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On May 9, 1:56*pm, wrote:
Tom, OK, I tried what you suggested. I put my loading coil midway up a 20ft vertical wire in the EZNEC model. I reduced the number of turns to lift the resonant frequency to 5.6MHz. EZNEC predicted that the magnitude of the current at the top of the coil would be 77% of the magnitude at the bottom. Then I removed the coil in the model, replaced it with a straight wire containing an EZNEC lumped load, and adjusted that load for antenna resonance at 5.6MHz again. I needed +j1630. Given the dimensions of the coil, the Corum calculator predicted a lumped circuit equivalent reactance of *+j1573, and it predicted a current fall-off across the coil of 78%. Hi Steve, OK, I'm wondering now exactly what "Corum calulator" you are using that predices "a current fall-off across the coil of 78%." The inductance calculator on the HamWaves website that I thought we were talking about doesn't seem to say anything about "current fall-off" in coils, though perhaps I'm missing it. Cheers, Tom |
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Tom Ring wrote:
And denigrating slide rules is silly. Most of the world that surrounds you was calculated with a slide rule's resolution. When used properly they give answers that are as accurate as is needed for engineering. I was one of the last classes in school to use a slide rule - they went to calculators the next year. I have to say that using a slide rule changed my outlook on math in all it's forms. Took a absolute idiot at math to the dilettante I am today. 8^) I use calculators all the time now, but I still have a slide rule that I use in the garage.... - 73 de Mike N3LI - |
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Hi Tom,
I should have been more explicit. I took the "Axial Propagation Factor" (4.372 rad/m) figure which was given by the HamWaves calculator and multiplied it by the coil length (155mm) to find the effective electrical length of the coil (38.83 degrees). Then I took cos(38.83)=0.779 as the fall-off in current across the coil. 73, Steve G3TXQ On May 11, 2:46*am, K7ITM wrote: Hi Steve, OK, I'm wondering now exactly what "Corum calulator" you are using that predices "a current fall-off across the coil of 78%." *The inductance calculator on the HamWaves website that I thought we were talking about doesn't seem to say anything about "current fall-off" in coils, though perhaps I'm missing it. Cheers, Tom |
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wrote:
I took the "Axial Propagation Factor" (4.372 rad/m) figure which was given by the HamWaves calculator and multiplied it by the coil length (155mm) to find the effective electrical length of the coil (38.83 degrees). Then I took cos(38.83)=0.779 as the fall-off in current across the coil. Interesting. W8JI's coil through which he measured a 3 nS delay was 100t, 2" dia, 10" long, #18 wire. http://www.w8ji.com/inductor_current_time_delay.htm Converting everything to metric and entering the data into the HamWaves calculator at 4 MHz, yields a calculated delay of 21.5 nS through the W8JI coil and a VF of ~0.04 at 4 MHz. So which are we to believe? W8JI's measurements or ON4AA's calculator. There's a 7x difference between 3 nS and 21 nS. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
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On May 11, 2:26*am, wrote:
Hi Tom, I should have been more explicit. I took the "Axial Propagation Factor" (4.372 rad/m) figure which was given by the HamWaves calculator and multiplied it by the coil length (155mm) to find the effective electrical length of the coil (38.83 degrees). Then I took cos(38.83)=0.779 as the fall-off in current across the coil. 73, Steve G3TXQ Hi Steve, OK, so I suppose you are assuming that the current distribution will follow a cosine along electrical degrees of your antenna, with a maximum at the base/feedpoint. If that's the case, then would you not account for the bottom 10 feet of wire, about 20.5 electrical degrees? If I do that and assume 1 amp at the feedpoint, I should see about .9367 amps at 20.5 degrees and 0.5101 amps at (20.5+38.83) electrical degrees. 0.5101/.9367 would then be the ratio of currents between the ends of the coil, and that's 0.5446, only a 45.54 percent fall-off. In fact, it seems to me that the idea of cos(38.83 degrees) = .779 would imply a fall-off of 22.1%... and that tells me that perhaps I'm still not understanding your model very well. Maybe you are NOT assuming the current along the electrical degrees of the antenna, up from the feedpoint, will have a cosine distribution. At this point, I have to say that I'm just not at all sure what your model really is. Perhaps you are making different assumptions about the current distribution... Also, if you still have the model around, try adding a top hat to the upper wire. For simplicity, you can just use a simple "T" structure, where the top horizontal wire is, say, five feet long total. With such a configuration, what's the current distribution along the radiating element going to be? Of course, what I'm suggesting here is that one must be careful to test ones models at corner cases before putting too much faith in them, and even then, one must always be wary of cases where the model may go awry. Cheers, Tom |
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K7ITM wrote:
OK, so I suppose you are assuming that the current distribution will follow a cosine along electrical degrees of your antenna, with a maximum at the base/feedpoint. This is a good assumption for horizontal 1/2WL thin-wire dipoles as presented by Kraus. It doesn't seem to be valid for loaded vertical antennas where there is an instantaneous phase shift at the impedance discontinuities. There is a definite change in the slope of the current profile at such boundaries. And there is the nagging current bulge in the loading coil causing a rise in current in adjacent turns. Normally a current maximum would indicate a purely resistive impedance but that doesn't seem to be the case inside a loading coil. Years ago, I gave up on the current cosine argument for loaded mobile antenna current in favor of loading the coil with its characteristic impedance and using traveling wave current to measure the electrical length of the coil. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
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On Sun, 10 May 2009 14:52:06 -0700, "Tom Donaly"
wrote: The presence of anything at all near the coil should lower its resonant frequency. Even the measuring apparatus should have an effect. I think it would require very careful planning and implementation to find an exact resonant frequency. You'd have to ask Richard Clark how to do it if you wanted high accuracy. I'm unwilling to find fault with either Corum or EZNEC at this point. Making accurate models can be just as hard as making valid experiments, and I wish you luck working with your models. I do urge you to make a coil to test your results against, though. It isn't difficult, and with a little help from some of your fellow experimenters, you should get results that are very close to being meaningful. 73, Tom Donaly, KA6RUH Hi Tom, Thanx for the flowers. In point of fact, inductor and capacitor standards are shielded. They are three terminal devices. To remove the effects of the shield you drive it at the same potential (which is to say the shield is floating with respect to everything/one around it). For the practicality of things, Reggie was never very far off the mark and you following him as an exemplar is suitable to other's inventions of proximities that have no defining moment in their references. I can well guess the remainder of your method as it was well defined in most Ham manuals (derived from conventional EE methods) when I read up on it 40 odd years ago. If Cecil every gets over this intellectual pebble in the path, please quote it so that I can see how much strain that ascent took. 73's Richard Clark, KB7QHC |
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Richard Clark wrote:
I note how little Corrum really has to offer when you had to take the same: effective electrical length of the coil (38.83 degrees) and change it (to the same effective electrical length? I think not.) to fit the same available wire, at the same specific frequency - only at a different height along the available wire. Richard, I explained that phenomenon in a posting last week which you obviously didn't read. Please go back and read my posting of 5-9-09 at 1:08pm to this thread. It is also explained on my web page at: http://www.w5dxp.com/shrtstub.htm -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
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Tom,
Firstly, I'm guilty of a "sloppy" choice of words. Whenever I've been using the phrase "drop off in current" I've meant the current at the top of the coil as a percentage of the current at the bottom. So when I've quoted 70% the current will have reduced by 30%. Apologies! Secondly, you're testing the limits of my understanding with the overall current distribution from base section, through the coil, to the top section. However I think the point is that you can't simply "add electrical degrees" through the various sections when the characteristic impedances of the sections are so disparate. That was Cecil's point in the very first posting. We also know that, as expected, summing the "degrees" for the three sections gets nowhere near a total of 90 degrees, so clearly you can't assume a cosine distribution that is contiguous across all three sections. I'll investigate what happens with a "top hat". 73, Steve G3TXQ On May 11, 6:56*pm, K7ITM wrote: Hi Steve, OK, so I suppose you are assuming that the current distribution will follow a cosine along electrical degrees of your antenna, with a maximum at the base/feedpoint. *If that's the case, then would you not account for the bottom 10 feet of wire, about 20.5 electrical degrees? *If I do that and assume 1 amp at the feedpoint, I should see about .9367 amps at 20.5 degrees and 0.5101 amps at (20.5+38.83) electrical degrees. *0.5101/.9367 would then be the ratio of currents between the ends of the coil, and that's 0.5446, only a 45.54 percent fall-off. In fact, it seems to me that the idea of cos(38.83 degrees) = .779 would imply a fall-off of 22.1%... and that tells me that perhaps I'm still not understanding your model very well. *Maybe you are NOT assuming the current along the electrical degrees of the antenna, up from the feedpoint, will have a cosine distribution. *At this point, I have to say that I'm just not at all sure what your model really is. Perhaps you are making different assumptions about the current distribution... Also, if you still have the model around, try adding a top hat to the upper wire. *For simplicity, you can just use a simple "T" structure, where the top horizontal wire is, say, five feet long total. *With such a configuration, what's the current distribution along the radiating element going to be? Of course, what I'm suggesting here is that one must be careful to test ones models at corner cases before putting too much faith in them, and even then, one must always be wary of cases where the model may go awry. Cheers, Tom |
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Richard Clark wrote:
If Cecil every gets over this intellectual pebble in the path, please quote it so that I can see how much strain that ascent took. What you don't seem to realize is that the loaded antenna can be assumed to be lossless in free space with a 4-wire radial ground plane and the E-fields and H-fields are within 10% of their real-world values, i.e. you are complaining about relatively small secondary effects. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
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Cecil Moore wrote:
What you don't seem to realize is that the loaded antenna can be assumed to be lossless in free space with a 4-wire radial ground plane and the E-fields and H-fields are within 10% of their real-world values, i.e. you are complaining about relatively small secondary effects. As far as conditions on the antenna are concerned, you are complaining about relatively small secondary effects. Of course, there are large effects on radiation and ground loss, but those items are not the subject of this discussion. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
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Hi Richard,
I wont even attempt to answer the "intimidating" questions - they're far too tough for me! But just a couple of comments: 1) The change in coil size when I swapped from a base-loaded to a mid- loaded model was nothing more than a convenience to reduce the total number of segments and reduce the computation time. It was not borne out of any electrical considerations, so please don't read anything more than that into it. In retrospect it was a silly thing to do because it has probably introduced a "red herring". 2) You suggest that the Corum method has little utility. However, the inductance calculator based on the method appears to give usefully accurate predictions of "equivalent lumped reactance" and SRF (jury still out on that one). If that calculator was not available, it seems to me that designing a coil for something like a mobile whip loading application would require tedious iterations of the helix generator in EZNEC. 73, Steve G3TXQ On May 11, 9:19*pm, Richard Clark wrote: Hi Steve, I don't often drop into this side-thread as the topic had drifted into a stagnated intellectual backwater. On this and one prior posting by you: On Sat, 9 May 2009 13:56:31 -0700 (PDT), wrote: OK, I tried what you suggested. I put my loading coil midway up a 20ft vertical wire in the EZNEC model. I reduced the number of turns to lift the resonant frequency to 5.6MHz. I note how little Corrum really has to offer when you had to take the same:effective electrical length of the coil (38.83 degrees) and change it (to the same effective electrical length? *I think not.) to fit the same available wire, at the same specific frequency - only at a different height along the available wire. By my quick read on the stale crisis of current "fall-off" and proving Corum by EZNEC; it seems quite apparent that EZNEC (the authority) is driving the coil requirements which are then force fitted by Corum's inappropriate application. After all, Corum says nothing of: 1. *Application; 2. *Base loading; 3. *Mid or Top loading; 4. *Stinger selection; and yet all solutions seem to derive from their math with the elegance of an ad-hoc "missing degrees" provision (that is quickly discarded as shown above when current becomes the focus). Corum DOES say that the formula is only applicable for certain constraints which I note are NEVER observed in the application nor the breach. *All of the commentary proceeds through equation (32) when every argument is an instance of equation (31). How much are you willing to accept of that paper (which is another way of asking how much you are willing to discard)? I will ask one ace-buster question that I expect no one will answer: * * * * Show me the computation for M (= tau · a) which would be appropriate for the NON-quarterwave resonance of the coil in question at 3.85 MHz. For extra credit: 1. *What is the wave number, k for 3.85 MHz? 2. *What is the phase velocity for the original (not changed) coil? 3. *What is tau for the original (not changed) coil at 3.85 MHz? Yes, this is intimidating to ask; but seeing there are so many authorities on Corum; and that these considerations would have been done by the authors themselves; then their solutions must reside somewhere in notes or as marginalia for quick reporting (or could be summoned up through running through the same math as before). 73's Richard Clark, KB7QHC |
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Tom,
One further puzzling featu When I look at the EZNEC currents in the bottom 10ft of my 20ft mid- loaded model there is *NO* current reduction from bottom to top: 1A at the bottom and 0.99996A at the junction with the coil. So no evidence of a cosine shape starting at the bottom. Brain hurts - time for bed! 73, Steve G3TXQ |
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wrote:
When I look at the EZNEC currents in the bottom 10ft of my 20ft mid- loaded model there is *NO* current reduction from bottom to top: 1A at the bottom and 0.99996A at the junction with the coil. So no evidence of a cosine shape starting at the bottom. In many center-loaded antennas, the current increases from the feedpoint through the base section to the bottom of the coil. Converting that non-cosine current into an equivalent cosine current with the proper phasing/delay may take some doing. I don't know of anyone who has accomplished that feat so far. However, it would be a very useful algorithm. One way to do such would be to compare the current in an ideal transmission line with the current through the loading coil as reported by EZNEC. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
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On May 11, 2:09*pm, wrote:
Hi Richard, I wont even attempt to answer the "intimidating" questions - they're far too tough for me! But just a couple of comments: 1) The change in coil size when I swapped from a base-loaded to a mid- loaded model was nothing more than a convenience to reduce the total number of segments and reduce the computation time. It was not borne out of any electrical considerations, so please don't read anything more than that into it. In retrospect it was a silly thing to do because it has probably introduced a "red herring". 2) You suggest that the Corum method has little utility. However, the inductance calculator based on the method appears to give usefully accurate predictions of "equivalent lumped reactance" and SRF (jury still out on that one). If that calculator was not available, it seems to me that designing a coil for something like a mobile whip loading application would require tedious iterations of the helix generator in EZNEC. 73, Steve G3TXQ For what it's worth, I've been using a coil program for quite a few years now that is able to calculate the performance of a coil based on a helical transmission line model. It was developed out of travelling wave tube theory. It turns out I discovered a bug in the program and reported it to the author, who very kindly corrected it. I've come to trust it to come up with answers that are very useful in an engineering sense. I would not expect it to tell me inductance or other parameters (e.g., first parallel self resonance and first series self resonance) accurately enough to be used as a precision lab standard, but that's not what I use the program for. When I became aware of the HamWaves web page, I was curious about how well its answers compared with the ones I'd become used to trusting. They do differ a little, but again, for what I do with them, I trust them both. Either one will provide results I can use to wind a coil for a filter and know I won't have to much to adjust the coil to being "right on." And in fact, I also found a very small bug (or at least an anomaly or inconsistency) in the HamWaves calculation, and reported that to Serge, who likewise very graciously acknowledged it and who I believe corrected it. So I'd strongly support your thought that the HamWaves calculator provides useful results. Understand that they won't be perfect, but also understand that you may have trouble making measurements accurate enough to know how much they are in error. But for almost everything I do with coils, what I care about is whether the filter or tank circuit or antenna in which the coil is used actually works like I want. My trust in these programs comes from being able to build a lot of filters over the years that all work like I designed them to work, with very little effort to tweak the coils I built per the programs' predictions. I'll adjust my expectations if I ever find cases where the programs lead me astray. Cheers, Tom |
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K7ITM wrote:
So I'd strongly support your thought that the HamWaves calculator provides useful results. So who are we to believe? W8JI's 3 nS delay measurements through a large 75m loading coil, or the HamWaves 21.5 nS prediction? -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
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Richard Clark wrote:
When that happens, all that is required is that you suspend your doubt that if that coil at the base of a fixed height antenna were moved, it would fulfill resonating that fixed height antenna with the same number of Corum "electrical degrees" in migration. Using standard stub theory and transmission lines, I have shown how moving parts of dual-Z0 stubs from one place to another requires a change in the length of parts of the stub. Why do you have such difficulty applying this standard transmission line theory to loading coils? Could it be that you are dismissing technical facts because you are incapable of understanding them? If so, you have lots of company down through history. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
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Richard Clark wrote:
Hi Tom, Thanx for the flowers. In point of fact, inductor and capacitor standards are shielded. They are three terminal devices. To remove the effects of the shield you drive it at the same potential (which is to say the shield is floating with respect to everything/one around it). For the practicality of things, Reggie was never very far off the mark and you following him as an exemplar is suitable to other's inventions of proximities that have no defining moment in their references. I can well guess the remainder of your method as it was well defined in most Ham manuals (derived from conventional EE methods) when I read up on it 40 odd years ago. If Cecil every gets over this intellectual pebble in the path, please quote it so that I can see how much strain that ascent took. 73's Richard Clark, KB7QHC Hi Richard, In point of fact, I just used a dip-meter-frequency-counter combination to see if I could get somewhere near the results that ON4AA's calculator suggested. Later, I cut the coil at its center point, attached a cheap antenna analyzer there and looked for a frequency of least impedance. The dip meter indicated about 8.93 Mhz and the analyzer indicated 8.98 Mhz. I consider the closeness of the two readings to be pure accident. However, they do reinforce each other in leading me to believe that the Corum calculator has some serious deficiencies. Serious enough, that those who claim its correctness should do some practical investigation into its merits in order to spare themselves the jibes of their more analytical brethren. 73, Tom Donaly, KA6RUH |
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On Mon, 11 May 2009 16:28:04 -0700, "Tom Donaly"
wrote: Hi Richard, In point of fact, I just used a dip-meter-frequency-counter combination to see if I could get somewhere near the results that ON4AA's calculator suggested. Hi Tom, I wouldn't have expected any other method based on your "tease." It answers the need for lightly coupling which responds to your admonition of not presenting disturbances to the measurement. About the only variation to this would be in how you could lighten up the coupling further. I don't see Cecil struggling for the low fruit here, so I'm not expecting to see him make this into a rum punch. Later, I cut the coil at its center point, attached a cheap antenna analyzer there and looked for a frequency of least impedance. The dip meter indicated about 8.93 Mhz and the analyzer indicated 8.98 Mhz. I consider the closeness of the two readings to be pure accident. Pursuing an alternative method helps validate them both, another hallmark of good bench work. That Steve finds two values that correlate through software begs the question of what parameters were used. As such, two in silicon against two at the bench - something's got to give. The differences are not deep in the decimal places. However, they do reinforce each other in leading me to believe that the Corum calculator has some serious deficiencies. Serious enough, that those who claim its correctness should do some practical investigation into its merits in order to spare themselves the jibes of their more analytical brethren. Tom subscribes to Corum (if I read his posts correctly), to the extent of his needs. That seems sufficient for me, but it does not attach a proof to the conjectures and it doesn't serve the glaring points by the authors that their model works only with resonating coils (if I am reading them correctly), or unless you derive your own M factor (no one stepping up to the plate for that suggests they have no deep interest in the topic). They allow roughly 10% error as it stands, and I observe debates trying to leverage 5% positions. 73's Richard Clark, KB7QHC |
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K7ITM wrote:
On May 11, 2:09 pm, wrote: Hi Richard, I wont even attempt to answer the "intimidating" questions - they're far too tough for me! But just a couple of comments: 1) The change in coil size when I swapped from a base-loaded to a mid- loaded model was nothing more than a convenience to reduce the total number of segments and reduce the computation time. It was not borne out of any electrical considerations, so please don't read anything more than that into it. In retrospect it was a silly thing to do because it has probably introduced a "red herring". 2) You suggest that the Corum method has little utility. However, the inductance calculator based on the method appears to give usefully accurate predictions of "equivalent lumped reactance" and SRF (jury still out on that one). If that calculator was not available, it seems to me that designing a coil for something like a mobile whip loading application would require tedious iterations of the helix generator in EZNEC. 73, Steve G3TXQ For what it's worth, I've been using a coil program for quite a few years now that is able to calculate the performance of a coil based on a helical transmission line model. It was developed out of travelling wave tube theory. It turns out I discovered a bug in the program and reported it to the author, who very kindly corrected it. I've come to trust it to come up with answers that are very useful in an engineering sense. I would not expect it to tell me inductance or other parameters (e.g., first parallel self resonance and first series self resonance) accurately enough to be used as a precision lab standard, but that's not what I use the program for. When I became aware of the HamWaves web page, I was curious about how well its answers compared with the ones I'd become used to trusting. They do differ a little, but again, for what I do with them, I trust them both. Either one will provide results I can use to wind a coil for a filter and know I won't have to much to adjust the coil to being "right on." And in fact, I also found a very small bug (or at least an anomaly or inconsistency) in the HamWaves calculation, and reported that to Serge, who likewise very graciously acknowledged it and who I believe corrected it. So I'd strongly support your thought that the HamWaves calculator provides useful results. Understand that they won't be perfect, but also understand that you may have trouble making measurements accurate enough to know how much they are in error. But for almost everything I do with coils, what I care about is whether the filter or tank circuit or antenna in which the coil is used actually works like I want. My trust in these programs comes from being able to build a lot of filters over the years that all work like I designed them to work, with very little effort to tweak the coils I built per the programs' predictions. I'll adjust my expectations if I ever find cases where the programs lead me astray. Cheers, Tom Hi Tom, A testimonial from you goes a long way toward building some trust in ON4AA's coil calculator. I was concerned because I haven't seen much in the way of empirical data to substantiate the claims made for it. I would have thought that the creators would have at least provided a link to some data, or to a description of their own coil-making efforts. 73, Tom Donaly, KA6RUH |
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Tom Donaly wrote:
A testimonial from you goes a long way toward building some trust in ON4AA's coil calculator. Testimonials do not make technical information true or false. This technical information has been available for the past 5-8 years. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
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Richard Clark wrote:
On Mon, 11 May 2009 16:28:04 -0700, "Tom Donaly" wrote: Hi Richard, In point of fact, I just used a dip-meter-frequency-counter combination to see if I could get somewhere near the results that ON4AA's calculator suggested. Hi Tom, I wouldn't have expected any other method based on your "tease." It answers the need for lightly coupling which responds to your admonition of not presenting disturbances to the measurement. About the only variation to this would be in how you could lighten up the coupling further. I don't see Cecil struggling for the low fruit here, so I'm not expecting to see him make this into a rum punch. Later, I cut the coil at its center point, attached a cheap antenna analyzer there and looked for a frequency of least impedance. The dip meter indicated about 8.93 Mhz and the analyzer indicated 8.98 Mhz. I consider the closeness of the two readings to be pure accident. Pursuing an alternative method helps validate them both, another hallmark of good bench work. That Steve finds two values that correlate through software begs the question of what parameters were used. As such, two in silicon against two at the bench - something's got to give. The differences are not deep in the decimal places. However, they do reinforce each other in leading me to believe that the Corum calculator has some serious deficiencies. Serious enough, that those who claim its correctness should do some practical investigation into its merits in order to spare themselves the jibes of their more analytical brethren. Tom subscribes to Corum (if I read his posts correctly), to the extent of his needs. That seems sufficient for me, but it does not attach a proof to the conjectures and it doesn't serve the glaring points by the authors that their model works only with resonating coils (if I am reading them correctly), or unless you derive your own M factor (no one stepping up to the plate for that suggests they have no deep interest in the topic). They allow roughly 10% error as it stands, and I observe debates trying to leverage 5% positions. 73's Richard Clark, KB7QHC Hi Richard, And then there is Cecil. I was hoping I could crowd him into slapping leather over this and get him to do some experimenting. I should have known better. 73, Tom Donaly, KA6RUH (P.S. Excuse the shamefully unattributed extract from Shane.) |
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Tom Donaly wrote:
And then there is Cecil. I was hoping I could crowd him into slapping leather over this and get him to do some experimenting. I should have known better. Sorry, first things first. I am a newlywed (Feb. 28) and all my equipment is still packed in boxes after squeezing into a new QTH. I am presently not even on the air. I reported my experimental results years ago and was satisfied with the results. Hint: My experiments do not affect (or effect) technical facts. Neither do your beliefs or anyone's testimonials. Those technical facts have been staring you in the face for 5+ years now. What have you been doing for the past 5 years - anything except ad hominem attacks? -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
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On May 11, 6:29*pm, "Tom Donaly" wrote:
K7ITM wrote: On May 11, 2:09 pm, wrote: Hi Richard, I wont even attempt to answer the "intimidating" questions - they're far too tough for me! But just a couple of comments: 1) The change in coil size when I swapped from a base-loaded to a mid- loaded model was nothing more than a convenience to reduce the total number of segments and reduce the computation time. It was not borne out of any electrical considerations, so please don't read anything more than that into it. In retrospect it was a silly thing to do because it has probably introduced a "red herring". 2) You suggest that the Corum method has little utility. However, the inductance calculator based on the method appears to give usefully accurate predictions of "equivalent lumped reactance" and SRF (jury still out on that one). If that calculator was not available, it seems to me that designing a coil for something like a mobile whip loading application would require tedious iterations of the helix generator in EZNEC. 73, Steve G3TXQ For what it's worth, I've been using a coil program for quite a few years now that is able to calculate the performance of a coil based on a helical transmission line model. *It was developed out of travelling wave tube theory. *It turns out I discovered a bug in the program and reported it to the author, who very kindly corrected it. *I've come to trust it to come up with answers that are very useful in an engineering sense. *I would not expect it to tell me inductance or other parameters (e.g., first parallel self resonance and first series self resonance) accurately enough to be used as a precision lab standard, but that's not what I use the program for. When I became aware of the HamWaves web page, I was curious about how well its answers compared with the ones I'd become used to trusting. They do differ a little, but again, for what I do with them, I trust them both. *Either one will provide results I can use to wind a coil for a filter and know I won't have to much to adjust the coil to being "right on." *And in fact, I also found a very small bug (or at least an anomaly or inconsistency) in the HamWaves calculation, and reported that to Serge, who likewise very graciously acknowledged it and who I believe corrected it. So I'd strongly support your thought that the HamWaves calculator provides useful results. *Understand that they won't be perfect, but also understand that you may have trouble making measurements accurate enough to know how much they are in error. *But for almost everything I do with coils, what I care about is whether the filter or tank circuit or antenna in which the coil is used actually works like I want. *My trust in these programs comes from being able to build a lot of filters over the years that all work like I designed them to work, with very little effort to tweak the coils I built per the programs' predictions. *I'll adjust my expectations if I ever find cases where the programs lead me astray. Cheers, Tom Hi Tom, * * * * *A testimonial from you goes a long way toward building some trust in ON4AA's coil calculator. I was concerned because I haven't seen much in the way of empirical data to substantiate the claims made for it. I would have thought that the creators would have at least provided a link to some data, or to a description of their own coil-making efforts.. 73, Tom Donaly, KA6RUH Well, I'm flattered, but I'd invite you and anyone else here who might build coils for practical purposes to report back how that calculator, or any other, worked for them. The homebrew newsgroup might be a better place to do that. And if you think you've come up with a situation where any calculator seems significantly in error, don't be shy about reporting it to the author or maintainer of the calculator. I've found most to be quite happy to hear about bugs, especially if they are well documented, if they are told in a nice way. I tend to not push the limits on coil calculations, because I know that I'll get the best volumetric efficiencies with coils over a relatively small range of diameter-to-length ratios, and for air-core solenoid RF coils used between a couple MHz and a few hundred MHz, I know what physical size I'll need for any particular required Qu. So you very well may find cases of more extreme D:L ratios where a calculator I've learned to trust isn't so hot -- and honestly, I'd love to know about such limits. Cheers, Tom Cheers, Tom |
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Richard Clark wrote:
That's OK. Even the Corums didn't answer them and it accounts for the rather thin material being leveraged into the new-age science we get discussed here. Giving rise to the phrase, "Lack of De-corum". (cymbal crash) - Just catching up here...... 73 de Mike N3LI - |
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Cecil Moore wrote:
Sorry, first things first. I am a newlywed (Feb. 28) and all my equipment is still packed in boxes after squeezing into a new QTH. Congratulations on the recent nuptials, Cecil, My regards to the new Mrs Moore. - 73 de Mike N3LI - |
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"Richard Harrison" wrote ... Art wrote: "Thus Kraus`s antennas are not in equilibrium and thus deviated away from Maxwell`s laws." Impossible. Maxwell`s laws are all that is nscessary and sufficient to describe radiation from any antenna. On page 37 of Kraus & Marthelka`s "Antennas for All Applications" one can read: "Although a charge moving with uniform velocity along a sreaighr conductor does not radiate, a charge moving back and forth in simple harmonic motion along the conductor is subject to aceleration (and deceleration) and radiates." Tell us than from which part of Hertz apparatus a radio waves are radiated? (http://people.seas.harvard.edu/~jone...Hertz_exp.html Are they transverse or longitudinal? S* |
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"Dave Platt" wrote ... Art Unwin wrote: I don't know about waves but my understanding is that all colors come from the mixing of the three basic colors, or is it four? Your understanding is in error... at least, if you're referring to colors in terms of actual photon behavior (energy and wavelength) rather than to the human *perception* of color. That's the RGB standard designed for fooling human eyes into seeing more than just red, green, and blue. Yup. And, the red/green/blue system is an artifact of the human visual system... most of us happen to have three different types of photo-sensitive molecules in the cone cells in our eyes, and these three types of molecules have their peak receptivities at the frequencies that we refer to as "red", "green", and "blue." There seems to be some amount of genetic variation, among humans, in the exact frequencies at which the peak sensitivies lie. And, some people have are missing one or more of these types of photoreceptor, and are referred to as "colorblind". There are apparently some humans who have four different types of photopigment, and thus may have an improved ability to perceive distinctions between colors. Certain species of animal are known to have four photopigments (one for e.g. UV sensitivity) and I wouldn't be surprised if some species have five or more variants. Photons in nature come in *all* EM frequencies. Yup again. It's an interesting process: - Light comes in a continuous range of frequencies. - Our eyes "sample" this continous range, with three types of sensor having different-but-overlapping sensitivities. Each sensor generates a variable amplitude (or pulse train) based on the intensity that it's detecting, within its sensitivity range. - Our nervous system maps the three amplitudes back into a perception of a continuous range of colors. The process is far from perfect... information is lost during the sampling process, and thus the perception of a continuous spectrum is necessarily flawed and imperfect. This is why a mixture of two different pure colors (e.g. red and green) can look like a single pure color to our eyes (e.g. yellow or amber)... it happens to excite the red and green photosensors in the same proportion that a single, pure-yellow light would. Mixed together, the colors look like one... split them apart with a prism and you can easily distinguish them and see the trick. Sometimes the screen on TV or cinema is perfectly white. This in cinema reflect. This reflected light splitted with the prism has only three frequences? [Almost] All Is Illusion. S* |
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"Art Unwin" wrote ... On May 6, 7:05 pm, Cecil Moore wrote: Art Unwin wrote: I don't know about waves but my understanding is that all colors come from the mixing of the three basic colors, or is it four? That's the RGB standard designed for fooling human eyes into seeing more than just red, green, and blue. Photons in nature come in *all* EM frequencies. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com Cecil Seems like this thing called photon is the magic article that created the big bang. You attribute everything to the photon but I don't think physics as got a proper handle on it! Heck, only a few years ago they said a particle could exist without mass.If a particle emitted from the Sun's boundary( lepton?) deaccellerated in a particular medium and broke apart into many electrons, then would not heat or light be emitted as kinetic energy contained in the particles of different sizes representing the spectrum of a particular color with respect to potential energy contained in the various sized particles? Does your photon come in different sizes, color and potential energy? My understanding is that there are about seven leptons that break away from the Sun's boundary, three of which contains color attributes along with other flavours which is indicative of temperature and change in momentum. I think it is to early to argue about such a subject. May be it is time to return to the beginning. To the Hertz experiment. See: (http://people.seas.harvard.edu/~jone...Hertz_exp.html What and from radiated? 1. Maxwell's waves from the big sparks (the big sparks are in full analogy to lightning which also radiate radio waves), 2. Electric waves from the two plates (there appear and disappear a huge charges - electrons are compressible and have mass), 3. Photons S* |
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Szczepan Białek wrote:
Heck, only a few years ago they said a particle could exist without mass. Photons have zero *rest* mass. If they had mass at rest, they could not travel at the speed of light. The mass of a photon is due to its velocity, c in free space. When a photon slows to less than the speed of light in a medium, it gives up its energy to another particle, e.g. an electron, and disappears. 3. Photons EM radiation from amateur radio antennas is photonic. RF energy is supplied to the antenna system by our transmitters. Free electrons are accelerated and decelerated. Photons are emitted and absorbed by those free electrons. Some of the photons escape into space as coherent radiation. One can learn a lot about EM waves by understanding the nature of photons. For instance, standing waves consist of photons that cannot stand still. The illusion of a "standing" wave is just two waves of photons moving in opposite directions at the speed of light. Photons are not like mashed potatoes. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
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In article , Szczepan Białek wrote: Sometimes the screen on TV or cinema is perfectly white. This in cinema reflect. This reflected light splitted with the prism has only three frequences? They're likely to be three bands of frequencies rather than three narrow single-frequency lines, because the technologies used to create the frequencies aren't narrow-band. But, yes, what you are seeing as "perfectly white" under these circumstances is often *not* a smooth, continuous spectrum. In the case of a TV screen, you're seeing either: - The mixed emissions of a set of red, green, and blue phosphors, individually excited by electron beams [for CRT displays], or - The emission from the phosphors of a cold-cathode fluorescent backlighting lamp (a complex spectrum with multiple peaks) filtered through red, green, and blue pixel-sized filters (for most LCD tubes). In traditional film cinema, you're seeing the emissions of an incandescent or halogen bulb (fairly continuous spectrum) filtered through three colors of dye in the film print. The fact that these complex mixtures of overlapping color spectra can look "pure white" to our eyes, is due in large part to our complex nervous systems. Our eye/brain systems adapt to the mix of colors present under differnet lighting conditions, and interpret different combinations as "pure white" depending on what's available at the time. This is why, for example, indoor fluorescent lighting can actually look half-decent to our eyes once we get used to it (we "see" a fairly complete range of colors there) but what looks "white" to use under fluorescents will actually have a distinctly greenish cast to a film or digital camera. It's also why a rather curious phenomenon can be demonstrated. The *exact* same mix of color emissions may look very different to us, under different ambient lighting conditions... what might look greenish outdoors will look pure white or even slightly pinkish under indoor fluorescent lighting, because our brains *interpret* that input differently due to the different surroundings. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
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"Cecil Moore" wrote ... Szczepan Białek wrote: Heck, only a few years ago they said a particle could exist without mass. It wrote Art. Photons have zero *rest* mass. If they had mass at rest, they could not travel at the speed of light. The mass of a photon is due to its velocity, c in free space. When a photon slows to less than the speed of light in a medium, it gives up its energy to another particle, e.g. an electron, and disappears. 3. Photons EM radiation from amateur radio antennas is photonic. RF energy is supplied to the antenna system by our transmitters. Free electrons are accelerated and decelerated. Photons are emitted and absorbed by those free electrons. Some of the photons escape into space as coherent radiation. One can learn a lot about EM waves by understanding the nature of photons. For instance, standing waves consist of photons that cannot stand still. The illusion of a "standing" wave is just two waves of photons moving in opposite directions at the speed of light. Photons are not like mashed potatoes. Are photons like transverse wave or like longitudinal? S* |
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On Sat, 16 May 2009 20:11:34 +0200, Szczepan Bia?ek
wrote: One can learn a lot about EM waves by understanding the nature of photons. For instance, standing waves consist of photons that cannot stand still. The illusion of a "standing" wave is just two waves of photons moving in opposite directions at the speed of light. Photons are not like mashed potatoes. Are photons like transverse wave or like longitudinal? Do two trolls' imaginary contributions resonate at the interface? 73's Richard Clark, KB7QHC |
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"Dave Platt" wrote ... In article , Szczepan Białek wrote: Sometimes the screen on TV or cinema is perfectly white. This in cinema reflect. This reflected light splitted with the prism has only three frequences? They're likely to be three bands of frequencies rather than three narrow single-frequency lines, because the technologies used to create the frequencies aren't narrow-band. But, yes, what you are seeing as "perfectly white" under these circumstances is often *not* a smooth, continuous spectrum. I was thinking that some transparent and semitransparent substances are phosphorescent (some time in dark) but ALL are less or more fluorescent (rework frequency). Rube in laser rewoork into one. But in laser are many passes. But what happens in one pass? May be that it rework also but only a little. Raman discovered that some substances can rework one frequency into many (also in higher). May be that a cotton screan also rework. In the case of a TV screen, you're seeing either: - The mixed emissions of a set of red, green, and blue phosphors, individually excited by electron beams [for CRT displays], or - The emission from the phosphors of a cold-cathode fluorescent backlighting lamp (a complex spectrum with multiple peaks) filtered through red, green, and blue pixel-sized filters (for most LCD tubes). In traditional film cinema, you're seeing the emissions of an incandescent or halogen bulb (fairly continuous spectrum) filtered through three colors of dye in the film print. The fact that these complex mixtures of overlapping color spectra can look "pure white" to our eyes, is due in large part to our complex nervous systems. Our eye/brain systems adapt to the mix of colors present under differnet lighting conditions, and interpret different combinations as "pure white" depending on what's available at the time. Yes. But for me is interesting the phenomenon at reflecting, scatering and refraction. May be that "polarisation" is an effect of that. This is why, for example, indoor fluorescent lighting can actually look half-decent to our eyes once we get used to it (we "see" a fairly complete range of colors there) but what looks "white" to use under fluorescents will actually have a distinctly greenish cast to a film or digital camera. It's also why a rather curious phenomenon can be demonstrated. The *exact* same mix of color emissions may look very different to us, under different ambient lighting conditions... what might look greenish outdoors will look pure white or even slightly pinkish under indoor fluorescent lighting, because our brains *interpret* that input differently due to the different surroundings. Is the light polarisation the hard prove that light vaves are transversal? S* -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
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Szczepan Białek wrote:
Are photons like transverse wave or like longitudinal? The EM fields embodied by photons are transverse. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
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Cecil Moore wrote:
EM radiation from amateur radio antennas is photonic. EM radiation from anything is both particles and waves. For instance, standing waves consist of photons that cannot stand still. As opposed to consisting of photons that _can_ stand still? :-) Interference is an example of the wavelike nature of light. ac6xg |
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"Szczepan Bialek" wrote in message
... Raman discovered that some substances can rework one frequency into many (also in higher). May be that a cotton screan also rework. This is a subject I have considerable experience in. My group at Eastman developed a process Raman spectrometer that used communications grade fibers to transmit both the excitation wavelength and the anti-Stokes Raman scattered light. Chalcogenide fibers, at around $1K per foot, would be needed to transmit the IR wavelengths needed for the analysis we were doing. The communication grade fibers cost less than one foot of the expensive fibers for the entire several hundred feet needed to separate the analyzer from the chemical process. Our patents were eventually licensed to the Rosemount division of Emerson Electric. Raman spectroscopy is based on the _non-linear_ (inelastic) scattering of photons. It is quite weak; more than 100 million photons are reflected by the linear (elastic) Rayleigh scattering for every photon reflected by Raman scattering. I am convinced now that Szczepan Bialek is nothing more than an offensive troll. It is best to ignore him as the physics newsgroups seem to have done. May he bask in his own stupidity! Or perhaps he and Art and the gays and the gay bashers could form their own "alt.troll" newsgroup. -- 73, Dr. Barry L. Ornitz WA4VZQ -- 73, Dr. Barry L. Ornitz WA4VZQ |
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Jim Kelley wrote:
For instance, standing waves consist of photons that cannot stand still. As opposed to consisting of photons that _can_ stand still? :-) Some people will argue that EM standing waves are actually standing still which implies that photons can stand still which they cannot. This is easy to see if one visualizes standing waves of light in free space as Hecht does in "Optics". There's no voltage or current to muddy the issue. One is forced to deal with photonic E-fields and H-fields in free space. It's the same old misconception. If net energy transfer is zero, some believe that means the energy carriers are not moving. But as Hecht says, it is the *profile* of the standing wave that doesn't move. The standing wave profile is a human abstraction and according to Hecht, standing waves do not deserve to be called waves at all: "They might better not be called waves at all, since they do not transport energy and momentum." "Standing waves" is a misnomer, i.e. they don't stand still and they do not meet the definition of "wave". On another newsgroup, I pointed out the above concept of EM waves just standing there is similar to the idea that since the number of northbound vehicles on the Golden Gate Bridge equal the number of southbound vehicles, there is no net traffic flow and therefore no maintenance of the bridge is required. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
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