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#11
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'Doc wrote in message ...
Richard, My peashooter is racked. Guess that means I'm just lurking? Nah, it means your in your usual position, riding on someone else's shirt tail. |
#12
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Hi Gary, seems like your the only one that is interesred in antennas on this
Jerry Springer group, so an answer there is. Piddle means to mess around with things, since I am from East London it could well be Olde English With regard to efficiency per unit length. It is well known that the ends of a 1/2 wave dipole can be lopped off without any noticable difference which can be seen by the area lost under the normal current flow diagrams, so efficiency can immediatly improved. When shortening the dipole even more we get a transition to a straight line current flowline inplace of the sino soidal curve which again shows a further inefficient portion at the ends that can be lopped of. What this then shows that we can have a higher current distribution per unit length with the mainly efficient portion in the center of the dipole. Now one is in position to introduce a phase change where one can have two dipoles in the same space taken up in the beginning, collinier in form and containing only the mainly high efficient portions of the center of a normal dipole. I see no reason why this transition can be followed over and over again until the radiator contains an area under the current curve that is uniform. Transformation to spot radiation is totaly another matter which I believe should be left to our descendents. Since you are an experimentor I would be happy to discuss my thoughts privately rather than take up valuable space that is required for auguments and pea shooters Best regards Art Unwin "JGBOYLES" wrote in message ... He may well be correct if we are all lemmings. Are they the rats that jump off the cliff into the sea? If they are, I am not one of them. people who piddle with antennas are a different breed. I experiment with antennas, but piddle? I thought in Olde English that meant something else. The rest of you post was interesting, could you provide more detail? What is "Yagi syndrome" and lossless coupling to the transmitter? 73 Gary N4AST |
#13
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Art Unwin KB9MZ wrote:
Piddle means to mess around with things, ... My unabridged dictionary says it has a second meaning. There are many piddling contests on r.r.a.a :-) -- 73, Cecil, W5DXP |
#14
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![]() Jaro, Thanks! Still batting a 1000, I see... All wrong. 'Doc |
#15
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Art wrote,
With regard to efficiency per unit length. It is well known that the ends of a 1/2 wave dipole can be lopped off without any noticable difference which can be seen by the area lost under the normal current flow diagrams, so efficiency can immediatly improved. When shortening the dipole even more we get a transition to a straight line current flowline inplace of the sino soidal curve which again shows a further inefficient portion at the ends that can be lopped of. Hi, Art, The above is untrue. Efficiency only has to do with the ratio of radiation resistance to total resistance. Also, the idea that the only part of an antenna that contributes to radiation is the center part because it carries most of the current is also untrue. The claim probably originates from the fact that most antenna parameters can be calculated given a knowledge of current distribution. It's a false leap of logic to conclude that there are portions of a half wave dipole that don't radiate, though. Since those areas have high changing charge densities which are associated with changing electrical fields which..., and so on, they radiate quite well. I don't think most amateurs want to diddle around with infinitesimal dipoles, anyway, Art, which is what they'd end up with if they implemented your ideas. An array of infinitesimal dipoles such as you're suggesting would be fun to make, but I doubt the wisdom of expecting increased efficiency from it. 73, Tom Donaly, KA6RUH (P.S. Art, I hope you don't equate disagreement with ridicule. I reserve all my ridicule for Cecil since he can take it.) |
#16
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Tdonaly wrote:
(P.S. Art, I hope you don't equate disagreement with ridicule. I reserve all my ridicule for Cecil since he can take it.) .... .. .... .. Tom, I notice you have not posted your calculations for the phase angles of those superposed phasors I presented yesterday. Did you come up with any phase angle other than zero and 180 degrees? Do you understand why Kraus' phase graph for standing wave current contains only two possible values of phase? -- 73, Cecil, W5DXP |
#17
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In message , Art Unwin
KB9MZ writes Antenna engineers have become so focussed on the half wave patterns that they have completely ignored the low efficiency portions at the ends of a half wave antenna. Yes, the midldle high current bit generates the H field, but you forget that the end high voltage bits are needed to generate the E field. The antenna 1/4 wave physical length is needed to get these in the correct phase. Now it should be possible to make a compact antenna where you can generate the H field from a current element and the electric field from a voltage element, making sure that the 1/4 phasing is preserved between the voltage and current. Naah it wouldn't work ![]() Brian GM4DIJ -- Brian Howie |
#18
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![]() "Tdonaly" wrote in message ... Art wrote, With regard to efficiency per unit length. It is well known that the ends of a 1/2 wave dipole can be lopped off without any noticable difference which can be seen by the area lost under the normal current flow diagrams, so efficiency can immediatly improved. When shortening the dipole even more we get a transition to a straight line current flowline inplace of the sino soidal curve which again shows a further inefficient portion at the ends that can be lopped of. Hi, Art, The above is untrue. Efficiency only has to do with the ratio of radiation resistance to total resistance. Also, the idea that the only part of an antenna that contributes to radiation is the center part because it carries most of the current is also untrue. The claim probably originates from the fact that most antenna parameters can be calculated given a knowledge of current distribution. It's a false leap of logic to conclude that there are portions of a half wave dipole that don't radiate, though. Don't make up a false augument, nowhere do I say that parts of a dipole does not radiate, soon you will have half the neibourhood up in arms regarding something I didn't say. As for your parlying the term 'false' so liberaly it is clear that you were sleeping during class, but then even those who know little of radiation can have an oponion. So what is your vision of the future with respect to antenna and are you doing anything to make that vision come true i.e. walking the walk.or are your jollies gained by shooting at those such as Cecil that does have the required knoweledge? On top of all that read carefully regarding' efficiency' since I have qualified it as ' per unit length' Best regards Art Unwin Since those areas have high changing charge densities which are associated with changing electrical fields which..., and so on, they radiate quite well. I don't think most amateurs want to diddle around with infinitesimal dipoles, anyway, Art, which is what they'd end up with if they implemented your ideas. Lots of words but all meaningless, I never said that I was persueing the ultimate point radiation suggestion. I experiment to the point that all antennas regardles of frequency can be made such that they are rotatable in the horisontal mode which means for 160 meters inovation has to be involved to reduced such a monster such that it can be rotated around its center point. I HVE REACHED THAT POINT AT THE PRESENT TIME and am now looking at ways to reduce it further, but maybe the next generation will achieve that jump.! I fully expect that somebody will say I have violated a law of old but until then I will continue to use it on the bands An array of infinitesimal dipoles such as you're suggesting would be fun to make, but I doubt the wisdom of expecting increased efficiency from it. 73, Tom Donaly, KA6RUH (P.S. Art, I hope you don't equate disagreement with ridicule. I reserve all my ridicule for Cecil since he can take it.) I don't see why he should take it! We have lost so many talented people from this group Tom,Gary Roy and so on but we are still not at the point where Richard and his followers ( not Richard Harrison ) pseudo Doktors and what ever have the forum completely to themselves. Regards Art Unwin KB9MZ.....XG |
#19
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Hmmmm
They said that the idea of break dancing was an impossibility but they have classes for same in East St Louis Students are not allowed to graduate until thay exhibit the ability of removing a hub cap off of a moving vehicle ! They probably have the same class in The Goebals Regards Art "Brian Howie" wrote in message ... In message , Art Unwin KB9MZ writes Antenna engineers have become so focussed on the half wave patterns that they have completely ignored the low efficiency portions at the ends of a half wave antenna. Yes, the midldle high current bit generates the H field, but you forget that the end high voltage bits are needed to generate the E field. The antenna 1/4 wave physical length is needed to get these in the correct phase. Now it should be possible to make a compact antenna where you can generate the H field from a current element and the electric field from a voltage element, making sure that the 1/4 phasing is preserved between the voltage and current. Naah it wouldn't work ![]() Brian GM4DIJ -- Brian Howie |
#20
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Art,
You just received two serious and legitimate responses from Tom and Brian. You proceeded to trash each of them for their contributions. How do you expect to get useful input if you are not willing to accept anything that does not agree with your preconceived notions? YOU are the one with the loaded pea shooter. Shame on you! 73, Gene W4SZ Art Unwin KB9MZ wrote: Hmmmm They said that the idea of break dancing was an impossibility but they have classes for same in East St Louis Students are not allowed to graduate until thay exhibit the ability of removing a hub cap off of a moving vehicle ! They probably have the same class in The Goebals Regards Art |
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