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Antenna physical size
On Mar 25, 1:31 pm, Cecil Moore wrote:
Richard Harrison wrote: He who scoffs at Terman is at great peril. If radiation was *only* perpendicular to the antenna, wouldn't the beam width be fixed to the length of the antenna? Wouldn't cloverleaf patterns be impossible? What am I missing? -- 73, Cecil http://www.w5dxp.com Cecil, he is not interested in finding the new, he is more comfortable of staying with the old people of his era. He doesn,t need proof and doesn.t know how to handle it. Terman is the one thing left in life he has, maybe we should leave him alone for eventual sainthood ceremonies for Terman when they get to the milky way. If he is looking for the Proof at the present time then we may never hear from him again. No one has come to his aid with a computor analysis realising that he is firmly set in his ways. Heck, he won't even try our a computor and probably doesn't have a new fangled television |
Antenna physical size
Cecil Moore wrote:
"What am I missing?" Radio waves spread during propagation. Huygens` principle is a cause. Huygens says: Each point on a primary wave front can be considered as a new source of a secondary spherical wave and that a secondary spherical wave front can be constructed as the envelope of these secondary waves. This is illustrated in Fig. 5-37 on page 144 of the 3rd edition of Kraus` "Antennas". Best regards, Richard Harrison, KB5WZI |
Antenna physical size
On Tue, 25 Mar 2008 12:43:49 -0700 (PDT), Art Unwin
wrote: a new fangled television TV as the hallmark of the new age? More like a silver plated drool cup in the age of the Internet. 73's Richard Clark, KB7QHC |
Antenna physical size
Art Unwin wrote:
Cecil, he is not interested in finding the new, he is more comfortable of staying with the old people of his era. I'm just trying to understand what Terman said. Did he say that all of the radiation is perpendicular to the radiating element or that most of the radiation is perpendicular to the radiating element or that none of the radiation is off the ends of the element? -- 73, Cecil http://www.w5dxp.com |
Antenna physical size
Richard Harrison wrote:
Cecil Moore wrote: "What am I missing?" Radio waves spread during propagation. Huygens` principle is a cause. But the Method Of Moments used by NEC for antenna radiation patterns calculates the interference at a point in space based on radiation from different elementary dipole sections of the antenna. For instance, when the antenna is two wavelengths long there is no more broadside radiation than there is radiation off the ends. In "Antenna Theory" by Balanis, in Chapter 8, page 407, on Moment Method, he illustrates the method using radiation angles less than 45 degrees to the radiating element. -- 73, Cecil http://www.w5dxp.com |
Antenna physical size
Cecil Moore wrote:
"But the Method Of Moments used by NEC for antenna radiation patterns calculates the interference at a point in space based on radiation from different elementary dipole sections of the antenna." Completely logical and it works. Interference or vector sum? Terman illustrates radiation from an elementary doublet (dipole) , and it is mostly at right angles to the antenna axis, on page 865 of his 1955 opus. On page 866 he shows an actual antenna consisting of numerous elementary doublets and on page 867 he says: "The result is that the fields radiated from different elementary sections of a long wire add vectorially to give a sum that depends on direction." Kraus devotes Chapter 14 in the 3rd edition of "Antennas" to: "The Cylindrical Antenna and the Moment Method (MM)." Best regards, Richard Harrison, KB5WZI |
Antenna physical size
I find this topic very interesting, including the mandrill part :)
We all want to have small, broadband, eficient antennas. I believe Art is right in his original post, today we can have all these characteristics in the same package. There is no law of physics forbidding that. Through advances in computation power we can achieve today in months what took decades in the past and there is much research directed at these kinds of new antennas. Eventually everyone will be able to choose and model his own antenna based on the characteristics one wants, but without the cumbersome dimensions, without significant bandwith limitations, without major efficiency compromises. I believe the tradeoff (for it has to exist one) will be ease of manufacturing. Incidentally these new antennas have a lot to do with what Art defines as equilibrium although I don't think he has a clear enough definition. But it's all related to patterns, patterns which can be found everywhere in nature an which can be expressed almost entirely through matemathical formulas. Scaling of antennas is clearly possible, despite of what the Chu-Harrington limit states ( or to be fair, by applying them in a new way ). I eagerly await the day when the 80 meter dipole will be replace by a small device the size of a shoe box ( although it might be a bit larger in the beginning :) ). Regards, Robert |
Antenna physical size
"Richard Clark" wrote in message ... On Mon, 31 Mar 2008 14:11:00 -0700 (PDT), wrote: Eventually everyone will be able to choose and model his own antenna based on the characteristics one wants, but without the cumbersome dimensions, without significant bandwith limitations, without major efficiency compromises. Hi Robert, 50 years ago they said Electricity would be so easy to produce they would pay us to use it. They ignored Hiroshima and discovered Chernobyl. 40 years ago they said DNA and genetics would allow us to design our own babies. They ignored Thalidomide and discovered Dolly the sheep that died before her time. 30 years ago they invented modeling software that would allow us to create the Gaussian dipole (or whatever) and discovered every dipole that came before it performed better. Nearly 20 years ago Johnny Carson retired and we are still getting jokes. Not nearly 10 years ago with the Dow at 11658 and a budget surplus at 230 billion, the Republicans promised prosperity was around the corner and their voters are now living in cardboard boxes with the Dow at 12176 and the national debt up 50%. Scaling of antennas is clearly possible, despite of what the Chu-Harrington limit states ( or to be fair, by applying them in a new way ). But you don't know how, and have never seen one either. 73's Richard Clark, KB7QHC Hi Richard, I have a pair of computer speakers sitting on my desk that completely out perform the so called ultimate hi-fi floor mounted tower system speakers I bought 35 years ago for the equivalent of several thousand dollars in today's money. The old speakers still work just fine but the audio experts have learned how to squeeze that performance out of a speaker that old audio theory predicted couldn't possibly work. Just how does a 3 inch speaker in a cabinet the size of a couple of books manage to produce notes from 20 Hz - 20 kHz? To be fair, the small speakers can't fill a room with sound in the same smooth way that a larger speaker cabinet can, but for everyday use in a small modern house or apartment they are more than adequate for the majority of people. It seems to me that Art and others are pursuing a similar path at RF. The aim being to produce an antenna that punches out a signal from a physically small area. It may not perform quite as well as a full size half or full wavelength antenna, but it will work well enough for most people with small gardens or limited real estate for an antenna farm. Clearly there are considerable differences in dealing with sound waves and RF but I believe that a principle has been established that it is possible to 'simulate' the performance of a larger system using physically small components. Art may not be the first to get there, but he seems to be having a damn good try and someone, somewhere will eventually succeed. Mike G0ULI |
Antenna physical size
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Antenna physical size
On Mar 31, 5:47 pm, "Mike Kaliski" wrote:
"Richard Clark" wrote in message ... On Mon, 31 Mar 2008 14:11:00 -0700 (PDT), wrote: Eventually everyone will be able to choose and model his own antenna based on the characteristics one wants, but without the cumbersome dimensions, without significant bandwith limitations, without major efficiency compromises. Hi Robert, 50 years ago they said Electricity would be so easy to produce they would pay us to use it. They ignored Hiroshima and discovered Chernobyl. 40 years ago they said DNA and genetics would allow us to design our own babies. They ignored Thalidomide and discovered Dolly the sheep that died before her time. 30 years ago they invented modeling software that would allow us to create the Gaussian dipole (or whatever) and discovered every dipole that came before it performed better. Nearly 20 years ago Johnny Carson retired and we are still getting jokes. Not nearly 10 years ago with the Dow at 11658 and a budget surplus at 230 billion, the Republicans promised prosperity was around the corner and their voters are now living in cardboard boxes with the Dow at 12176 and the national debt up 50%. Scaling of antennas is clearly possible, despite of what the Chu-Harrington limit states ( or to be fair, by applying them in a new way ). But you don't know how, and have never seen one either. 73's Richard Clark, KB7QHC Hi Richard, I have a pair of computer speakers sitting on my desk that completely out perform the so called ultimate hi-fi floor mounted tower system speakers I bought 35 years ago for the equivalent of several thousand dollars in today's money. The old speakers still work just fine but the audio experts have learned how to squeeze that performance out of a speaker that old audio theory predicted couldn't possibly work. Just how does a 3 inch speaker in a cabinet the size of a couple of books manage to produce notes from 20 Hz - 20 kHz? To be fair, the small speakers can't fill a room with sound in the same smooth way that a larger speaker cabinet can, but for everyday use in a small modern house or apartment they are more than adequate for the majority of people. It seems to me that Art and others are pursuing a similar path at RF. The aim being to produce an antenna that punches out a signal from a physically small area. It may not perform quite as well as a full size half or full wavelength antenna, but it will work well enough for most people with small gardens or limited real estate for an antenna farm. Clearly there are considerable differences in dealing with sound waves and RF but I believe that a principle has been established that it is possible to 'simulate' the performance of a larger system using physically small components. Art may not be the first to get there, but he seems to be having a damn good try and someone, somewhere will eventually succeed. Mike G0ULI Mike, I am already there. Regardless of the confidence I have in my own findings I have cinsented for a stanger in another state to test it in a way he feels comfortable with. I might also remind you that the antennas are Small full wave antennas which vastly different to electrically small antennas that is often written about by many including Chu! As far as equilibrium goes it is adviseable to go back a few hundred years when scientists observed a static bubble and wove a mathematical response to their puzzle. Most people on this thread do not have a thorough understanding of the masters laws which are derived around the term equilibrium. Many were agast at the idea of adding a time variable to Gaussian law since the correllation between a closed boundary and equilibrium was to complicated for them to understand. Then there were those who disliked the idea of static particles being electrons and wanted me to state it was a part of an electron that passed in a straight line thru the atmosphere. These people will go into a state of shock if I called partices by the name of neutrinos no less. All because of the stance they have taken that all is known about radiation. It was the small step that I took that scientists have been looking for for years when they began to lose faith in classical physics snd the laws of Newton and turned to address numourous new sciences for answers.Now they may retreat and bind themselves more firmly to the classical science and the pursuit of a universal law which Einstein seached so hard for. As far as 'all is known' older people hate change with a vengence and will fight to the death against it with the short time they have left on this earth . Fortunately the younger generation always comes along with an inquisitiveness that cannot be suppressed and are willing to rebuild where past structures disappear below the sands. Small FULL WAVE radiators are here now where a single element can supply the same gain as a planar array. Single elements that can be made with two degrees of freedom that can also be stacked to add an extra degree of freedom for the smallest WiFi device. I now await the standard comments that comes along after each of my patents, I new that already! It is really not all that special! It was me who gave you the idea in the first place. Anybody can get a patent ! That was already known and invented before. It is not my fault that people didn't make it earlier! What use is it? We already have good antennas! Yup. Small full wave antennas are now here that can cover all frequencies, not just all bands! Moxon was just a tad to late to see the new antennas for small gardens in the U.K. Best regards Art Unwin KB9MZ....xg (uk) |
Antenna physical size
On Mar 26, 11:04 am, (Richard Harrison)
wrote: Cecil Moore wrote: "But the Method Of Moments used by NEC for antenna radiation patterns calculates the interference at a point in space based on radiation from different elementary dipole sections of the antenna." Completely logical and it works. Interference or vector sum? Terman illustrates radiation from an elementary doublet (dipole) , and it is mostly at right angles to the antenna axis, on page 865 of his 1955 opus. On page 866 he shows an actual antenna consisting of numerous elementary doublets and on page 867 he says: "The result is that the fields radiated from different elementary sections of a long wire add vectorially to give a sum that depends on direction." Kraus devotes Chapter 14 in the 3rd edition of "Antennas" to: "The Cylindrical Antenna and the Moment Method (MM)." Best regards, Richard Harrison, KB5WZI Richard, Surely you are aware of the two vectors which represent the electrical field and the magnetic field If the current carrying member is a diamagnetic material both of thes vectors will be in the same direction. But the diamagnetic material is just a myth of mine right ? So I will go along with you and say the vectors are at right angles to each other just like all your books say. But later in your books they then refer to the vector "curl. This vector must be added to the two vectors at right angles to each other so a resultant vector can be found. Now you and the books state that radiation is at right angle to the axis of current flow. So the question becomes'Where must the 'curl' vector be placed in general terms to justify the right angle radiation statment that all your books apparently parrot? Simple question isn't it? Did all your learning get discarded because of books because you are unwilling to challenge them? Terman was not made a saint, nor was Kraus or Feldman or even Einstein. None of these would state that they never have made a mistake. Stop imitating Andy Capp and draw on your own thoughts for once Art |
Antenna physical size
Richard Clark wrote:
But you don't know how, and have never seen one either. Dear Richard - some people contribute to human knowledge through their optimism regarding things to come that are presently out of reach. Some people would prefer that we live forever in the dark ages. Which one are you? -- 73, Cecil http://www.w5dxp.com |
Antenna physical size
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Antenna physical size
On Mon, 31 Mar 2008 23:47:00 +0100, "Mike Kaliski"
wrote: Hi Richard, I have a pair of computer speakers sitting on my desk that completely out perform the so called ultimate hi-fi floor mounted tower system speakers I bought 35 years ago for the equivalent of several thousand dollars in today's money. Hi Mike, I have a set of 30 year old Pioneers that still kick ass. The Pioneer amp feeding any other set drives them into distortion where the Pioneer speakers still have more range to go. Never needed to push the amp above 4 to be heard outside. OK, so much for the merits of qualitative reports, otherwise known as testimonials. Proves nothing. The old speakers still work just fine but the audio experts have learned how to squeeze that performance out of a speaker that old audio theory predicted couldn't possibly work. Magnetics got better, and theory stayed the same. Performance followed the theory's prediction of new magnetics is all. This isn't a mystery is it? Care to name your speakers' model and manufacturer, or did you form the cone and wind the voice coils around a selected magnet by hand? 73's Richard Clark, KB7QHC |
Antenna physical size
Mike Kaliski wrote:
Hi Richard, I have a pair of computer speakers sitting on my desk that completely out perform the so called ultimate hi-fi floor mounted tower system speakers I bought 35 years ago for the equivalent of several thousand dollars in today's money. The old speakers still work just fine but the audio experts have learned how to squeeze that performance out of a speaker that old audio theory predicted couldn't possibly work. Just how does a 3 inch speaker in a cabinet the size of a couple of books manage to produce notes from 20 Hz - 20 kHz? To be fair, the small speakers can't fill a room with sound in the same smooth way that a larger speaker cabinet can, but for everyday use in a small modern house or apartment they are more than adequate for the majority of people. It seems to me that Art and others are pursuing a similar path at RF. The aim being to produce an antenna that punches out a signal from a physically small area. It may not perform quite as well as a full size half or full wavelength antenna, but it will work well enough for most people with small gardens or limited real estate for an antenna farm. Nope.. there's a significant difference between the speakers and the antenna, and that's the fact that the amateur user of the antenna is power limited (by regulation). In the speaker case, they trade off efficiency (acoustic watts out for electrical watts out) because electrical watts are cheap these days (not so back in McIntosh tube amp days...) You can tolerate a 1% efficient design that puts out 100mW of acoustic power with 10W electrical power in. (note that 120dB SPL = 1 Watt.. a symphony orchestra, at full tilt, is about a watt of acoustic power, and I daresay you couldn't tolerate a whole orchestra in your office) OTOH, a 1% efficient antenna design is pretty crummy. A dipole is probably on the order of 70% efficient (RF power radiated into the far field vs RF power at the feedline). A mobile antenna (which everyone will agree is not particularly efficient, even if you argue about the actual magnitude) might be 5-10% efficient (10dB down). As a practical matter, you can get away with a 1% efficient antenna, particularly if you're not looking for "link reliability"... The propagation loss between you and some arbitrary point could easily vary by 100 dB, so you just wait until propagation is "good enough" to work the guy with the 0.1W you radiate. Of such are "worked 300 countries on two bedsprings" sorts of stories made. Folks work around the world on less than a watt radiated, just not "on demand".. they keep trying until conditions are just right and they "get lucky". So, on that basis, you could probably fire up your 1500W amplifier into a compact loop antenna that's a meter in diameter, and work the world, eventually. Clearly there are considerable differences in dealing with sound waves and RF but I believe that a principle has been established that it is possible to 'simulate' the performance of a larger system using physically small components. Art may not be the first to get there, but he seems to be having a damn good try and someone, somewhere will eventually succeed. Mike G0ULI |
Antenna physical size
On Mar 31, 7:52 pm, Jim Lux wrote:
wrote: I find this topic very interesting, including the mandrill part :) We all want to have small, broadband, eficient antennas. I believe Art is right in his original post, today we can have all these characteristics in the same package. There is no law of physics forbidding that. Uhhh. actually there ARE laws of physics putting some pretty severe constraints on it, if not actually forbidding it, if you also accept the constraint that the material of which you make the antenna has finite resistance. Through advances in computation power we can achieve today in months what took decades in the past and there is much research directed at these kinds of new antennas. Eventually everyone will be able to choose and model his own antenna based on the characteristics one wants, but without the cumbersome dimensions, without significant bandwith limitations, without major efficiency compromises. I believe the tradeoff (for it has to exist one) will be ease of manufacturing. Where ease might be defined in terms of being able to be made of actually realizable materials? Incidentally these new antennas have a lot to do with what Art defines as equilibrium although I don't think he has a clear enough definition. But it's all related to patterns, patterns which can be found everywhere in nature an which can be expressed almost entirely through matemathical formulas. Scaling of antennas is clearly possible, despite of what the Chu-Harrington limit states ( or to be fair, by applying them in a new way ). Chu and, later, Harrington said nothing about bandwidth, by the way. They were more concerned with directivity and size and stored energy (the latter of which ties to efficiency and bandwidth). Also, even if you created a very small antenna with high efficiency (e.g. with superconductors), the fields around such an antenna will be quite intense, so while the antenna may be small, its near field will be pretty much the same size as the dipole it replaces, so you'll need to put that tiny antenna way up in the air with a non-conductive, non-lossy support to get it away from everything else. Finding a feedline might be a bit of a challenge. One has to be careful when one draws "the boundary" of the antenna. In practical terms, the size of an antenna isn't just the dimensions of the metal, but the "keepout" area within which you can't tolerate any intrusions and still keep the same antenna performance (i.e. a 40m dipole laying on the ground doesn't work nearly as well as a dipole suspended 10 feet off the ground) For that matter, avoiding the breakdown of air might be a problem. Consider a tesla coil, which is basically a fairly inefficient (in terms of radiated power for RF input power) small antenna for 100 kHz or so. The limit on performance for the tesla coil isn't thermal heating of the coil, but HV breakdown. Even a few hundred watts into a "shoebox" sized coil will have breakdown problems (and this is fully predicted by Chu's analysis... it's that "energy stored in the field" problem) I eagerly await the day when the 80 meter dipole will be replace by a small device the size of a shoe box ( although it might be a bit larger in the beginning :) ). Regards, Robert |
Antenna physical size
On Mar 31, 7:52 pm, Jim Lux wrote:
wrote: I find this topic very interesting, including the mandrill part :) We all want to have small, broadband, eficient antennas. I believe Art is right in his original post, today we can have all these characteristics in the same package. There is no law of physics forbidding that. Uhhh. actually there ARE laws of physics putting some pretty severe constraints on it, if not actually forbidding it, if you also accept the constraint that the material of which you make the antenna has finite resistance. Through advances in computation power we can achieve today in months what took decades in the past and there is much research directed at these kinds of new antennas. Eventually everyone will be able to choose and model his own antenna based on the characteristics one wants, but without the cumbersome dimensions, without significant bandwith limitations, without major efficiency compromises. I believe the tradeoff (for it has to exist one) will be ease of manufacturing. Where ease might be defined in terms of being able to be made of actually realizable materials? Incidentally these new antennas have a lot to do with what Art defines as equilibrium although I don't think he has a clear enough definition. But it's all related to patterns, patterns which can be found everywhere in nature an which can be expressed almost entirely through matemathical formulas. Scaling of antennas is clearly possible, despite of what the Chu-Harrington limit states ( or to be fair, by applying them in a new way ). Chu and, later, Harrington said nothing about bandwidth, by the way. They were more concerned with directivity and size and stored energy (the latter of which ties to efficiency and bandwidth). Also, even if you created a very small antenna with high efficiency (e.g. with superconductors), the fields around such an antenna will be quite intense, so while the antenna may be small, its near field will be pretty much the same size as the dipole it replaces, so you'll need to put that tiny antenna way up in the air with a non-conductive, non-lossy support to get it away from everything else. Finding a feedline might be a bit of a challenge. One has to be careful when one draws "the boundary" of the antenna. In practical terms, the size of an antenna isn't just the dimensions of the metal, but the "keepout" area within which you can't tolerate any intrusions and still keep the same antenna performance (i.e. a 40m dipole laying on the ground doesn't work nearly as well as a dipole suspended 10 feet off the ground) For that matter, avoiding the breakdown of air might be a problem. Consider a tesla coil, which is basically a fairly inefficient (in terms of radiated power for RF input power) small antenna for 100 kHz or so. The limit on performance for the tesla coil isn't thermal heating of the coil, but HV breakdown. Even a few hundred watts into a "shoebox" sized coil will have breakdown problems (and this is fully predicted by Chu's analysis... it's that "energy stored in the field" problem) I eagerly await the day when the 80 meter dipole will be replace by a small device the size of a shoe box ( although it might be a bit larger in the beginning :) ). Regards, Robert Jim, With all due respect a discussion is futile if you stray from the concept of a small FULL WAVE antenna and use the ELECTRICALLY SMALL antenna as a straw man. The electrically small antenna is a fractional wave antenna which is represented by a series circuit. This is totally different to a parallel tank circuit. This correlates to a pendulum being cast as a weight that comes to a abrupt stop and instead of swinging up goes back from the bottom to the top from whence it came! A electrical small antenna assumes an awefull lot as to the mechanics of action involved in a full period. The tank circuit is a good example that shows that all segments of a period in terms of area are exactly the same where the tank circuit clearly shows that radiation occurres only in the last quarter of a period! The idea or concept of a fractional wave antenna came from the assumption that a sino soidal pattern can be seen as four areas under a line which can be considered the same as four times a quarter segment, a concept around which the NEC programs were formed. You NEVER get radiation at every quarter segment of a period. The concept implicit in Maxwells laws is that equilibrium is a given which means that the root C L portion is that of a full wave antenna as a minimum. All the laws of the masters are based on a stable boundary at the beginning and at the time for a period of time., Time has removed a lot of memory of the human race. I suspect that the NEC programs around the current flow OUTSIDE the arbitary boundary that allowed them the successes they have gained without having to consider the mechanics of the innards within the boundary. Regards Art Unwin |
Antenna physical size
On Mar 31, 7:00 pm, Richard Clark wrote:
Hi Robert, 50 years ago they said Electricity would be so easy to produce they would pay us to use it. They ignored Hiroshima and discovered Chernobyl. I believe ease of production is a subjective term. To obtain energy one must consume energy, there's no free lunch. But ease may be considered 'convenience' to us, i.e. what suits our production capability better. 40 years ago they said DNA and genetics would allow us to design our own babies. They ignored Thalidomide and discovered Dolly the sheep that died before her time. Genetics have indeed contributed to most important advances in our understanding of the human body. Instead of relying only on physiology and anatomy, we can now have a glimpse at the 'programming language' at the core. What use do we put it to, that's a different problem. 30 years ago they invented modeling software that would allow us to create the Gaussian dipole (or whatever) and discovered every dipole that came before it performed better. That's a bit of devil's advocate stance, isn't it? :) You can't seriously say that modelling software didn't bring something to the table. Nearly 20 years ago Johnny Carson retired and we are still getting jokes. Not nearly 10 years ago with the Dow at 11658 and a budget surplus at 230 billion, the Republicans promised prosperity was around the corner and their voters are now living in cardboard boxes with the Dow at 12176 and the national debt up 50%. Scaling of antennas is clearly possible, despite of what the Chu-Harrington limit states ( or to be fair, by applying them in a new way ). But you don't know how, and have never seen one either. That's true, I am not an expert in this field, I only try to stay up to date with the technology, feel free to correct me if I'm wrong, but I have seen many advancements in this direction lately. 73's Richard Clark, KB7QHC Best regards, Robert |
Antenna physical size
On Mar 31, 8:04 pm, Jim Lux wrote:
Mike Kaliski wrote: Hi Richard, I have a pair of computer speakers sitting on my desk that completely out perform the so called ultimate hi-fi floor mounted tower system speakers I bought 35 years ago for the equivalent of several thousand dollars in today's money. The old speakers still work just fine but the audio experts have learned how to squeeze that performance out of a speaker that old audio theory predicted couldn't possibly work. Just how does a 3 inch speaker in a cabinet the size of a couple of books manage to produce notes from 20 Hz - 20 kHz? To be fair, the small speakers can't fill a room with sound in the same smooth way that a larger speaker cabinet can, but for everyday use in a small modern house or apartment they are more than adequate for the majority of people. It seems to me that Art and others are pursuing a similar path at RF. The aim being to produce an antenna that punches out a signal from a physically small area. It may not perform quite as well as a full size half or full wavelength antenna, but it will work well enough for most people with small gardens or limited real estate for an antenna farm. Nope.. there's a significant difference between the speakers and the antenna, and that's the fact that the amateur user of the antenna is power limited (by regulation). In the speaker case, they trade off efficiency (acoustic watts out for electrical watts out) because electrical watts are cheap these days (not so back in McIntosh tube amp days...) You can tolerate a 1% efficient design that puts out 100mW of acoustic power with 10W electrical power in. (note that 120dB SPL = 1 Watt.. a symphony orchestra, at full tilt, is about a watt of acoustic power, and I daresay you couldn't tolerate a whole orchestra in your office) OTOH, a 1% efficient antenna design is pretty crummy. A dipole is probably on the order of 70% efficient (RF power radiated into the far field vs RF power at the feedline). A mobile antenna (which everyone will agree is not particularly efficient, even if you argue about the actual magnitude) might be 5-10% efficient (10dB down). As a practical matter, you can get away with a 1% efficient antenna, particularly if you're not looking for "link reliability"... The propagation loss between you and some arbitrary point could easily vary by 100 dB, so you just wait until propagation is "good enough" to work the guy with the 0.1W you radiate. Of such are "worked 300 countries on two bedsprings" sorts of stories made. Folks work around the world on less than a watt radiated, just not "on demand".. they keep trying until conditions are just right and they "get lucky". So, on that basis, you could probably fire up your 1500W amplifier into a compact loop antenna that's a meter in diameter, and work the world, eventually. Clearly there are considerable differences in dealing with sound waves and RF but I believe that a principle has been established that it is possible to 'simulate' the performance of a larger system using physically small components. Art may not be the first to get there, but he seems to be having a damn good try and someone, somewhere will eventually succeed. Mike G0ULI Believe it or not Jim but I presently have a 160 meter antenna (full wave) wound on a metre loop that is resonant and can be used to work the world. It is hanging in the yard right now and obviously is very efficient at what it does. Covers the whole band to. Paid a dollar at the dollar store for the hoola hoop! Don't need to add capacitors and inductances evry few KHZ ! Art |
Antenna physical size
On Mar 31, 8:52 pm, Jim Lux wrote:
wrote: Uhhh. actually there ARE laws of physics putting some pretty severe constraints on it, if not actually forbidding it, if you also accept the constraint that the material of which you make the antenna has finite resistance. Where ease might be defined in terms of being able to be made of actually realizable materials? The term 'actually realizable materials' seems to shift it's definition every time something new is discovered :) Chu and, later, Harrington said nothing about bandwidth, by the way. They were more concerned with directivity and size and stored energy (the latter of which ties to efficiency and bandwidth). True, I didn't imply that. Also, even if you created a very small antenna with high efficiency (e.g. with superconductors), the fields around such an antenna will be quite intense, so while the antenna may be small, its near field will be pretty much the same size as the dipole it replaces, so you'll need to put that tiny antenna way up in the air with a non-conductive, non-lossy support to get it away from everything else. Finding a feedline might be a bit of a challenge. One has to be careful when one draws "the boundary" of the antenna. Ok, it was my mistake to not clarify 'high efficiency'. By that I meant 'at the same order of efficiency as normal scale designs'. I am currenty interested by what I have seen claimed as 'compacted antennas', which behave similar to normal ones, except their dimensions are smaller, X-axis wise at least. That those designs do not perform as well or better than their counterparts is no problem to me, as long as the figures are in the same ballpark. That would mean they still are more efficient than previous designs which attempted to solve the problem of physical dimensions, which is an advancement in my book. That some other unexpected features as the broadband factor may appear is only a bonus, because we can achieve that with full scale antennas too. To be more specific, I was reffering to such designs that reduce the scale of antennas in at least one axis: http://adsabs.harvard.edu/abs/2004ITAP...52.1945P http://ctd.grc.nasa.gov/organization...i-antennas.htm http://ntrs.nasa.gov/details.jsp?R=362773 http://ntrs.nasa.gov/details.jsp?R=470415 I have seen some of them described as fractal trees, but the information is relatively scarce. I know research is continuing on this subject and even found some info at a website somewhere but I can't remember where. Since you probably know more about them than me, I would appreciate some guidance here too :) In practical terms, the size of an antenna isn't just the dimensions of the metal, but the "keepout" area within which you can't tolerate any intrusions and still keep the same antenna performance (i.e. a 40m dipole laying on the ground doesn't work nearly as well as a dipole suspended 10 feet off the ground) For that matter, avoiding the breakdown of air might be a problem. Consider a tesla coil, which is basically a fairly inefficient (in terms of radiated power for RF input power) small antenna for 100 kHz or so. The limit on performance for the tesla coil isn't thermal heating of the coil, but HV breakdown. Even a few hundred watts into a "shoebox" sized coil will have breakdown problems (and this is fully predicted by Chu's analysis... it's that "energy stored in the field" problem) I do not dispute that, however I get a feeling we're talking about different things. Best, Robert |
Antenna physical size
It is hanging in the yard right now and obviously is very efficient at what it does. You mean it's very efficient at hanging in the yard? :) Joking aside, I'd be interested in a *NEC file. Is it possible to model, or is it restricted by the number of segments? Robert |
Antenna physical size
On Mar 31, 9:26 pm, wrote:
On Mar 31, 8:52 pm, Jim Lux wrote: wrote: Uhhh. actually there ARE laws of physics putting some pretty severe constraints on it, if not actually forbidding it, if you also accept the constraint that the material of which you make the antenna has finite resistance. Where ease might be defined in terms of being able to be made of actually realizable materials? The term 'actually realizable materials' seems to shift it's definition every time something new is discovered :) Chu and, later, Harrington said nothing about bandwidth, by the way. They were more concerned with directivity and size and stored energy (the latter of which ties to efficiency and bandwidth). True, I didn't imply that. Also, even if you created a very small antenna with high efficiency (e.g. with superconductors), the fields around such an antenna will be quite intense, so while the antenna may be small, its near field will be pretty much the same size as the dipole it replaces, so you'll need to put that tiny antenna way up in the air with a non-conductive, non-lossy support to get it away from everything else. Finding a feedline might be a bit of a challenge. One has to be careful when one draws "the boundary" of the antenna. Ok, it was my mistake to not clarify 'high efficiency'. By that I meant 'at the same order of efficiency as normal scale designs'. I am currenty interested by what I have seen claimed as 'compacted antennas', which behave similar to normal ones, except their dimensions are smaller, X-axis wise at least. That those designs do not perform as well or better than their counterparts is no problem to me, as long as the figures are in the same ballpark. That would mean they still are more efficient than previous designs which attempted to solve the problem of physical dimensions, which is an advancement in my book. That some other unexpected features as the broadband factor may appear is only a bonus, because we can achieve that with full scale antennas too. To be more specific, I was reffering to such designs that reduce the scale of antennas in at least one axis:http://adsabs.harvard.edu/abs/2004IT...s.jsp?R=470415 I have seen some of them described as fractal trees, but the information is relatively scarce. I know research is continuing on this subject and even found some info at a website somewhere but I can't remember where. Since you probably know more about them than me, I would appreciate some guidance here too :) In practical terms, the size of an antenna isn't just the dimensions of the metal, but the "keepout" area within which you can't tolerate any intrusions and still keep the same antenna performance (i.e. a 40m dipole laying on the ground doesn't work nearly as well as a dipole suspended 10 feet off the ground) For that matter, avoiding the breakdown of air might be a problem. Consider a tesla coil, which is basically a fairly inefficient (in terms of radiated power for RF input power) small antenna for 100 kHz or so. The limit on performance for the tesla coil isn't thermal heating of the coil, but HV breakdown. Even a few hundred watts into a "shoebox" sized coil will have breakdown problems (and this is fully predicted by Chu's analysis... it's that "energy stored in the field" problem) I do not dispute that, however I get a feeling we're talking about different things. Best, Robert Robert, the Fractal can now be considered obsolete when compared to mine. The person who is testing my antenna is a member of this group. Maybe he will drop a bone regarding this new antenna of mine so I can have some credability. For years I have been insulted on my findings and frankly I am getting fed up.People stated that I did not have such an antenna, A $5000 stake was put up by an Aussie ( they bet on anything) to say that he believed me. Not one of the talking heads were willing to take on the Aussie and win big. As I stated they are mostly talking heads and nothing else. Regards Art |
Antenna physical size
On Mar 31, 9:39 pm, wrote:
It is hanging in the yard right now and obviously is very efficient at what it does. You mean it's very efficient at hanging in the yard? :) Joking aside, I'd be interested in a *NEC file. Is it possible to model, or is it restricted by the number of segments? Robert Restricted by the number of segments but I have tested enough of the diifferent designs to know what I am talking aboutand only a few can be programed but with limited segments it can only provide guidance. MAYBE one day I will supply the patent request number I received last year as well as the following patent number but the number of insults have ruled that possibility out. The person who is testing it never insulted me and wanted badly to be on the inside of this new antenna. Sooner or later the PTO will provide all. The hula hoop was just a design for checking, The one I have now is on a tip and turn set up for the top of my tower for use with a mesh dish for 160 and all other frequencies. I want to change the polarity in situ !. You never can stop learning once you get off the normal path and penetrate the underbrush. Suddenly the brush is behind and a clear valley bathed in sun light appears and you have little time to fully explore There are many different versions of this antenna primarily to get a complete range of impedences for use as well as determining tilt angle e.t.c. Regards Art |
Antenna physical size
Cecil Moore wrote:
Richard Clark wrote: But you don't know how, and have never seen one either. Dear Richard - some people contribute to human knowledge through their optimism regarding things to come that are presently out of reach. Some people would prefer that we live forever in the dark ages. Which one are you? Never forget that we need all types, Cecil. Imagine a world where complete suspension of disbelief made all theories equal. - 73 de Mike N3LI - |
Antenna physical size
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Antenna physical size
On Mar 31, 7:52 pm, Jim Lux wrote:
wrote: I find this topic very interesting, including the mandrill part :) We all want to have small, broadband, eficient antennas. I believe Art is right in his original post, today we can have all these characteristics in the same package. There is no law of physics forbidding that. Uhhh. actually there ARE laws of physics putting some pretty severe constraints on it, if not actually forbidding it, if you also accept the constraint that the material of which you make the antenna has finite resistance. Through advances in computation power we can achieve today in months what took decades in the past and there is much research directed at these kinds of new antennas. Eventually everyone will be able to choose and model his own antenna based on the characteristics one wants, but without the cumbersome dimensions, without significant bandwith limitations, without major efficiency compromises. I believe the tradeoff (for it has to exist one) will be ease of manufacturing. Where ease might be defined in terms of being able to be made of actually realizable materials? Incidentally these new antennas have a lot to do with what Art defines as equilibrium although I don't think he has a clear enough definition. But it's all related to patterns, patterns which can be found everywhere in nature an which can be expressed almost entirely through matemathical formulas. Scaling of antennas is clearly possible, despite of what the Chu-Harrington limit states ( or to be fair, by applying them in a new way ). Chu and, later, Harrington said nothing about bandwidth, by the way. They were more concerned with directivity and size and stored energy (the latter of which ties to efficiency and bandwidth). Also, even if you created a very small antenna with high efficiency (e.g. with superconductors), the fields around such an antenna will be quite intense, so while the antenna may be small, its near field will be pretty much the same size as the dipole it replaces, so you'll need to put that tiny antenna way up in the air with a non-conductive, non-lossy support to get it away from everything else. Finding a feedline might be a bit of a challenge. One has to be careful when one draws "the boundary" of the antenna. In practical terms, the size of an antenna isn't just the dimensions of the metal, but the "keepout" area within which you can't tolerate any intrusions and still keep the same antenna performance (i.e. a 40m dipole laying on the ground doesn't work nearly as well as a dipole suspended 10 feet off the ground) For that matter, avoiding the breakdown of air might be a problem. Consider a tesla coil, which is basically a fairly inefficient (in terms of radiated power for RF input power) small antenna for 100 kHz or so. The limit on performance for the tesla coil isn't thermal heating of the coil, but HV breakdown. Even a few hundred watts into a "shoebox" sized coil will have breakdown problems (and this is fully predicted by Chu's analysis... it's that "energy stored in the field" problem) I eagerly await the day when the 80 meter dipole will be replace by a small device the size of a shoe box ( although it might be a bit larger in the beginning :) ). Regards, Robert When the air breaks down around an antenna it is because the antenna is not in a state of equilibrium. When a dipole is replaced by a quad ala a series circuit is replaced by a tank circuit it clearly shows that the latter is more efficient.This was firmly proven in Quito.Maximum radiation efficiency requires equilibrium. Period Art |
Antenna physical size
On Mar 31, 9:39 pm, wrote:
It is hanging in the yard right now and obviously is very efficient at what it does. You mean it's very efficient at hanging in the yard? :) Joking aside, I'd be interested in a *NEC file. Is it possible to model, or is it restricted by the number of segments? Robert Let me clarify my answer. The natural resonance resistance can exceed 1000 ohms thought with the same design the resistance can be lowered at the expense of bandwidth. These design forms can be easily modelled with or without a dish reflector. I introduced twisted wire into the design to overcome the reduced bandwidth of the other design to bring the resistance down to the 50 to 100 ohm mark for easy match to existing components. Since the impedance resistance is drastically lowered when using the standard design on the computor I am inclined only to use the computor as a guide in that instance. The dish modelled consist of parallel elements which obviously would be a bear to tilt so many inaccuracies are built in except in the case of the assembly being tilted which I am presently researching. Art |
Antenna physical size
On Apr 1, 9:18 am, Art Unwin wrote:
When the air breaks down around an antenna it is because the antenna is not in a state of equilibrium. When a dipole is replaced by a quad ala a series circuit is replaced by a tank circuit it clearly shows that the latter is more efficient.This was firmly proven in Quito.Maximum radiation efficiency requires equilibrium. Period Art If you don't quit spewing all this blatant horse crap, I will be going into talking head mode again. BTW, I'm younger than you are. So your claims of age affecting vulnerability to the effects of constant bafflegab and horse caca will tested at great lengths in such an endeavor. The change of the fabled antenna at HCJB had nothing to do with efficiency. Period. |
Antenna physical size
On Apr 1, 12:57 pm, wrote:
On Apr 1, 9:18 am, Art Unwin wrote: When the air breaks down around an antenna it is because the antenna is not in a state of equilibrium. When a dipole is replaced by a quad ala a series circuit is replaced by a tank circuit it clearly shows that the latter is more efficient.This was firmly proven in Quito.Maximum radiation efficiency requires equilibrium. Period Art If you don't quit spewing all this blatant horse crap, I will be going into talking head mode again. BTW, I'm younger than you are. So your claims of age affecting vulnerability to the effects of constant bafflegab and horse caca will tested at great lengths in such an endeavor. The change of the fabled antenna at HCJB had nothing to do with efficiency. Period. You my friend are a good example of what a redneck thinks. In the past you have bragged about your lack of schooling spouting about the times you didn't go to school. Now you have a license to operate a radio where you can excercise your freedom of speech at will. Unfortunately, as soon as you start vibrating you vocal cords you instantly reveal who and what you are. This is of immense inportance to the rest of us when considering whether to use our precious time to your utterings. Go ahead and be a talking head but you will find that your audio lacks propagation in the subject of antennas Have a happy day and be nice to those around you. You will never know when that last day of yours comes around despite your youthful age. Art Unwin |
Antenna physical size
On Apr 1, 12:32 pm, Art Unwin wrote:
On Apr 1, 12:57 pm, wrote: On Apr 1, 9:18 am, Art Unwin wrote: When the air breaks down around an antenna it is because the antenna is not in a state of equilibrium. When a dipole is replaced by a quad ala a series circuit is replaced by a tank circuit it clearly shows that the latter is more efficient.This was firmly proven in Quito.Maximum radiation efficiency requires equilibrium. Period Art If you don't quit spewing all this blatant horse crap, I will be going into talking head mode again. BTW, I'm younger than you are. So your claims of age affecting vulnerability to the effects of constant bafflegab and horse caca will tested at great lengths in such an endeavor. The change of the fabled antenna at HCJB had nothing to do with efficiency. Period. You my friend are a good example of what a redneck thinks. In the past you have bragged about your lack of schooling spouting about the times you didn't go to school. Now you have a license to operate a radio where you can excercise your freedom of speech at will. Unfortunately, as soon as you start vibrating you vocal cords you instantly reveal who and what you are. This is of immense inportance to the rest of us when considering whether to use our precious time to your utterings. Go ahead and be a talking head but you will find that your audio lacks propagation in the subject of antennas Have a happy day and be nice to those around you. You will never know when that last day of yours comes around despite your youthful age. Art Unwin Prior Art... I have never "bragged" about not going to school. I was expelled from school. Which means I really didn't have a whole lot of choice in the matter past that stage. But in the general scheme of things this means little, as most schools don't teach antenna theory unless it's a specific college course. You have never heard my vocal cords vibrate, as you have never talked to me. I doubt if you have even heard me on the air. Being you are so highly educated, why is your spelling so bad? Seems to me you went to school, but either slept through it, or had other things to think about. In any case, you are the last horses ass that should be braying about my education. I educate myself, and have plenty of books laying around. It's funny, I am self educated and oft speak about antennas, but few people have any problems with what I write about. If they do, it's usually some fairly minor detail. You on the other hand, claim to be well educated, but almost everything you spout is challenged as bafflegab, pure untruth, or just plain horse crap. What is wrong with this picture? Prior Art, you make me feel gifted, being I seem to be ahead of you as far as antenna theory, and I didn't take *any* scholarly courses for it. I think you should learn to write and spell a little better if you are going to whine about other peoples lack of education. Your "Queens English" is a mess. What is your excuse for this problem? I absolutely hated English when in school, yet I seem to be doing a bit better writing it than you, even with my sub par education. At least I have an excuse though. Again, you make me feel downright gifted to be on par with such a highly educated man such as yourself. :/ MK |
Antenna physical size
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Antenna physical size
On Apr 1, 5:15 pm, wrote:
On Apr 1, 12:32 pm, Art Unwin wrote: On Apr 1, 12:57 pm, wrote: On Apr 1, 9:18 am, Art Unwin wrote: When the air breaks down around an antenna it is because the antenna is not in a state of equilibrium. When a dipole is replaced by a quad ala a series circuit is replaced by a tank circuit it clearly shows that the latter is more efficient.This was firmly proven in Quito.Maximum radiation efficiency requires equilibrium. Period Art If you don't quit spewing all this blatant horse crap, I will be going into talking head mode again. BTW, I'm younger than you are. So your claims of age affecting vulnerability to the effects of constant bafflegab and horse caca will tested at great lengths in such an endeavor. The change of the fabled antenna at HCJB had nothing to do with efficiency. Period. You my friend are a good example of what a redneck thinks. In the past you have bragged about your lack of schooling spouting about the times you didn't go to school. Now you have a license to operate a radio where you can excercise your freedom of speech at will. Unfortunately, as soon as you start vibrating you vocal cords you instantly reveal who and what you are. This is of immense inportance to the rest of us when considering whether to use our precious time to your utterings. Go ahead and be a talking head but you will find that your audio lacks propagation in the subject of antennas Have a happy day and be nice to those around you. You will never know when that last day of yours comes around despite your youthful age. Art Unwin Prior Art... I have never "bragged" about not going to school. I was expelled from school. Which means I really didn't have a whole lot of choice in the matter past that stage. But in the general scheme of things this means little, as most schools don't teach antenna theory unless it's a specific college course. You have never heard my vocal cords vibrate, as you have never talked to me. I doubt if you have even heard me on the air. Being you are so highly educated, why is your spelling so bad? Seems to me you went to school, but either slept through it, or had other things to think about. In any case, you are the last horses ass that should be braying about my education. I educate myself, and have plenty of books laying around. It's funny, I am self educated and oft speak about antennas, but few people have any problems with what I write about. If they do, it's usually some fairly minor detail. You on the other hand, claim to be well educated, but almost everything you spout is challenged as bafflegab, pure untruth, or just plain horse crap. What is wrong with this picture? Prior Art, you make me feel gifted, being I seem to be ahead of you as far as antenna theory, and I didn't take *any* scholarly courses for it. I think you should learn to write and spell a little better if you are going to whine about other peoples lack of education. Your "Queens English" is a mess. What is your excuse for this problem? I absolutely hated English when in school, yet I seem to be doing a bit better writing it than you, even with my sub par education. At least I have an excuse though. Again, you make me feel downright gifted to be on par with such a highly educated man such as yourself. :/ MK Pray tell me then why I am incorrect. You can salvage the answer from your own mind or even from a book. If you are going to decry my explanation you must have the reason at your finger tips. You heard mention of the Tesla coil earlier as a posters sample with respect to a particular point. What the poster did not state was that a Tesla coil is NOT in a state of equilibrium even tho it may be resonant! Why else would energy break out from a circuit in the form of a spark if there was more freedom to travel else where?l Same goes for the old spark plug system, it is not in equilibrium. So go ahead supply an educated reason as to why the sparks emminated from the dipole in Quito and why the closed circuit of a quad pushed the particular problem away. On the other hand give an educated answer to the direction of the three vectors involved in radiation that Harrison cannot give. You say you have books then go a head with respect to these two questions that nobody on this group has been able to resolve. With all the books you say you have then I would agree with you that even a high school drop out can knock hell out of me with respect to antennas. Have a happy day and smile Art. Ps. When younger I passed the Oxford and Cambridge entrance test on English but old age has taken its toll. |
Antenna physical size
"Richard Clark" wrote in message ... On Mon, 31 Mar 2008 23:47:00 +0100, "Mike Kaliski" wrote: Hi Richard, I have a pair of computer speakers sitting on my desk that completely out perform the so called ultimate hi-fi floor mounted tower system speakers I bought 35 years ago for the equivalent of several thousand dollars in today's money. Hi Mike, I have a set of 30 year old Pioneers that still kick ass. The Pioneer amp feeding any other set drives them into distortion where the Pioneer speakers still have more range to go. Never needed to push the amp above 4 to be heard outside. OK, so much for the merits of qualitative reports, otherwise known as testimonials. Proves nothing. The old speakers still work just fine but the audio experts have learned how to squeeze that performance out of a speaker that old audio theory predicted couldn't possibly work. Magnetics got better, and theory stayed the same. Performance followed the theory's prediction of new magnetics is all. This isn't a mystery is it? Care to name your speakers' model and manufacturer, or did you form the cone and wind the voice coils around a selected magnet by hand? 73's Richard Clark, KB7QHC Hi Richard, Never one to refuse a challenge. The old speakers were a pair of Celestion Ditton 15XR's with 30 watt per channel rating and a flat sound response output from around 20Hz to 20kHz, 104db at 1 yard driven with 1 watt. The XR stood for extended range indicating that the speaker design had been modified and upgraded from the original Ditton 15 specifications. The new speakers I mentioned are a pair of Creative T20's. 14 watts per channel from a built in amp and very nice to listen to. They don't really compare with the Celestions for the smooth mellow sound that only seems to come with wooden cabinets, but for the price they are excellent. Good point about the magnets though. The super high powered magnets, ultra rigid, lightweight fibre glass cones and developments in ported cabinet design have all contributed to the superb performance of the T20's. Apparently they have been out for a while now, but it was only when I was wandering about in a PC World store that I heard a pair up and running. I was stopped in my tracks by the sound coming out of these tiny devices and spent a good couple of minutes looking for the subwoofer unit that I felt sure was hidden away somewhere. There wasn't a subwoofer and after that, I just knew I had to buy a pair. I have no connection with Creative and in fact I am a bit annoyed with the company's attitude to (not) providing proper sound card drivers for Windows Vista. Anyway, just go and check out the web reviews. Sorry everyone else, but this bit hasn't really got anything at all to do with antennas. Cheers Mike |
Antenna physical size
"Mike Kaliski" wrote in
: Apparently they have been out for a while now, but it was only when I was wandering about in a PC World store that I heard a pair up and running. I was stopped in my tracks by the sound coming out of these tiny devices and spent a good couple of minutes looking for the subwoofer unit that I felt sure was hidden away somewhere. There wasn't a subwoofer and after that, I just knew I had to buy a pair. I have no connection with Creative and in fact I am a bit annoyed with the company's attitude to (not) providing proper sound card drivers for Windows Vista. Wait for Windows 8. It can't be worse! Anyway, just go and check out the web reviews. Sorry everyone else, but this bit hasn't really got anything at all to do with antennas. What must be really wonderful is how these speaker manufacturers have not only managed to change resonant points, but managed to get these very small systems to move the massive amounts of air needed with the small speaker systems involved! Oops, sorry, I got sarcastic.. While it is true that we can get better sound from smaller speaker systems than we have been able to in the past, we have to keep in mind that those advances are available for the full size systems too. IOW, all things being equal..... No new physics are needed. |
Antenna physical size
On Apr 2, 1:41 pm, Art Unwin wrote:
Pray tell me then why I am incorrect. You can salvage the answer from your own mind or even from a book. When the air breaks down around an antenna it is because the antenna is not in a state of equilibrium. Define equilibrium as it pertains to an antenna. Until you do, it's fairly hard to comment on the first statement. If you have corona discharge from an antenna, it's usually due to sharp points when using wire or a whip with a pointed tip. Thats why they stick round balls on whips, flagpoles, etc.. When a dipole is replaced by a quad ala a series circuit is replaced by a tank circuit it clearly shows that the latter is more efficient. What clearly shows this? This is the statement which drew my comment. The efficiency of a 1/2 WL dipole and a 1 WL loop are so close as to be almost unmeasurable in the real world. But you can take this even farther. Almost *any* size dipole or loop will radiate most all of what is fed to it. A 1/10 WL whip radiates almost all of the power applied to it, same as a 1/4 WL, 1/2 WL, or whatever you want to try. This not not conjecture. This is pretty much written in stone after many years of testing. Why you continue to ignore this simple fact boggles my mind. So your statement is so far from reality I would be amiss in my "talking head" duties if I did not comment. Don't take my word for it. Ask anyone you can think of that has a clue. They will tell you the same thing. What it going to spoil your "full size performance from a dinky radiator" picnic is not the radiator and it's abilities to be an efficient radiator. It's going to be actually feeding the power to such a small radiator and not turning a large amount of RF to heat in the process. No cheating letting the feed line be the antenna.. Look at "small" HF transmitting loops. Do you see any using 22 gauge wire? I doubt it. They will be using the fattest or widest strip of material they can get their hands on. There are other issues involved also in feeding such an antenna. Never do these small loops equal the performance of a full size antenna. They radiate enough to maybe let you operate, and thats about it. This was firmly proven in Quito.Maximum radiation efficiency requires equilibrium. Period Again, the change to quad loops at HCJB was to avoid the sharp points of the dipoles, yagi's, or whatever they were using. In the high alitudes of Quito, HV breakdown at the tips was a serious problem. The change had absolutely nothing to do with antenna efficiency. Not to mention that the whole idea of a loop being more efficient than a dipole is totally wrong. And I don't see how equilibrium has anything to do with it, whatever you might mean by that silly "E" word. Anything else you are curious about? BTW, no grabbing of books were needed to form this response. Art |
Antenna physical size
On Apr 2, 10:37 pm, wrote:
On Apr 2, 1:41 pm, Art Unwin wrote: Pray tell me then why I am incorrect. You can salvage the answer from your own mind or even from a book. When the air breaks down around an antenna it is because the antenna is not in a state of equilibrium. Define equilibrium as it pertains to an antenna. Until you do, it's fairly hard to comment on the first statement. I don't think I can do that for you, it would take to long. If you have corona discharge from an antenna, it's usually due to sharp points when using wire or a whip with a pointed tip. Thats why they stick round balls on whips, flagpoles, etc.. When you have a discharge it is a loss of energy When a dipole is replaced by a quad ala a series circuit is replaced by a tank circuit it clearly shows that the latter is more efficient. What clearly shows this? Well there is no discharge. This is becaquse that there is a route of a lesser impedance available This is the statement which drew my comment. The efficiency of a 1/2 WL dipole and a 1 WL loop are so close as to be almost unmeasurable in the real world. Almost doesn't count when measuring efficiency and in the real world many CAN tell the difference But you can take this even farther. Almost *any* size dipole or loop will radiate most all of what is fed to it. Again you are admitting to lower efficiency when you use the word "most" A 1/10 WL whip radiates almost all of the power applied to it, same as a 1/4 WL, 1/2 WL, or whatever you want to try. This not not conjecture. This is pretty much written in stone after many years of testing. Again you use the word "most" which is admitting less efficiency Why you continue to ignore this simple fact boggles my mind. So your statement is so far from reality I would be amiss in my "talking head" duties if I did not comment. Don't take my word for it. Ask anyone you can think of that has a clue. They will tell you the same thing. What it going to spoil your "full size performance from a dinky radiator" picnic is not the radiator and it's abilities to be an efficient radiator. It's going to be actually feeding the power to such a small radiator and not turning a large amount of RF to heat in the process. No cheating letting the feed line be the antenna.. I think you are missing the point here. My antenna has a full wave length of wire not a fraction there of. So the radiator has the same inductance and capacitance that one would expect from a full wave antenna spread out in a straight line where the wire surface is exposed to the atmosphere, so there is no reason for the energy to circumvent the wire circuit as it must do for a fractional wavelength. Look at "small" HF transmitting loops. Do you see any using 22 gauge wire? I doubt it. They will be using the fattest or widest strip of material they can get their hands on. What you are seeing as representing a loop antenna is a fractional wave length Often it comes with a HV variable capacitor for tuning. The loop that I made was a plastic loop with a full wave length of wire wound upon it. No high voltage capacitor needed as it coveres the whole band. As far as 22 gauge wire being used this is because there is no mechanical stresses imposed on it as would be for a stretched out radiator. So the main consideration is to supply enough skin depth since the diameter itself is not a factor in terms of fusing.current There are other issues involved also in feeding such an antenna. Never do these small loops equal the performance of a full size antenna. They radiate enough to maybe let you operate, and thats about it. If the scource impedance is one that you can match efficiently then you have at hand a efficient radiator of a wavelength where the normal loop you are refering to uses a metal loop as the radiator which is much shorter than a wavelength of wire wound on a plastic loop. The loop is now a small full wave radiator not a small fractional small wave antenna This was firmly proven in Quito.Maximum radiation efficiency requires equilibrium. Period Again, the change to quad loops at HCJB was to avoid the sharp points of the dipoles, yagi's, or whatever they were using. In the high alitudes of Quito, HV breakdown at the tips was a serious problem. The change had absolutely nothing to do with antenna efficiency. If the impedance is to high on the antenna compared to discharging through air to the transmitter ground then that is a very inefficient antenna Not to mention that the whole idea of a loop being more efficient than a dipole is totally wrong. The energy travels easily along the wire circuit without encountering a high impedance that it is forced to take a circuitous route thru ground to the transmitter ground. When the energy is passing thru ground it becomes a loss. And I don't see how equilibrium has anything to do with it, whatever you might mean by that silly "E" word. If a circuit is not balanced and a fractional wave length long it is not in equilibrium!. The energy supplied to the radiator will always encounter a energy wasting impedance in the wire itself if is not at least a wavelength long, and of the right material (diamagnetic) otherwise the energy will seek a route outside the wired circuit which can only lead to losses. Think of it this way, a fractional wave length radiator cannot avoid the energy taking a route thru ground and the ground is a loss. Hopefully you now see antennas in a different light. I do urge you to look up the tank circuit since it is quite an interesting circuit with its phase changes and effective resistances apparently changing without being diverted from the circuit wire confines. Another place where the books are in error is their association with the iron filing magnet experiment at HS which forms a magnetic field very different from that formed from aluminum, copper and other diamagnetic materials. When you pass a time varying current thru copper the magnetic field turns at right angles to the radiator axis and in fact compliments the electrical field vector ( they are not at right angles) Now you can see what lifts or ejects the static particles resting on the surface because they are repelled instead of bing magnetically atracted ( Static: nearly devoid of energy and of small mass) .. So the EH antennas which supposedly combines the EH fields just didn't understand that with a radiator the combination of vectors is already a given! I think you also are making a mistake that many books make when referring to small antennas instead of referring to ELECTRICALLY small antennas Anything else you are curious about? BTW, no grabbing of books were needed to form this response. Art Best regards, no offence intended Art Unwin ......KB9MZ..(uk) |
Antenna physical size
On Thu, 3 Apr 2008 02:33:20 +0100, "Mike Kaliski"
wrote: Hi Richard, Never one to refuse a challenge. The old speakers were a pair of Celestion Ditton 15XR's with 30 watt per channel rating and a flat sound response output from around 20Hz to 20kHz, 104db at 1 yard driven with 1 watt. The XR stood for extended range indicating that the speaker design had been modified and upgraded from the original Ditton 15 specifications. Hi Mike, Pretty impressive. My own Pioneers fall 10dB below that. The new speakers I mentioned are a pair of Creative T20's. 14 watts per channel from a built in amp and very nice to listen to. Good to have a recommendation there too. They don't really compare with the Celestions for the smooth mellow sound that only seems to come with wooden cabinets, but for the price they are excellent. Good point about the magnets though. The super high powered magnets, ultra rigid, lightweight fibre glass cones and developments in ported cabinet design have all contributed to the superb performance of the T20's. Apparently they have been out for a while now, but it was only when I was wandering about in a PC World store that I heard a pair up and running. I was stopped in my tracks by the sound coming out of these tiny devices and spent a good couple of minutes looking for the subwoofer unit that I felt sure was hidden away somewhere. There wasn't a subwoofer and after that, I just knew I had to buy a pair. I would have to agree. I have no connection with Creative and in fact I am a bit annoyed with the company's attitude to (not) providing proper sound card drivers for Windows Vista. Maybe with service pack 4. Anyway, just go and check out the web reviews. I will. Sorry everyone else, but this bit hasn't really got anything at all to do with antennas. But it does show how performance correlates to numbers to theory to practice - something dreadfully missing in Art's contributions, if you can call throwing claims against the wall to see what sticks as a contribution. 73's Richard Clark, KB7QHC |
Antenna physical size
Richard Clark wrote:
But it does show how performance correlates to numbers to theory to practice - something dreadfully missing in Art's contributions, if you can call throwing claims against the wall to see what sticks as a contribution. Or one's underwear... - 73 de Mike N3LI - |
Antenna physical size
On Apr 2, 11:12 pm, Art Unwin wrote:
On Apr 2, 10:37 pm, wrote: On Apr 2, 1:41 pm, Art Unwin wrote: Pray tell me then why I am incorrect. You can salvage the answer from your own mind or even from a book. When the air breaks down around an antenna it is because the antenna is not in a state of equilibrium. Define equilibrium as it pertains to an antenna. Until you do, it's fairly hard to comment on the first statement. I don't think I can do that for you, it would take to long. It hasn't stopped you from writing a novel on other issues.. If you have corona discharge from an antenna, it's usually due to sharp points when using wire or a whip with a pointed tip. Thats why they stick round balls on whips, flagpoles, etc.. When you have a discharge it is a loss of energy Not antenna efficiency though. It's more akin to running a dipole with poor end insulators.. When a dipole is replaced by a quad ala a series circuit is replaced by a tank circuit it clearly shows that the latter is more efficient. What clearly shows this? Well there is no discharge. This is becaquse that there is a route of a lesser impedance available Has nothing to do with antenna efficiency. This is the statement which drew my comment. The efficiency of a 1/2 WL dipole and a 1 WL loop are so close as to be almost unmeasurable in the real world. Almost doesn't count when measuring efficiency and in the real world many CAN tell the difference But you can take this even farther. Almost *any* size dipole or loop will radiate most all of what is fed to it. Again you are admitting to lower efficiency when you use the word "most" The only reason I use "most" is because no real world antenna will radiate 100% of the power applied to it. A 1/10 WL whip radiates almost all of the power applied to it, same as a 1/4 WL, 1/2 WL, or whatever you want to try. This not not conjecture. This is pretty much written in stone after many years of testing. Again you use the word "most" which is admitting less efficiency No, it's admitting that no real antenna will radiate 100% of the power fed to it. Has nothing to do with a comparison of the various types. Why you continue to ignore this simple fact boggles my mind. So your statement is so far from reality I would be amiss in my "talking head" duties if I did not comment. Don't take my word for it. Ask anyone you can think of that has a clue. They will tell you the same thing. What it going to spoil your "full size performance from a dinky radiator" picnic is not the radiator and it's abilities to be an efficient radiator. It's going to be actually feeding the power to such a small radiator and not turning a large amount of RF to heat in the process. No cheating letting the feed line be the antenna.. I think you are missing the point here. My antenna has a full wave length of wire not a fraction there of. So? From it's claimed performance, it's working as a great dummy load. You say it requires no matching to coax, and covers the whole 160m band.. This simple description tells me your antenna is a poor radiator of RF. It shows all the qualities of a air cooled dummy load. A truly efficient antenna of such a small size would require matching to the feedline, would be quite high Q, and the bandwidth would be very narrow. So narrow as to possibly restrict the audio quality of the average 2.5- 3 kc transmitter width .. :( You can actually hear the restriction on the air. I've noticed this many times when people try very small high Q antennas on that band.. This is reciprical, and will be noticed on receive also if you A/B between a full size antenna vs the small version. So the radiator has the same inductance and capacitance that one would expect from a full wave antenna spread out in a straight line You wish... where the wire surface is exposed to the atmosphere, so there is no reason for the energy to circumvent the wire circuit as it must do for a fractional wavelength. Oh, like it does with a 1/2 wave dipole... :/ Look at "small" HF transmitting loops. Do you see any using 22 gauge wire? I doubt it. They will be using the fattest or widest strip of material they can get their hands on. What you are seeing as representing a loop antenna is a fractional wave length Often it comes with a HV variable capacitor for tuning. The loop that I made was a plastic loop with a full wave length of wire wound upon it. No high voltage capacitor needed as it coveres the whole band. Didn't work very well as a radiator of RF did it... Good dummy load though I bet... As far as 22 gauge wire being used this is because there is no mechanical stresses imposed on it as would be for a stretched out radiator. So the main consideration is to supply enough skin depth since the diameter itself is not a factor in terms of fusing.current I didn't know you were trying to construct a fuse box... There are other issues involved also in feeding such an antenna. Never do these small loops equal the performance of a full size antenna. They radiate enough to maybe let you operate, and thats about it. If the scource impedance is one that you can match efficiently then you have at hand a efficient radiator Like a dummy load? of a wavelength where the normal loop you are refering to uses a metal loop as the radiator which is much shorter than a wavelength of wire wound on a plastic loop. The loop is now a small full wave radiator not a small fractional small wave antenna No, it's a small antenna, coil loaded with many feet of 22 gauge wire. In fact, the antenna is pretty much all coil. Not too much different than a wound loopstick used for MW. Their virtues as efficient radiators of RF are about nil.. :( This was firmly proven in Quito.Maximum radiation efficiency requires equilibrium. Period Again, the change to quad loops at HCJB was to avoid the sharp points of the dipoles, yagi's, or whatever they were using. In the high alitudes of Quito, HV breakdown at the tips was a serious problem. The change had absolutely nothing to do with antenna efficiency. If the impedance is to high on the antenna compared to discharging through air to the transmitter ground then that is a very inefficient antenna No. It has nothing to do with antenna efficiency. Antenna efficiency is reciprical from receive to transmit. It's like me taking a nearly fully efficient dipole and running it through a bunch of wet tree branches with poor insulators, and then running high power. An antenna that is truly inefficient will be inefficient on both transmit and receive. Obviously in the case of the dipole, this is not the case. When receiving only, I bet it works just fine. Not to mention that the whole idea of a loop being more efficient than a dipole is totally wrong. The energy travels easily along the wire circuit without encountering a high impedance that it is forced to take a circuitous route thru ground to the transmitter ground. When the energy is passing thru ground it becomes a loss. Where does ground enter the picture? And I don't see how equilibrium has anything to do with it, whatever you might mean by that silly "E" word. If a circuit is not balanced and a fractional wave length long it is not in equilibrium!. But you won't define the E word, so this means little to me... The energy supplied to the radiator will always encounter a energy wasting impedance in the wire itself if is not at least a wavelength long, and of the right material (diamagnetic) Wire resistance does not go away if you use larger lengths of wire vs shorter when using an equal wire gauge. otherwise the energy will seek a route outside the wired circuit which can only lead to losses. Think of it this way, a fractional wave length radiator cannot avoid the energy taking a route thru ground and the ground is a loss. What about the 1/2 wave dipole? Hopefully you now see antennas in a different light. Nope.. Why would I? I do urge you to look up the tank circuit since it is quite an interesting circuit with its phase changes and effective resistances apparently changing without being diverted from the circuit wire confines. I've already read about tank circuits.. Another place where the books are in error is their association with the iron filing magnet experiment at HS which forms a magnetic field very different from that formed from aluminum, copper and other diamagnetic materials. When you pass a time varying current thru copper the magnetic field turns at right angles to the radiator axis and in fact compliments the electrical field vector ( they are not at right angles) Now you can see what lifts or ejects the static particles resting on the surface because they are repelled instead of bing magnetically atracted ( Static: nearly devoid of energy and of small mass) RF is never static.. . So the EH antennas which supposedly combines the EH fields just didn't understand that with a radiator the combination of vectors is already a given! Which means what? I think you also are making a mistake that many books make when referring to small antennas instead of referring to ELECTRICALLY small antennas You are thinking wrong. |
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