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#41
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On Thu, 03 Dec 2009 13:37:05 -0800, Richard Clark
wrote: Yes indeed. If those wires were not, in themselves, decoupled; then they became radiators. Further discussion about these wires allowing RF to slither through what would ordinarily be impenetrable holes. Those holes, whose circulating currents prohibit any coupling of fields through them, as long as they are very small in relation to the wavelength, can turn into free-flowing fountains of power with some rather simple additions. As mentioned, merely pass an insulated wire through the hole. If that wire reaches into the interior where an RF field presents a very high potential difference to the Faraday shield, then you have a capacitive coupling to the exterior of the shield, through the hole, along that wire. On the other hand, if you loop that interior wire back onto the interior surface of the shield, AND that loop resides within the RF field where it presents a very high magnetic component; then you have an inductive coupling to the exterior of the shield, through the hole, along that wire. Simply terminate the outside extension of that wire to a suitable load, observing the conventions of matching, and remove as much power as is practicable. This is nothing more complex than the usual design conventions already discussed under the coaxial transmission line considerations in the post this derives from. The point of this aside is to remark how easily (or difficulty) the Faraday shield can be corrupted through indifference to first principles. 73's Richard Clark, KB7QHC |
#42
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On Thu, 03 Dec 2009 16:51:05 -0500, Registered User
wrote: On Tue, 01 Dec 2009 16:42:00 -0800, Richard Clark wrote: On Tue, 01 Dec 2009 16:22:08 -0500, Registered User wrote: I'm under the impression the current flow is identical whether metal rods or wire mesh is used in the antenna's construction. A discone does not exhibit any quality of shielding, so it wanders off in that regard. Maybe I'm confused and can't distinguish between Art's all-band mesh antennas and his mesh Faraday shields. I can understand the confusion. To return to your question above, there is NOTHING about the discone that falls under the topic of Faraday shield. I was questioning Art's statement -quote- When you feed a time varying current to the mesh it is best to view it in small parts, say a square in the mesh. The hole is a static field alongside the applied current flows. - end quote - The idea of examining the characteristics of a single square of mesh seems impractical. The impact of adjacent squares should be accounted for otherwise the single square is a loop. I discussed both the single mesh opening, and the total contribution of all mesh openings. To respond to your last statement, yes, the single square is a loop. A very, very inefficient coupler of energy. Either way I've learned as current varies the fields it produces will vary. If the fields vary they're not static. Too simplistic? What am I missing? Static comes in two flavors. One means "not moving." The other means high potential (which can be "not moving" AND, ironically, "moving"). Such is the legacy of electrostatic potential covering DC to Gamma. The difference between rods, number of rods, thickness of rods, and mesh all speak to bandwidth. 2, 3, or 4 rods will not be remarkable. 16 rods will closely approximate a cone of sheet metal (as would a grid of similar spacing). The same can be said of the rod/rods/mesh/sheet in the upper section approximating a solid disk. IIUC the current flows around the cone of a discone regardless of solid, sheet or mesh construction. This appears to be contrary to the quote above where current flows around each individual hole in the mesh. Well, language can be a barrier here when you say "around the cone." Go to: http://www.antenna-theory.com/antenn...rture/slot.php I don't endorse this page, but it gives you a beginning for slot antennas and especially the construction mimicry between them and a dipole. Note in figure two that a "source" appears across the two. In the case of the slot antenna, this source would give rise to a circulating current. If you were to approach this with knowing the current alone, it would follow that the source is "apparent." In other words, the two models (or experiences) are equivalent. Do not confuse this circulating current with a larger, general current UNLESS that more general one can spawn the circulating one. I wrote to this already and to put it shortly, it is physical length vs. wave length dependant. Again, all these "appearances" are a strict function of wavelength to physical length and spacing relationships. I've built several discones over the years and understand these relationships. How well is subject to conjecture hi. http://www.qsl.net/kb7qhc/antenna/Discone/discone.htm will illustrate how varying the flare of the skirt shifts the operating properties of the discone. 73's Richard Clark, KB7QHC |
#43
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On Dec 3, 3:37*pm, Richard Clark wrote:
On Thu, 03 Dec 2009 10:29:53 -0800, Richard Clark wrote: This small, resonant plate load, is quite specifically designed for RF with low in resistive loss - and yet it is miserable as a propagator of that same RF. *The physical size compared to the wavelength size dominates that efficiency with a fourth power law. To extend this to Art's misinterpretation of Faraday Shields: In the old days, breadboard design was exactly that - your rig was built on (hammered to) a breadboard. *It was open wiring with open components. *It radiated well with an antenna, and poorly without one. However, as poorly as it radiated without an antenna, if you had a separate receiver, you would hear yourself. *This was sometimes useful and gave us what is called "side tone." * The monitor was born. Of course, with antennas connected, the receiver was bound to get more than enough of that anyway and if the two were closely spaced, feedback could drive all circuits into saturation. *Not a good thing. The Faraday shield for the transmitter was born. It, as many can witness from simple observation, was composed of a fine grid mesh of wire either tied to ground, or to a heavily AC/RF filtered DC potential. *As with all Faraday shields that came before it (indeed since Faraday invented it), it completely encapsulated the RF power source. *The screen or mesh was simply a contrivance to allow cool air to move in and hot air to move out. *Modern implementations use finned constructions and heat wicks - but this is topic drift. With this added to the breadboard, other circuits also came to be shielded, and generally so with the appearance of sheet metal chassis with suitably wavelength small openings for access and heat transfer. As the breadboard went into this RF impenetrable shell for both receivers and transmitters (and with even more care for transceivers), there arose a problem: *What about the wires that go in and out? Yes indeed. *If those wires were not, in themselves, decoupled; then they became radiators. *The lesson to be learned was that those wires had to be held at the same potential as the Faraday shield. *This could be accomplished by a simple connection, but with more than one wire this leads to dead shorts between wires. *Not a good thing. The solution was to use AC/RF shorts (capacitors) to the shield from the wire and the wire could only penetrate the shield through a very small (in proportion to wavelength) opening. *This was not always a good thing. A capacitor could be good, but it exhibits a roll-off of only 6dB per octave, or 10dB per decade isolation. *If your line going in and out was a DC control line, and your principle frequency was 1MHz (talking about the old days now); then you had 6 decades of separation between 1Hz and 1MHz - pretty good. *If in the intervening years you pushed the technology envelope and added voice modulation and that came through the same wire; then your system shrunk to 3 decades of separation between 10,000Hz and 1MHz. *This might work, sometimes it didn't. As the years spun on, more wires penetrated that RF barrier, and they needed to not only be isolated from the RF, but each other; and often they contained very small signals that needed suitable signal to noise ratio (noise being that soup of RF that was stewing inside the shield). * Inline bypass filters were born. The lines that penetrate a Faraday shield now appear to be more multi-stage low pass filters with repeating sections of shunt capacitors and series inductors. *Their common (ground to the old brass pounder) was the shield which was RF free (as it was decoupled to a sanctioned earth ground). *And lest we forget the principle penetration of that old time Faraday shield: The coaxial transmission line was born. By all appearances, this line satisfies the convention of a small opening through the Faraday shield. *It's diameter is easily very small in relation to the wavelength of the RF power it reaches into the shield to tap. *In a sense, it extends that hole in the shield to some very remote area that is far from the operating position, and then allows a wire(s) to emerge without regard for further shielding: The antenna is born. Funny thing, however, is that presumption of the shield of the coax being inert, un-perturbing, quiescent, invisible, benign - for that presumption is an illusion, a grand delusion. *The line is very long with respect to wavelength, it is in the field of excitation that has been drawn out of the soup within the cage, and it is as much an antenna as the wire that emerged from its end. *Many familiar problems rise from the ashes of this illusion. *The exterior of the coaxial cable appears to the field to be a very long, grounded radiator. However, at any appreciable length (wavelength raises its familiar visage with an ironic grin), this exterior surface ceases to be the familiar DC grounding strap material, and becomes a full-fledge radiator according to its physical length vs. wavelength relationship. Not a very good thing, untill: The transmission line choke is born. To decouple the OUTSIDE of the coaxial line, the convention that has been observed (to widespread validation) is to either wind some sections of the line into Inductive chokes, or to add ferrites which serve the same purpose. *These chokes, to be fully useful to their purpose, should be found at not only one point along the line, but at several so as to suppress (wavelength based) couplings along the line, by the line and by the field. When the combination of all these methods are employed, then the Faraday shield does what it has done for these several hundred years while allowing the migration of RF power to a remote drive point, and without allowing that RF power to re-intrude into the shield, nor along the coaxial cable. *Thus, the only evidence of RF from inside the Faraday shield is that which arrives over-the-air from the remote antenna. Any other claim is a profanation of Faraday. 73's Richard Clark, KB7QHC So after a degree in literature you have taken to reading up on science. But you have only regurgutated what you have read in a physics book. When I introduced this group to first principles every body on this group were apaulled. When I stated, and it was confirmed by Dr Davis, all started waving the hands and insulted Davis and I." What" you said "you can mix up statics with electromechanics"? "What foolishness is being stated here." In your posting you never mentioned any thing of that! You and nobody in the group has presented anything that refutes what I have stated. All this group have agreed on is that I am promoting a new fangled science where all is already known. Now Avitar has never stated any sort of physics that shows that he has studied in college other than waving his hands. Ofcourse we have the ham who got kicked out of high school so he couldn't graduate. Not his fault I might add, just some mis understandings why he would not go to school, and it goes on. And then we have Richard who says, why do we need new design antennas, we have the yagi, what more can you want? So the group is not going to rely on physics to disprove my comments because they have found that deformation, insults and loud voices is all they have to crush my claims, and it is just not working. Have they made one? No. They know the true facts on radiation so they continue to sit on the couch and wave their hands and yell |
#44
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On Dec 3, 4:24*pm, Art Unwin wrote:
You and nobody in the group has presented anything that refutes what I have stated. I have, and on more than one occasion. But it goes through your head faster than a blue light special announcement to the average K-mart shopper. They know the true facts on radiation so they continue to sit on the couch and wave their hands and yell I don't sit on a couch. I sit in an office style chair. And it probably should be replaced as it tends to molest my differential after a while. Needs more particuls between the frame and the top particul retaining cover. Due to the weak force of my differential constantly being supported by these particuls, they have achieved equilibrium and no longer want to do any useful work. |
#45
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On Dec 3, 5:35*pm, wrote:
On Dec 3, 4:24*pm, Art Unwin wrote: You and nobody in the group has presented anything that refutes what I have stated. I have, and on more than one occasion. But it goes through your head faster than a *blue light special announcement to the average K-mart shopper. They know the true facts on radiation so they continue to sit on the couch and wave their hands and yell I don't sit on a couch. I sit in an office style chair. And it probably should be replaced as it tends to molest my differential after a while. Needs more particuls between the frame and the top particul retaining cover. Due to the weak force of my differential constantly being supported by these particuls, they have achieved equilibrium and no longer want to do any useful work. No you have not! Every thing comes back to the initial finding that by adding a time varying current to the arbitrary border of Gauss which surrounds a field of static particles provides the same conditions implied by Maxwell's equations. The group denies this fact possibly because the word equilibrium was not of their understanding. Without understanding the connection between Maxwell and Gauss with respect to the addition of time makes to a static field ala a dynamic field, it is impossible to procede with respect to radiation. If one starts from the middle of the story where coupling of waves is considered a basic physics understanding the debate leads no where. Now I am not asking people to follow solely the path of mathematics but of the concepts involved where the presence of particles is present., To start from a small portion of the current flow and thinking in terms of DC or the suggestion that time varying fields cannot surround a static field is just ludicrous. The subject is Classical Physics and one should keep on subject if one is to fully understand radiation. Denial of select parts of classical physics without supplying reason ans substituting insults instead is not going to solve anything. And as you did not graduate from high school it is perfectly understandable that you will find difficulties in parts of the debate and yet you would like to contribute to the debate. But insults will not get the job done. Of course one can go back to the basics of mathematics way back in Arabic times where the mere presence of an equal sign denotes equilibrium or balance. The equal sign is part of Maxwells equations so equilibrium is in effect. This immediatly tells you that any radiator considered must be a function of a full wavelength or a period with respect to a continuing variable sign wave. Immediately one should note that a half wave has no place in our calculations as the two areas under curve for a period can never be the same because of overshoot phenomina, thus it is the period that is repeatable and to be used. One can also deduce that a radiator must be in equilibrium to be part of the same reasoning thus resonance on its own is not part of the mathematics. There are plenty of ways to see how current thinking on antennas is certainly not inline with the equations of Maxwell, thus it is very important to start from "first "principles and not just accept the books. And that the importance of adding time to a static field enclosed by an arbitrary boundary to ensure the correct metrics will be used at the outset. Art |
#46
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On Dec 3, 12:25*am, Lostgallifreyan wrote:
( Richard Feynman lectures) ... I don't know if he's written anything a layman can easily work through, that doesn't come with lots of maths without which accompanying text doesn't help much, but if he has I'll try to read it. I think one of the key things that made his physics lectures popular is that they were delivered without a whole lot of math. You could get into that if you wanted, but you could also get a lot out of just listening to the _ideas_. If you drop me an email, perhaps I can send you a bit more about this particular lecture... Cheers, Tom |
#47
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On Dec 3, 6:52*pm, K7ITM wrote:
On Dec 3, 12:25*am, Lostgallifreyan wrote: ( *Richard Feynman lectures) ... I don't know if he's written anything a layman can easily work through, that doesn't come with lots of maths without which accompanying text doesn't help much, but if he has I'll try to read it. I think one of the key things that made his physics lectures popular is that they were delivered without a whole lot of math. *You could get into that if you wanted, but you could also get a lot out of just listening to the _ideas_. If you drop me an email, perhaps I can send you a bit more about this particular lecture... Cheers, Tom That is oh so true! The masters started with an observation of an occurence and not from a rendering of mathematics. With more observations it became natural to align the Universe via mathematics which, as with a jig saw puzzle, fits together nicely., It would seem today that scientists today are using mathematics via a computer to churn out bundles of equations leaving the operator to think of an observation that would fit the math. Of course, mathematics provide imaginary answers similar to a quadratic equation that finish up as multiple of false leads and deductions which eventually requires the multiple use of constants to provide a semblance of understanding of what has been provided. |
#48
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Art Unwin wrote:
No you have not! Temper, temper little boy. Every thing comes back to the initial finding that by adding a time varying current to the arbitrary border of Gauss which surrounds a field of static particles provides the same conditions implied by Maxwell's equations. Made up physics again. Unproven by any math or demonstrable effects. Try a new line of argument, this one gets you nowhere. The group denies this fact possibly because the word equilibrium was not of their understanding. Without understanding the connection between Maxwell and Gauss with respect to the addition of time makes to a static field ala a dynamic field, it is impossible to procede with respect to radiation. If one starts from the middle of the story where coupling of waves is considered a basic physics understanding the debate leads no where. Denied by the group because it contradicts everything that is proven to work, as well as all published and mathematically backed theories. And provide some proof. Even just a little. Rhetoric doesn't count. You accuse others of sitting on their asses and not building antennas and measuring them, when you have never once done it yourself. I have built many antennas and provided many independent performance measurements right here. And so has almost evreyone you argue with. We all make things and MEASURE them. You don't. Now I am not asking people to follow solely the path of mathematics but of the concepts involved where the presence of particles is present., To start from a small portion of the current flow and thinking in terms of DC or the suggestion that time varying fields cannot surround a static field is just ludicrous. The subject is Classical Physics and one should keep on subject if one is to fully understand radiation. Denial of select parts of classical physics without supplying reason ans substituting insults instead is not going to solve anything. And as you did not graduate from high school it is perfectly understandable that you will find difficulties in parts of the debate and yet you would like to contribute to the debate. But insults will not get the job done. Of course one can go back to the basics of mathematics way back in Arabic times where the mere presence of an equal sign denotes equilibrium or balance. The equal sign is part of Maxwells equations so equilibrium is in effect. This immediatly tells you that any radiator considered must be a function of a full wavelength or a period with respect to a continuing variable sign wave. Immediately one should note that a half wave has no place in our calculations as the two areas under curve for a period can never be the same because of overshoot phenomina, thus it is the period that is repeatable and to be used. One can also deduce that a radiator must be in equilibrium to be part of the same reasoning thus resonance on its own is not part of the mathematics. There are plenty of ways to see how current thinking on antennas is certainly not inline with the equations of Maxwell, thus it is very important to start from "first "principles and not just accept the books. And that the importance of adding time to a static field enclosed by an arbitrary boundary to ensure the correct metrics will be used at the outset. Uh Art? There are no rational concepts in your presentation, please provide some. And there's no "math" at all in your mathematical presentations, just a bunch of bafflegab. Please provide math. Oh, I forgot, you can't. All you can do is babble. And accuse people of foolishness in their disbelief. I must say, you are entertaining when you don't take your medications. And you still can't spell or put together a sentence. I would suggest a spell checker at the very least. tom K0TAR |
#49
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On Dec 3, 6:42*pm, Art Unwin wrote:
On Dec 3, 5:35*pm, wrote: On Dec 3, 4:24*pm, Art Unwin wrote: You and nobody in the group has presented anything that refutes what I have stated. I have, and on more than one occasion. But it goes through your head faster than a *blue light special announcement to the average K-mart shopper. They know the true facts on radiation so they continue to sit on the couch and wave their hands and yell I don't sit on a couch. I sit in an office style chair. And it probably should be replaced as it tends to molest my differential after a while. Needs more particuls between the frame and the top particul retaining cover. Due to the weak force of my differential constantly being supported by these particuls, they have achieved equilibrium and no longer want to do any useful work. No you have not! Every thing comes back to the initial finding that by adding a time varying current to the arbitrary border of Gauss which surrounds a field of static particles provides the same conditions implied by Maxwell's equations. The group denies this fact possibly because the word equilibrium was not of their understanding. Without understanding the connection between Maxwell and Gauss with respect to the addition of time makes to a static field ala a dynamic field, it is impossible to procede with respect to radiation. If one starts from the middle of the story where coupling of waves is considered a basic physics understanding the debate leads no where. Now I am not asking people to follow solely the path of mathematics but of the concepts involved where the presence of particles is present., To start from a small portion of the current flow and thinking in terms of DC or the suggestion that time varying fields cannot surround a static field is just ludicrous. The subject is Classical Physics and one should keep on subject if one is to fully understand radiation. Denial of select parts of classical physics without supplying reason ans substituting insults instead is not going to solve anything. And as you did not graduate from high school it is perfectly understandable that you will find difficulties in parts of the debate and yet you would like to contribute to the debate. But insults will not get the job done. Of course one can go back to the basics of mathematics way back in Arabic times where the mere presence of an equal sign denotes equilibrium or balance. The equal sign is part of Maxwells equations so equilibrium is in effect. This immediatly tells you that any radiator considered must be a function of a full wavelength or a period with respect to a continuing variable sign wave. Immediately one should note that a half wave has no place in our calculations as the two areas under curve for a period can never be the same because of overshoot phenomina, thus it is the period that is repeatable and to be used. One can also deduce that a radiator must be in equilibrium to be part of the same reasoning thus resonance on its own is not part of the mathematics. There are plenty of ways to see how current thinking on antennas is certainly not inline with the equations of Maxwell, thus it is very important to start from "first "principles and not just accept the books. And that the importance of adding time to a static field enclosed by an arbitrary boundary to ensure the correct metrics will be used at the outset. Art Bla, bla, bla, bla.. We need to get you a new needle that doesn't skip and play the same broken record over and over again. :/ You whine and moan about my education, which BTW, you have no idea of knowing what I have learned in the 35 years since then, but you stun us with such proof of your all knowing knowledge by referring to sine waves as "sign waves".. Chortle.. Give me a break.. Your education in things RF is probably not much greater than mine is being as you didn't take the relevant courses in school. It might even be less being as I have a decent library and I don't distrust everything I read without actually testing it first. And I actually build and test the antennas I talk about. On the air. In front of real people. I've got nothing to hide. When was the last time you actually compared one of your antennas to a known benchmark? At at a testing range. Or on the air.. In front of real people... I'm afraid using mumbo jumbo pseudoscience theories are not going to propel your obviously inefficient antenna designs to greatness. I realize this must distress you greatly, but it's a situation that can be dealt with with the proper medications and therapy. |
#50
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On Dec 3, 8:39*pm, tom wrote:
Art Unwin wrote: No you have not! Temper, temper little boy. Every thing comes back to the initial finding that by adding a time varying current to the arbitrary border of Gauss which surrounds a field of static particles provides the same conditions implied by Maxwell's equations. Made up physics again. *Unproven by any math or demonstrable effects. Try a new line of argument, this one gets you nowhere. The group denies this fact possibly because the word equilibrium was not of their understanding. Without understanding the connection between Maxwell and Gauss with respect to the addition of time makes to a static field ala a dynamic field, it is impossible to procede with respect to radiation. If one starts from the middle of the story where coupling of waves is considered a basic physics understanding the debate leads no where. Denied by the group because it contradicts everything that is proven to work, as well as all published and mathematically backed theories. And provide some proof. *Even just a little. *Rhetoric doesn't count. You accuse others of sitting on their asses and not building antennas and measuring them, when you have never once done it yourself. I have built many antennas and provided many independent performance measurements right here. *And so has almost evreyone you argue with. *We all make things and MEASURE them. *You don't. Now I am not asking people to follow solely the path of mathematics but of the concepts involved where the presence of particles is present., To start from a small portion of the current flow and thinking in terms of DC or the suggestion that time varying fields cannot surround a static field is just ludicrous. The subject is Classical Physics and one should keep on subject if one is to fully understand radiation. Denial of select parts of classical physics without supplying reason ans substituting insults instead is not going to solve anything. And as you did not graduate from high school it is perfectly understandable that you will find difficulties in parts of the debate and yet you would like to contribute to the debate. But insults will not get the job done. Of course one can go back to the basics of mathematics way back in Arabic times where the mere presence of an equal sign denotes equilibrium or balance. The equal sign is part of Maxwells equations so equilibrium is in effect. This immediatly tells you that any radiator considered must be a function of a full wavelength or a period with respect to a continuing variable sign wave. Immediately one should note that a half wave has no place in our calculations as the two areas under curve for a period can never be the same because of overshoot phenomina, thus it is the period that is repeatable and to be used. One can also deduce that a radiator must be in equilibrium to be part of the same reasoning thus resonance on its own is not part of the mathematics. There are plenty of ways to see how current thinking on antennas is certainly not inline with the equations of Maxwell, thus it is very important to start from "first "principles and not just accept the books. And that the importance of adding time to a static field enclosed by an arbitrary boundary to ensure the correct metrics will be used at the outset. Uh Art? *There are no rational concepts in your presentation, please provide some. And there's no "math" at all in your mathematical presentations, just a bunch of bafflegab. *Please provide math. Oh, I forgot, you can't. *All you can do is babble. *And accuse people of foolishness in their disbelief. I must say, you are entertaining when you don't take your medications. And you still can't spell or put together a sentence. *I would suggest a spell checker at the very least. tom K0TAR Tom Give me a clue whether you are in junior high school or have a track record of achieving something higher. You have never enunciated or even given a clue that you have ever taken a physics course or for that matter any engineering course in any of your postings. It seems like you are awful young and not yet an adult to put some scence or logic to any thing that you say! You talk of no "rational" in my statements, but as yet have not presented anything to back you up. I have read thru a lot of your postings but as yet have not come across anything from which I can gauge some of your knowledge and expertise with respect to antennas and radiation. I have gathered that you have had some experience in installing consumer dishes and I recall you stating that dishes can only be used in the giga hertz range, without mention that it is the size of the antenna determines whether a dish orreflecter is pertinant or not. Very strange! Because of lack of comment from others one can assume that they know you better than I do and are content with a glance in the air with a sigh and maybe I should follow like wise. I read your post again and note that you want the math. If I gave you a starter with respect to Gauss and Maxwell would you give me a hint with respect to your present understandings with mathematics. Lets face it, you never proved the mathematics wrong when it was presented to you by the good doctor where every body also denied its correctness, so it is awfully difficult to proceed when you deny the feasability of the initiating statement. If it makes you feel good then continue with your insults in leu of not knowing anything else to say. |
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