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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 |
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