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Yagi efficiency
Jerry, if I came across a bit loud I apologize.. I usually skim down
the latest chatter and then just post to the group off the bottom message, often having no direct bearing on the particular post it spins off from... Also, I skim a number of groups and topics and I run a business so I can miss a post that puts a different spin on things... If I ruffled your feathers it was not intentional... Let me comment that I absolutely agree with you that claiming a Yagi is inefficient from the perspective of I2R losses shows a lack of basic knowledge... Having said that, let me also note that closing the spacing, i.e. tighter than the classical Yagi-Uda array, and putting the beam into Supergain territory has consequences... Moxon has a non mathematical discussion of the supergain antennas with a graph of spacing v/s gain v/s impedence, and I Krauss mentioned that he designed his flat top array stimulated from a paper by Brown (I think it was) where he discussed arrays that have more than additive gain by tight spacing... Anyway I digress; the point of all this mumble is that these supergain "Yagi" arrays can have quite high I2R losses... But the commercial Yagi-Uda today is not in that class... Anyway, Cheers ... denny / k8do |
Yagi efficiency
No Jimmie you are not open minded you are just looking for auguments. I
am not a electrical engineer so I have had no formal education in the antenna field but it is my hobby nothing else just a hobby. I dont mind stating an error or making a mistake because I do not have a resume to protect so you will have to wait until it is published at that point you can weigh in as to the ridiculousness of what I have proposed olr give an excuse like; oh, I thought that you were......... Jimmie D wrote: "art" wrote in message ups.com... Interesting Jimmy Could you show me how me how a vector directed at a socalled reflector behaves with respect to a constant plane without the implication of a neutralising effect. Now the reflector "works" only as a part of a particular plane so please go on from there. I often read of additive and subtractive radiation in books written by the masters and I have seemed to have got the wrong idea about these matters Art Then give a reference to what you are talking about if you are so familar with the "masters". Jimmie D wrote: "art" wrote in message oups.com... From a theoretical way of getting at the answer it seems a logical way of proceding. So now to the rest of the task.1 how do we determine volumes that you talk about that are a result of deflection 2 How do we determine radiation that was cancelled or neutralised and 3 How do you determine the radiation volume created by ground reflection so we can work back to search for ground losses. That last one really bothers me as I have never got a good handle on the contribution of ground reflection to any particular part of the radiation envelope. Art Denny wrote: For those who wish to actually learn and not just insult each other, get a calculator, learn how to calculate Cosine Theta a trivial math problem that any 9th grader can be taught in 5 minutes flat, get a BIG piece of paper reason to come, and actually calculate the shape and vector length of the lobes of a two element Yagi-Uda antenna... Do the calculation in both the horizonal and vertical planes... From that you can calculate the volume of each lobe, which is proportional to the percentage of power in each lobe... From that number you can very simply calculate what percentage went into the lobes you prefer and what went in the lobes you don't prefer... Now, the reason for the BIG piece of paper... The antenna patterns you see on the screen with EZNEC, or in the antenna handbooks, are logarithmic, not linear and there are flavors to them, ARRL, linear logarithmic, modified logarithmic... So, the patterns are distorted... Why is that? Because if they were linear and the front lobe and the rear lobe are to the same scale the front lobe will take up the entire length of the screen/paper and the rear lobe will need a magnifying glass to be seen... A rear lobe that is 20dB down from the front lobe is down by the power ratio of 100... So, if your forward lobe calculates out to be 10 inches long, the rear lobe will be be 1/10 of an inch.... I'll let you figure out the size of a lobe that is 30dB down (get out your microscope) For those who want to review do a search on Joseph Reisert, who has published numerous writings on antennas and patterns... There many are others also, but Joe is published on the web, and very readable... cheers ... denny / k8do The radiation IS NOT cancelled or Neutralized. You need to learn more about what is going on with an antenna. I suggest you do some serious reading, actually reading with an open mind and not reading trying to find little phrases that seem to you to prove your beliefs. It should be fairly obvious that if an antenna worked by neutralization or cancelation that it would take more energy to cancel out radiation in the undesired direction of a yagi than is available in the desired direction. Therefore a Yagi or any other antenna does not work by cancellation. I gues I could express this a lot better but its late and whats the use. |
Yagi efficiency
Hi Denny The fact is, I probably get "ruffled" too easily, probably because I'm insecure. I'm not the sharpest antenna designer around. My way of antenna design relies mainly on actual, measured data, so I am a little short on convincing theoretical data. But, my approach to determining relative efficiency would be based on measured data. If *I* had made any statement on the efficiency of *any* antenna, you can be sure I would include some measured data. Measuring Yagi antenna loss is probably too mundane for Art. He already knows things that would require me months of testing to 'check up on'. If I wanted to know the "I squared R loss" efficiency of one antenna compared to another antenna, I'd need to conduct time consuming experiments. Jerry "Denny" wrote in message s.com... Jerry, if I came across a bit loud I apologize.. I usually skim down the latest chatter and then just post to the group off the bottom message, often having no direct bearing on the particular post it spins off from... Also, I skim a number of groups and topics and I run a business so I can miss a post that puts a different spin on things... If I ruffled your feathers it was not intentional... Let me comment that I absolutely agree with you that claiming a Yagi is inefficient from the perspective of I2R losses shows a lack of basic knowledge... Having said that, let me also note that closing the spacing, i.e. tighter than the classical Yagi-Uda array, and putting the beam into Supergain territory has consequences... Moxon has a non mathematical discussion of the supergain antennas with a graph of spacing v/s gain v/s impedence, and I Krauss mentioned that he designed his flat top array stimulated from a paper by Brown (I think it was) where he discussed arrays that have more than additive gain by tight spacing... Anyway I digress; the point of all this mumble is that these supergain "Yagi" arrays can have quite high I2R losses... But the commercial Yagi-Uda today is not in that class... Anyway, Cheers ... denny / k8do |
Yagi efficiency
Cecil, I find that very interesting, my antenna is designed around
resonant elements as you know which provides a more linear SWR curve which I translated into less losses. I admit I never exceeded the yagi gain tho I must admit I am pursuing the formation of other types of radiation including circular When looking at different types of radiation as well as making desired variables measurements move in concert with each other so that we can diminish the compromises that come with untuned elements.I have a lot of ground to cover Art Cecil Moore wrote: art wrote: Cecil Moore wrote: Actually Art, adding reactance reduces the current in the element thus *decreasing* losses below what a resonant passive element would have. Pure reactance is lossless. Whoa Cecil i dont follow that at all Resonant passive elements absorb more power than do non-resonant passive elements. Resonant passive elements therefore dissipate more heat than non-resonant passive elements. With EZNEC, check out the feedpoint impedance of a two element Yagi when both elements are resonant Vs when one element is 5% longer and a non-resonant reflector. The following values are not optimized by any means but will give you an idea. With ten foot spacing between two 33 foot elements The gain is virtually bidirectional at 10.7 dBi. The feedpoint impedance is 20 ohms and the current induced in the passive element is 0.84 amps. Keeping everything else the same and adding one foot to the reflector yields the following results. The gain increases to 11.9 dBi with a F/B ratio of about 8 dB. The feedpoint impedance is 30 ohms and the current induced in the passive element is lower at 0.75 amps. Making the reflector non-resonant causes its current to fall by about 0.1 amp thus reducing losses while the feedpoint impedance has increased by 50% and the gain has increased by 1.2 dB. There doesn't seem to be any downside to non-resonant passive elements. -- 73, Cecil http://www.w5dxp.com |
Yagi efficiency
Well let me take you on a thinking journey OK? I will do it in stages
so there will be no reason to jump the gun with questions unless it is pertinent to what I have said. Maybe a new thread would be better before I start out on explaining new thoughts about antennas which are away from the traditional designs which really requires an open mind Look out for the Gaussian Antenna heading and we will get started. You can read up on Gaussian antennas under Google in the mean time to get up to speed.The wife just got out of hospital so bear with me as I am having to do different things Art John Smith wrote: art wrote: Tom Ring wrote: art wrote: They are of a group that everything is known about antennas and is written in books. If you refer to something that is not in the books Art: If you refer to something that is "not in the books" one should take great care. Why I do think evidence can be brought out and can be demonstrated that some of the ways we "think" antennas are working is not real, however, great men have developed thinking models and formulas which are able to let us design and use WORKING antennas which are PRACTICAL. I site that mysterious 377 ohms as an example, or for another, incorporating the spin rate of the earth into antenna formulas (time), ridiculous (but useful!) But, those "old books" contain methods and means to develop antennas which do work and which do work well, we owe much to those who have gone before us ... I am only hoping that by refusing to allow "magic numbers" to be embedded into equations without any suitable explanation of what those numbers are "REALLY ABOUT" will one day awake the man who can form the vision and see what the others have all been unable to, Tesla seemed to have had an excellent ability which I hold as example of the type of "vision seer" I mean. I have an open mind, I guess you are as likely as the next guy to "be the one!" Never hurts to try anyway ... However, thank God practical antennas work and we have the tools to design and build them. Regards, JS |
Yagi efficiency
Well let me take you on a thinking journey OK? I will do it in stages
so there will be no reason to jump the gun with questions unless it is pertinent to what I have said. Maybe a new thread would be better before I start out on explaining new thoughts about antennas which are away from the traditional designs which really requires an open mind Look out for the Gaussian Antenna heading and we will get started. You can read up on Gaussian antennas under Google in the mean time to get up to speed.The wife just got out of hospital so bear with me as I am having to do different things Art John Smith wrote: art wrote: Tom Ring wrote: art wrote: They are of a group that everything is known about antennas and is written in books. If you refer to something that is not in the books Art: If you refer to something that is "not in the books" one should take great care. Why I do think evidence can be brought out and can be demonstrated that some of the ways we "think" antennas are working is not real, however, great men have developed thinking models and formulas which are able to let us design and use WORKING antennas which are PRACTICAL. I site that mysterious 377 ohms as an example, or for another, incorporating the spin rate of the earth into antenna formulas (time), ridiculous (but useful!) But, those "old books" contain methods and means to develop antennas which do work and which do work well, we owe much to those who have gone before us ... I am only hoping that by refusing to allow "magic numbers" to be embedded into equations without any suitable explanation of what those numbers are "REALLY ABOUT" will one day awake the man who can form the vision and see what the others have all been unable to, Tesla seemed to have had an excellent ability which I hold as example of the type of "vision seer" I mean. I have an open mind, I guess you are as likely as the next guy to "be the one!" Never hurts to try anyway ... However, thank God practical antennas work and we have the tools to design and build them. Regards, JS |
Yagi efficiency
Jerry Martes wrote:
Hi Denny The fact is, I probably get "ruffled" too easily, probably because I'm insecure. I'm not the sharpest antenna designer around. My way of antenna design relies mainly on actual, measured data, so I am a little short on convincing theoretical data. But, my approach to determining relative efficiency would be based on measured data. If *I* had made any statement on the efficiency of *any* antenna, you can be sure I would include some measured data. Measuring Yagi antenna loss is probably too mundane for Art. He already knows things that would require me months of testing to 'check up on'. If I wanted to know the "I squared R loss" efficiency of one antenna compared to another antenna, I'd need to conduct time consuming experiments. Jerry "Denny" wrote in message s.com... Jerry, if I came across a bit loud I apologize.. I usually skim down the latest chatter and then just post to the group off the bottom message, often having no direct bearing on the particular post it spins off from... Also, I skim a number of groups and topics and I run a business so I can miss a post that puts a different spin on things... If I ruffled your feathers it was not intentional... Let me comment that I absolutely agree with you that claiming a Yagi is inefficient from the perspective of I2R losses shows a lack of basic knowledge... Having said that, let me also note that closing the spacing, i.e. tighter than the classical Yagi-Uda array, and putting the beam into Supergain territory has consequences... Moxon has a non mathematical discussion of the supergain antennas with a graph of spacing v/s gain v/s impedence, and I Krauss mentioned that he designed his flat top array stimulated from a paper by Brown (I think it was) where he discussed arrays that have more than additive gain by tight spacing... Anyway I digress; the point of all this mumble is that these supergain "Yagi" arrays can have quite high I2R losses... But the commercial Yagi-Uda today is not in that class... Anyway, Cheers ... denny / k8do Jerry: I didn't really disagree with you, ALL antennas are 100% efficient radiators (dummy loads are excellent too!), only a real fool would argue that one! But this is california, I don't need the infrared radiations all that much; never had trouble with ice sickles on the 'tenna. grin. Warmest regards, JS |
Yagi efficiency
art wrote:
pertinent to what I have said. Maybe a new thread would be better before I start out on explaining new thoughts about antennas which are away from the traditional designs which really requires an open mind Art: You are correct. I have always longed for a "proper" newsgroup for these discussions, maybe: rec.amateur.ridiculous.antenna rec.amateur.unconventional.antenna rec.amateur.alien-designed.antennas rec.amateur.mystic-psychic.antennas rec.amateur.opium-dreams.antenna etc. Only kidding a bit here, but who cares its name, I think it worth while to strain the sands for a bit or piece of 'theory' which has been replaced with a 'magic number', which some unexplored, or unused bit of physics lies behind. One just gets used to using developed formulas and terms and forgets to question where they came from ... Indeed, I even suspect we may, eventually, discover time! However, our earth spinning is NOT it! Nor, I seriously doubt, is the speed of light, rather these are only two things subject to the "Universal Time Frame." At least we should be able to be rid of hecklers! Regards, JS |
Yagi efficiency
"John Smith" wrote in message ... Jerry Martes wrote: Hi Denny The fact is, I probably get "ruffled" too easily, probably because I'm insecure. I'm not the sharpest antenna designer around. My way of antenna design relies mainly on actual, measured data, so I am a little short on convincing theoretical data. But, my approach to determining relative efficiency would be based on measured data. If *I* had made any statement on the efficiency of *any* antenna, you can be sure I would include some measured data. Measuring Yagi antenna loss is probably too mundane for Art. He already knows things that would require me months of testing to 'check up on'. If I wanted to know the "I squared R loss" efficiency of one antenna compared to another antenna, I'd need to conduct time consuming experiments. Jerry "Denny" wrote in message s.com... Jerry, if I came across a bit loud I apologize.. I usually skim down the latest chatter and then just post to the group off the bottom message, often having no direct bearing on the particular post it spins off from... Also, I skim a number of groups and topics and I run a business so I can miss a post that puts a different spin on things... If I ruffled your feathers it was not intentional... Let me comment that I absolutely agree with you that claiming a Yagi is inefficient from the perspective of I2R losses shows a lack of basic knowledge... Having said that, let me also note that closing the spacing, i.e. tighter than the classical Yagi-Uda array, and putting the beam into Supergain territory has consequences... Moxon has a non mathematical discussion of the supergain antennas with a graph of spacing v/s gain v/s impedence, and I Krauss mentioned that he designed his flat top array stimulated from a paper by Brown (I think it was) where he discussed arrays that have more than additive gain by tight spacing... Anyway I digress; the point of all this mumble is that these supergain "Yagi" arrays can have quite high I2R losses... But the commercial Yagi-Uda today is not in that class... Anyway, Cheers ... denny / k8do Jerry: I didn't really disagree with you, ALL antennas are 100% efficient radiators (dummy loads are excellent too!), only a real fool would argue that one! But this is california, I don't need the infrared radiations all that much; never had trouble with ice sickles on the 'tenna. grin. Warmest regards, JS Hi John I didnt mean to imply that any antenna is 100 percent efficient. I would suggest that the amount of power lost to I squared R losses in a well built Yagi would be so low that they would be time consuming to evaluate. I have even thought about how I'd try testing the I^2R losses in a Yagi, as compared to another antenna design. But, that would be long learning process for me. I'd sure like to see Art's data before I'd start a test of yagi efficiency. Jerry |
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