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Loading Coils; was : Vincent antenna
On Sun, 02 Dec 2007 14:34:23 -0600, Cecil Moore
wrote: I don't know about Art, Richard, but I detest your trying to mind fornicate with me. A contorted sentiment suitable for a schoolgirl's diary. :-0 I do believe we are discussing the delay characteristic of current in a coil. How does a Texas bumpkin manage to strain through two such heavily mannered expressions? Surprise us with a chorus of "Feelings" and maybe it will be you who gets rolled out of the nest. |
Loading Coils; was : Vincent antenna
Owen Duffy wrote in
: A further issue is the accuracy of the estimate of the coil's electrical length when represented as a transmission line. Using the length of the wire in the coil (as is sometimes done) is too simplistic. The Corum paper referenced at the calculator above describes a method that appears to be more reliable. I should have added... but what are you going to do with a more accurate estimate of the equivalent electrical length of the coil anyway? Owen |
Loading Coils; was : Vincent antenna
Owen Duffy wrote:
One of the proponents posted on eham, the following solution to a loading coil for 160m: "The VF of a 6" dia., 4 TPI coil on 160m would be about 0.02. Whatever number of degrees you want the coil to occupy, wind it accordingly.", note the independence of coil size and location on the monopole. HUH??? THE LENGTH OF THE COIL IS NOT INDEPENDENT OF COIL SIZE!!! THE LOCATION ON THE MONOPOLE IS NOT INDEPENDENT OF LOCATION!!! The number of turns is dependent on coil size needed. The number of degrees required is dependent upon location. Please reread what I wrote until you understand those facts. A greater number of degrees is obviously needed for center- loading than for base-loading. This concept is extremely easy to demonstrate in a an open-circuit stub. ************************************************** ************* When the Z0 at the impedance discontinuity *increases*, electrical degrees are *lost*. When the Z0 at the impedance discontinuity *decreases*, electrical degrees are *gained*. ************************************************** ************* For a base-loaded mobile antenna, electrical degrees are *gained* at the coil to stinger junction. For a center-loaded mobile antenna, electrical degrees are *lost* at the base element to coil junction and *gained* at the coil to stinger junction. Therefore, a center-loading coil has to be longer than a base-loaded coil - all other dimensions being equal. It is really simple transmission line analysis. Please perform the following exercise to understand the concepts involved. Example 1: ---600 ohm line---+---100 ohm line---open-circuit The 100 ohm line is 10 degrees long. How many degrees does the 600 ohm line have to occupy to be equivalent to a 1/4WL stub? Example 2: --100 ohm line--+--600 ohm line--+--100 ohm line--open-circuit Each section of 100 ohm line is 5 degrees long, the same 10 degrees of total length as the 100 ohm line in the first example. How many degrees does the 600 ohm line have to occupy to be equivalent to a 1/4WL stub? Hint: In the second example, the 600 ohm line will need to be a lot longer because we have moved it from the base of the stub to the center of the stub. Does this sound like what happens when we move a coil from the base to the center of a mobile antenna? When one understands the above examples based on simple transmission line stubs, one will understand what is happening inside a loaded mobile antenna (but Richard, this has nothing to do with radiation patterns). -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
Earlier, I wrote:
AI4QJ wrote: In an inductor, current lags voltage. If you connect a resitor and a coil in parallel and apply AC, EE101 tells you that, although the phase of the voltage across them stays the same, the current is "delayed" by the phase angle in the inductor when compared to current resistor. No, it isn't - the phase of the current around the circuit has to stay the same. Think of the simplest possible circuit: an AC voltage source (of zero internal impedance) with one terminal wired to R, lumped L in series, and directly back to the other terminal of the AC source. If the phase of the current were delayed through L as you suggest, there would then be a difference in phase between the two terminals of the AC source... which is obviously not true. It's the magnitude and phase of the voltage that varies at different points around the circuit; but the magnitude and phase of the current has to remain the same all the way around the loop. In more formal terms, Kirchhoff's current law applies all around the circuit; and it most certainly applies between the two terminals of a lumped inductance. My apologies to AI4QJ. He was talking about a parallel R-L circuit, and my reply was about a series R-L circuit. Each of our statements was correct in its own context. Thanks to Tom B for pointing this out. -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Loading Coils; was : Vincent antenna
John Smith wrote:
[stuff] Cecil Moore wrote: [more stuff] John Smith wrote: [even more stuff] Cecil: When one is well armored and prepared to face the slings are arrows of the religiously devout, one is able to contemplate and verbalize personal visions/guess/questions of how the capacitive coupling and EM coupling between turns in a humble-multi-turn coil might REALLY be acting/interacting ... indeed, some may desire accurate formula to describe this in finite detail, those I find are only "ball-park." Perhaps an area for dreamers--I simply find it keeps me from bars and loose women! :-P Regards, JS |
Loading Coils; was : Vincent antenna
Owen Duffy wrote:
The key thing is that the transmission line solution passes to lumped elements when the coil length is sufficiently short, so they are not inconsistent. It is questionable whether the transmission line solution is worth the trouble for short coils. That's a Catch-22, Owen. All lumped coils are short. Therefore, the transmission line solution is never needed. A 160m bugcatcher coil is *NOT* short!!!! It is an appreciable percentage of the delay through the 10 foot long mobile antenna. -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
Ian White GM3SEK wrote:
- the phase of the current around the circuit has to stay the same. Only in a standing-wave environment. The phase of the current does NOT stay the same in a traveling-wave environment. That is the key technical fact that the r.r.a.a gurus have been missing and it can be blamed directly on the short-cut models which deviate from reality, sometimes considerably. In a traveling-wave environment, the phase changes every inch around the circuit and I can calculate that phase change for you if you are incapable of doing it for yourself. -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
On Sun, 02 Dec 2007 21:58:34 GMT, Cecil Moore
wrote: Some of the signal skips from coil to coil reducing the phase shift through the coil. In what, about 2-4 ns? Skips along, talk about technically rigorous. This is more schoolgirl diary writing. |
Loading Coils; was : Vincent antenna
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Loading Coils; was : Vincent antenna
Jimmie D wrote:
Isnt the effect of needing more inductance as you go up the antenna related to the fact that there is less capacitance between the coil and the counterpoise? See my stub example posting. It is related to losing electrical degrees at the bottom of the coil. -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
Richard Clark wrote:
Your parenthetical is EXACTLY what devastates the logic of forcing the real inductor to observe a constant angular length according to Cecil's misapplication of the so-called Corum rule. Sorry, that's a falsehood. I said the angular length is within 10% accuracy just as Dr. Corum said. -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
Jimmie D wrote:
If the delay in the coil Cecil has talked about is measured without the appropriate C and R would not this affect the normal parameters of the coil. The delay through a delayline or a loading coil is dependent on more than just L. If the delay is measured using only a traveling-wave, nothing except the coil parameters matter. -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
Richard Clark wrote:
You have proven through a very simple logic that Cecil's fixed angular specification for a coil (a la the prostitution of Corum) fails utterly. OTHERWISE, one coil would have satisfied all placements along the length of the short monopole! Absolute nonsense from an ignorant person. Please perform my stub example calculations and get back to us. Why does it take a longer length of 600 ohm line to perform the resonating function when the 600 ohm line is placed in the middle of the two 5 degree 100 ohm lines rather than at the bottom end of the 10 degree 100 ohm line? Until you understand that simple stub example you are just full of you know what. -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
Jimmie D wrote:
I think most anyone should be able to tell that the loading coil of an 80M mobile antenna is going to make up for most of the delay in the antenna. 3 to 4 nsec is obviously wrong, the problem for me is, where was the mistake made. The mistake was using standing-wave current, devoid of phase, to measure phase. He should have used traveling-wave current but that is hard to come by in a standing-wave antenna. -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
John Smith wrote:
This is most likely a gray area because of the lack of apparatus available to most "normal" amateurs, which can do meaningful measurements ... But what is to explain the lack of mental apparatus available on this newsgroup? :-) -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
Richard Clark wrote:
... Skips along, talk about technically rigorous. This is more schoolgirl diary writing. Oh, I am sure he is quite sorry, if he knew some would be limited of resources and need a detailed "picture", I am sure he would have provided it ... in its' absence: "Skips along", as in some portion of the signal is coupled to adjacent turns in the form of capacitve coupling, this leads the signal being carried the wire. Another portion of the signal is coupled to adjacent turns, this lags the signal being carried by the wire--magnetic field follows current--naturally ... Now, I am sure you have a much better picture of what he is inferring .... :-O JS |
Loading Coils; was : Vincent antenna
Richard Clark wrote:
Surprise us with a chorus of "Feelings" and maybe it will be you who gets rolled out of the nest. You are the "Feelings" guru, Richard. To you, I admit, I cannot even hold a candle. -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
Owen Duffy wrote:
I should have added... but what are you going to do with a more accurate estimate of the equivalent electrical length of the coil anyway? Prove W8JI absolutely wrong? :-) -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
Richard Clark wrote:
Cecil Moore wrote: Some of the signal skips from coil to coil reducing the phase shift through the coil. In what, about 2-4 ns? No, it increases the VF by roughly 2x in a typical coil. Why don't you already know that fact? -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
Owen Duffy wrote:
It seems reasonable that a stand alone coil can be characterised as a transmission line having a delay that equates to an electrical length in degrees, radians, wavelengths or a velocity factor. In fact the inductance calculator at http://hamwaves.com/antennas/inductance.html is based on that approach and shows the calculated value of Beta. But, but, but, Owen, the first reference in that web page is the very Corum IEEE paper that I referenced that has been completely and totally debunked by most of the gurus on this newsgroup. -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
Ian White GM3SEK wrote:
My apologies to AI4QJ. He was talking about a parallel R-L circuit, and my reply was about a series R-L circuit. Each of our statements was correct in its own context. Sorry, but your statement is still incorrect. In a traveling-wave circuit, the current phase varies every inch along the circuit path. If it didn't, rhombic antennas wouldn't work. -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
Cecil Moore wrote:
Gene Fuller wrote: As far as I can tell, W8JI did not do any math or other type of analysis to come up with the 3 ns delay. There was some surrounding discussion, but the delay itself was simply read from an instrument. So let me repeat my earlier questions. I previously answered your question in capital letters. What went wrong? Why is that number incorrect? This is about the 20th time that I have explained the error that W8JI made. The signal he used to measure phase shift didn't possess a phase shift. W7EL made the same mistake in his "delay through a loading coil" measurements. When the phase of the total current changes hardly at all from one end of a 1/2WL dipole to the other, that current CANNOT even be used to measure the delay through the wire. Why do you, W8JI, and W7EL think a current with an essentially unchanging phase can be used to measure phase shift? This is all explained on my web page. And for the 21st time, we are talking about delay, not phase shift. That point seems difficult for you to fathom. One of the reasons this entire issue goes on and on is that the terminology is a bit foggier than it might first appear. The revolutionary Corum "n=0 sheath helix waveguide mode" is derived for a single frequency in steady-state conditions. So how does one even define "delay" under that condition? If you add some sort of marker signal, the measurement of "delay" will be for the propagation of that marker signal, not the original underlying steady-state wave. By the way, Corum does not mention delay at all, with one minor exception. 73, Gene W4SZ |
Loading Coils; was : Vincent antenna
Owen Duffy wrote:
[snip] If you use the inductance calculator at http://hamwaves.com/antennas/inductance.html to determine Beta, you get 2.008 rad/m. The coil is .254m long, so that suggests a one-way phase delay of 0.51 rad, or 29.2°. Some suggest that this coil will replace the equivalent electrical length in a quarter wave monopole to shorten it with inductive loading, and irrespective of the position of the loading coil... which is not consistent with experience that a larger loading coil is needed the further it is from the base. Something to consider about the Hamwaves calculator. This Corum calculation appears to analyze everything in terms of the "n=0 sheath helix waveguide mode", whether it is appropriate or not. This web page does not contain any of the caveats that were in the Telsiks article. Try some extreme numbers and you can see that the expected results do not occur. It is somewhat ironic that the work of David Knight, referenced by Corum, appears to refute quite of bit of Corum's claim. Knight recognizes, as many people do, that there is a transition between a lumped model regime and the quarter wave resonance regime. The resonance model does not apply when the coil is shorter or the frequency is lower. 73, Gene W4SZ |
Loading Coils; was : Vincent antenna
Gene Fuller wrote:
And for the 21st time, we are talking about delay, not phase shift. That point seems difficult for you to fathom. They are related in a traveling-wave environment. They are virtually unrelated in a standing-wave environment. W8JI asserts that the delay through a 100T coil at 4 MHz is 3 ns which is impossible. If he had asserted that the standing-wave current undergoes a 4.5 degree phase shift through that coil, we wouldn't be having this argument because the phase of standing-wave current is virtually constant over the length of a 1/2WL dipole. At the ends of a dipole longer than 1/2WL, it does an abrupt 180 degree phase shift. W8JI and W7EL seem to be totally ignorant of that fact of physics since they both tried to use standing- wave current to "measure" phase-shift/delay. -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
Gene Fuller wrote:
Try some extreme numbers and you can see that the expected results do not occur. A 10TPI, 2" dia., 100T coil used on 4 MHz is NOT an extreme example. Why don't you just admit that you and W8JI have been wrong for years and get it over with? -- 73, Cecil http://www.w5dxp.com |
Loading Coils; was : Vincent antenna
Cecil Moore wrote:
Owen Duffy wrote: It seems reasonable that a stand alone coil can be characterised as a transmission line having a delay that equates to an electrical length in degrees, radians, wavelengths or a velocity factor. In fact the inductance calculator at http://hamwaves.com/antennas/inductance.html is based on that approach and shows the calculated value of Beta. But, but, but, Owen, the first reference in that web page is the very Corum IEEE paper that I referenced that has been completely and totally debunked by most of the gurus on this newsgroup. Cecil, I don't believe anyone has actually challenged what Corum *says*. What *has* been challenged is your misreading of the paper, especially the required conditions for the validity of the analysis. 73, Gene W4SZ |
Loading Coils; was : Vincent antenna
Cecil Moore wrote:
Gene Fuller wrote: Try some extreme numbers and you can see that the expected results do not occur. A 10TPI, 2" dia., 100T coil used on 4 MHz is NOT an extreme example. Why don't you just admit that you and W8JI have been wrong for years and get it over with? I never said that condition was extreme. Try the calculator at 40 kHz and see what you get. 73, W4SZ Gene |
Loading Coils; was : Vincent antenna
Cecil Moore wrote:
Gene Fuller wrote: And for the 21st time, we are talking about delay, not phase shift. That point seems difficult for you to fathom. They are related in a traveling-wave environment. They are virtually unrelated in a standing-wave environment. W8JI asserts that the delay through a 100T coil at 4 MHz is 3 ns which is impossible. If he had asserted that the standing-wave current undergoes a 4.5 degree phase shift through that coil, we wouldn't be having this argument because the phase of standing-wave current is virtually constant over the length of a 1/2WL dipole. At the ends of a dipole longer than 1/2WL, it does an abrupt 180 degree phase shift. W8JI and W7EL seem to be totally ignorant of that fact of physics since they both tried to use standing- wave current to "measure" phase-shift/delay. Cecil, As usual you clipped out the interesting part of the message. By the way, saying something is "impossible" is religion, not science. The distance from one end of the coil to the other is clearly within reach without violating the speed of light. 73, Gene W4SZ |
Loading Coils; was : Vincent antenna
Gene Fuller wrote:
Cecil Moore wrote: Gene Fuller wrote: Try some extreme numbers and you can see that the expected results do not occur. A 10TPI, 2" dia., 100T coil used on 4 MHz is NOT an extreme example. Why don't you just admit that you and W8JI have been wrong for years and get it over with? I never said that condition was extreme. Try the calculator at 40 kHz and see what you get. 73, W4SZ Gene Where did the calculator gets its' method/formula/equation(s) from, W8JI :-o Regards, JS |
Loading Coils; was : Vincent antenna
On Sun, 02 Dec 2007 14:23:33 -0800, John Smith
wrote: "Skips along", as in some portion of the signal is coupled to adjacent turns As you admit this is a struggle of concepts, are we talking about picoSeconds? 73's Richard Clark, KB7QHC |
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Richard Clark wrote:
... As you admit this is a struggle of concepts, are we talking about picoSeconds? 73's Richard Clark, KB7QHC Richard: I have no horse in this race ... I am just interested in the discussion. Warm regards, JS |
Loading Coils; was : Vincent antenna
"AI4QJ" wrote in
: .... With the coil in series with its internal resitance, the phase angle of the current will be the same throughout all components in the circuit. Of course with parallel components, the vector sums of the current though each component must follow kirchoff's law. In parallel Then you are doing a lumped element approximation. It is probably adequate for analysis of a short loading coil. That is probably not a suitable method to analyse a helically loaded monopole (where the monopole consists of nothing but a helix). Owen |
Loading Coils; was : Vincent antenna
Owen Duffy wrote:
"AI4QJ" wrote in : ... With the coil in series with its internal resitance, the phase angle of the current will be the same throughout all components in the circuit. Of course with parallel components, the vector sums of the current though each component must follow kirchoff's law. In parallel Then you are doing a lumped element approximation. It is probably adequate for analysis of a short loading coil. That is probably not a suitable method to analyse a helically loaded monopole (where the monopole consists of nothing but a helix). Owen Interesting ... a thought jumps to mind, an equation to determine the "most efficient" pitch/dia-to-length helix, with freq being the determining factor ... esoteric? Maybe. Ahh, perhaps I just wish a break in exoteric knowledge. Regards, JS |
Loading Coils; was : Vincent antenna
On Sun, 02 Dec 2007 17:59:18 -0800, John Smith
wrote: As you admit this is a struggle of concepts, are we talking about picoSeconds? I have no horse in this race ... I am just interested in the discussion. Then you shouldn't lay down on the track. 73's Richard Clark, KB7QHC |
Loading Coils; was : Vincent antenna
On Sun, 02 Dec 2007 22:32:50 GMT, Cecil Moore
wrote: In what, about 2-4 ns? No, it increases the VF by roughly 2x in a typical coil. Why don't you already know that fact? So, 4-8 nS? |
Loading Coils; was : Vincent antenna
Richard Clark wrote:
[quite normal chit--for him] 73's Richard Clark, KB7QHC Don't attempt to jockey another mans' ride, nor temp him to another race/horse ... JS |
Loading Coils; was : Vincent antenna
On Sun, 02 Dec 2007 20:58:45 -0800, John Smith
wrote: Don't attempt to jockey another mans' ride, nor temp him to another race/horse ... Last month when I was in Africa's airports, I heard better English there than I heard when I landed at Dulles. Are you trying to place a bet, or complaining about your shorts? 73's Richard Clark, KB7QHC |
Loading Coils; was : Vincent antenna
Richard Clark wrote:
On Sun, 02 Dec 2007 20:58:45 -0800, John Smith wrote: Don't attempt to jockey another mans' ride, nor temp him to another race/horse ... Last month when I was in Africa's airports, I heard better English there than I heard when I landed at Dulles. Are you trying to place a bet, or complaining about your shorts? 73's Richard Clark, KB7QHC Richard: In all the world, the only person I've run into that even strikes me as the "type" of personality as you possess is my mother in law, thank gawd she has little use for shakespeare--gawd bless her soul ... LOL Regards, JS |
Loading Coils; was : Vincent antenna
On Dec 2, 2:02 pm, Cecil Moore wrote:
... In a traveling-wave environment, the phase changes every inch around the circuit and I can calculate that phase change... OK, I live in a very cold environment (freespace) and I've discovered I can make and use high-temperature superconductors here, so I can wind very small coils that still have high Q. In fact, the Q is practically infinite, even for small coils. I've made a dipole from 0.1 inch diameter wire, 16 feet long total (192 inches). Four feet from each end I've put a coil of about 390 turns (gets a bit hard to keep track of the count) of very fine wire in a helix 0.1 inches diameter and 0.2 inches long. This seems to give me resonance at 3.9MHz, though a rather nasty low feedpoint impedance. Master guru, can you tell me please the travelling-wave phase change from one end of one of those coils to the other end of the same coil, at 3.9MHz, in the described environment? And can you tell me why I should care about that? I'm also experimenting with capacitively loaded long antennas, and I have another dipole that's 180 feet long, also made from 0.1" diameter wire. I've put tiny capacitors 45 feet in (25% of the total length) from each end, and adjusted them for resonance at 3.9MHz. This yields a much easier to feed feedpoint impedance. They are, like the coils, the same diameter as the wire, and about 0.04 inches long. Master guru, can you tell me please the travelling-wave phase change from one end of one of those capacitors to the other end of the same capacitor, at 3.9MHz, in the described environment? And can you tell me why I should care about that? (And how about trying to surprise us all, and quote and answer the whole thing, not just some select part, huh?) |
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