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Missing Degrees in Mobile Antennas?
There seems to be an assumption by some posters here that
a mobile antenna must be electrically 90 degrees in length. Here's a simple transmission line example to illustrate why that is not true in the case of a loading coil used with straight sections of antenna. In the following example, all transmission lines are lossless. We want to build a stub that is electrically 90 degrees long, i.e. a 1/4WL open-circuited stub. The impedance at the mouth of the 1/4WL open-circuited stub will be 0-j0 ohms, a short circuit. The first stage of the stub is made from Z0=450 ohm transmission line and is 30 degrees long. 0-j0 ----30 deg of 450 ohm line----+----50 ohm line---open-circuit The question is: How many degrees of 50 ohm line do we need to add to get 1/4WL in all. Sounds simple, huh? Just add 60 degrees and we will have our stub. But that is NOT what happens. The impedance at '+' is -j259 ohms. That is -j.0575 on the 450 ohm Smith Chart but is -j5.175 on the 50 ohm Smith Chart. So it takes only 11 degrees of 50 ohm line to replace the function of 60 degrees of 450 ohm line. Want to stuff 90 degrees of function into a 41 degree long stub? Make it a two-stage stub as above and take advantage of the impedance discontinuity. There is 60 degrees between -j0.575 and infinity on a Smith Chart. There is 11 degrees between -j5.175 and infinity on a Smith Chart. The Z01/Z02 impedance discontinuity has provided the "missing" 49 degrees of the stub. The stub is only 41 degrees in physical length yet it functions just like a 90 degree stub. The same thing holds true for mobile antennas with loading coils. The difference between the Z0 of the straight section and the Z0 of the loading coil provides the "missing" degrees of the antenna. There is no requirement that the antenna be physically 90 degrees long. There is no requirement that the delay through the coil plus the delay through the straight sections add up to 90 degrees. The impedance discontinuity provides the "missing" number of degrees. -- 73, Cecil, W5DXP |
Missing Degrees in Mobile Antennas?
On Thu, 27 Apr 2006 20:28:12 GMT, "Cecil Moore"
wrote: There seems to be an assumption by some posters here that a mobile antenna must be electrically 90 degrees in length. "Some?" In fact, only one and he cites you (which is notable in its irony for many reasons) as his authority on this subject. Why don't you simply email him your contribution? |
Missing Degrees in Mobile Antennas?
Richard Clark wrote:
On Thu, 27 Apr 2006 20:28:12 GMT, "Cecil Moore" wrote: There seems to be an assumption by some posters here that a mobile antenna must be electrically 90 degrees in length. "Some?" In fact, only one and he cites you (which is notable in its irony for many reasons) as his authority on this subject. Why don't you simply email him your contribution? Hang on, that was Cecil that said that!?!? Mister "a coil fills in the missing degrees on the stinger"? tom K0TAR |
Missing Degrees in Mobile Antennas?
Richard Clark wrote:
On Thu, 27 Apr 2006 20:28:12 GMT, "Cecil Moore" wrote: There seems to be an assumption by some posters here that a mobile antenna must be electrically 90 degrees in length. "Some?" In fact, only one and he cites you (which is notable in its irony for many reasons) as his authority on this subject. Why don't you simply email him your contribution? Or, to put it more "accurately", from Cecil's perspective, it fills in the missing degrees at the position the coil sits. tom K0TAR |
Missing Degrees in Mobile Antennas?
Tom Ring wrote:
Or, to put it more "accurately", from Cecil's perspective, it fills in the missing degrees at the position the coil sits. No, in the case of a base-loaded antenna, the "missing" degrees are filled in at the impedance discontinuity *between* the coil and the stinger. -- 73, Cecil http://www.qsl.net/w5dxp |
Missing Degrees in Mobile Antennas?
Cecil Moore wrote:
Tom Ring wrote: Or, to put it more "accurately", from Cecil's perspective, it fills in the missing degrees at the position the coil sits. No, in the case of a base-loaded antenna, the "missing" degrees are filled in at the impedance discontinuity *between* the coil and the stinger. And that differs from your bugcatcher how? tom K0TAR |
Missing Degrees in Mobile Antennas?
On Thu, 27 Apr 2006 21:58:07 -0500, Tom Ring
wrote: No, in the case of a base-loaded antenna, the "missing" degrees are filled in at the impedance discontinuity *between* the coil and the stinger. And that differs from your bugcatcher how? Hi Tom, His has an event horizon, beyond which all missing degrees disappear by superimposition. 73's Richard Clark, KB7QHC |
Missing Degrees in Mobile Antennas?
Tom Ring wrote:
Cecil Moore wrote: No, in the case of a base-loaded antenna, the "missing" degrees are filled in at the impedance discontinuity *between* the coil and the stinger. And that differs from your bugcatcher how? The whole point is that it doesn't differ. That's how my bugcatcher works. Here are the three parts to the answer. 1. The base-loading coil furnishes a delay equal to a certain number of degrees which is nowhere near zero degrees. Half of a coil self-resonant at 4 MHz would provide 45 degrees of shift. 2. Using EZNEC to add a stinger to resonate the antenna on 4 MHz, I find that's 11.5 degrees of straight element. 45 degrees plus 11.5 degrees is 56.5 degrees. 3. 90 - 56.5 = 33.5 degrees which is the "missing" degrees filled in by the impedance discontinuity. We can even estimate the ratio of the Z0 of the coil to the Z0 of the stinger to be 5.0. -- 73, Cecil http://www.qsl.net/w5dxp |
Missing Degrees in Mobile Antennas?
There seems to be an assumption by some posters here that a mobile antenna must be electrically 90 degrees in length. Must be? Must is only death and taxes! Resonant monopole must be 90 electrical degrees and resonant dipole must be 180 electrical degrees long. But that "must" does not apply to antennas as chosen by users. You can use light bulb, screwdriver, bedsprings, wet noodle or any piece of RF conducting material of any length, shape you like, just question how good of antenna it is. We used 90 deg. monopole in discussion to show typical loaded or mobile antenna in order to avoid detours to la-la land (cases when current can be and is equal) and to stay on the subject of current magnitude along the typical loading coil. 73 Yuri, K3BU |
Missing Degrees in Mobile Antennas?
Yuri Blanarovich wrote:
We used 90 deg. monopole in discussion to show typical loaded or mobile antenna in order to avoid detours to la-la land (cases when current can be and is equal) and to stay on the subject of current magnitude along the typical loading coil. Take a look at the rest of the posting, Yuri. I show where a 1/4WL stub can be made up of 30 degrees of 450 ohm line plus 11 degrees of 50 ohm line. The impedance discontinuity (at a point) furnishes the "missing" 49 degrees of stub. At 4 MHz, that would make a 1/4WL stub only 23.4 ft long or about 10% of a wavelength instead of 25%. Has anything been published on using multiple Z0's to shorten the physical length of a stub? -- 73, Cecil http://www.qsl.net/w5dxp |
Missing Degrees in Mobile Antennas?
Poor Yuri.
Hanging his hat on Cecil, but now Cecil is getting the picture and yanking the rug out from under Yuri and his "missing electrical degree cutrrent taper and phase shift theory". It only took three or four years, but at least that's better than Fractenna. :-) Cecil Moore wrote: The whole point is that it doesn't differ. That's how my bugcatcher works. Here are the three parts to the answer. 1. The base-loading coil furnishes a delay equal to a certain number of degrees which is nowhere near zero degrees. Half of a coil self-resonant at 4 MHz would provide 45 degrees of shift. 2. Using EZNEC to add a stinger to resonate the antenna on 4 MHz, I find that's 11.5 degrees of straight element. 45 degrees plus 11.5 degrees is 56.5 degrees. 3. 90 - 56.5 = 33.5 degrees which is the "missing" degrees filled in by the impedance discontinuity. We can even estimate the ratio of the Z0 of the coil to the Z0 of the stinger to be 5.0. -- 73, Cecil http://www.qsl.net/w5dxp |
Missing Degrees in Mobile Antennas?
"Cecil Moore" wrote in message . com... Tom Ring wrote: Cecil Moore wrote: There seems to be an assumption by some posters here that a mobile antenna must be electrically 90 degrees in length. Here's a simple transmission line example to illustrate why that is not true in the case of a loading coil used with straight sections of antenna. In the following example, all transmission lines are lossless. ... 73, Cecil http://www.qsl.net/w5dxp You guys sure like to go on-and-on starting with someones "rule of thumb" or catch phrase, taking either correct or not so correct math to prove or disprove what you may or may not already know...or just wave your flag in otheres faces. I guess my real point is that I see many uses of "electrical length" and "physical length" many of which are not used correctly. If the mental model(s) we have and are trying to use as a basis for a field of study don't quite work well enough to be useful most all the time, then they probably aren't correct. The best model is one that always applies when applied appropriately and you won't know what appropriate means unless you have a good model to base it on. I know this soulds like circular reasonong, but that's the way it works and the best way I can descxribe it. I think "electrical length of a conbination of components" is a poor way to look at it and therefore a poor mental model to use. Bring in an uneeded term called "electrical length" or looking for the "missing degrees" is pretty much a red herring complication. I maintain that trying to fit an "electricall length" to such a combination helps none in the understanding. You do the math, get the correct answer and you are done. You don't need an extra "name". My point would be that "elecreical length" is only correctly applicable to _A_ single length of Transmisison line. trying to force it into every other situation is only causing confusion and I should rest my case here, but.... We need it because there is a velocity factor and therefore, the phisical length is no longer good enough for discussion. It is obvious that hooking up different lengths of different characteristic impedance transmisison line has a complex effect on what you wind up with and it is therefore inapropriate to use that specific terminology to describe the complex situation. I didn't check Cecil's math, but assuming he did it correctly, this is no surprise - it is expected as a result. However, have a need to ascribe a TOTAL "electrical length" based on individual "electrical lengths" of a complex combination of lines is inappropriate - not helpful for real nunderstanding. You might be inclined, and therefore properly understood, if you talk about the finished product in a slightly different mannor. If the phase angle and impedance is the same as you would have gotten with some (single hunk of) reference line, then you could say that it "appears equivalent to" a such-and-such line with an electrical length of X degrees, but the complex combinatin no longer has something we can rightly call an electrical length because it is not an _it_, but a _them_...if you get my drift. You guys are going to use up all the words for the rest of us... (:-) 73, Steve, K9DCI asbestos shorts fresh out of the wash... |
Missing Degrees in Mobile Antennas?
wrote: Hanging his hat on Cecil, but now Cecil is getting the picture and yanking the rug out from under Yuri and his "missing electrical degree cutrrent taper and phase shift theory". Is the purpose of this newsgroup to smear individuals or to get to the technical facts? Nobody is 100% correct 100% of the time. The coil still occupies tens of degrees and still suffers a current taper because of that delay. It only took three or four years, but at least that's better than Fractenna. :-) I wouldn't laugh just yet, Tom. There's plenty of misconceptions on both sides. The delay through the loading coil is still tens of degrees, not anywhere close to the near-zero degrees that you have been asserting for years. The delay through a typical 75m bugcatcher coil appears to be about ~35 degrees with ~11 degrees of stinger. The "missing" ~44 degrees occurs at the impedance discontinuity between the coil and the stinger just as it does in my 450/50 ohm stub example. The 3 nS delay measured by you and the undetectable delay measured by W7EL were invalid measurements of delay. Standing wave current suffers zero delay all along a 1/2WL dipole whether it be in a wire or in a coil. The delay through a typical mobile loading coil on 4 MHz appears to be about 25 nS about half of what one would get in a straight wire equal to the wire used in the coil. -- 73, Cecil, W5DXP |
Missing Degrees in Mobile Antennas?
Steve N. wrote:
You might be inclined, and therefore properly understood, if you talk about the finished product in a slightly different mannor. If the phase angle and impedance is the same as you would have gotten with some (single hunk of) reference line, then you could say that it "appears equivalent to" a such-and-such line with an electrical length of X degrees, but the complex combinatin no longer has something we can rightly call an electrical length because it is not an _it_, but a _them_...if you get my drift. Steve, I put "missing" in quotes because there is no missing part of the antenna. I've been saying for months that a 75m mobile antenna doesn't have to be 90 degrees long to be resonant. All that is required is that (Vfor+Vref) be in phase with (Ifor+Iref) where those are phasor additions. The real world phase shift accomplished by an impedance discontinuity is caused by instantaneous interference and doesn't require a delay. The basics of such an event are covered in my '05 magazine article available at http://www.qsl.net/w5dxp/energy.htm -- 73, Cecil http://www.qsl.net/w5dxp |
Missing Degrees in Mobile Antennas?
wrote in message ups.com... Poor Yuri. Hanging his hat on Cecil, but now Cecil is getting the picture and yanking the rug out from under Yuri and his "missing electrical degree cutrrent taper and phase shift theory". It only took three or four years, but at least that's better than Fractenna. :-) "Brilliant" Tom! putting words in my mouth, twisting and trying to weasel out of technical arguments by spewing personal crapattack. Argument is about you claiming current in a loading coil is ALWAYS the same, which has been shown to be WRONG and crap on your web site is still proof of it. You can make up stories about my theories, it will not prove you RIGHT. Where did you get your "engineering" degree Tom and by what rights you use "JI Engineering"? That smells with fraud!!! Care to continue with bul****? Grove up or get help! 73 Yuri |
Missing Degrees in Mobile Antennas?
"Cecil Moore" wrote in message . net... Steve N. wrote: ...if you get my drift. Steve, I put "missing" in quotes because there is no missing part of the antenna. I think I understand your intent. What I say is drop the following sentence: "I've been saying for months that a 75m mobile antenna doesn't have to be 90 degrees long to be resonant. Forget electrical length discussions in regard to anything but a single transmission line piece. I don't think it makes any improvement in understanding what is going on to add talk about something you want to call the electrical length of a complex system of lines and components. I think it adds unnecessary complication. My opinion is that this is taking a concept used in transmission line discussions and applying it where it is not needed. Though I didn't verify your math on the original example, I don't find the type of result surprising and doing he math is all that is needed. I would not have expected that the "degrees" of electrical length to add up to 90, or whatever an equivalent antenna or t-line length would have been. I do understand the desire to form what I call a "mental model" which allows us to understand how things work so that we can use them. Lord knows that waves need some kind of help to get them into our minds so we can feel comfortable about how this all fits together. In fact, sometimes I get the impression these discussions become a battle between two mental models that may work for the individual posters, but don't fit into the other's model and many words ensue trying to pull each other over to the other's mental model paradigm. Talk such as the following it sufficient. (although I'd have to think about the specific thing you say here since I don't think about transmission line things in those terms) All that is required is that (Vfor+Vref) be in phase with (Ifor+Iref) where those are phasor additions. ...detail snipped -- 73, Cecil http://www.qsl.net/w5dxp Whatever lights your fire. It is fun reading some of the discussions, though 73, Steve, K9DCI |
Missing Degrees in Mobile Antennas?
Cecil Moore wrote: wrote: Hanging his hat on Cecil, but now Cecil is getting the picture and yanking the rug out from under Yuri and his "missing electrical degree cutrrent taper and phase shift theory". Is the purpose of this newsgroup to smear individuals or to get to the technical facts? I don't know. You and Yuri seem to be playing that game as much or more than anyone else. It's tough for both sides to behave and anyone to learn anything when all this strange stuff goes on, but this thread (in various forms) is very similar to the famous Fractenna threads. Nobody is 100% correct 100% of the time. .....and that obviously includes you as well as the rest of us. The key is to speak like friends and be honest rather than make this stuff into a long "Fractenna" thread. The coil still occupies tens of degrees and still suffers a current taper because of that delay. The coil does NOT have to occupy tens of degrees nor does it have to provide any current phase delay from end to end. It does have to have SOME delay and some current taper since it occupies space, but it can be so small we can't reliably measure it. The phase delay and current taper is tied to the load impedance on the open end of the coil and the construction of the coil, not to the electrical degrees. It appears you know that now. It only took three or four years, but at least that's better than Fractenna. :-) I wouldn't laugh just yet, Tom. There's plenty of misconceptions on both sides. My opinion is Lewallen and maybe a dozen others have a good handle on how it works. It appears you have gradually came more to center also, but I'm not quite positive how far. At least you no longer apperar to be saying the coil represents missing electrical degrees. The delay through the loading coil is still tens of degrees, not anywhere close to the near-zero degrees that you have been asserting for years. Be careful there. I have NOT been asserting that for years. My initial assertions years ago was there was no delay, but that was because I considered the inductor an inductance and was speaking of an inductance. Over two or three years ago I posted this: http://www.w8ji.com/mobile_and_loaded_antenna.htm which explains it is a matter of stray capacitance to the outside world compared to load inmpedance terminating the coil that causes deviations from a "perfect" coil. I also measured antenna current and posted the results at: http://www.w8ji.com/mobile_antenna_c...ts_at_w8ji.htm The delay through a typical 75m bugcatcher coil appears to be about ~35 degrees with ~11 degrees of stinger. The "missing" ~44 degrees occurs at the impedance discontinuity between the coil and the stinger just as it does in my 450/50 ohm stub example. I'd bet money I can build a coil that has very low phase delay. I'd also bet I could build one with larger phase delay **at the same point and frequency in the same system**. The problem is one of the stray capaciatnce from the coil to the outside world compared to terminating impedance of the coil. The 3 nS delay measured by you and the undetectable delay measured by W7EL were invalid measurements of delay. So you say. We have only your opinion or view on that, and that dosagrees with other people's opinions. You are not the final word. Standing wave current suffers zero delay all along a 1/2WL dipole whether it be in a wire or in a coil. The delay through a typical mobile loading coil on 4 MHz appears to be about 25 nS about half of what one would get in a straight wire equal to the wire used in the coil. Again it depends on the form factor of the coil. By altering the coil with no other changes it can be made to vary quite a bit. 73 Tom |
Missing Degrees in Mobile Antennas?
wrote:
The coil does NOT have to occupy tens of degrees nor does it have to provide any current phase delay from end to end. The coil has to obey the laws of physics. Most real-world 75m loading coils occupy tens of degrees of the mobile antenna. Your assertion that nearly 100% of the coils link nearly 100% of the total flux is unrealistic. The effect of coil flux linkage approximately doubles the VF from e.g. ~0.02 to ~0.04, not from 0.02 to near 1.0, as you assert. A speed up by a factor of 2 is a lot more realistic than a speed up by a factor of 50. The phase delay and current taper is tied to the load impedance on the open end of the coil and the construction of the coil, not to the electrical degrees. Reference my stub example which contains *NO COIL*. There is a *short circuit* looking into the stub. ---30 deg 450 ohm line---+---11 deg 50 ohm line---open The 450 ohm line provides 30 deg of phase shift. The impedance discontinuity at '+' provides 49 deg of phase shift. The 50 ohm line provides 11 deg of phase shift. All this happens without any coil in sight. A very similar thing happens with a 75m mobile antenna. The base loading coil provides tens of degrees of phase shift. The impedance discontinuity between the coil and the stinger provides tens of degrees of phase shift. The stinger provides tens of degrees of phase shift. You seem to have taken the tens of degrees of phase shift in the coil and transferred those number of degrees to the impedance discontinuity. That is a mistake based on the presuppositions of the lumped circuit model. Asserting such is akin to asserting that there is no delay in the 450 ohm line section in the stub above. My opinion is Lewallen and maybe a dozen others have a good handle on how it works. It appears you have gradually came more to center also, but I'm not quite positive how far. At least you no longer appear to be saying the coil represents missing electrical degrees. For months I have been saying that the mobile antenna doesn't have to be 90 degrees long. It has been a couple of years since I said that the coil represents missing electrical degrees. You know that but still attempt through inuendo to make hay from a mistake I made two years ago. I correct my mistakes in real time. It doesn't matter what I said two years ago. And you object when someone does that to you. For months I have been saying that the coil delay is what it is and nobody has made a valid measurement of that delay. The best information available on that subject (to the best of my knowledge) is Dr. Corum's paper at: http://www.ttr.com/TELSIKS2001-MASTER-1.pdf I'd bet money I can build a coil that has very low phase delay. I'd also bet I could build one with larger phase delay **at the same point and frequency in the same system**. We are not discussing how smart or tricky you can be in producing one special case coil. We are discussing real-world 75m bugcatcher coils. Whatever you assert has to apply to all coils, not one special case. It doesn't matter that you can create one coil that matches your assertions about all coils. That's like asserting that all cars are white and producing one white car as proof. W5DXP wrote: The 3 nS delay measured by you and the undetectable delay measured by W7EL were invalid measurements of delay. So you say. We have only your opinion or view on that, and that disagrees with other people's opinions. You are not the final word. It's my view based on all the facts. If I'm wrong, I will freely admit it and correct my misconceptions. However, at the present time, I think I have proven that standing wave current on a standing wave antenna cannot be used to measure the delay through a wire, much less through a coil. You and W7EL both used standing wave current, with its unchanging phase, in your phase measurements. W7EL says that EZNEC agrees with me on that point. So he is in the position of either disagreeing with EZNEC or admitting that his phase measurements though accurate were meaningless. EZNEC proves that standing wave current phase cannot be used to measure phase shift through a wire, much less through a coil. As recently as last month, you appeared not to know that fact as illustrated by this previous posting. ************************************************** ****************** Cecil Moore wrote: I made self-resonance measurements on loading coils and standing wave current measurements on a 6m dipole. W8JI said my measurements were in error. W7EL said my measurements agreed with EZNEC. Replying to my measurements, here are your words and W7EL's words: W8JI wrote on 3-16-06: Your measurements are probably wrong. ... After we resolve the error in current, we can move on. W7EL replied on 3-16-06: The measurement looks good to me. The phase is exactly what EZNEC predicts -- constant along the wire. ************************************************** *************** W7EL agrees that the phase is "constant along the wire". How can a signal with constant phase be used to measure phase shift through a wire? or through a coil? After a year, there is still no answer provided for this technical question. The answer provided by EZNEC is at: http://www.qsl.net/w5dxp/travstnd.GIF Standing wave current suffers zero delay all along a 1/2WL dipole whether it be in a wire or in a coil. The delay through a typical mobile loading coil on 4 MHz appears to be about 25 nS about half of what one would get in a straight wire equal to the wire used in the coil. Again it depends on the form factor of the coil. By altering the coil with no other changes it can be made to vary quite a bit. We are talking about 75m bugcatcher coils, Tom, not one special case coil engineered by you. If your assertions fail for a 75m bugcatcher coil, then they fail in reality. You assertions have to be valid for all cases or else they are invalid. Finding one special case that agrees with your assertions, e.g. your previous toroidal coil measurement, may boost your ego but doesn't really matter one iota in the overall scheme of technical fact. -- 73, Cecil http://www.qsl.net/w5dxp |
Missing Degrees in Mobile Antennas?
Cecil Moore wrote: We are talking about 75m bugcatcher coils, Tom, not one special case coil engineered by you. If your assertions fail for a 75m bugcatcher coil, then they fail in reality. You assertions have to be valid for all cases or else they are invalid. Finding one special case that agrees with your assertions, e.g. your previous toroidal coil measurement, may boost your ego but doesn't really matter one iota in the overall scheme of technical fact. -- 73, Cecil http://www.qsl.net/w5dxp Actually that statement proves YOUR theory wrong Cecil, not mine. I'm saying that in an antenna of fixed length with a fixed coil location on a given frequency, I can change ONLY the coil design, still maintain resonance, and have phase delay of current change significantly. YOU are the one who appears to be saying all coils and stubs are equal within a small range. The theory I believe to be correct is the capacitance from the inductor to the rest of the world compared to termination impedance determines phase shift in current and current taper. What is it you think determines current phase shift at each end and current taper? Explain the logic behind your idea in a way that makes the toroid work, or a compact equal form factor inductor have very low phase shift compared to an entire helice. My example works in every case. Your's fails, and you cannot just toss out the obvious disagreement and expect people to take you seriously. 73 Tom |
Missing Degrees in Mobile Antennas?
|
Missing Degrees in Mobile Antennas?
On 29 Apr 2006 09:47:25 -0700, wrote:
What is it you think determines current phase shift at each end and current taper? GROAN.... |
Missing Degrees in Mobile Antennas?
wrote:
I'm going to ask a couple of technical question at the beginning rather than getting them trimmed and ignored in the body: 1. You seem ready to admit that there is 10 degrees of delay through a 10 degree long stinger. Yet, if you measured that delay using standing wave current phase, you would measure a zero phase shift through the stinger. Why aren't you arguing that there is no phase shift in the stinger? 2. There is no appreciable standing wave current phase shift from feedpoint to the tip of the stinger in a 75m mobile bugcatcher antenna. To be consistent, don't you have to argue that the 75m mobile bugcatcher antenna is zero degrees long? Cecil Moore wrote: So you are saying the loading coil is "7's of feet long". Is that correct? Compared to a straight wire at 4 MHz, yes, that's what I am saying. A 75m bugcatcher coil uses about 42 feet of wire. The delay through that coil is *roughly* equal to about half that number of feet of straight wire. The reason it is not equal to 42 feet of straight wire is the flux coupling between the coils. Your assertion that nearly 100% of the coils link nearly 100% of the total flux is unrealistic. I never said that. But it would necessarily have to be true for the velocity factor of the coil to be anywhere near 1.0 and you did say that. What's your point in making that switch? We were talking about loading coils, now you are switching to stubs. Why? THE EFFECT EXISTS WHETHER THE COIL EXISTS OR NOT. Which indicates it is the nature of standing wave current, not coils, that you do not understand. The standing wave current phase is unchanging whether a coil exists or not. ONE CANNOT EVEN USE STANDING WAVE CURRENT PHASE TO MEASURE THE PHASE SHIFT THROUGH A WIRE, much less through a coil. Given that standing wave current phase cannot be used to measure the delay through a wire, coil, or anything else, it follows that nobody has provided any valid measurements for the delay through a coil. A very similar thing happens with a 75m mobile antenna. The base loading coil provides tens of degrees of phase shift. How do you know that? The stub involves two different Z0's. The 75m mobile antenna involves two different Z0's, one for the coil, the other for the stinger. It's the same principles using the same equations. The phase shift at the impedance discontinuity depends upon the ratio of those two Z0's. The higher the ratio, the greater the phase shift. The ratio of 450 to 50 is obviously 9:1. A rough estimate of the Z0 of the coil is around 2400 ohms and a rough estimate of the Z0 of the stinger is around 400 ohms. That makes the Z0 ratios roughly 6:1. I'm happy to see you no longer agree with the misplaced notion the coil replaces missing electrical degrees, but puzzled why you resist understanding the mechanism that allows the phase shift to change with coil design. Speaking of what we both believed two years ago: I'm happy to see you no longer agree with the misplaced notion that the coil has equal current magnitudes and phases at each end, but puzzled why you resist understanding the low velocity factor associated with helical loading coils. The velocity factor of 75m bugcatcher loading coils is typically less than 0.1 From the Dr. Corum paper, we have an equation for velocity factor for coils passing a litmus test. A 75m bugcatcher coil passes that litmus test with flying colors. The resulting VF is in the ballpark of 0.04 which is in the ballpark of Reg's VF calculations which is in the ballpark of Richard Harrison's calculations. Your VF of 1.0 along the length of the coil is the one that is completely out of the ballpark. Take your 100uH coil and measure its self-resonant frequency directly over a large metal ground plane. Keeping everything, including frequency, the same, cut the coil in half. Add a stinger to the bottom half of the coil to bring the system back into resonance at the fixed frequency. We know the delay through the coil is roughly 45 degrees. We know the stinger is roughly 10 degrees. The impedance discontinuity at the coil to stinger junction is causing roughly 35 degrees of phase shift. That tells us that the Z0 ratio of the coil to stinger is about 6:1. I have been through the above exercise using EZNEC. -- 73, Cecil http://www.qsl.net/w5dxp |
Missing Degrees in Mobile Antennas?
wrote:
I'm saying that in an antenna of fixed length with a fixed coil location on a given frequency, I can change ONLY the coil design, still maintain resonance, and have phase delay of current change significantly. So can I - so what? It's the same thing as changing the Z0 of one of the pieces of feedline in my two-Z0 stub example. No coil is required, indicating once again that your misconception involves standing waves, not coils. IMO, you are never going to understand this topic until you take time out to understand standing waves. What is it you think determines current phase shift at each end and current taper? I explained that at the start of the argument two years ago and it has been posted on my web page ever since then. http://www.qsl.net/w5dxp/current.htm Scroll down to: "Why the Net Current is not Constant Through a Loading Coil" My example works in every case. No it doesn't. Your own current measurements prove that the current is *NOT* equal at both ends of a coil (and your phase measurements were invalid). Only one special case toroid showed the currents at the ends of the coil to be equal. All the other cases proved that the currents are *NOT* equal. As Gene Fuller said, the standing wave current phase information is contained in the magnitude. With a current of 2.0 amps at one end of the coil and a current of 1.414 amps at the other end of the coil, it exactly matches the example on my web page. One of your measurements was very close to 1 amp at one end and 0.7 amps at the other end. It fits perfectly. -- 73, Cecil http://www.qsl.net/w5dxp |
Missing Degrees in Mobile Antennas?
Cecil Moore wrote: 1. You seem ready to admit that there is 10 degrees of delay through a 10 degree long stinger. Yet, if you measured that delay using standing wave current phase, you would measure a zero phase shift through the stinger. Why aren't you arguing that there is no phase shift in the stinger? Cecil, Earlier we both agreed the current we measure with a magnetic probe, which is the most common and widely accepted measurement device, is the actual current that causes radiation, heating, and the magnetic induction field. It is the current that heats the element and moves a thermocouple meter, it is the current that cause I^2R heating, and the current that moves past one point in the system if we stopped and counted charges, or if we calculated current based on drift velocity of charge carriers. So what current is it you are measuring? Charges cannot flow two directions at the same time at the same point in a system. There cannot be drift velocity in two dorections at the same time. Are you talking about a pulse of current and the return echo? 2. There is no appreciable standing wave current phase shift from feedpoint to the tip of the stinger in a 75m mobile bugcatcher antenna. To be consistent, don't you have to argue that the 75m mobile bugcatcher antenna is zero degrees long? It is however long it is. If it is 7 feet long it is about ten electrical degrees long on 75 meters, because every foot is about .7 degrees. Speaking of what we both believed two years ago: I'm happy to see you no longer agree with the misplaced notion that the coil has equal current magnitudes and phases at each end, Maybe two years ago I knew that and published it, so I am happy you finally see I did. puzzled why you resist understanding the low velocity factor associated with helical loading coils. The velocity factor of 75m bugcatcher loading coils is typically less than 0.1 ......and you know that because? From the Dr. Corum paper, we have an equation for velocity factor for coils passing a litmus test. A 75m bugcatcher coil passes that litmus test with flying colors. The resulting VF is in the ballpark of 0.04 which is in the ballpark of Reg's VF calculations which is in the ballpark of Richard Harrison's calculations. Your VF of 1.0 along the length of the coil is the one that is completely out of the ballpark. I never said 1.0, as a matter of fact the coil I measured had a vF (when compared to physical length) of about .5 I measured delay through an approximately 100uH coil at: http://www.w8ji.com/inductor_current_time_delay.htm You can see the big change at self-resonance near 16 MHz. 3.8 MHz is not near 16MHz, so the behavior is quite different at the two frequencies. Take your 100uH coil and measure its self-resonant frequency directly over a large metal ground plane. Keeping everything, including frequency, the same, cut the coil in half. Sorry, I won't cut the last few pieces of miniductor I have like that in half. So what current are you measuring? 73 Tom |
Missing Degrees in Mobile Antennas?
Cecil Moore wrote: wrote: I'm saying that in an antenna of fixed length with a fixed coil location on a given frequency, I can change ONLY the coil design, still maintain resonance, and have phase delay of current change significantly. So can I - so what? It's the same thing as changing the Z0 of one of the pieces of feedline in my two-Z0 stub example. No coil is required, indicating once again that your misconception involves standing waves, not coils. Now Cecil, get serious. We all know a stub has distributed capacitance and distributed inductance. We all know an inductor has the same thing. We can solve the problem equally well using a network of distributed components as many others have shown. IMO, you are never going to understand this topic until you take time out to understand standing waves. Well, I could say the same to you about coils and capacitors. :-) What is it you think determines current phase shift at each end and current taper? I explained that at the start of the argument two years ago and it has been posted on my web page ever since then. So you don't want to say, or can't say in a few words? 73 Tom |
Missing Degrees in Mobile Antennas?
wrote:
Earlier we both agreed the current we measure with a magnetic probe, which is the most common and widely accepted measurement device, is the actual current that causes radiation, heating, and the magnetic induction field. It is the current that heats the element and moves a thermocouple meter, it is the current that cause I^2R heating, and the current that moves past one point in the system if we stopped and counted charges, or if we calculated current based on drift velocity of charge carriers. It is the current that has the equation: Itot = Io*cos(kx)*cos(wt) Until you take time out to understand the implications of that equation, you will *never* understand what I am talking about. That current cannot be used to measure delay. Yet, that is exactly what you and W7EL did and, in your ignorance, reported as valid measurements of delay through a coil. If you had a clue to what you are saying, you would feel ignorant in the extreme. So what current is it you are measuring? Charges cannot flow two directions at the same time at the same point in a system. There cannot be drift velocity in two dorections at the same time. Just as two water waves can flow in opposite directions using the same water molecules, two EM waves can flow in opposite directions using the same electrons. Are you talking about a pulse of current and the return echo? You know that I am talking about the distributed network model, a superset of the lumped circuit model. Instead of rehashing it here, please refer to my magazine article at: http://www.qsl.net/w5dxp/energy.htm and tell me what it is about that article that you don't understand. 2. There is no appreciable standing wave current phase shift from feedpoint to the tip of the stinger in a 75m mobile bugcatcher antenna. To be consistent, don't you have to argue that the 75m mobile bugcatcher antenna is zero degrees long? It is however long it is. Exactly the same argument holds for a coil. Think about it. You cannot deny the validity of standing wave current phase measurements through a stinger and then turn around and deny that same argument when it applies to a coil. If W7EL's phase measurements were invalid for a stinger, then they were equally invalid for a coil. I never said 1.0, as a matter of fact the coil I measured had a vF (when compared to physical length) of about .5 Sorry, that's still about 1000% too high, still completely out of the ballpark. What I suspect is that you measured zero delay through the coil and reported 3 nS because you knew zero was obviously wrong. -- 73, Cecil http://www.qsl.net/w5dxp |
Missing Degrees in Mobile Antennas?
wrote:
So you don't want to say, or can't say in a few words? I know one of your tactics used to "win" an argument is to wear the opponent down to a nub where it is not worth the effort to continue even when he is right and you are wrong. I'm not going to play your silly game. All the information is there on my web page at: http://www.qsl.net/w5dxp/current.htm -- 73, Cecil http://www.qsl.net/w5dxp |
Missing Degrees in Mobile Antennas?
On 29 Apr 2006 14:17:20 -0700, wrote:
So you don't want to say, or can't say in a few words? GROAN |
Missing Degrees in Mobile Antennas?
W8JI wrote:
So what current is it you are measuring? Charges cannot flow two directions at the same time at the same point in a system. There cannot be drift velocity in two dorections at the same time. Cecil Moore wrote: Just as two water waves can flow in opposite directions using the same water molecules, two EM waves can flow in opposite directions using the same electrons. That's where you are wrong Cecil. While the effects of energy and reflection of current and voltage can be considered as a real actionl, current actually can only flow one direction at one time at one point in one conductor . There is no other way. You are confusing a model that is supposed to aid people in solutions as the "real" thing happening. Every single thing that can be done with standing waves can be done with circuit solutions, and we cannot have charges moving two directions at the same time at any one point in the system. The radiation from a short antenna is easily tied directly to ampere-feet, and the amperes that cause that radiation **is** the current Roy and I measured. The current Roy and I measured is the current level causing heat. Be assured that along the short length of the conductor at any fixed instant of time in one spot, you cannot possible have two potentials or charge differences causing charges to move two directions at once. What you are saying is you have something that cannot actually happen and even if it could it has no effect and cannot be measured, and that is what is important to you and makes the rest of the world wrong. No wonder no one can agree with you! 73 Tom |
Missing Degrees in Mobile Antennas?
Cecil Moore wrote: wrote: I never said 1.0, as a matter of fact the coil I measured had a vF (when compared to physical length) of about .5 Sorry, that's still about 1000% too high, still completely out of the ballpark. What I suspect is that you measured zero delay through the coil and reported 3 nS because you knew zero was obviously wrong. Sorry Cecil, I cannot get into my network analyzer and make it show a delay on a printout that isn't actually there. I push the button, it prints the data it takes. In an attempt to justify your odd conclusions, you are now altering my measurements. At this point any further exchange is useless, because you have now resorted to calling the other person a liar when measured data disagrees with your preconcieved notions. I'm done with you. |
Missing Degrees in Mobile Antennas?
wrote:
Sorry Cecil, I cannot get into my network analyzer and make it show a delay on a printout that isn't actually there. I push the button, it prints the data it takes. Yes, and you have previously said that any answer is better than no answer at all, presumably including answers obtained using invalid measurement techniques. If you take your network analyzer and measure the current phase shift from end to end in a 1/2WL thin-wire dipole, you can prove that dipole to be almost zero degrees long, just like you did with the coil. In an attempt to justify your odd conclusions, you are now altering my measurements. Please don't blame my faulty memory on any ulterior motive. It was an honest mistake easily proven to be wrong. (And a VF of 0.5 is just as unbelievable as a VF of 1.0 for a foot long 8 tpi coil.) At this point any further exchange is useless, because you have now resorted to calling the other person a liar when measured data disagrees with your preconcieved notions. I apologize for my faulty memory, Tom, and everyone knows that I didn't call you a liar. I accidentally misquoted you and you corrected me. Your measured data simply disagrees with known technical facts. Until you take time to understand the technical implications behind the standing wave current phase that you used for your measurements, Itot = Io*cos(kx)*cos(wt) you will never understand why using such a signal to measure phase is an invalid thing to do. Hint: the phase of the above standing wave current doesn't vary with 'x' so it cannot be used to measure a phase shift between point 'x1' and point 'x2' on a wire or through a coil. -- 73, Cecil http://www.qsl.net/w5dxp |
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