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Yagi efficiency
Art:
OK, so I've read all of your posts, and all of the replies, but somehow, I still don't know where you're trying to work Europe from.... Maybe I'm dense, or can't comprehend the previous posts, but the best I've been able to find is that you have a 4000 mile path. Still, that could be quite a number of locations, given a 4000 mile circle around europe, though it may not really make much difference... What bands are you trying to use? Where are you located? Why are you so concerned about high angle radiation? The vagarities of multi-hop propagation often provide some really interesing contacts from high angle radiation... Please provide actual information, instead of vagarities... Thanks --Rick AH7H art wrote: Hans, you are so full of it, like Andy Capp waving his hands around in the air to vent his fraustration. Go back to the initial posting and what it says. All of your comments refer to side issues brought up that are not relavent to the initial question wthich also is not a guessing game to those skilled in the art Ar KØHB wrote: "Denny" wrote in message groups.com... You are right... You are so far ahead of this group that we can not even comprehend the question... Denny, This is all apparently intended as a guessing game, as art has given us just one single parameter of the exercise --- he wants to communicate with the UK in the winter. From where? At what time(s) of day? On what QRG(s)? What construction constraints? (budget, zoning, etc.) 73, de Hans, K0HB -- Homepage: http://www.home.earthlink.net/~k0hb Member: ARRL http://www.arrl.org SOC http://www.qsl.net/soc VWOA http://www.vwoa.org A-1 Operator Club http://www.arrl.org/awards/a1-op/ TCDXA http://www.tcdxa.org MWA http://www.w0aa.org TCFMC http://www.tcfmc.org FISTS http://www.fists.org LVDXA http://www.upstel.net/borken/lvdxa.htm NCI http://www.nocode.org |
Yagi efficiency
Rick my call is KB9MZ My antenna which is not of the Yagi design has a
TOA of 10 degrees and hopefully will be up before the weather gets to cold. I am restricted in height to 120 feet So as you can see I am pretty well committed to what array I am using. But the initial posting was not about antennas per se but about the efficiency of the Yagi with respect to desired radiation. Some would have you believe that radiation which is not within the main lobe is miniscual so I suggest you imagine two models one of which has all lobes removed except the main lobe Do you feel that both models now need to be labelled to avoid confusion as they look so much alike?. As for other side comments regarding TOA I suggest one reads the post from Mac which I whole heartedly agree with (Thanks Mac, tried to get in touch with you a few months ago but E mail was rejected) Art Rick Frazier wrote: Art: OK, so I've read all of your posts, and all of the replies, but somehow, I still don't know where you're trying to work Europe from.... Maybe I'm dense, or can't comprehend the previous posts, but the best I've been able to find is that you have a 4000 mile path. Still, that could be quite a number of locations, given a 4000 mile circle around europe, though it may not really make much difference... What bands are you trying to use? Where are you located? Why are you so concerned about high angle radiation? The vagarities of multi-hop propagation often provide some really interesing contacts from high angle radiation... Please provide actual information, instead of vagarities... Thanks --Rick AH7H art wrote: Hans, you are so full of it, like Andy Capp waving his hands around in the air to vent his fraustration. Go back to the initial posting and what it says. All of your comments refer to side issues brought up that are not relavent to the initial question wthich also is not a guessing game to those skilled in the art Ar KØHB wrote: "Denny" wrote in message groups.com... You are right... You are so far ahead of this group that we can not even comprehend the question... Denny, This is all apparently intended as a guessing game, as art has given us just one single parameter of the exercise --- he wants to communicate with the UK in the winter. From where? At what time(s) of day? On what QRG(s)? What construction constraints? (budget, zoning, etc.) 73, de Hans, K0HB -- Homepage: http://www.home.earthlink.net/~k0hb Member: ARRL http://www.arrl.org SOC http://www.qsl.net/soc VWOA http://www.vwoa.org A-1 Operator Club http://www.arrl.org/awards/a1-op/ TCDXA http://www.tcdxa.org MWA http://www.w0aa.org TCFMC http://www.tcfmc.org FISTS http://www.fists.org LVDXA http://www.upstel.net/borken/lvdxa.htm NCI http://www.nocode.org |
Yagi efficiency
It is a long time since I completed the Oxford and Cambridge entrance
exam on written english so I probably have lost some of my style because of my under pinninings of being a Cockney It took a while working in America to obtain communication skills but not long ago while in San Diego I came across the college for American spoken english which I was unaware of. However because of a broken brain which is the result of a heart attack it is too late for corrective action. Fortunately I have no difficulty in the comprehension of the main style american language which allows for a modicom of understanding Art Roy Lewallen wrote: Owen Duffy wrote: On Fri, 22 Sep 2006 13:21:47 -0700, Roy Lewallen wrote: Egad. There's no point in my wasting time by attempting to contribute further to this. I'll leave you to your alternate reality. Roy, it was obviously a troll, and many of us have been caught (again). Art's lead in "one can see that the yagi is very inefficient" should have been recognised by us all as bait. No, whatever art's problems are, I don't believe he's a troll. I'm confident that he's sincere in his statements and questions. It's just that he often makes no sense to me, and when he does, it's sometimes so contrary to established physics that it's reminiscent of the new age folks. His unconventional use of "efficiency" is typical, like the use of "energy" by the paraphysical crowd. Once in a while I make an honest try to contribute something rational, but usually end up just making him mad and provoking even sillier statements -- as happened again this time. So there's really no point in it. Roy Lewallen, W7EL |
Yagi efficiency
ORIGINAL MESSAGE:
On 21 Sep 2006 19:09:38 -0700, "art" wrote: Well this is where I am comming from, I am presently building an antenna for this winter where I will be communicating with the U.K. Thus my major lobe needs to be robust between about 10 degtrees and 4 degrees to ensnare most of the communication. ------------ REPLY FOLLOWS ------------ A parabolic dish about 500 feet across will fit your needs just fine. Once again, proving how a little knowledge is a dangerous thing. As if more proof were needed. :-) Bill, W6WRT |
Yagi efficiency
Some would have you believe that radiation which is not within the main
lobe is miniscual so I suggest you imagine two models one of which has all lobes removed except the main lobe Do you feel that both models now need to be labelled to avoid confusion as they look so much alike?. How do you suggest that the power that is not in the main lobe is removed? You either have to somehow concentrate it into the main lobe or dissipate as heat in a load. If you concentrate it into the main lobe then the gain of the main lobe will go up, if you dissipate it as heat then the gain will remain the same. If either were possible they would not look like the original yagi. You seem to miss the point that the gain in the main lobe is effectively the power in the area illuminated by the main lobe divided by the power in all other directions. Reduce the power in the sidelobes then the gain must go up, (unless it is dissipated as heat, which is not possible in a yagi). 73 Jeff |
Yagi efficiency
*Sigh*. Guess I'll try one more time.
Suppose that the Yagi has a front/back ratio of only 6 dB, and that the angular span ("height" and "width") of the rear lobe is the same as that of the front lobe. 1. Figure out how much power is contained in the rear lobe compared to the front lobe. 2. Express that ratio in dB. That's the amount you'd gain by eliminating all the power in the rear lobe, and moving it into the front lobe -- if you can do it without increasing the angular span of the front lobe. Repeat with a 10 dB front/back ratio or whatever you think your present Yagi has. Now, that wasn't so hard, was it? Roy Lewallen, W7EL Jeff wrote: Some would have you believe that radiation which is not within the main lobe is miniscual so I suggest you imagine two models one of which has all lobes removed except the main lobe Do you feel that both models now need to be labelled to avoid confusion as they look so much alike?. How do you suggest that the power that is not in the main lobe is removed? You either have to somehow concentrate it into the main lobe or dissipate as heat in a load. If you concentrate it into the main lobe then the gain of the main lobe will go up, if you dissipate it as heat then the gain will remain the same. If either were possible they would not look like the original yagi. You seem to miss the point that the gain in the main lobe is effectively the power in the area illuminated by the main lobe divided by the power in all other directions. Reduce the power in the sidelobes then the gain must go up, (unless it is dissipated as heat, which is not possible in a yagi). 73 Jeff |
Yagi efficiency
On Sun, 24 Sep 2006 09:48:24 +0100, "Jeff" wrote:
You seem to miss the point that the gain in the main lobe is effectively the power in the area illuminated by the main lobe divided by the power in all other directions. An unconventional definition of the term "gain". How can there be rational discussion of principles when some people must invent their own meaning for terms that have well defined conventional meaning? Owen -- |
Yagi efficiency
You seem to miss the point that the gain in the main lobe is effectively
the power in the area illuminated by the main lobe divided by the power in all other directions. An unconventional definition of the term "gain". How can there be rational discussion of principles when some people must invent their own meaning for terms that have well defined conventional meaning? Owen -- |
Yagi efficiency
I'm sorry, I didn't say what I intended to. What I meant for step 2 was:
2. Assume for a moment that all the power was in a single front lobe. Calculate how much, in dB, that front lobe power would be reduced by putting the fraction in the rear lobe which you calculated in step 1. It's been a long, long time since I took an amateur exam. But I'd think the ability to make these calculations would be within the reach of anyone who passed the General class exam. Roy Lewallen, W7EL Roy Lewallen wrote: *Sigh*. Guess I'll try one more time. Suppose that the Yagi has a front/back ratio of only 6 dB, and that the angular span ("height" and "width") of the rear lobe is the same as that of the front lobe. 1. Figure out how much power is contained in the rear lobe compared to the front lobe. 2. Express that ratio in dB. That's the amount you'd gain by eliminating all the power in the rear lobe, and moving it into the front lobe -- if you can do it without increasing the angular span of the front lobe. Repeat with a 10 dB front/back ratio or whatever you think your present Yagi has. Now, that wasn't so hard, was it? Roy Lewallen, W7EL |
Yagi efficiency
Owen Duffy wrote:
How can there be rational discussion of principles when some people must invent their own meaning for terms that have well defined conventional meaning? How about "power", Owen. Some physicists say that a Poynting vector contains no power until some work is done - that if an EM wave in free space never encounters anything to which to transfer its energy, its ExH watts are not power. My question is: If an EM wave's ExH watts are not power, what are those watts called? i.e. the units of power are watts, but if in some cases, watts are not power, what are they? -- 73, Cecil http://www.w5dxp.com |
Yagi efficiency
Dear "Jeff" (no call sign):
Please read and study an antenna text such as Kraus' third edition of Antennas. His first edition (published in 1950) is also an excellent reference for this issue. The terms you use have been well defined for many decades. Only patent attorneys are entitled to define word meanings that differ from convention - and then only in a patent application. Words have meanings. Regards, Mac N8TT |
Yagi efficiency
"J. Mc Laughlin" wrote Words have meanings. Not always the *same* meanings to each of us, and it would seem pretty arrogant to for one to presume that only *their* meaning is correct. I'm reminded of a passage by Lewis J. Carroll...... 'When I use a word,' Humpty Dumpty said, in a rather scornful tone,' it means just what I choose it to mean, neither more nor less.' 'The question is,' said Alice, 'whether you can make words mean so many different things.' 'The question is,' said Humpty Dumpty, 'which is to be master - that's all.' 73, de Hans, K0HB -- Homepage: http://www.home.earthlink.net/~k0hb Member: ARRL http://www.arrl.org SOC http://www.qsl.net/soc VWOA http://www.vwoa.org A-1 Operator Club http://www.arrl.org/awards/a1-op/ TCDXA http://www.tcdxa.org MWA http://www.w0aa.org TCFMC http://www.tcfmc.org FISTS http://www.fists.org LVDXA http://www.upstel.net/borken/lvdxa.htm NCI http://www.nocode.org |
Yagi efficiency
As my girlfriend likes to say "WORDS MEAN THINGS!"
Having a weird definition of efficiency doesn't help anyone out. Needing an antenna with super-high-gain at one particular elevation and azimuth angle is a weird, but... sort of valid question... but has nothing to do with the efficiency of said antenna. Dan |
Yagi efficiency
On 24 Sep 2006 11:29:08 -0700, "
wrote: As my girlfriend likes to say "WORDS MEAN THINGS!" Having a weird definition of efficiency doesn't help anyone out. Needing an antenna with super-high-gain at one particular elevation and azimuth angle is a weird, but... sort of valid question... but has nothing to do with the efficiency of said antenna. Dan Hi Dan, From discussions of years past with the chipster, his novel k2 fractal flyer antenna (heavily constrained with unique parameters) offered the "best" gain at 10 degrees that couldn't be bettered by anyone. He took umbrage when this claim was examined in the modeler ("you can't make a copy of that antenna! I own the rights!"): http://www.qsl.net/kb7qhc/antenna/fr...r/k2/index.htm It turned out that the word "Best" meant -4.63 dBi - which I promptly bettered by more than half a dB (in an unpublished design I call the Foolish fractal Flyer). The chipster also made efficiency claims similar to Art's (that is, using the same corruption of language). It didn't take long to flush that efficiency with the same merits. The moral of inventing meanings for words is that those meanings have a short shelf life. This kind of thing doesn't even last out a week in the white house press room. 73's Richard Clark, KB7QHC |
Yagi efficiency
The moral of inventing meanings for words is that those meanings have
a short shelf life. This kind of thing doesn't even last out a week in the white house press room. True, true. If only all this word-twisting energy could be harnessed as valid antenna design... the chipster seems to have relegated himself these days to fairly innocuous posts elsewhere regarding staying on the good side of your neighbors' graces by putting up visually low profile antennas... Certainly a change from the f-word antenna wars of old. I was a regular reader of r.r.a.a. in those days... not much of a poster back then, though. I wonder if a thousand-mile long, five mile high stack of rhombics might meet Art's requirements... of course, at that point you could just run open wire line to any distant receiver. That would be quite efficient, from Art's standpoint. 73, Dan |
Yagi efficiency
Dan,
you know quite well what the post that started this thread asked for. I only added the TOA comments to fill in some body where I was coming from not for advice on what antenna to build. People are quibling over the word "efficiency" which I find rather wierd especially since I am supposed to be in the company of fellow engineers. The subject was antenna radiation patterns and ascertaining the relative volume of the main lobe which is the reason for an antenna and comparing it to the total volume of the array which one accepts to obtain the desirable primary lobe. Oh yes, when we talk of efficiency one must multiply the ratio by 100 Some may have forgotten that! Obviously this group comprises of a swarm of tadpoles with a few little goldfish in a small pond none of which are qualified to be termed faculty. Now you have something to get your teeth into since you deign to respond to the initial post This term "I don't understand" is usually used by student who enter class after late night partying and it didn't work then either. A dull brain is a dull brain unless one activates it. Carry on with a thread of your own choice and quibble amongst yourselves about what "is" is really meant by use of the word "is" For what was a very short question this thread has gone amok and is way to long Art wrote: The moral of inventing meanings for words is that those meanings have a short shelf life. This kind of thing doesn't even last out a week in the white house press room. True, true. If only all this word-twisting energy could be harnessed as valid antenna design... the chipster seems to have relegated himself these days to fairly innocuous posts elsewhere regarding staying on the good side of your neighbors' graces by putting up visually low profile antennas... Certainly a change from the f-word antenna wars of old. I was a regular reader of r.r.a.a. in those days... not much of a poster back then, though. I wonder if a thousand-mile long, five mile high stack of rhombics might meet Art's requirements... of course, at that point you could just run open wire line to any distant receiver. That would be quite efficient, from Art's standpoint. 73, Dan |
Yagi efficiency
Dan,
you know quite well what the post that started this thread asked for. I only added the TOA comments to fill in some body where I was coming from not for advice on what antenna to build. People are quibling over the word "efficiency" which I find rather wierd especially since I am supposed to be in the company of fellow engineers. The subject was antenna radiation patterns and ascertaining the relative volume of the main lobe which is the reason for an antenna and comparing it to the total volume of the array which one accepts to obtain the desirable primary lobe. Oh yes, when we talk of efficiency one must multiply the ratio by 100 Some may have forgotten that! Obviously this group comprises of a swarm of tadpoles with a few little goldfish in a small pond none of which are qualified to be termed faculty. Now you have something to get your teeth into since you deign to respond to the initial post This term "I don't understand" is usually used by student who enter class after late night partying and it didn't work then either. A dull brain is a dull brain unless one activates it. Carry on with a thread of your own choice and quibble amongst yourselves about what "is" is really meant by use of the word "is" For what was a very short question this thread has gone amok and is way to long Art wrote: The moral of inventing meanings for words is that those meanings have a short shelf life. This kind of thing doesn't even last out a week in the white house press room. True, true. If only all this word-twisting energy could be harnessed as valid antenna design... the chipster seems to have relegated himself these days to fairly innocuous posts elsewhere regarding staying on the good side of your neighbors' graces by putting up visually low profile antennas... Certainly a change from the f-word antenna wars of old. I was a regular reader of r.r.a.a. in those days... not much of a poster back then, though. I wonder if a thousand-mile long, five mile high stack of rhombics might meet Art's requirements... of course, at that point you could just run open wire line to any distant receiver. That would be quite efficient, from Art's standpoint. 73, Dan |
Yagi efficiency
Dan,
you know quite well what the post that started this thread asked for. I only added the TOA comments to fill in some body where I was coming from not for advice on what antenna to build. People are quibling over the word "efficiency" which I find rather wierd especially since I am supposed to be in the company of fellow engineers. The subject was antenna radiation patterns and ascertaining the relative volume of the main lobe which is the reason for an antenna and comparing it to the total volume of the array which one accepts to obtain the desirable primary lobe. Oh yes, when we talk of efficiency one must multiply the ratio by 100 Some may have forgotten that! Obviously this group comprises of a swarm of tadpoles with a few little goldfish in a small pond none of which are qualified to be termed faculty. Now you have something to get your teeth into since you deign to respond to the initial post This term "I don't understand" is usually used by student who enter class after late night partying and it didn't work then either. A dull brain is a dull brain unless one activates it. Carry on with a thread of your own choice and quibble amongst yourselves about what "is" is really meant by use of the word "is" For what was a very short question this thread has gone amok and is way to long Art wrote: The moral of inventing meanings for words is that those meanings have a short shelf life. This kind of thing doesn't even last out a week in the white house press room. True, true. If only all this word-twisting energy could be harnessed as valid antenna design... the chipster seems to have relegated himself these days to fairly innocuous posts elsewhere regarding staying on the good side of your neighbors' graces by putting up visually low profile antennas... Certainly a change from the f-word antenna wars of old. I was a regular reader of r.r.a.a. in those days... not much of a poster back then, though. I wonder if a thousand-mile long, five mile high stack of rhombics might meet Art's requirements... of course, at that point you could just run open wire line to any distant receiver. That would be quite efficient, from Art's standpoint. 73, Dan |
Yagi efficiency
Dan,
you know quite well what the post that started this thread asked for. I only added the TOA comments to fill in some body where I was coming from not for advice on what antenna to build. People are quibling over the word "efficiency" which I find rather wierd especially since I am supposed to be in the company of fellow engineers. The subject was antenna radiation patterns and ascertaining the relative volume of the main lobe which is the reason for an antenna and comparing it to the total volume of the array which one accepts to obtain the desirable primary lobe. Oh yes, when we talk of efficiency one must multiply the ratio by 100 Some may have forgotten that! Obviously this group comprises of a swarm of tadpoles with a few little goldfish in a small pond none of which are qualified to be termed faculty. Now you have something to get your teeth into since you deign to respond to the initial post This term "I don't understand" is usually used by student who enter class after late night partying and it didn't work then either. A dull brain is a dull brain unless one activates it. Carry on with a thread of your own choice and quibble amongst yourselves about what "is" is really meant by use of the word "is" For what was a very short question this thread has gone amok and is way to long Art wrote: The moral of inventing meanings for words is that those meanings have a short shelf life. This kind of thing doesn't even last out a week in the white house press room. True, true. If only all this word-twisting energy could be harnessed as valid antenna design... the chipster seems to have relegated himself these days to fairly innocuous posts elsewhere regarding staying on the good side of your neighbors' graces by putting up visually low profile antennas... Certainly a change from the f-word antenna wars of old. I was a regular reader of r.r.a.a. in those days... not much of a poster back then, though. I wonder if a thousand-mile long, five mile high stack of rhombics might meet Art's requirements... of course, at that point you could just run open wire line to any distant receiver. That would be quite efficient, from Art's standpoint. 73, Dan |
Yagi efficiency
art KB9MZ wrote:
Thus my major lobe needs to be robust between about 10 degtrees and 4 degrees to ensnare most of the communication. I don't recall you stated which band but I'll assume 20 meters. Assuming flat terrain (for your Indiana QTH), a single Yagi at 120' (your maximum possible) would cover these angles best. 140' (or 2 wavelengths high if it is not 20m) would be the optimum heightl to center your main lobe at 7 degrees. Two stacked Yagis at 60' and 120' would be better than a single one at 120' or 140' for 4-10 degrees, but obviously this means more work and expense. If your terrain is not relatively flat, and if you are lucky to be on a hill with a gentle slope in the direction of England, the optimum height will be much less. However you would need to model this using HFTA in the most recent Antenna Handbook or YT in older editions. 73, Bill W4ZV |
Yagi efficiency
On 24 Sep 2006 13:41:43 -0700, "art" wrote:
you know quite well what the post that started this thread asked for. Yes, it is quite clearly offered in the Subject line, isn't it? People are quibling over the word "efficiency" which I find rather wierd And that is the second word of only two words in the Subject line, isn't it? when we talk of efficiency one must multiply the ratio by 100 Are we to expect 96 more duplications of your post? 73's Richard Clark, KB7QHC |
Yagi efficiency
Bill,
None of that is really a problem to me.I have multi points to which I can feed for different patterns depending on the time of the day as well as option of tilting the array. If I don't get my elmer I will assume he is not on the air and yes it is twenty meters and I am located in the couintryside that I understand is the highest between Chicago and New Orleans and since this is the bread basket of the U.S the ground loam is excellent. I use 7/8 andrews plus a long length underground and the tower is hinged in two places as well as another one for array tilting. I have power gain over a yagi but I was just curious as to how much more radiation energy was available to ensnare which Is why I referred to array volume since gain is really dependant on half power beam width required or one can live with I once had a 80 foot yagi and with the looseness in my prop pitch rotor combined with the narrow beam one was never sure if one was really taking advantage oif gain available. Pretty simple question for those who know the answer after all you start off with 3 db gain in two different directions thereffore it would seem to me that a yagi was only 50% efficient but people are quarrelling about every thing except the posed question to excuse them selves from real thought. Reg would have come up with the solution after a bottle of wine after noticing the english provided by the cue Regards Art wrote: art KB9MZ wrote: Thus my major lobe needs to be robust between about 10 degtrees and 4 degrees to ensnare most of the communication. I don't recall you stated which band but I'll assume 20 meters. Assuming flat terrain (for your Indiana QTH), a single Yagi at 120' (your maximum possible) would cover these angles best. 140' (or 2 wavelengths high if it is not 20m) would be the optimum heightl to center your main lobe at 7 degrees. Two stacked Yagis at 60' and 120' would be better than a single one at 120' or 140' for 4-10 degrees, but obviously this means more work and expense. If your terrain is not relatively flat, and if you are lucky to be on a hill with a gentle slope in the direction of England, the optimum height will be much less. However you would need to model this using HFTA in the most recent Antenna Handbook or YT in older editions. 73, Bill W4ZV |
Yagi efficiency
art wrote:
The subject was antenna radiation patterns and ascertaining the relative volume of the main lobe which is the reason for an antenna and comparing it to the total volume of the array which one accepts to obtain the desirable primary lobe. Take the integral of the gain of the antenna over the angles in azimuth and elevation that you consider to define the boundaries of the main lobe and divide that by the integral of the gain of the antenna over all angles . You'll need your gain as a function of the angles. That's the number you're looking for, I suppose. I guess it's a decent measure of sidelobe suppression... but so is the ratio of the gain of the main lobe to the gain of the biggest sidelobe. 73, Dan |
Yagi efficiency
Dan wrote:
"---of course at that point you could just run open wire line to any distant receiver." Yes, if it isn`t too distant. If the 1000-mile open wire line lost 0.1 dB per 100 feet, loss would be 52.8 dB per mile or about 53 thousand db in its entire length, hardly a useable transmission line. On the other hand, suppose the wavelength were 160 meters. In the first wavelength of a radio signal radiated in free space, you would lose 22 dB. In the second, you would lose an additional 6 dB. Doubling the distance again to a total of 7 wavelengths, or 1120 meters, total space loss would be 34 dB. At a distance of 2240 meters from the transmitter, the loss is 40 dB which is less that our open wire line would lose in its 1st mile, a shorter distance. Every mile of wire line extracts the same loss. Very long wire lines become useless without repeaters to boost signal above the noise level. Doubling line-of-sight radio path distance only increases path loss 6dB, no matter how long the path is. As for efficiency, J.D. Kraus says: "The efficiency of an antenna is defined as the ratio between the power radiated by it and the power delivered into the antenna." (page 866 of 3rd ed. of "Antennas". Best regards, Richard Harrison, KB5WZI |
Yagi efficiency
And what about deflected energy at right angles to the reflector as
well as energy in the lobe above the main lobe? You can squeese the main lobe as much as you want for extra gain but it will not change the vbolume of the main lobe one iota Art wrote: art wrote: The subject was antenna radiation patterns and ascertaining the relative volume of the main lobe which is the reason for an antenna and comparing it to the total volume of the array which one accepts to obtain the desirable primary lobe. Take the integral of the gain of the antenna over the angles in azimuth and elevation that you consider to define the boundaries of the main lobe and divide that by the integral of the gain of the antenna over all angles . You'll need your gain as a function of the angles. That's the number you're looking for, I suppose. I guess it's a decent measure of sidelobe suppression... but so is the ratio of the gain of the main lobe to the gain of the biggest sidelobe. 73, Dan |
Yagi efficiency
Richard Harrison wrote: Dan wrote: "---of course at that point you could just run open wire line to any snip. As for efficiency, J.D. Kraus says: "The efficiency of an antenna is defined as the ratio between the power radiated by it and the power delivered into the antenna." (page 866 of 3rd ed. of "Antennas". I would think that the definition quoted was more applicable for a radiator than a antenna since the latter consists of addative and so called destructive radiation. If an antennas radiative field was totally destructive the definition stated would include that as an efficient antenna ! Art Best regards, Richard Harrison, KB5WZI |
Yagi efficiency
Hi Art,
A few points below, but first just remember that the TOA of any horizontally polarized antenna is primarily a function of ground reflections which vary according to height above ground. Previously you mentioned that your antenna was designed for a TOA of 10 degrees. That cannot be true except for a specific height above ground. Whether Yagi, Quad, Log, Rhombic or any non-vertically stacked antenna. Something like a Sterba curtain is different because it has multiple elements stacked vertically which CAN be steered by phasing. art wrote: yes it is twenty meters and I am located in the couintryside that I understand is the highest between Chicago and New Orleans and since this is the bread basket of the U.S the ground loam is excellent. 1. Absolute height above sea level means nothing. What is important to TOA is your relative height above the terrain within a mile or two of your tower. I operated from Colorado for ~30 years and always got a chuckle from the guys who said, "My antenna is over 1 mile high". In fact what is important for determining TOA is not height above sea level but height above surrounding terrain. 2. Ground conductivity has minimal effect on horizontally polarized ground reflections. You may be thinking of vertically polarized antennas like verticals where it has a huge effect. HFTA does have conductivity as an input parameter but it has minimal effect, at least in my case (average ground versus salt water). I use 7/8 andrews plus a long length underground and the tower is hinged in two places as well as another one for array tilting. Phsical tilting has minimal effect on the ground reflections for the angles of interest (4-10 degrees) because the vertical lobe is not very narrow (typically a Yagi has ~50 degree 3 dB vertical beamwidth). In other words tilting has a far secondary effect on TOA versus changing the antenna height. You can prove this to yourself by modeling with a program like EZNEC (HFTA does not allow tilting because it is physically impractical and has little effect). Pretty simple question for those who know the answer after all you start off with 3 db gain in two different directions thereffore it would seem to me that a yagi was only 50% efficient I believe you're referring to a dipole which has 2+ dB gain over isotropic in the two directions broadside to the element. If we add ~6 dB from ground reflection gain, we get 8 dB gain over isotropic, but this is ONLY for a specific TOA which is determined by the antenna's height above ground. Of course a good Yagi will typically have 25-30 dB Front to Rear, so its backward lobe has very little of the total energy (far less than 50%). Bottom line to all of this is that your antenna's height above ground has the primary influence on TOA. The only other way to "steer" the vertical lobe is to mount your antenna on a motorized tower (unless you go to vertically stacked elements and phasing). Put your single antenna at 120' and the vertical pattern will be centered on about 9 degrees (assuming flat terrain). 73 & GL! Bill W4ZV P.S. Here are some results using HFTA for my 10 meter 3-stack: http://users.vnet.net/btippett/terrain_&_toas.htm |
Yagi efficiency
Aren't you comparing kinetic versus potential without thought
to energy conservation Regards Art Cecil Moore wrote: Owen Duffy wrote: How can there be rational discussion of principles when some people must invent their own meaning for terms that have well defined conventional meaning? How about "power", Owen. Some physicists say that a Poynting vector contains no power until some work is done - that if an EM wave in free space never encounters anything to which to transfer its energy, its ExH watts are not power. My question is: If an EM wave's ExH watts are not power, what are those watts called? i.e. the units of power are watts, but if in some cases, watts are not power, what are they? -- 73, Cecil http://www.w5dxp.com |
Yagi efficiency
Aren't you comparing kinetic versus potential without thought
to energy conservation Regards Art Cecil Moore wrote: Owen Duffy wrote: How can there be rational discussion of principles when some people must invent their own meaning for terms that have well defined conventional meaning? How about "power", Owen. Some physicists say that a Poynting vector contains no power until some work is done - that if an EM wave in free space never encounters anything to which to transfer its energy, its ExH watts are not power. My question is: If an EM wave's ExH watts are not power, what are those watts called? i.e. the units of power are watts, but if in some cases, watts are not power, what are they? -- 73, Cecil http://www.w5dxp.com |
Yagi efficiency
wrote: Hi Art, A few points below, but first just remember that the TOA of any horizontally polarized antenna is primarily a function of ground reflections which vary according to height above ground. Previously you mentioned that your antenna was designed for a TOA of 10 degrees. That cannot be true except for a specific height above ground. Whether Yagi, Quad, Log, Rhombic or any non-vertically stacked antenna. Something like a Sterba curtain is different because it has multiple elements stacked vertically which CAN be steered by phasing. That is entirely correct for known technology........... at this time ! art wrote: yes it is twenty meters and I am located in the couintryside that I understand is the highest between Chicago and New Orleans and since this is the bread basket of the U.S the ground loam is excellent. 1. Absolute height above sea level means nothing. What is important to TOA is your relative height above the terrain within a mile or two of your tower. I operated from Colorado for ~30 years and always got a chuckle from the guys who said, "My antenna is over 1 mile high". In fact what is important for determining TOA is not height above sea level but height above surrounding terrain. It is the highest point for the U.K. period 2. Ground conductivity has minimal effect on horizontally polarized ground reflections. You may be thinking of vertically polarized antennas like verticals where it has a huge effect. HFTA does have conductivity as an input parameter but it has minimal effect, at least in my case (average ground versus salt water). Agreed, there was a Australian article that showd that very well I use 7/8 andrews plus a long length underground and the tower is hinged in two places as well as another one for array tilting. Phsical tilting has minimal effect on the ground reflections for the angles of interest (4-10 degrees) because the vertical lobe is not very narrow (typically a Yagi has ~50 degree 3 dB vertical beamwidth). In other words tilting has a far secondary effect on TOA versus changing the antenna height. Lawson W2PV wrote about that while he was working in Schenectady G.E. on the computor that replaced zillions of vacuum valves but with respect to planar arrays Mine is not a planar array You can prove this to yourself by modeling with a program like EZNEC (HFTA does not allow tilting because it is physically impractical and has little effect). As I said above mine is not a planar array. The computor program I use is AO-PRO by Beasley Pretty simple question for those who know the answer after all you start off with 3 db gain in two different directions thereffore it would seem to me that a yagi was only 50% efficient I believe you're referring to a dipole which has 2+ dB gain over isotropic in the two directions broadside to the element. Yes, I rounded it off to 3 If we add ~6 dB from ground reflection gain, we get 8 dB gain over isotropic, but this is ONLY for a specific TOA which is determined by the antenna's height above ground. Fully undertstood when referring to planar arrays Of course a good Yagi will typically have 25-30 dB Front to Rear, so its backward lobe has very little of the total energy (far less than 50%). F/B for planar arrays is for a single angle , front to rear is more appealing but at the same time it ignores pattern lobes in all directions including upwards. I have found that TOA on its own is pretty wothless as one can get the gain of a larger antenna with a wider but narrower lobe that follows the bottom half of a higher gain lobe. Lets face it for planar arrays gain is obtained at the axpense of half power area. Bottom line to all of this is that your antenna's height above ground has the primary influence on TOA. The only other way to "steer" the vertical lobe is to mount your antenna on a motorized tower (unless you go to vertically stacked elements and phasing). Obviously height is important and totally constrictive of all planar arrays where the TOA is captive. As soon as you add another vector such that the array is three dimensional as with a stack things change Put your single antenna at 120' and the vertical pattern will be centered on about 9 degrees (assuming flat terrain). I assume you mean vertical elevation and yes mine cannot be much over 100 feet and I will have various lobes available at various TOA's and most important variable beam depth to accommodate propagation changes as arrival angles change Thanks for the contact The most interesting thing that I am looking forward to is operation at the bottom of the cycle to see if there is still propagation but only for low angles. As you gat older you look for any excuse to stay indoors Art 73 & GL! Bill W4ZV P.S. Here are some results using HFTA for my 10 meter 3-stack: Yup there was an extensive article on that for the NE area where it shows the impact of a ground projection on a collective angle. http://users.vnet.net/btippett/terrain_&_toas.htm |
Yagi efficiency
On 24 Sep 2006 16:11:33 -0700, "art" wrote:
You can squeese the main lobe as much as you want for extra gain but it will not change the vbolume of the main lobe one iota Art, You know that your arguments sound like you are trying to crucify yourself and expect applause? When we discard the errant nonsense, almost every posting you make here is weighed with material of self-defeating goals. The quote above is a remarkable admission that you reject the solution you seek. When you paint yourself into a corner, what color is the floor? 73's Richard Clark, KB7QHC |
Yagi efficiency
Hi Art,
art wrote: It is the highest point for the U.K. period I don't understand. I thought you were in Indiana and wanting to optimize your path to England. As I said above mine is not a planar array. The computor program I use is AO-PRO by Beasley That's the best there is in my opinion. You are fortunate to have a copy since he no longer sells to hams. Thanks for the contact The most interesting thing that I am looking forward to is operation at the bottom of the cycle to see if there is still propagation but only for low angles. As you gat older you look for any excuse to stay indoors You're welcome. Here is a long but interesting story related to low angle TOAs. W3CRA was a legend and I can vividly remember him working one Asian after another that I could not detect the slightest trace of using a 3 element Yagi at 60' from my home in NC at that time: http://users.vnet.net/btippett/w3cra.htm Good luck with your new system! 73, Bill W4ZV |
Yagi efficiency
Just read your page... very interestin. We don't have large hills in
Illinois but a helicoptor pilot stated that this town is visible for miles around and another ham told me that the DX bureu staed that this town got more cards than all of Chicago I remember once when I gave a local talk where I spoke about Lawson and his work and I repeated some of his statements. Well I was challenged on some things but since I am not a DXer they and the suurounding counties waited until a rare station was comming on and taking only three stations from each district. Boy I got a shock with the noise and pandemonium and couldnt see how any station could be picked out but I was fortunate plus two in the Chicago area. I know I was very lucky and have no idea why people collect those things or enter contests... the noise is horrible I think I had 13 elements on a 60 foot boom at that time plus a couple of reflectors to experiment with. From that moment on I gave up on aluminum elements and now use exclusively telescopic fishing poles with an aluminum shell as it is cheaper in the long run and not susceptable to ice build up Art Artl wrote: Hi Art, art wrote: It is the highest point for the U.K. period I don't understand. I thought you were in Indiana and wanting to optimize your path to England. As I said above mine is not a planar array. The computor program I use is AO-PRO by Beasley That's the best there is in my opinion. You are fortunate to have a copy since he no longer sells to hams. Thanks for the contact The most interesting thing that I am looking forward to is operation at the bottom of the cycle to see if there is still propagation but only for low angles. As you gat older you look for any excuse to stay indoors You're welcome. Here is a long but interesting story related to low angle TOAs. W3CRA was a legend and I can vividly remember him working one Asian after another that I could not detect the slightest trace of using a 3 element Yagi at 60' from my home in NC at that time: http://users.vnet.net/btippett/w3cra.htm Good luck with your new system! 73, Bill W4ZV |
Yagi efficiency
Richard
why don't you get with it instead of the constant adverserial role Go to the library and get a good book on antennas and maybe study up on curls? Oh shucks I forgot you were bald... Never mind keep talking to yourself and maybe there will be an echo for you to talk to and belittle. Frankly to me you are just a bore that struts around in shakesperian tights and write in the language of my forefathers and glory only in your perceived triumps in the repair shop. Why not go back and try to repair some shoes of some people which you cannot fill See you finally got a response but don't bank on a lot more until you become less adverserial with respect to all work other than your own and provide the same respect that you one time would like to receive Put me in your plonk file and I will respond also Art Richard Clark wrote: On 24 Sep 2006 16:11:33 -0700, "art" wrote: You can squeese the main lobe as much as you want for extra gain but it will not change the vbolume of the main lobe one iota Art, You know that your arguments sound like you are trying to crucify yourself and expect applause? When we discard the errant nonsense, almost every posting you make here is weighed with material of self-defeating goals. The quote above is a remarkable admission that you reject the solution you seek. When you paint yourself into a corner, what color is the floor? 73's Richard Clark, KB7QHC |
Yagi efficiency
"art" wrote in message I know I was very lucky and have no idea why people collect those things or enter contests... the noise is horrible I think I had 13 elements on a 60 foot boom at that time plus a couple of reflectors to experiment with. Art, Why do people run Marathons, race cars, boats, airplanes or turtles? Some like to walk, some roll in the mud, some like to compete in the stadium. Contesters like to prove that they can design better antennas, assemble better stations and prove that they are better operators. It is also real test for antenna designs and propagation knowledge and how to exploit both for better results that can quantify the performance and weed out junk and junk science. It takes years of devotion to show up in the top ten listings. If you have revolutionary design, we contesters will be first, dying to use it and cream the competition - that's the real test and not mumbo-jumbo claims. BTW I have a "secret weapon" too, it is a ferrite stick in the dish. Very efficient, no side lobes, one sharp beam, no side or back lobes. It is right up there with EH, Freaktals and perpetual motion machines. If you assume that propagation between you and UK is as you describe, you are way off. We are also ducting, use skewed path and changing angles depending on the point in the sunspot cycle, sun' activity, etc. etc. So for optimum propagation one needs either antenna that has wider beamwidth or sharp and stearable one in H and V planes. Can you enlighten us about your new revolutionary invention? Is it better than your patented reflector that is shorter than the driven element? 73 |
Yagi efficiency
Wow Yuri has arrived
I remember that long discusting arguement he had with Tom Rauch that brought words to the fore that brought shame to amateur radio I'm gone, I want no part of what is now on the near horizon Have a great year fellars I enjoyed the short visit while it lasted Art Yuri Blanarovich wrote: "art" wrote in message I know I was very lucky and have no idea why people collect those things or enter contests... the noise is horrible I think I had 13 elements on a 60 foot boom at that time plus a couple of reflectors to experiment with. Art, Why do people run Marathons, race cars, boats, airplanes or turtles? Some like to walk, some roll in the mud, some like to compete in the stadium. Contesters like to prove that they can design better antennas, assemble better stations and prove that they are better operators. It is also real test for antenna designs and propagation knowledge and how to exploit both for better results that can quantify the performance and weed out junk and junk science. It takes years of devotion to show up in the top ten listings. If you have revolutionary design, we contesters will be first, dying to use it and cream the competition - that's the real test and not mumbo-jumbo claims. BTW I have a "secret weapon" too, it is a ferrite stick in the dish. Very efficient, no side lobes, one sharp beam, no side or back lobes. It is right up there with EH, Freaktals and perpetual motion machines. If you assume that propagation between you and UK is as you describe, you are way off. We are also ducting, use skewed path and changing angles depending on the point in the sunspot cycle, sun' activity, etc. etc. So for optimum propagation one needs either antenna that has wider beamwidth or sharp and stearable one in H and V planes. Can you enlighten us about your new revolutionary invention? Is it better than your patented reflector that is shorter than the driven element? 73 |
Yagi efficiency
On 24 Sep 2006 19:34:22 -0700, "art" wrote:
Put me in your plonk file Shirley, you jest! And miss all the weeping and your lush interpretation of Camille at the Hammerlund? It took you 30 posts to get around to one significant factor in propagation: the frequency you were working! 73's and XOXOXOXOX Richard Clark, KB7QHC |
Yagi efficiency
art wrote: When one looks at a.radiating array pattern one can see that the yagi is very inefficient. Does anybody know of the relative volume contained in the main radiation lobe versus the total volume of the entire pattern? I know there are a lot of different type antenna gains and arrangement but I am trying to determine in an informal way the efficiency ratio and compare it to what would appear to be a very efficient antenna such as a dish. A casual look at a yagi radiation pattern would suggest Does anyone know why the efficiency of the Stanford Big Dish (150 feet) is only 35% on 1420MHz, compared to 55% on 150 and 400MHz? http://www-star.stanford.edu/rsg/bigdish.php --Zack Lau W1VT that it is less than 50% efficient at best especially when considering DX work where even the main lobe is less than 50% efficient when looking at available signal paths beyond 4000 miles which are somewhat below 12 degrees and where the main lobe itself is centered between 13 and 14 degrees with an average amateur antennah Art |
Yagi efficiency
On 26 Sep 2006 10:31:14 -0700, "Zack" wrote:
Does anyone know why the efficiency of the Stanford Big Dish (150 feet) is only 35% on 1420MHz, compared to 55% on 150 and 400MHz? http://www-star.stanford.edu/rsg/bigdish.php Hi Zack, You may be confusing (or have been confused with the content of this thread) antenna effeciency with system efficiency. The page makes the point of there being a feed "appropriateness." I would suspect the method of feed makes the difference (and those issues that lie beyond that include method of detection, noise, and so on). As for putting it to the antenna's merit, the roughness is far more significant to shorter wavelengths (roughness is on order of eight wave). This in itself produces problems of phase control, and phase control is the name of the game in directivity. 73's Richard Clark, KB7QHC |
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