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Antenna future
I found it interesting to read on a particular
antenna page that the antenna future will revolve around what the person was presenting. He may well be correct if we are all lemmings but people who piddle with antennas are a different breed. Personaly I see antennas gyrating towards smaller antennas where radiation per unit length will finish at the top of the heap 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. Future antennas most surely will remove these low efficient radiator parts together with the addition of coupling techniques that will help to move away from the Yagi syndrome, together with resolving the of a "lossless" coupling direct to the transmitter that will obsolete the need of matching interface. Ofcourse this is where my intersts lie, but does this vision of the future match yours or am I thinking of the impossible? One noted Russion scientist stated that theoretically radiation can come from a single point, is this part of our future or just an impossible dream ? Best regards, and please put your pea shooters aside and try to get along rather than looking for ten seconds of cheap glory. Art Unwin KB9MZ......XG |
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 |
Art wrote,
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. What low efficiency portions? 73, Tom Donaly, KA6RUH |
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On Fri, 16 Jan 2004 02:39:56 GMT, " Art Unwin KB9MZ"
wrote: Hitting the juice again eh? Danny, K6MHE And your reason for saying that is......... what? Art Probably because you passed up four technical questions: could you provide more detail? What is "Yagi syndrome" lossless coupling to the transmitter? What low efficiency portions? to indulge yourself asking this. |
For goodness sake why don't you and Danny put away your pea shooters and
handle yourselves in an orderly manner. I have not avoided or passed up any questions, I am just in a standby mode to see what others visualise as what the future might bring or what they would like to see ,after which I will elaborate on my thoughts even tho some lurkers such as yourself may well be concentrating on distance and accuracy of their pea shooters. Art "Richard Clark" wrote in message ... On Fri, 16 Jan 2004 02:39:56 GMT, " Art Unwin KB9MZ" wrote: Hitting the juice again eh? Danny, K6MHE And your reason for saying that is......... what? Art Probably because you passed up four technical questions: could you provide more detail? What is "Yagi syndrome" lossless coupling to the transmitter? What low efficiency portions? to indulge yourself asking this. |
Richard, My peashooter is racked. Guess that means I'm just lurking? But I'm really enjoying the turkey shoot. 'Doc |
On Fri, 16 Jan 2004 04:14:14 GMT, " Art Unwin KB9MZ"
wrote: I have not avoided or passed up any questions, could you provide more detail? What is "Yagi syndrome" lossless coupling to the transmitter? What low efficiency portions? Twice denied |
"Art Unwin KB9MZ" wrote in message m... I found it interesting SNIP and try to get along rather than looking for ten seconds of cheap glory. Art Unwin KB9MZ......XG Ten seconds of cheap glory is often all you get. Ed wb6wsn |
'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. |
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 |
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 |
Jaro, Thanks! Still batting a 1000, I see... All wrong. 'Doc |
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.) |
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 |
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 :p Brian GM4DIJ -- Brian Howie |
"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 |
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 :p Brian GM4DIJ -- Brian Howie |
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 |
Cecil, are you discussing 'pea soup'?
Cecil Moore wrote: 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 |
Gene I suspect your Google has yet to be updated
but if not look up Tom's responses to me just for this month. As for Brian I did not trash him ! I think he said at the end it was impossible ! I suspect you are a new person on this newsgroup so I suppose one has to accept such statements and not take to much notice of such bland conclusions.......Now do you have anything to contribute? Regards Art "Gene Fuller" wrote in message ... 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 |
Gene,
Brian is a fellow Brit why would I trash a fellow 'G' Come to think of it why are you trashing me when you contributed nothing ? Just try to get along and you are home free Art "Gene Fuller" wrote in message ... 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 |
Cecil,
I am not Tom, but I will respond anyhow. It is so hard to keep up with you. This entire thread started a few days ago with a debate between you and Roy. You chastised Roy for considering the net current instead of the individual components. Now you have switched back to talking about net currents resulting from the addition of individual phasor currents. Which one do you want to talk about? It is unlikely that anyone reading this newsgroup is confused regarding the back and forth nature of the current on a thin wire. To insinuate such is merely a cheap shot that appears intended to intimidate. (Go ahead, take your best shot.) 8-) The concept of phasors is a common and useful tool for visualization and some elementary numerical solutions. The simple standing wave analysis currently under discussion and debate is certainly an appropriate subject for phasor treatment. However, once outside of the realm of ideal one-dimensional systems the use of phasors gets much more complicated. The use of conventional mathematics for such problems is pretty standard. The typical equation describing a standing wave is: I = A * sin (kx) sin (wt) The spatial phase of this equation is "kx", while the temporal phase is "wt". At no time do these phases suddenly reverse direction. The resulting value for I ranges through positive and negative values, and again it is unlikely that anyone is confused. If you choose to call the switch from current flow in the positive direction to the negative direction a 180 degree phase shift, so be it. I prefer to keep the phase in its place and let the sine function do its thing to reverse the value of the equation. 73, Gene W4SZ Cecil Moore wrote: 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 |
Art wrote,
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 Actually, Art, I have come up with a small antenna that radiates well enough, although I don't see any point in making anything out of it since I can't get it to do anything impossible. ( A full-size antenna would work better.) I apologize if I misunderstood you. You might pause to consider, however, that a half-wave dipole at the correct height is quite efficient, anyway, and improving it from, say, 98% to 99% won't gain you much advantage, even if your idea has merit. 73, Tom Donaly, KA6RUH |
Art,
OK, here is my contribution. Short antennas are quite thoroughly understood. Most of the analytical treatments of antenna theory I have seen start with short dipoles and then expand to longer dipoles and other types of antennas. There have been any number of segmented antennas proposed and built, including multiple trap antennas, multiple capacitor antennas, curtain antennas, fractal antennas, and so on. Do you have some new idea that has not already been tried? Short antennas radiate just fine, IF one can feed the power into the antenna and avoid losing too much to non-radiative losses. It has already been pointed out that all parts of a dipole antenna contribute to the radiation. Sure, it is possible to shorten the antenna and even maintain the same total radiated power. However, the pattern will change and the antenna may become more difficult to feed. It is not clear what issue you find with Yagi antennas. Keep in mind that it is unlikely that one can achieve high directionality and gain from an antenna with a size that is a tiny fraction of the wavelength. This is the case for radio waves, optics, or any other wave phenomena. The reason people choose to use large Yagi antennas is gain, not efficiency or cost. Soooo, the bottom line is that there are large antennas, and there are small antennas. Different applications favor one type over others. Do you expect to develop some new antenna design concepts or even some new science? If the former, then the field is well-plowed, even if it is theoretically still infinite. If the latter, well, good luck. 73, Gene W4SZ Art Unwin KB9MZ wrote: Gene, Brian is a fellow Brit why would I trash a fellow 'G' Come to think of it why are you trashing me when you contributed nothing ? Just try to get along and you are home free Art |
Art wrote,
Gene I suspect your Google has yet to be updated but if not look up Tom's responses to me just for this month. What responses? I don't normally respond to your posts, Art. 73, Tom Donaly, KA6RUH |
Cecil wrote,
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 What! And get into a 500 post exchange with you? You must think I'm mad. 73, Tom Donaly, KA6RUH |
Gene Fuller wrote:
It is so hard to keep up with you. This entire thread started a few days ago with a debate between you and Roy. You chastised Roy for considering the net current instead of the individual components. Now you have switched back to talking about net currents resulting from the addition of individual phasor currents. Which one do you want to talk about? Nice try, Gene. What got Roy into trouble is forgetting that the net current consists of two components. One can choose to talk about either the components or the net as long as one realizes that the net is the sum of the components. Roy has said, in so many words, that I am stupid to worry about the components when all I need to worry about is the net. It's obvious that Kraus worries about the components and, therefore, I have good reason for such. Great insight is afforded to he who considers the primary components of the sum instead of ignoring them. At no time do these phases suddenly reverse direction. Aha, so you disagree with Kraus and apparently don't understand the thin wire analysis of standing waves in his book. If you choose to call the switch from current flow in the positive direction to the negative direction a 180 degree phase shift, so be it. A DDS chip can generate a sine wave. Are you telling me that +0.001 volts out of a DDS chip is not 180 degrees different from a -0.001 volts out of a DDS chip? At exactly what voltage level does it have to get to to call it a 180 degree phase shift? If all you see is a step from +0.001 volts to -0.001 volts, does the information that you don't know dictate whether is is a 180 degree phase shift or some other phase shift? If so, you are in deep doo-doo, my friend, and you cannot trust any measurements because there are always unknowns. This situation of math models dictating reality (instead of vice-versa) is worse than I thought. In reality, there is no imaginary current when the real current is zero. All current in the real-world is real. I suppose that all current in the imaginary world is imaginary but that's not the world I live in. If the real current is zero then, for people living in the real world, the current is zero - there ain't no more. In reality, God doesn't control everything about the universe according to his whim. HE allows HIS physical laws to run the universe. If a 180 degree reversal in the direction of flow of current is not a 180 degree reverse in reality, exactly what is it? If you have a square wave with one amp as the maximum, and -0.1 amp as the minimum, is that not a 180 degree phase shift? If you have a square wave with 0.00001 amp as the maximum and 0.00001 amp as the minimum is that not a 180 degree phase shift? Is the quantum shift from +0.0000...01 volts to -0.0000...01 volts not a shift of 180 degrees? Gene, I hate to burst your (sacred cow) bubble, but the imaginary part of the current doesn't actually exist in my universe. If it exists in yours, I suggest you subscribe to r.r.a.a in that universe, wherever it might be. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Tdonaly wrote:
Cecil wrote, 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? What! And get into a 500 post exchange with you? You must think I'm mad. Heh, heh, it won't be a 500 post exchange if you got the same answer as Kraus and I did (50 years ago). :-) -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Cecil,
What in the world are you blathering on about? (That's a rhetorical question. No answer needed.) I stated my position, and I have nothing more to add. Feel free to continue to amuse yourself. 73, Gene W4SZ Cecil Moore wrote: Gene Fuller wrote: It is so hard to keep up with you. This entire thread started a few days ago with a debate between you and Roy. You chastised Roy for considering the net current instead of the individual components. Now you have switched back to talking about net currents resulting from the addition of individual phasor currents. Which one do you want to talk about? Nice try, Gene. What got Roy into trouble is forgetting that the net current consists of two components. One can choose to talk about either the components or the net as long as one realizes that the net is the sum of the components. Roy has said, in so many words, that I am stupid to worry about the components when all I need to worry about is the net. It's obvious that Kraus worries about the components and, therefore, I have good reason for such. Great insight is afforded to he who considers the primary components of the sum instead of ignoring them. At no time do these phases suddenly reverse direction. Aha, so you disagree with Kraus and apparently don't understand the thin wire analysis of standing waves in his book. If you choose to call the switch from current flow in the positive direction to the negative direction a 180 degree phase shift, so be it. A DDS chip can generate a sine wave. Are you telling me that +0.001 volts out of a DDS chip is not 180 degrees different from a -0.001 volts out of a DDS chip? At exactly what voltage level does it have to get to to call it a 180 degree phase shift? If all you see is a step from +0.001 volts to -0.001 volts, does the information that you don't know dictate whether is is a 180 degree phase shift or some other phase shift? If so, you are in deep doo-doo, my friend, and you cannot trust any measurements because there are always unknowns. This situation of math models dictating reality (instead of vice-versa) is worse than I thought. In reality, there is no imaginary current when the real current is zero. All current in the real-world is real. I suppose that all current in the imaginary world is imaginary but that's not the world I live in. If the real current is zero then, for people living in the real world, the current is zero - there ain't no more. In reality, God doesn't control everything about the universe according to his whim. HE allows HIS physical laws to run the universe. If a 180 degree reversal in the direction of flow of current is not a 180 degree reverse in reality, exactly what is it? If you have a square wave with one amp as the maximum, and -0.1 amp as the minimum, is that not a 180 degree phase shift? If you have a square wave with 0.00001 amp as the maximum and 0.00001 amp as the minimum is that not a 180 degree phase shift? Is the quantum shift from +0.0000...01 volts to -0.0000...01 volts not a shift of 180 degrees? Gene, I hate to burst your (sacred cow) bubble, but the imaginary part of the current doesn't actually exist in my universe. If it exists in yours, I suggest you subscribe to r.r.a.a in that universe, wherever it might be. |
Art said, in part; "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." You are right, you didn't say that the ends of a dipole do not radiate. But, by the above quote, you have implied just the opposite. 'Doc PS - Peashooter is back on the rack again. |
"Gene Fuller" wrote in message ... Art, OK, here is my contribution. Short antennas are quite thoroughly understood. Yes but all knoweledge obtained has not been utilised or consideredin this area even tho the use of this knoweledge is considered beforehand as useless. Most of the analytical treatments of antenna theory I have seen start with short dipoles and then expand to longer dipoles and other types of antennas. There have been any number of segmented antennas proposed and built, including multiple trap antennas, multiple capacitor antennas, curtain antennas, fractal antennas, and so on. Do you have some new idea that has not already been tried? Yes, you may well want to look at some old antenna patents of mine, I wrote them up myself in a way I thought the patent office wanted it and then they changed the hell out of it but I think the drawings I made should be enough for anybody to follow. Some locals built them from the same drawings. They are not considered valid by the gurus associated with this group. Short antennas radiate just fine, IF one can feed the power into the antenna and avoid losing too much to non-radiative losses. Exactly, a receiving antenna that many use can not be transmitted on where as mine is a perfect match that are as good as say a beverage in terms of gain yet are only a smidgeon of it's length. It has already been pointed out that all parts of a dipole antenna contribute to the radiation. Sure, it is possible to shorten the antenna and even maintain the same total radiated power. Good thinking However, the pattern will change and the antenna may become more difficult to feed. But what if the match is a perfect one? It is not clear what issue you find with Yagi antennas. Keep in mind that it is unlikely that one can achieve high directionality and gain from an antenna with a size that is a tiny fraction of the wavelength. Unlikely but I have done it! This is the case for radio waves, optics, or any other wave phenomena. The reason people choose to use large Yagi antennas is gain, not efficiency or cost. Well my last yagi ( 20 metres )I built had a boom length of 80 feet if I remember wrightly with 13 elements two of which were reflectors. After that antenna I decided to devote time to small antennas of a type that has not been written up before that are mathematically proven, duplicated by a pro computor program and of course used by me on various frequencies albiet not very often.. Some of the antennas broke over the years but were easily duplicated. Soooo, the bottom line is that there are large antennas, and there are small antennas. Different applications favor one type over others. Do you expect to develop some new antenna design concepts or even some new science? If the former, then the field is well-plowed, even if it is theoretically still infinite. If the latter, well, good luck. Thank you but one never gets to the end..It is also hard to believe the new when over the years so many people have made false claims which makes it relatively safe to call all new claims as bogus and the claiment is a lier. When I had to fill out papers to come to this country I was asked what my rank was in the boy scouts,had I eve committed adultery and several other penetrating questions. I would suggest it would be rather odd if a lying pattern started only after I arrived in this country and after I retired from G.E. but I suppose it could happen. Art 73, Gene W4SZ Art Unwin KB9MZ wrote: Gene, Brian is a fellow Brit why would I trash a fellow 'G' Come to think of it why are you trashing me when you contributed nothing ? Just try to get along and you are home free Art |
"I would suggest it would be rather odd if a lying pattern started only after I arrived in this country and after I retired from G.E. but I suppose it could happen." .... No, I won't do it. It would be just too easy... 'Doc |
Cecil, W5DXP wrote:
"If a 180 degree reversal in the direction of flow of current ia not a 180 degree reversal in reality, exactly what is it?" From the 1937 second edition of Terman`s "Radio Engineering" page 70: "In the case of both open- and short-circuited receivers (transmission line loads) the voltage and current are substantially 90-degrees out of phase at all places along the line except in the vicinity of the quarter-wave-length points where the phase angle rapidly shifts from nearly 90-degrees on one side of unity power factor to nearly 90-degrees on the other side of unity power factor. The voltages on opposite sides of a voltage minimum are therefore substantially 180-degrees out of phase, as are also the currents on opposite sides of a current minimum. In order to show this change of phase, the voltage and current distributions in circuits with distributed constants are frequently drawn as shown in Fig. 34---." It helps to have Terman`s Figs. 33 and 34 in front of you to be persuaded of the abrupt phase transistions. Terman can be accepted on faith and his truth eventually sinks in. Best regards, Richard Harrison, KB5WZI |
My understanding is that the phase of the forward and reflected waves
varies along the transmission line. One 'rotates clockwise' the other 'rotates counterclockwise'. In the case of 'perfect reflection', a mathematical study condition, the sum of these two waves varies along the transmission line. The resultant sum produces the minimum and maximum voltage we observe in a slotted line. It is to be noted that the phase shifts at the all half wave points from the load, by convention, rotate from the 'positive' two quadrants to the negative two quadrants. Therefore, a polarity change exists. Is this the 180 degree phase shift being discussed? Deacon Dave, W1MCE + + + SNIP At no time do these phases suddenly reverse direction. Aha, so you disagree with Kraus and apparently don't understand the thin wire analysis of standing waves in his book. If you choose to call the switch from current flow in the positive direction to the negative direction a 180 degree phase shift, so be it. SNIP |
Dave Shrader wrote:
My understanding is that the phase of the forward and reflected waves varies along the transmission line. One 'rotates clockwise' the other 'rotates counterclockwise'. In the case of 'perfect reflection', a mathematical study condition, the sum of these two waves varies along the transmission line. The resultant sum produces the minimum and maximum voltage we observe in a slotted line. It is to be noted that the phase shifts at the all half wave points from the load, by convention, rotate from the 'positive' two quadrants to the negative two quadrants. Therefore, a polarity change exists. If a current is 0 + j1.0 amps, exactly where is that one amp of current located? The real component of phasor current always lies along the 'x' real axis. A change from +0.001 amp at zero degrees through a zero magnitude to -0.001 amp at 180 degrees is a 180 degree phase shift in *real* current that exists in the real world. Imaginary current is, well, imaginary, and is an artifact of the phasor math model. Has anyone ever measured j1.0 amps of current at a point where the real current is zero? Is this the 180 degree phase shift being discussed? Originally, the 180 degrees phase shift being discussed was concerning a current standing wave in a thin wire where the forward current and reflected current are equal in magnitude. The phase of the net current is 0 degrees for awhile and then shifts abruptly to 180 degrees according to Kraus. There are only two directions in a wire. For an AC signal, the current is flowing one direction for 1/2 cycle and the other direction for the other 1/2 cycle. The *real* magnitude of the current varies with physical length (sin kL) and can be analyzed without any reference to phase. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Piddle means to mess around with things So does that mean an experimenter attaching an antenna to his chimney is a piddler on the roof? Duane, N6JPO |
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Art, KB9MZ wrote:
"Personally, I see antennas gyrating towards smaller antennas where radiation per unit length will finish at the top of the heap." Kraus, W8JK is somewhat famous among many reasons for his experience with close-spaced antenna elements. On page 184 of the 3rd edition of Kraus` "Antennas for All Applications", is Figure 6-12 containing an ordinarily-spaced broadside driven-array of two dipoles and a driven array radiating in the plane of the two dipoles (an end-fire array), the W8JK array. A feature of the W8JK array is close-spacing (1/8-wavelength). Gain of the W8JK array is a tiny bit more than that of the 4X wider-spaced broadside array. It`s a pity if you don`t have a copy of Kraus available. Kraus says in his earl;ier 1950 edition of "Antennas" on page 295: "The end-fire array of two side-by-side out-of-phase 1/2-wavelength elements discussed in Sec. 11-3 produces substantial gains even when the spacing is decreased to small values." To my eye, the W8JK array resembles the Adcock antenna if so spaced and polarized. The 1955 edition of Terman has the Adcock on page 1050. Terman has a comment on page 906 of his 1955 edition regarding "Close-spaced Arrays-Super-gain Antennas. A review of the behavior of broadside and end-fire arrays make it appear that in order to achieve high gain it is necessary that the antenna system be distributed over a considerable space. However, the antennas of Figs. 23-35 and 23-39 obtain enhanced directivity by employing antennas that are closely spaced. Moreover, it can be shown that an end-fire (like a Yagi) type of array that is short compared with a wavelength can theoretically achieve any desired directive gain provided enough radiators are employed and they are suitably phased. Such antennas which give great gain using small over-all dimensions are referred to as super-gain antennas." Read on. There is a fly in the ointment. Terman says: " A characteristic of all close-spaced arrays is that as the ratio of size to antenna gain is reduced, the radiation resistance also goes down; this is illustrated by Fig. 23-36. The result is a practical limit to the amount of gain that can be achieved in compact antenna systems, since as the radiation resistance goes down the fraction of the total power dissipated in the antenna loss resistance goes up. The Yagi antenna of Fig.23-39 andf the corner reflector represent about the best that can be achieved----." So, Art may be on to something to some extent. Best regards, Richard Harrison, KB5WZI |
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