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'SMALL' ANTENNA CRITERIA
My present antenna, which is for 160m and above, is about the size of
two shoe boxes and is less than 2:1 swr (50 ohm) across the band when situatedat the top of my tower. I have googled a lot over the last month or so to determine if there has been claims for the 'smallest' transmitting antenna and what the criteria consisted of. If I knew what it was I would concentrate on making my antenna smaller to reflect something more close to point radiation which has been theorized as being possible. Seems like that there is no real definition of what a 'small' compact antenna actually comprises of together with power handling capabilities! True, for receiving only there are many contestants all with different criteria, but for the ham community there is absolutely nothing for anybody to compare with other than such claims as 'mine is the smallest and I work anything I can hear' !. Can anybody point to a transmitting antenna that can be considered 'small ' without the need for a ground plane, which thus puts it into the 'antenna systems' class ? For a point of interest, I am presently using a reflector made from a garbage can lid, but it is not acting in anyway a dish antenna works when the reflector is grounded! As an aside, most posters to the group are aware that a modest sum was offered who could disprove my claim but with no takers. So can we put that particular subject aside and concentrate only on the request of this posting which should cut off most of the insults ? Best regards to all Art Unwin |
'SMALL' ANTENNA CRITERIA
art wrote:
My present antenna, which is for 160m and above, is about the size of two shoe boxes and is less than 2:1 swr (50 ohm) across the band when situatedat the top of my tower. I have googled a lot over the last month or so to determine if there has been claims for the 'smallest' transmitting antenna and what the criteria consisted of. If I knew what it was I would concentrate on making my antenna smaller to reflect something more close to point radiation which has been theorized as being possible. Seems like that there is no real definition of what a 'small' compact antenna actually comprises of together with power handling capabilities! True, for receiving only there are many contestants all with different criteria, but for the ham community there is absolutely nothing for anybody to compare with other than such claims as 'mine is the smallest and I work anything I can hear' !. Can anybody point to a transmitting antenna that can be considered 'small ' without the need for a ground plane, which thus puts it into the 'antenna systems' class ? For a point of interest, I am presently using a reflector made from a garbage can lid, but it is not acting in anyway a dish antenna works when the reflector is grounded! As an aside, most posters to the group are aware that a modest sum was offered who could disprove my claim but with no takers. So can we put that particular subject aside and concentrate only on the request of this posting which should cut off most of the insults ? Best regards to all Art Unwin Hi Art, Get a copy of Balanis' _Antenna Theory, Analysis and Design_, second edition, and read section 11.5, Fundamental Limits of Electrically Small Antennas. Also, in the _Antenna Engineering Handbook_, third edition, read section 6, Small Antennas by Harold A. Wheeler. I won't vouch for any of the information, but it should give you some ideas on what the practical limits of small antennas are supposed to be by reputable people who have thought the subject through. 73, Tom Donaly, KA6RUH |
'SMALL' ANTENNA CRITERIA
On 13 Feb, 20:34, "Tom Donaly" wrote:
art wrote: My present antenna, which is for 160m and above, is about the size of two shoe boxes and is less than 2:1 swr (50 ohm) across the band when situatedat the *top of my tower. I have googled a lot over the last month or so to determine if there has been claims for the 'smallest' transmitting antenna and what the criteria consisted of. If I knew what it was I would concentrate on making my antenna smaller to reflect something more close to point radiation which has been theorized as being possible. Seems like that there is no real definition of what a 'small' compact antenna actually comprises of *together with power handling capabilities! *True, for receiving only there are many contestants all with different criteria, but for the ham community there is absolutely nothing for anybody to compare *with other than such claims as 'mine is the smallest and I work anything I can *hear' !. Can anybody point to a transmitting antenna that can be considered *'small ' *without the need for a ground plane, which thus puts *it into the *'antenna systems' *class ? For a point of interest, I am presently using a reflector made from a garbage can lid, but it is not acting in anyway a dish antenna works when the reflector is grounded! As an aside, most posters to the group are aware that a modest sum was offered who could disprove my claim but with no takers. So can we put that particular subject *aside and concentrate only on the request of this posting which should cut off most of the insults ? Best regards to all Art Unwin Hi Art, * * * * *Get a copy of Balanis' _Antenna Theory, Analysis and Design_, second edition, and read section 11.5, Fundamental Limits of Electrically Small Antennas. Also, in the _Antenna Engineering Handbook_, third edition, read section 6, Small Antennas by Harold A. Wheeler. I won't vouch for any of the information, but it should give you some ideas on what the practical limits of small antennas are supposed to be by reputable people who have thought the subject through. 73, Tom Donaly, KA6RUH- Hide quoted text - - Show quoted text - Understood Tom. Wheeler looks at the subject from many angles but does not get into overall specifics. For instance, the smallest volume antenna can be based on wire size which in turn is based on power output. This effectively states that the smallest radiater is the size of a pinhead! Practicality states that the wire diameter is exceedingly small diameter plus extremely low power, all of which is based on a arrangement that is resonant. In practical terms I would point to a Fractal antenna however, the criteria for 'smallness' or 'compact' must factor in efficiency with respect to wave length where the latter antenna would fail. Same goes for the EH antenna which only can be regarded as a 'system'. Or for that matter a resister which as a load is just a heat exchanger. In the amateur field one should incorporate max power allowed on key down for a certain period of time without loading of any sort and where radiation is rated with respect to a unit volume. With that in mind I have found nothing to aim for to qualify as a 'small' or 'compact' antenna. Looking at the trade magazine 'Antenna' there is always demands for a "smaller" design antenna as something that is holding up electronic progress, but at the same time zero reference as to what defines 'small' since design is covered by Maxwell and not by Congress Best regards Art Unwin. |
'SMALL' ANTENNA CRITERIA
Art,
I am convinced that you are experimenting in an area of antenna practices that has been neglected... I am always interested in advances on the art and practice of antennas... You hereby offered the opportunity to drop by my qth with your reduced size 160 antenna... If transportation is a problem I will fly my airplane to your area and bring you back to Michigan, or arrange other transportation for you at my expense... I will personally mount your antenna at the top of a 150 foot tower and we can measure the near field intensity and far field signal strength developed by the antenna, compared to my normal size antennas which are off another tower at a distance .. I am sure I can convince a few of the regulars on here to be on the band and be ready to participate with signal strength measurements, spectrum analyzers, etc... This would form an excellent basis for an article for you to publish - complete with reports from third parties - on a major advance in the theory and practice of antennas... If I am not convenient to you then I suspect that W8JI or others would offer a similar testing range and I still would be happy to provide transportation just to be a part of an exciting new chapter in radio experimentation... cordially, denny - k8do |
'SMALL' ANTENNA CRITERIA
On 14 Feb, 04:28, Denny wrote:
Art, I am convinced that you are experimenting in an area of antenna practices that has been neglected... I am always interested in advances on the art and practice of antennas... You hereby offered the opportunity to drop by my qth with your reduced size 160 antenna... If transportation is a problem I will fly my airplane to your area and bring you back to Michigan, or arrange other transportation for you at my expense... I will personally mount your antenna at the top of a 150 foot tower and we can measure the near field intensity and far field signal strength developed by the antenna, compared to my normal size antennas which are off another tower at a distance .. *I am sure I can convince a few of the regulars on here to be on the band and be ready to participate with signal strength measurements, spectrum analyzers, etc... *This would form an excellent basis for an article for you to publish - complete with reports from third parties - on a major advance in the theory and practice of antennas... If I am not convenient to you then I suspect that W8JI or others would offer a similar testing range and I still would be happy to provide transportation just to be a part of an exciting new chapter in radio experimentation... cordially, denny - k8do That is very kind of you but there is no need for any all out effort regarding travel. What I will do is look around for some copper scraps and make one for you and use the normal mail. Since I will probably be using scrap that I can find my guess is that it would behove you to use 500 watts or less for your playing around. I will send it off about 14 days or less from now and hopefully the weather will be warmer for you.If I don't find any scraps then I will send the one on the tower even tho it is not of the optimum design use can use it as is on different bands. At the moment I am making one that can fit into a trouser pocket so that may be the one you get. Best regards Art Unwin |
'SMALL' ANTENNA CRITERIA
Denny wrote:
Art, I am convinced that you are experimenting in an area of antenna practices that has been neglected... I am always interested in advances on the art and practice of antennas... You hereby offered the opportunity to drop by my qth with your reduced size 160 antenna... If transportation is a problem I will fly my airplane to your area and bring you back to Michigan, or arrange other transportation for you at my expense... I will personally mount your antenna at the top of a 150 foot tower and we can measure the near field intensity and far field signal strength developed by the antenna, compared to my normal size antennas which are off another tower at a distance .. I am sure I can convince a few of the regulars on here to be on the band and be ready to participate with signal strength measurements, spectrum analyzers, etc... This would form an excellent basis for an article for you to publish - complete with reports from third parties - on a major advance in the theory and practice of antennas... If I am not convenient to you then I suspect that W8JI or others would offer a similar testing range and I still would be happy to provide transportation just to be a part of an exciting new chapter in radio experimentation... cordially, denny - k8do I suggest that you take pains to make sure the feedline is well decoupled - a couple of current baluns, one at the feedpoint and one a quarter wave down the line, should be adequate. An extra measure would be to measure the common mode feedline current to make sure it's minimal. That would go a long way toward silencing critics (like me) who believe that reported good results from such small antennas are often the result of feedline radiation -- that is, that the feedline is the primary radiator and the "antenna" plays only a minor role. Roy Lewallen, W7EL |
'SMALL' ANTENNA CRITERIA
On 14 Feb, 12:08, Roy Lewallen wrote:
Denny wrote: Art, I am convinced that you are experimenting in an area of antenna practices that has been neglected... I am always interested in advances on the art and practice of antennas... You hereby offered the opportunity to drop by my qth with your reduced size 160 antenna... If transportation is a problem I will fly my airplane to your area and bring you back to Michigan, or arrange other transportation for you at my expense... I will personally mount your antenna at the top of a 150 foot tower and we can measure the near field intensity and far field signal strength developed by the antenna, compared to my normal size antennas which are off another tower at a distance .. *I am sure I can convince a few of the regulars on here to be on the band and be ready to participate with signal strength measurements, spectrum analyzers, etc... *This would form an excellent basis for an article for you to publish - complete with reports from third parties - on a major advance in the theory and practice of antennas... If I am not convenient to you then I suspect that W8JI or others would offer a similar testing range and I still would be happy to provide transportation just to be a part of an exciting new chapter in radio experimentation... cordially, denny - k8do I suggest that you take pains to make sure the feedline is well decoupled - a couple of current baluns, one at the feedpoint and one a quarter wave down the line, should be adequate. An extra measure would be to measure the common mode feedline current to make sure it's minimal. That would go a long way toward silencing critics (like me) who believe that reported good results from such small antennas are often the result of feedline radiation -- that is, that the feedline is the primary radiator and the "antenna" plays only a minor role. Roy Lewallen, W7EL- Hide quoted text - - Show quoted text - I understand all that. If Tom wishes to add one for his own satisfaction that's fine by me. If he wants to test it then I am confident he will do what ever is necessary without comment from me. I have no wish to influence him in any way. He cam make his own call even if it means that it burns up. I have no experience with 180 M and have only loaded it for 100W. As I have stated before, I have not been active for years because of illnesses etc and I would not presume that Tom would need any assistance from a blithering idiot and liar such as I. W8TI Tom laughed his socks off when I mentioned resonant tank circuits in equilibrium and refused to give me any time for discussion. On the other hand, Tom in Michigan has always been polite to me and appears to have a genuine interest in new ideas, so I have worked all day today in getting things together so I can get one to him as quickly as possible. |
'SMALL' ANTENNA CRITERIA
Art wrote:
"My present antenna, which is for 160 m and above, is about the size of two shoe boxes and is less than 2:1 swr (50 ohm) across the band when situated at the tip of my tower." Outstanding! An effective antenna needs to be an appreciable portion of wavelength in some dimension. If Art`s antenna is an appreciable portion of 525 feet it can radiate well on 160 meters. Any length of wire carrying an RF current is capable of radiation. Significant radiation from a short wire requires much current. With a garbage can lid for a reflector, a helical antenna can be made. Were it 3 feet across in diameter (0.9 meter) the helix might work on 3 meters as the diameter needs to be about 0,3 lambda. Terman gives helical antenna information on page 909 of his 1955 opus. His best bets for small antenas are the corner reflector and the Yagi. Best regards, Richard Harrison, KB5WZI |
'SMALL' ANTENNA CRITERIA
Shucks, I have an antenna that's no bigger than a baseball, and it gives
better than a 1.5:1 SWR over more than the whole HF band when I connect it directly to my transmitter. If I hang it up real high, the SWR gets better yet. Roy Lewallen, W7EL Richard Harrison wrote: Art wrote: "My present antenna, which is for 160 m and above, is about the size of two shoe boxes and is less than 2:1 swr (50 ohm) across the band when situated at the tip of my tower." Outstanding! An effective antenna needs to be an appreciable portion of wavelength in some dimension. If Art`s antenna is an appreciable portion of 525 feet it can radiate well on 160 meters. Any length of wire carrying an RF current is capable of radiation. Significant radiation from a short wire requires much current. With a garbage can lid for a reflector, a helical antenna can be made. Were it 3 feet across in diameter (0.9 meter) the helix might work on 3 meters as the diameter needs to be about 0,3 lambda. Terman gives helical antenna information on page 909 of his 1955 opus. His best bets for small antenas are the corner reflector and the Yagi. Best regards, Richard Harrison, KB5WZI |
'SMALL' ANTENNA CRITERIA
On 15 Feb, 15:29, (Richard Harrison) wrote:
Art wrote: "My present antenna, which is for 160 m and above, is about the size of two shoe boxes and is less than 2:1 swr (50 ohm) across the band when situated at the tip of my tower." Outstanding! An effective antenna needs to be an appreciable portion of wavelength in some dimension. If Art`s antenna is an appreciable portion of 525 feet it can radiate well on 160 meters. Any length of wire carrying an RF current is capable of radiation. ******* Yes, but it is not useable if C and L for the length involved and frequency of use is not adhered to. Implicit in Maxwell's laws is that a radiator can be any size or shape as long as it is in equilibrium. Without the inclusion of that last word all laws of the masters are invalid. Significant radiation from a short wire requires much current. With a garbage can lid for a reflector, a helical antenna can be made. Were it 3 feet across in diameter (0.9 meter) the helix might work on 3 meters as the diameter needs to be about 0,3 lambda. Terman gives helical antenna information on page 909 of his 1955 opus. His best bets for small antenas are the corner reflector and the Yagi. ###### It is not the physical size that is important whith respect to a dish it is the wavelength between the two objects that counts. A simple helix antenna can use a reflector in place of a ground plane not as an optical ray deflector.Such an array is not in a state of equilibrium Best regards, Richard Harrison, KB5WZI |
'SMALL' ANTENNA CRITERIA
Roy Lewallen wrote:
Shucks, I have an antenna that's no bigger than a baseball, and it gives better than a 1.5:1 SWR over more than the whole HF band when I connect it directly to my transmitter. If I hang it up real high, the SWR gets better yet. Roy Lewallen, W7EL Well heck, I have one the size of 2 shoe boxes that will handle a KW from 160m through 70cm with less than 1.35:1. Bird made it. Decades old and still works perfectly. tom K0TAR |
'SMALL' ANTENNA CRITERIA
On Feb 15, 6:46 pm, art wrote:
On 15 Feb, 15:29, (Richard Harrison) wrote: Art wrote: "My present antenna, which is for 160 m and above, is about the size of two shoe boxes and is less than 2:1 swr (50 ohm) across the band when situated at the tip of my tower." Outstanding! An effective antenna needs to be an appreciable portion of wavelength in some dimension. If Art`s antenna is an appreciable portion of 525 feet it can radiate well on 160 meters. Any length of wire carrying an RF current is capable of radiation. ******* Yes, but it is not useable if C and L for the length involved and frequency of use is not adhered to. Implicit in Maxwell's laws is that a radiator can be any size or shape as long as it is in equilibrium. Without the inclusion of that last word all laws of the masters are invalid. Define equilibrium. As far as I can tell, you seem to infer that being in "equilibrium", means that it is resonant. I hate to break it to you, but being resonant is no sure road to efficiency as a radiator of RF. How many hundreds of feet of wound 22 gauge wire does this device contain? Seems to me, if I ponder all the laws of the "masters", you have reinvented an air cooled dummy load that probably won't handle too much power before it becomes so hot as to melt whatever is close to it. Maybe I suggest a Heathkit "Cantenna" as a better oil cooled substitute that can be ground mounted for ease of use. You can blast it with your 8877 for short periods of time, and I doubt it will melt any plastic that is lying next to it. Requires no tower, and no need for garbage can lids. According to the law of Art, it is in equilibrium, and should satisfy all the requirements of the masters, whoever they may be, and wherever they may lie. MK |
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'SMALL' ANTENNA CRITERIA
Art wrote:
"It is not physical size that is important with respect to a dish it is the wavelength between two objects that counts. A simple helix antenna can use a reflector in place of a ground plane not used as an optical ray reflector." Yes, but, size matters even when you are told it doesn`t. A dish usually makes the path length equal between its frontal plane and focal point for all rays by the parabolic curvature of its reflector. Everything stays in phase by virtue of traveling the same distance through the same medium. The bigger the dish, the higher the gain. On the helix antenna invented by Kraus, Terman writes on page 909 of his 1955 opus: "The directive gain is appreciable, a six-turn helix having a diameter of 0.30 lambda sith a spacing of 0.30 lambda between turns developing a gain of 45 when provided with a reflecting screen at the input and that is normal to the helix axis. A helical antenna is relatively broadband in its characteristics." Best regards, Richard Harrison, KB5WZI |
'SMALL' ANTENNA CRITERIA
Gentlemen.
It is now over two weeks since Art made his offer to Denny to supply a model of his new antenna for testing, ( and should by now have been delivered ), which gives all the naysayers a last chance to nail their colours to the mast. For my part it is my belief that Art's antenna will be a major advance in the design of antenna's of the future, so, what say you gentlemen, do you agree, or disagree?. Just to make things even, it is my belief that someone, who has the respect of most ham's in this group,( including the indomitable Richard) has a finger in this pie. Derek. |
'SMALL' ANTENNA CRITERIA
On Mar 4, 5:52 am, Derek wrote:
Gentlemen. It is now over two weeks since Art made his offer to Denny to supply a model of his new antenna for testing, ( and should by now have been delivered ), which gives all the naysayers a last chance to nail their colours to the mast. For my part it is my belief that Art's antenna will be a major advance in the design of antenna's of the future, so, what say you gentlemen, do you agree, or disagree?. Sorry, I don't believe in the tooth fairy, free lunches, or dummy loads on sticks. Or should I say dummy loads on towers... Just to make things even, it is my belief that someone, who has the respect of most ham's in this group,( including the indomitable Richard) has a finger in this pie. Well, Yoda is pretty good at what he does. But I doubt if even the forceŽ can save this project. Like I have said, if I thought it was possible to achieve full size performance from a shoe box sized jumble of several hundred feet of thin 22 gauge wire, I would have already built one. But unfortunately, I have no such delusions of RF grandeur. BTW, if even both of the Richards, "I'm not sure which one you consider indomitable", had a finger in the pie, but the rest of the world refused to stick their finger in the pie, how would that make things even? Myself, I have trouble seeing either one of them falling for this fairy tale of full size antenna performance from a mini sized dummy load on a stick. Even if it is air cooled. Does this help clarify my stance on this small sized subject? I try to avoid any gray areas that might give the impression that I think this device even has a remote chance of it's claimed full sized success as a radiator of RF. But in case some still get confused by what I say, let me rephrase in a manner that most all will understand. What a load of horse manure says I... MK |
'SMALL' ANTENNA CRITERIA
Derek wrote:
Gentlemen. It is now over two weeks since Art made his offer to Denny to supply a model of his new antenna for testing, ( and should by now have been delivered ), which gives all the naysayers a last chance to nail their colours to the mast. For my part it is my belief that Art's antenna will be a major advance in the design of antenna's of the future, so, what say you gentlemen, do you agree, or disagree?. Just to make things even, it is my belief that someone, who has the respect of most ham's in this group,( including the indomitable Richard) has a finger in this pie. Derek. There are people who will happily believe most anything without any credible evidence. Examples abound - believers in homeopathy, astrology, and alien abductions to name just a very few. Believers in Art's antenna claims are in this category. I'm not. Roy Lewallen, W7EL |
'SMALL' ANTENNA CRITERIA
Roy Lewallen wrote:
There are people who will happily believe most anything without any credible evidence. Examples abound - believers in homeopathy, astrology, and alien abductions to name just a very few. Believers in Art's antenna claims are in this category. I'm not. However, you and W8JI seem to believe that the delay through a 75m bugcatcher loading coil can be 3 ns. Compared to that belief, astrology seems pretty logical. -- 73, Cecil http://www.w5dxp.com |
'SMALL' ANTENNA CRITERIA
"Roy Lewallen" wrote in message
... Derek wrote: Gentlemen. It is now over two weeks since Art made his offer to Denny to supply a model of his new antenna for testing, ( and should by now have been delivered ), which gives all the naysayers a last chance to nail their colours to the mast. For my part it is my belief that Art's antenna will be a major advance in the design of antenna's of the future, so, what say you gentlemen, do you agree, or disagree?. Just to make things even, it is my belief that someone, who has the respect of most ham's in this group,( including the indomitable Richard) has a finger in this pie. Derek. There are people who will happily believe most anything without any credible evidence. Examples abound - believers in homeopathy, astrology, and alien abductions to name just a very few. Believers in Art's antenna claims are in this category. I'm not. Roy Lewallen, W7EL Don't forget the Audiophools! John, KD5YI |
'SMALL' ANTENNA CRITERIA
Art did ship me one of his antennas a week or two back... I have it in my shop... I will indeed put this interesting antenna to an objective and thorough testing with a full report here... I am always excited to learn something new... It is 19F outside this morning and blowing hard, with wind and snow forecast through the week and into the weekend, and I am unlikely to climb the big tower in this... I will attempt within a week to put it on a small 50' tower I have attached to my shop and get some baseline impedence and field strength measurements... Then as soon as the weather allows I will move it to the big tower for a good test against my full size antennas... I am sorry to have to put this off a bit, but given the weather and that my family is hurting at the moment my free time is limited... denny / k8do |
'SMALL' ANTENNA CRITERIA
I highly recommend that you decouple the feedline with a current balun
(common mode choke). Better yet would be two, spaced about a quarter wavelength apart. Small antennas can be made to look a lot better than they really are if the feedline is allowed to become part of the radiating antenna system, so unless the feedline is decoupled well, any measurements you make will be subject to speculation as to whether the radiation was from the antenna or the feedline. Roy Lewallen, W7EL Denny wrote: Art did ship me one of his antennas a week or two back... I have it in my shop... I will indeed put this interesting antenna to an objective and thorough testing with a full report here... I am always excited to learn something new... It is 19F outside this morning and blowing hard, with wind and snow forecast through the week and into the weekend, and I am unlikely to climb the big tower in this... I will attempt within a week to put it on a small 50' tower I have attached to my shop and get some baseline impedence and field strength measurements... Then as soon as the weather allows I will move it to the big tower for a good test against my full size antennas... I am sorry to have to put this off a bit, but given the weather and that my family is hurting at the moment my free time is limited... denny / k8do |
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Roy Lewallen wrote:
I highly recommend that you decouple the feedline with a current balun (common mode choke). Better yet would be two, spaced about a quarter wavelength apart. Methinks if Denny does that, Art should have used bigger wire for his coil. -- 73, Cecil http://www.w5dxp.com |
'SMALL' ANTENNA CRITERIA
In article ,
Roy Lewallen wrote: I highly recommend that you decouple the feedline with a current balun (common mode choke). Better yet would be two, spaced about a quarter wavelength apart. Small antennas can be made to look a lot better than they really are if the feedline is allowed to become part of the radiating antenna system, so unless the feedline is decoupled well, any measurements you make will be subject to speculation as to whether the radiation was from the antenna or the feedline. It would also be interesting to use a simple current probe to sweep along the feedline, and see what sorts of currents might be flowing along the outside of the feedline, both with and without a good common-mode choke or two in the feedline. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
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On Mar 5, 3:14 pm, (Dave Platt) wrote:
In article , Roy Lewallen wrote: I highly recommend that you decouple the feedline with a current balun (common mode choke). Better yet would be two, spaced about a quarter wavelength apart. Small antennas can be made to look a lot better than they really are if the feedline is allowed to become part of the radiating antenna system, so unless the feedline is decoupled well, any measurements you make will be subject to speculation as to whether the radiation was from the antenna or the feedline. It would also be interesting to use a simple current probe to sweep along the feedline, and see what sorts of currents might be flowing along the outside of the feedline, both with and without a good common-mode choke or two in the feedline. I agree. I think it's quite possible that even a decoupled feedline will add enough radiation to make the antenna noticeably better than it really is. I'd prefer to see the source mounted *at* the antenna to make it a decent comparison. One problem with the decoupling that I can see, is if it's used on 160m, a quarter wave is about 125-130 feet plus or minus... So even if you stack two chokes or baluns a quarter wave apart, I can see the feedline noticeably radiating above the lower choke. Of course, this condition will exist for all types of antennas, but on the other hand, most antennas will be radiating quite a bit more from the antenna, vs the feedline. So the difference between the two sources are much larger, and the feedline radiation is more likely to be swamped and made a non issue as far as the total radiation. But with such an inefficient small antenna, the feedline radiation will be a much larger part of the total radiation. My guess on the performance? Probably about the same as the usual Isotron antenna used on 160m. And even in the case of the Isotron, I bet a good portion of the radiation is actually from the feedline. I don't recall ever seeing any documentation of the Isotron that recommended decoupling the feedline. I don't have to stretch my mind to far to wonder why... :/ To quiet the naysayers, "like me", I'd mount a radio directly to the base of the antenna with a coax union and do FS tests at certain distances, and then likewise with the full size antennas. That would cure the feedline issue real fast.. lol.. Course, that may be more work than Denny wants to take on.. You could compare it to a mobile set up though, and keep things on the ground level for ease of testing. I bet my mobile antenna would whip that thing. It should, being it's bigger and has more efficient loading. MK |
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wrote:
I agree. I think it's quite possible that even a decoupled feedline will add enough radiation to make the antenna noticeably better than it really is. I'd prefer to see the source mounted *at* the antenna to make it a decent comparison. __________ Unless this antenna is itself balanced, most likely for best efficiency when operating in this configuration there would need to be a conductor running from the elevated tx chassis to a good r-f ground of some kind, either buried in the earth or in the form of a counterpoise. Radiation from that "ground" conductor could be many times greater than from what is considered to be the antenna -- even though no feedline is present.. This is a common configuration used for so-called Part 15 AM installations to get greater groundwave coverage from the 100 mW tx input power allowed under FCC Part 15.219, by ignoring the 3-meter limit on the length of the radiating structure given there. RF |
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Denny wrote:
Art did ship me one of his antennas a week or two back... I have it in my shop... I will indeed put this interesting antenna to an objective and thorough testing with a full report here... I am always excited to learn something new... Hi Denny, What is the test protocol that you are using? - 73 de Mike N3LI - |
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'SMALL' ANTENNA CRITERIA
Michael Coslo wrote:
But if the major radiation is from the feedline, that will mean the antenna won't work as it is supposed to. Since this is voodoo antennaland stuff, the antenna needs to be tested as Art would suggest, not as we might like. And since most of the chaps here are a lot smarter than me, I suspect everyone knows that his antenna just might need that feedline radiation in order to work "properly". Now after the initial tests in whatever manner Art dictates, *then* the feedline should be isolated to determine where the major radiation is coming from. At that point, your source at the antenna method is the ticket. That would remove feedline effects altogether. . . . Fair enough. But only the naive will be impressed by an antenna system that has to be electrically large (including the feedline) in order to be efficient, unless it also has some property that's significantly different than the radiating feedline alone. For example, it would be interesting if it's highly directional when fed with a vertical feedline, but not if it just looks like another vertical. If the feedline is radiating, you can expect the antenna performance to be quite sensitive to the conductive path from the transmitter to the Earth, as well as the feedline length and orientation. Consequently, different people will likely get considerably different results, even with identical antennas and feedlines. So the entire path from the transmitter to the Earth will have to be specified and carefully duplicated in order to get meaningful and repeatable results if the feedline is a critical part of the system. Roy Lewallen, W7EL |
'SMALL' ANTENNA CRITERIA
On Mar 5, 3:23 am, wrote
.. Does this help clarify my stance on this small sized subject? I try to avoid any gray areas that might give the impression that I think this device even has a remote chance of it's claimed full sized success as a radiator of RF. But in case some still get confused by what I say, let me rephrase in a manner that most all will understand. What a load of horse manure says I... MK Spoken like a true neanderthal, they also refused to embrace new ways of doing things and look what happened to them. You are living in the past, keep on digging. Derek |
'SMALL' ANTENNA CRITERIA
On Mar 5, 6:55 am, Roy Lewallen wrote:
There are people who will happily believe most anything without any credible evidence. Examples abound - believers in homeopathy, astrology, and alien abductions to name just a very few. Believers in Art's antenna claims are in this category. I'm not. Roy Lewallen, W7EL The difference is I believe there is more to be learned in the design of anntena's, I have listened to what Art has to say and checked out his theories for myself and find them compelling, unlike yourself who gives the impression that you know it "all and there is nothing left to learn that would be of any use to you, you have a knee jerk reaction to reject any thing that Art put's forward regardless, To you also keep digging Derek |
'SMALL' ANTENNA CRITERIA
On Thu, 6 Mar 2008 15:11:41 -0800 (PST), Derek
wrote: I have listened to what Art has to say and checked out his theories for myself Give us an example of what you have done, not what you've read. 73's Richard Clark, KB7QHC |
'SMALL' ANTENNA CRITERIA
On Mar 7, 3:45 am, Roy Lewallen wrote:
wrote: On Mar 5, 3:14 pm, (Dave Platt) wrote: In article , Roy Lewallen wrote: I highly recommend that you decouple the feedline with a current balun (common mode choke). Better yet would be two, spaced about a quarter wavelength apart. Small antennas can be made to look a lot better than they really are if the feedline is allowed to become part of the radiating antenna system, so unless the feedline is decoupled well, any measurements you make will be subject to speculation as to whether the radiation was from the antenna or the feedline. It would also be interesting to use a simple current probe to sweep along the feedline, and see what sorts of currents might be flowing along the outside of the feedline, both with and without a good common-mode choke or two in the feedline. I agree. I think it's quite possible that even a decoupled feedline will add enough radiation to make the antenna noticeably better than it really is. I'd prefer to see the source mounted *at* the antenna to make it a decent comparison. . . . Even that might not be adequate, depending on the design of the transmitter. Any power or other wires connected to the transmitter could easily become part of the radiator, so they'd have to be decoupled. A small, battery-powered transmitter with no connected wires would avoid this potential problem. Roy Lewallen, W7EL You still don't understand! you are talking bull**** you have no idea of the design of Art's antenna or of how it works or it's needs yet you put up your remedies for old style antenna's. I am sure Denny is a competent and independant operator and will be aware of all the pitfall's of testing a new antenna and does not need you to tell him how to go about it. As Art said in a previous post Denny is free to do as he wishes Art will have no input in the testing of the antenna, and nor should you Keep on digging the hole is getting bigger. Derek |
'SMALL' ANTENNA CRITERIA
On Mar 7, 8:20 am, Richard Clark wrote:
On Thu, 6 Mar 2008 15:11:41 -0800 (PST), Derek wrote: I have listened to what Art has to say and checked out his theories for myself Give us an example of what you have done, not what you've read. 73's Richard Clark, KB7QHC I will give you nothing. would you care to start digging? Derek |
'SMALL' ANTENNA CRITERIA
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'SMALL' ANTENNA CRITERIA
"Derek" wrote:
You still don't understand! you are talking bull**** you have no idea of the design of Art's antenna or of how it works or it's needs yet you put up your remedies for old style antenna's. I am sure Denny is a competent and independant operator and will be aware of all the pitfall's of testing a new antenna and does not need you to tell him how to go about it. As Art said in a previous post Denny is free to do as he wishes Art will have no input in the testing of the antenna, and nor should you ____________ Objectively, Derek, for what reasons are you are so willing to believe the claims that art makes for his "highly-efficient," shoe-box MW antenna, and for your confidence in Denny's ability to measure its radiation characteristics scientifically? No BS, please. Facts count -- emotion does not. RF |
'SMALL' ANTENNA CRITERIA
On Thu, 6 Mar 2008 15:30:50 -0800 (PST), Derek
wrote: Give us an example of what you have done, not what you've read. I will give you nothing. would you care to start digging? That was a start as any reasonable reader could see. 73's Richard Clark, KB7QHC |
'SMALL' ANTENNA CRITERIA
On Mar 6, 4:49 pm, Derek wrote:
Spoken like a true neanderthal, they also refused to embrace new ways of doing things and look what happened to them. You are living in the past, keep on digging. Derek Well, where is the beef? Do you have any actual data to support these magic claims? Hummm.. Thought not.. I'm using actual experience with antennas to support my disbelief. If what he says is true, I'd likely already be using one.. I'm not against a dinky 160m antenna with full size performance. But until I actually see one work... Well, you might get it, or you might not.. How can I live in the past? I can only remember the past. And *nowhere* in the past have I ever seen such a device actually work as claimed. So put up the data, or you get to digging... You kind of remind me of that "Bret" dude who calls himself John Smith, or whatever... :/ I'd rather be a slopehead than believe in the tooth fairy, free lunches, and antennas that don't follow the rules of science. I have no doubt his antenna may radiate some.. But then again, most dummy loads do also.. Tales of QSO's using light bulb dummy loads used to be quite common back in the past, which I can still remember going back to the time of swatting at colorful plastic butterflies hanging above my head in my baby crib. MK |
'SMALL' ANTENNA CRITERIA
On Mar 6, 6:07 am, "Richard Fry" wrote:
wrote: I agree. I think it's quite possible that even a decoupled feedline will add enough radiation to make the antenna noticeably better than it really is. I'd prefer to see the source mounted *at* the antenna to make it a decent comparison. __________ Unless this antenna is itself balanced, most likely for best efficiency when operating in this configuration there would need to be a conductor running from the elevated tx chassis to a good r-f ground of some kind, either buried in the earth or in the form of a counterpoise. Radiation from that "ground" conductor could be many times greater than from what is considered to be the antenna -- even though no feedline is present.. This is a common configuration used for so-called Part 15 AM installations to get greater groundwave coverage from the 100 mW tx input power allowed under FCC Part 15.219, by ignoring the 3-meter limit on the length of the radiating structure given there. RF For some reason, I'd always got the impression that the antenna was symmetrical and balanced.. But who ever knows for sure with Art... If this is the case, I wonder why he needs the garbage can lid, or whatever metal he is using under it.. I had the impression in his various posts that he was trying to avoid ground connections. But whoever knows for sure except Art, and now maybe Denny... :/ MK |
'SMALL' ANTENNA CRITERIA
Derek wrote:
On Mar 5, 3:23 am, wrote . Does this help clarify my stance on this small sized subject? I try to avoid any gray areas that might give the impression that I think this device even has a remote chance of it's claimed full sized success as a radiator of RF. But in case some still get confused by what I say, let me rephrase in a manner that most all will understand. What a load of horse manure says I... MK Spoken like a true neanderthal, they also refused to embrace new ways of doing things and look what happened to them. You are living in the past, keep on digging. Are we required to suspend disbelief for every new idea that comes along? That would be chaos. - 73 de Mike N3LI - |
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