric as mass ! Art |
Loading coils: was Dish reflector
steveeh131047 wrote:
On Apr 23, 4:42 pm, Jim Kelley wrote: For a more quantitative illustration of how distributed reactance in transmission lines causes delay seehttp://www.rhombus-ind.com/dlcat/app1_pas.pdf 73, ac6xg Jim, thanks for the reference. Perhaps I should have expressed myself more clearly. What I've not seen, for example, is a lumped-element analysis which takes just the coil dimensions as input, and predicts theoretically - without a lot of empirical "tweaking" - the reactance at a particular frequency; particularly a frequency close to self-resonance. There may be one out there, but I've not yet found it! In contrast, the ON4AA calculator - based on Corums' transmission-line analysis - does just that, and produces results which seem to match well the EZNEC modelling results. Regards, Steve G3TXQ EZNEC is a mathematical model just as the transmission line model is a model. EZNEC doesn't use a transmission line analog in order to reach its conclusions. If you're really interested in this subject, you have to read Schelkunoff and others who did the research on this years ago. A big, honking loading coil doesn't act much like a lumped component. It makes a pretty shabby transmission line, too. If you want to understand it, you have to study electromagnetics and approach it from that standpoint, which may not be easy. Finally, a modest question: if you have EZNEC, why would you be wasting time with something inferior? The gold standard is the gold standard. Or are you on some philosophical quest, like Cecil? 73, Tom Donaly, KA6RUH |
Loading coils: was Dish reflector
On Apr 23, 12:22*pm, Art Unwin wrote:
On Apr 23, 11:16*am, Art Unwin wrote: On Apr 23, 10:07*am, Cecil Moore wrote: steveeh131047 wrote: I'm inclined to try to understand it better, because it's this derived Characteristic Impedance, along with the axial Velocity Factor, that generates the reactance values which seem such a good match to experimental and modeled results. Steve, you will find some old-fashioned concepts here based on the lumped-circuit model rather than the distributed network EM wave reflection model. One can easily disprove the assertion that a single wire in free space doesn't have a characteristic impedance by asking the question: Does a single electromagnetic wave traveling through free space (without a wire) encounter a characteristic impedance? If so, why doesn't a single wave traveling through a wire in free space encounter a characteristic impedance? Of course, the ratio of the electric field to the magnetic field, whatever that turns out to be, is the characteristic impedance of a single wire in free space. It, like the characteristic impedance of free space, seems to be a few hundred ohms. There are lots of old wives tales asserted by the gurus on this newsgroup. One must be careful what one accepts as technical fact. "A single conductor doesn't have a characteristic impedance." is a preposterous assertion. If free space itself has a characteristic impedance, what are the chances that a single wire in free space would not have a characteristic impedance??? Zero, at best??? :-) Some will say: "Where is the return path for the current?" I will respond: Where is the return path for the "current" arriving from the Sun that can be captured by a solar panel? Good Grief! -- 73, Cecil, IEEE, OOTC, *http://www.w5dxp.com Cecil, reference you comment that a straight wire does NOT have a characteristic impedance, this is one place where you misunderstanding things. A charge rests on the surface and when it is radiating it instantly is removed from the surface by the displacement current in coordination with the applied current. If the radiator is not a full wave length there is no surface for a displacement current to exist thus the direction of charge is not elevated away from the surface but continuing the parallel to the surface direction which is the observed as "end effect" If the concept of a bounce back of charge was maintained then the amount of charge must also change as time revolves around a full period where eventually the charge totally reaches the scource when the bouncing around coincided with a period. Thus if the charge is in "standing wave" form the impedance changes during every circuit of the charge back to the source and that can never be. Characteristic impedance is that seen only with a closed anti resonant point or in other words at the point of equilibrium which is represented by a period. Looking at things from a different angle, when the time varying field becomes a constant which is then the application of DC then you have a tesla coil where the spark or energy and thus radiation is parallel to the conductor and where the period covered by over shoot, a one time event, where radio radiation is shown by the area of the curve during the time of that event. Best regards Art Cecil, You based your proof of a magnetic wave in a vacuum but it is an accelerating charge which obviously must have mass, that is radiation ala the particle. If you have a Tesla set up in a vacuum the speed of the particle/spark/ light is the approximation of the speed of light.( I say approximation since I am using the metric of Earth's vacuum and not that of the Universe) The velocity factor is the true ratio of the mismatch with the travel of a electric current on Earth with all its relavent factors and comparing it to the speed of light in the average metric of vacuum of the Universe. Bottom line is particles are part of radiation as is light, "waves" are not involved other than a bevy of particles separated by a fraction of a period. Art When students perform an experiment to proove the laws of Nature it really does belittle seeing is believing. To change the statistics of what we are seeing which is the situation on Earth, this alludes the"relative" term of Einstein, then to bring what we deduced by seeing by the conversion of weight to mass. This correction thus brings in to focus what Einstein meant by relativity because it depends on the gravitational pull relative to what part of the Universe the experiment was performed. What we term as Classical physics is the behavior of the Universe and the laws that govern it. Thus mass is the carrier of potential energy where decay is synonamous with the break off of a particle which contains a portion of the potential energy where the brake off is the decelleration of the partical when it enters a different gravitational field and thus turns to kinetic energy and where this change is seen as light i.e Kinetic energy that is transformed to heat which also governs light. Thus when considering a perfect conductor ie zero resistance which is also a measure of the datum level of zero movement of electrons within mass there is zero movement within mass to affect the passage of current and thus the current travels at the speed of light. When temperature in not at the datum level it is the movement of electron within mass that provides the resistance to current flow and thus we have what is known as the "velocity factor", and it is the circular movement of displacement current which is also a movement of current flow that applies what we know as displacement current. Thus there is a Universal law of nature because all things revolve about the relative movement of particles compared to that of a static particle which if the change is instantaneous we have what Hawkings calls the BIG BANG. All of the above emphasises where all the participants of this thread are argueing about the same problem but from different relative positions within the Universe Lesson. All scientific debate is correlated to the whole of the Universe and not the metric datum of vacuum as represented by the size of a arbitrary fieldwithin the Universe This is what is meant by CLASSICAL PHYSICS. Enuff said. Art Unwin |
Loading coils: was Dish reflector
steveeh131047 wrote:
Cecil: that's a VERY significant result. If I feed the dimensions of W8JI's coil into Equation 32 in the Corum Bros paper it predicts an axial Velocity Factor of 0.033. That would equate to a time delay of 24.7nS across the 10" long coil !!!! Regards, Steve G3TXQ Let's see how well the principles involved are understood. What is the delay through a physically very small toroidal coil with the same inductance as the solenoidal coil? Why? Roy Lewallen, W7EL |
Loading coils: was Dish reflector
Jim Kelley wrote:
steveeh131047 wrote: Cecil: that's a VERY significant result. If I feed the dimensions of W8JI's coil into Equation 32 in the Corum Bros paper it predicts an axial Velocity Factor of 0.033. That would equate to a time delay of 24.7nS across the 10" long coil !!!! You're right. The numbers are amazingly close - almost as if his 'experimental apparatus' had calculated the result rather than measure it. Why do you say "approximately 25 nS" and 24.7 nS are amazingly close? "Approximately 25 nS" might include an unknown measurement inaccuracy. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
Loading coils: was Dish reflector
Art Unwin wrote:
Cecil, reference you comment that a straight wire does NOT have a characteristic impedance, this is one place where you misunderstanding things. That quote was not mine, Art, it was Roy's. My argument is that since free space itself has a characteristic impedance then a wire in free space must also have a characteristic impedance and act as a waveguide of sorts. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
Loading coils: was Dish reflector
On Apr 23, 1:34*pm, "Tom Donaly" wrote:
steveeh131047 wrote: On Apr 23, 4:42 pm, Jim Kelley wrote: For a more quantitative illustration of how distributed reactance in transmission lines causes delay seehttp://www.rhombus-ind.com/dlcat/app1_pas.pdf 73, ac6xg Jim, thanks for the reference. Perhaps I should have expressed myself more clearly. What I've not seen, for example, is a lumped-element analysis which takes just the coil dimensions as input, and predicts theoretically - without a lot of empirical "tweaking" - the reactance at a particular frequency; particularly a frequency close to self-resonance. There may be one out there, but I've not yet found it! In contrast, the ON4AA calculator - based on Corums' transmission-line analysis - does just that, and produces results which seem to match well the EZNEC modelling results. Regards, Steve G3TXQ EZNEC is a mathematical model just as the transmission line model is a model. EZNEC doesn't use a transmission line analog in order to reach its conclusions. If you're really interested in this subject, you have to read Schelkunoff and others who did the research on this years ago. A big, honking loading coil doesn't act much like a lumped component. It makes a pretty shabby transmission line, too. If you want to understand it, you have to study electromagnetics and approach it from that standpoint, which may not be easy. Finally, a modest question: if you have EZNEC, why would you be wasting time with something inferior? The gold standard is the gold standard. Or are you on some philosophical quest, like Cecil? 73, Tom Donaly, KA6RUH Tom,TomTom. Eznec DOES use the transmission line analogy because like Gauss it uses an abitrary border where the contents are in equilibriumn or in a state of balance where all forces are accounted for when a time varying field is applied. The same goes for a transmission line where the radiation factor is also accounted for. The radiation force losses are accounted for by the depreciating impedance with time which is also shown by the deprecating amplitude of occilation where each period loss of amplitude represents radiation energy. If the amplitude showed no change then you have a tank circuit without friction or other losses. No losses means perpetual motion and vica versa. If on Earth friction is always there which is also equal to the energy for an acceleration of a particle. On the reverse side, a deccelerating force on a particle represents kinetic energy as opposed to the potential energy supplied for radiation where the product is seen as light. As with a light bulb radiant heat is what we know as light. Just classical physics no less Art |
Loading coils: was Dish reflector
On Apr 23, 7:34*pm, "Tom Donaly" wrote:
Finally, a modest question: if you have EZNEC, why would you be wasting time with something inferior? The gold standard is the gold standard. Or are you on some philosophical quest, like Cecil? Tom, Yes I have EZNEC and recognise what a great tool it is. Its predictions were the benchmark against which I tested the various coil models I read about, and no-one has yet suggested that it can't be trusted for modelling a helix. I'm not on some "philosophical quest" - I'm just an old, retired, guy who still likes learning and wants to understand more about how things work; I hope that never leaves me! I stumbled on this discussion quite by chance and tried to understand the various "positions" being taken. Perhaps I'm over-simplifying, but it seemed to me there was a group who favoured the transmission-line model and a group against it. I've tried dispassionately to understand the various arguments and to form my own conclusions. Now here's my problem: * The results I get using a model based on transmission-line analysis are very close to my EZNEC predictions - not perfect, but way better than any lumped-element analysis results * I don't see quantitative, non-empirical, arguments being put forward to support lumped-element analysis * I see numeric arguments being put forward by Cecil to support a transmission-line approach - they look convincing to me and, although I see a lot of unpleasant personal attacks on him, I don't see any scientific challenge to his figures * On the other hand I see folk whose work I rate highly, seemingly willfully to misunderstand some of the points which Cecil puts forward Please don't think I'm trying to defend Cecil - I wouldn't be so presumptuous, and anyway he's old enough to look after himself! I'm just trying to understand why, what seems to me to be such a persuasive argument, generates such opposition. Either there's some glaring technical error here which I haven't yet spotted, or perhaps there's a long "history" between various "personalities" of which I'm ignorant? Still confused, Steve G3TXQ |
Loading coils: was Dish reflector
steveeh131047 wrote:
In contrast, the ON4AA calculator - based on Corums' transmission-line analysis - does just that, and produces results which seem to match well the EZNEC modelling results. I don't see where that calculator gives the Z0 and VF of the loading coil so I have generated an EXCEL file that gives those two parameters based on the formulas in Dr. Corum's IEEE paper. Note that 75m loading coils are slow-wave devices with a VF in the neighborhood of 0.02 for a Texas Bugcatcher coil or 0.033 for w8ji's skinny 10 TPI, 2" diameter coil. http://www.w5dxp.com/CoilZ0VF.xls -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
Loading coils: was Dish reflector
Cecil Moore wrote:
Jim Kelley wrote: steveeh131047 wrote: Cecil: that's a VERY significant result. If I feed the dimensions of W8JI's coil into Equation 32 in the Corum Bros paper it predicts an axial Velocity Factor of 0.033. That would equate to a time delay of 24.7nS across the 10" long coil !!!! You're right. The numbers are amazingly close - almost as if his 'experimental apparatus' had calculated the result rather than measure it. Why do you say "approximately 25 nS" and 24.7 nS are amazingly close? I was being facetious. "Approximately 25 nS" might include an unknown measurement inaccuracy. There's that, and as any good dry labber knows, it's a dead giveaway to report a precision greater than one can actually measure. :-) 73, ac6xg |
Loading coils: was Dish reflector
Tom Donaly wrote:
Finally, a modest question: if you have EZNEC, why would you be wasting time with something inferior? The gold standard is the gold standard. Perhaps more the silver or electrum standard. EZNEC doesn't do dielectric loading, for instance. (unless you get the Nec4 engine from Roy) And, it's a MoM code, so things not well represented by collections of wires aren't necessarily modeled well. |
Loading coils: was Dish reflector
On Apr 23, 2:29*pm, Roy Lewallen wrote:
* steveeh131047 wrote: Cecil: that's a VERY significant result. If I feed the dimensions of W8JI's coil into Equation 32 in the Corum Bros paper it predicts an axial Velocity Factor of 0.033. That would equate to a time delay of 24.7nS across the 10" long coil !!!! Regards, Steve G3TXQ Let's see how well the principles involved are understood. What is the delay through a physically very small toroidal coil with the same inductance as the solenoidal coil? Why? Roy Lewallen, W7EL A toroidal coil retains magnetism via hysteresis versus zero hysteresis for a coil made of a diamagnetic material. A coil is in equilibrium because all forces are accounted for over one or more periods. A toroidal coil is not in equilibrium because the energy that provides the hysterisis happens only once per unit of time where as for equilibrium that same energy is provided for every period and cancelled by same. If a unit of energy is supplied to a radiator in equilibrium then the unit of energy must be added to or increased to represent the hysteresis lossesof the toroid The ratio of the original unit of energy will represent the difference in time or delay required to represent balance between the two. The above is based on a coil in the medium of air and not magnetic core as the term "solenoid" suggests. Roy doesn't see my posts either so somebody else has to pass this on. Art |
Loading coils: was Dish reflector
Roy Lewallen wrote:
steveeh131047 wrote: Cecil: that's a VERY significant result. If I feed the dimensions of W8JI's coil into Equation 32 in the Corum Bros paper it predicts an axial Velocity Factor of 0.033. That would equate to a time delay of 24.7nS across the 10" long coil !!!! Regards, Steve G3TXQ Let's see how well the principles involved are understood. What is the delay through a physically very small toroidal coil with the same inductance as the solenoidal coil? Why? As in a coil wound on a toroidal magnetic core? or a air cored solenoid bent in a circle? |
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