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Gaussian antenna aunwin
On 27 Feb, 11:16, "JIMMIE" wrote:
On Feb 23, 11:35 pm, "art" wrote: On 23 Feb, 20:05, Gene Fuller wrote: art wrote: On 23 Feb, 15:07, Gene Fuller wrote: To keep it simple, Gauss' Law is precisely one of the four standard Maxwell Equations. Gauss' Law has been part of electromagnetics and antenna theory for eons. As for electromechanics, who knows? 73, Gene W4SZ Gene, forgive me if I am incorrect but I am going to assume you have an engineering degree and are fully conversant with the work of the masters. I f I am not correct then we can stop at this point Otherwise I fully recommend that you check out the web foe a book on fields and waves or something like that by a professor at Rutgers University. In chapter 21 he delves very deeply into an array consisting of four elements all of which are resonant. Ofcourse he doesn't mention anything of mine but you will notice that the array he chose is actually what I refer to as a Gaussian array since it meets all the requirements that I have expoused on my page. He doesn't use computor programs but basic mathematics to provide all the desirables plus a radiation field. This array is really a derivitation of one designed some 50 years ago and is the only one I know that exists in literature. If you study this chapter and relate it to what I am expousing then possible you will see things with fresh eyes. But again if you are not fully educated in this field save your self from the bother. I personaly have a program that if you isert any fugure and tell it to obtain maximim gain I assure you it will not produce a yagi but a gaussian array........ and I am thrilled with that. Nuff said Art Art, You seem to have misunderstood my point. AAALLLLLL antennas, regardless of structure, material, efficiency, resonance, location, or phase of the moon are Gaussian. Gauss' Law is an integral part of classical electromagnetics. Nothing can escape. No, I do not have an engineering degree, but I do have several degrees in physics. Unfortunately, I am significantly dumber than a rock, so I have no more to offer in this thread. 73, Gene W4SZ- Hide quoted text - - Show quoted text - Watch out Gene, I stated that Statics was a subset of electromagnetics and I caught hell from everybody. Seems like things are infectional around here.The book that I proferred would really be to much for a lot of people no matter how much they over estimate their abilities especially when they try to debate reasons why the writer is incorrect! When I asked for academic help regarding research I got an Email from a guy at the space antenna agency who referred me to chapter 1 and 21. I never dreamt that I would find an actual array with all elements resonant being discussed Art- Hide quoted text - - Show quoted text - no need to be surprised at having an antenna with elements that are all phased. I doubt if ther is anyone on the news group that doesnt know that a Yagi Uda antenna doesnt represent some kind of comprimise to an antenna with all of the elements feed. No one has ever said otherwise although you have claimed they have. The problem with having all the elements feed is that it is impractical to control power distribution and phasing when changing frequencies. The Yagi Uda overcomes this problem at a slight cost in gain. Your idea of an antenna with multiple fed resonant elements is a giant step backwards to a day when high gain steerable antennas were impractical most of the hams who didnt have the money or the real estate for huge arrays Antenna with multiple resonant element all being fed is very common in RADAR and space communication, you can achive very high gains in this manner just as you have stated. It is also very expensive, has narrow bandwidth and is a mechanical nightmare. NASA, AM BCB, commercial shortwave stations and various other agencies and private companies sometimes have a need for this type of antenna and they they have the money to build them, few hams do. The Yagi Uda antenna just fills a practical niche in antenna requirements. No ham I know of ever thought the Yagi antenna was the end-all of antennas as you have claimed. While it may not have the highest gain it certainly is the most practical antenna for a lot of us. Jimmie- Hide quoted text - - Show quoted text - Jimmie, I have to congratulate you on your posting and your width of knoweledge. I for one was unaware that what I call a gaussian array was in publication and I would really appreciate a pointer where I could obtain more information on this. I have a multitude of books with respect to fields and waves plus antennas but with the advance of new technologies it is difficult for my bill fold to keep pace. As a further favor could you repeat the program test I proffered in my latest posting? I am asking since I know that your responses would be very worthwhile in reading since you appear to be a scholar that searches for truth and you would not be afraid to publisize your program used and result for the benefit of all. Thank you for your input and hopefully you will continue sharing Best regards Art KB9MZ |
Gaussian antenna aunwin
On 27 Feb, 11:16, "JIMMIE" wrote:
On Feb 23, 11:35 pm, "art" wrote: On 23 Feb, 20:05, Gene Fuller wrote: art wrote: On 23 Feb, 15:07, Gene Fuller wrote: To keep it simple, Gauss' Law is precisely one of the four standard Maxwell Equations. Gauss' Law has been part of electromagnetics and antenna theory for eons. As for electromechanics, who knows? 73, Gene W4SZ Gene, forgive me if I am incorrect but I am going to assume you have an engineering degree and are fully conversant with the work of the masters. I f I am not correct then we can stop at this point Otherwise I fully recommend that you check out the web foe a book on fields and waves or something like that by a professor at Rutgers University. In chapter 21 he delves very deeply into an array consisting of four elements all of which are resonant. Ofcourse he doesn't mention anything of mine but you will notice that the array he chose is actually what I refer to as a Gaussian array since it meets all the requirements that I have expoused on my page. He doesn't use computor programs but basic mathematics to provide all the desirables plus a radiation field. This array is really a derivitation of one designed some 50 years ago and is the only one I know that exists in literature. If you study this chapter and relate it to what I am expousing then possible you will see things with fresh eyes. But again if you are not fully educated in this field save your self from the bother. I personaly have a program that if you isert any fugure and tell it to obtain maximim gain I assure you it will not produce a yagi but a gaussian array........ and I am thrilled with that. Nuff said Art Art, You seem to have misunderstood my point. AAALLLLLL antennas, regardless of structure, material, efficiency, resonance, location, or phase of the moon are Gaussian. Gauss' Law is an integral part of classical electromagnetics. Nothing can escape. No, I do not have an engineering degree, but I do have several degrees in physics. Unfortunately, I am significantly dumber than a rock, so I have no more to offer in this thread. 73, Gene W4SZ- Hide quoted text - - Show quoted text - Watch out Gene, I stated that Statics was a subset of electromagnetics and I caught hell from everybody. Seems like things are infectional around here.The book that I proferred would really be to much for a lot of people no matter how much they over estimate their abilities especially when they try to debate reasons why the writer is incorrect! When I asked for academic help regarding research I got an Email from a guy at the space antenna agency who referred me to chapter 1 and 21. I never dreamt that I would find an actual array with all elements resonant being discussed Art- Hide quoted text - - Show quoted text - no need to be surprised at having an antenna with elements that are all phased. I doubt if ther is anyone on the news group that doesnt know that a Yagi Uda antenna doesnt represent some kind of comprimise to an antenna with all of the elements feed. No one has ever said otherwise although you have claimed they have. If I did it was unintensional. I have always stated that a Yagi because of its constructional ease is difficult to beat The problem with having all the elements feed is that it is impractical to control power distribution and phasing when changing frequencies. All problems can be overcome and I only pointed that out because in this case it was a possibility The Yagi Uda overcomes this problem at a slight cost in gain. Pretty hard to comment here since I am not sure of the application in mind Your idea of an antenna with multiple fed resonant elements is a giant step backwards to a day when high gain steerable antennas were impractical most of the hams who didnt have the money or the real estate for huge arrays If size is what you consider important then the gaussian array deserves to be looked into in that it maximises the use of volume and not of length to obtain a desirable which means less property area for a desired gain. Antenna with multiple resonant element all being fed is very common in RADAR and space communication, you can achive very high gains in this manner just as you have stated. Yes I have seen this in Antennas for everyone especially the crossed versions True they are resonant but they follow a empirical design where as the Gaussian design can be seen as superior It is also very expensive, has narrow bandwidth and is a mechanical nightmare. Absolutely not true, if an antenna uses parasitic elements it is the worst possible choice for antenna bandwidth. Progression of curves produced by the addition of reactances clearly points this out. NASA, AM BCB, commercial shortwave stations and various other agencies and private companies sometimes have a need for this type of antenna and they they have the money to build them, few hams do. Really they have to know about them before they can be considered of use and that is for industrial experts to decide. Checking thru patent files of the U.S. the only reference I came across under the heading of a gaussian antenna was not even a specific design of an antenna but a means of interpretation and channelisation of information gained using mathematical theorems of Gauss and Green. Can you help me in that area? The Yagi Uda antenna just fills a practical niche in antenna requirements. Absolutely but science moves on No ham I know of ever thought the Yagi antenna was the end-all of antennas as you have claimed. Well it is extremely popular tho I am sure that many would consider discarding it if it improved a Yagi a smidgeon, contesters are insane about that sort of thing While it may not have the highest gain it certainly is the most practical antenna for a lot of us. I totally agree, for the amateur operator it meets all rational means unless his plot width is half the width reqyuired for the gain provided by a yagi At that point many would be willing to look at alteranatives. Pretty hard to swing a long boom yagi around on a small ship so you look for alternatives. Weather people are devising means of measuring weather conditions by overlaying reflections of weather systems from vertical and horizontal radiation and then overlaying them with a minimum fo time difference which needs a different aproach to antennas. You can not tie up the advance of science by tying it to a Yagi. I am not saying you are of that attitude but there are so many that resiswt change regardless of the cost Jimmie- Hide quoted text - - Show quoted text - Very nice discussion, thanks, not like some of the abusive forms that have been directed at me which presented zero substance in support of provided content which amplifys their inadequacies to all Very best regards and thanks. Art KB9MZ |
phased array practicality was Gaussian antenna aunwin
On Feb 27, 11:16 am, "JIMMIE" wrote:
no need to be surprised at having an antenna with elements that are all phased. I doubt if ther is anyone on the news group that doesnt know that a Yagi Uda antenna doesnt represent some kind of comprimise to an antenna with all of the elements feed. No one has ever said otherwise although you have claimed they have. The problem with having all the elements feed is that it is impractical to control power distribution and phasing when changing frequencies. This is just not true. A SteppIR does it mechanically by changing the element lengths. A 4 square does it by switching ports around on a phasing network. One can buy everything you need to build a generic 4 element HF phased array with computer adjustable LC networks for less than a few thousand dollars. (see, e.g. LDG's AT200PC tuner with an RS232 interface) The Yagi Uda overcomes this problem at a slight cost in gain. Your idea of an antenna with multiple fed resonant elements is a giant step backwards to a day when high gain steerable antennas were impractical most of the hams who didnt have the money or the real estate for huge arrays hardly backwards. Phased arrays may well save the day in this era of ever increasing community resistance to traditional Beam on rotator on tower installations. Antenna with multiple resonant element all being fed is very common in RADAR and space communication, you can achive very high gains in this manner just as you have stated. You can get low gains too. or just sharp adjustable nulls, which is probably more useful. It is also very expensive, has narrow bandwidth and is a mechanical nightmare. Expensive compared to what? We're not talking about a electronically steered phased array radar here with thousands of elements. I'll bet the hardware cost of a electronically steered phased array for HF suitable for ham use is comparable to the hardware cost of a big tower, rotator, and Yagi.. the phased array just isn't available as an off the shelf product yet. NASA, AM BCB, commercial shortwave stations and various other agencies and private companies sometimes have a need for this type of antenna and they they have the money to build them, few hams do. A ham could build an adjustable directional array of verticals, essentially identical to an AM broadcast directional array, for several thousand dollars. Yep, that's a bunch o'bux compared to a Rockmite and a wire over the balcony railing. But it's not a bunch o'bux in the context of a big station with a legal limit amp, a state of the art transceiver, etc. If you're willing to homebrew and scrounge, you can build computer controlled phasing networks with stepper motors (or servos), roller inductors and variable caps. Adjusting it is non trivial, but so is learning Morse code, or how to use NEC or lots of other things in ham radio.. it's just not particularly common. All the math and design information is laid out in detail in ON4UN's book, with the implementation left "as an exercise for the reader". Jim, W6RMK |
phased array practicality was Gaussian antenna aunwin
wrote in message ps.com... On Feb 27, 11:16 am, "JIMMIE" wrote: the phased array just isn't available as an off the shelf product yet. sure it is, i have one for 80m, and one for 40m that were off the shelf phasing systems... comtek sells lots of them. and i have a home made one for 160m. |
phased array practicality was Gaussian antenna aunwin
On 27 Feb, 17:12, "Dave" wrote:
wrote in message ps.com... On Feb 27, 11:16 am, "JIMMIE" wrote: the phased array just isn't available as an off the shelf product yet. sure it is, i have one for 80m, and one for 40m that were off the shelf phasing systems... comtek sells lots of them. and i have a home made one for 160m. Look guys all of this is very silly, seems like the interest is more fore arguments sake than the search for the real truth. I beg you to use Google to read up on a conservative field, it probably will be insinia or something like that. It clearly states that curl is part and parcel of what constitutes a concervative field. Now in this case they point out that curl is zero but at the same time they point out it cannot be left out and state why. So you all that are so clever can scan the bottom where an indication on further information is given on curl. Following up on that tip who find an expresion that includes time i.e. dt. But you are comfortable with expedias discussion on conservative fields and as Roy would say as an out, I don't understand! So we look at the mathematics and decide for a conservative field there are only two cartesian dimensions used in the equation and we all are aware that it is paramount when dealing with equations equilibrium must be maintained at all times and you cannot destable an "equal " sign". Since curl was stated in dt terms when we looked it up to maintain equilibrium on both sides of the equation which extends Gaussian law with " the adition of a moment in time". All very simple, all laws are followed and equilibrium is maintained. All we have done is used all cartesian vectors instead of just two which allows us to broarden the equation to include a time variant field. Gentlemen this is what it is all about! I know many are not interested and look at it as an opportunity to spout off. Some with a bit of education say whoa you can't do that, but for why? Some people want me to write out mathematical formula which my keyboard is not capable of but why not argue with expedia instead of me. Now it is being said by some that it is acknoweledged that the yagi can be beaten! Does your NEC program confirm that with a sample or does it always print off a yagi. If you have got a program that can test that out then do it for your own good. If you haven't then point out the mathematical errors stated if not for your own good and satisfaction. I know it is difficult to get a horse to drink but eventually one comes along unaware of the situation tries things for himself and then looks up and ask what everybody is waiting for! I have given two areas that you can research in moments so that you can debate my errors.For goodneas sake put aside all pettines and one upman ship and show all that you really are men.If you are a mathematician then debate around that point. If you are just a hobbyist but have a computor program then follow that route to cut me down, but do something that is worthwhile. How many have an answer to the computor test I gave, probably nobody because their findings were embareasing. Who with a knoweledge of physics is willing to put his stake in the ground and debate from that side, probably none. Quit babling about "I want" and think more in line with "I can" Art Art |
phased array practicality was Gaussian antenna aunwin
"Dave" wrote in message news:4G4Fh.15798$sv6.284@trndny08... wrote in message ps.com... On Feb 27, 11:16 am, "JIMMIE" wrote: the phased array just isn't available as an off the shelf product yet. sure it is, i have one for 80m, and one for 40m that were off the shelf phasing systems... comtek sells lots of them. and i have a home made one for 160m. And 160 and 80 and 40 is where these antennas have there niche. Where the big yagi isnt so popular or practical. I wouldnt think of putting up a Yagi for 80 either but I might put of a couple of towers I can run in or out of phase. Jimmie |
phased array practicality was Gaussian antenna aunwin
Jim wrote:
I'll bet the hardware cost of a electronically steered phased array for HF suitable for ham use is comparable to the hardware cost of a big tower, rotator, and Yagi.. the phased array just isn't available as an off the shelf product yet. The fully steerable phased array that can also handle 1.5kW TX power is not available as a HAM product off the shelf yet... but we can already see where the future is headed. Many people already have four-square phased arrays for the lower HF bands, but we have hardly begun to tap their true potential. The design company Plextek has a downloadable demonstration which shows what a four-square phased array can really do: http://download.plextek.co.uk/AKS06.zip The user interface is a bit clunky, but stay with it... The program starts with an omnidirectional pattern, receiving signal 1 coming from 90deg (blue arrow at 3 o'clock). The thermometer bar at the top right is showing a positive signal/noise ratio (green). Click in the 'Interferers' columns to bring up either one or two interfering stations which are the yellow arrows. The thermometer bar now shows a negative s/n ratio on the wanted signal (red). Now the fun starts: in the 'Algorithm' column, click on 'SMART' to turn on Plextek's proprietary adaptive array software - watch the phased array reconfigure itself automatically. The pattern adapts to null out *both* of the interfering signals, while still keeping a lobe pointing towards the wanted signal. The wanted signal reappears from under the QRM and its s/n ratio increases dramatically. You can then drag the interfering signals to different directions, and the array keeps on adapting. The only case where it can't give any improvement is where the interfering signal comes from exactly the same direction as the wanted signal. All this is done by varying the amplitude and phasing of the signals from each of the elements before combining them. The 'WEIGHTS' table at centre right shows what is required. On transmit, the same directional patterns could be achieved by applying the same weightings to the currents that are fed to the four elements - or of course you could switch to a different pattern while transmitting. OK, this is only a demonstration. It doesn't consider signals at a range of different vertical angles; it doesn't consider the big practical problems of achieving the correct current weightings when all four elements are interacting; and it doesn't consider how to handle the TX power. Even so, it will open your eyes to what a phased array can really do. It's all down to the magic phasing box at the centre of the array. Whatever goes into that box will be hard to design, complicated to control, and expensive to build... but most four-square owners would be happy to have even a fraction of those extra capabilities. -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
phased array practicality was Gaussian antenna aunwin
On Feb 28, 12:29 am, Ian White GM3SEK wrote:
Jim wrote: I'll bet the hardware cost of a electronically steered phased array for HF suitable for ham use is comparable to the hardware cost of a big tower, rotator, and Yagi.. the phased array just isn't available as an off the shelf product yet. The fully steerable phased array that can also handle 1.5kW TX power is not available as a HAM product off the shelf yet... but we can already see where the future is headed. --------- snip ---------- It's all down to the magic phasing box at the centre of the array. Whatever goes into that box will be hard to design, complicated to control, and expensive to build... but most four-square owners would be happy to have even a fraction of those extra capabilities. I think it might be a bit of time before it's an off the shelf product (lack of demand is part of the reason). It also depends a bit on just how good you want the performance to be (null depth, primarily.. forward gain is not very sensitive to phasing and amplitude accuracy), and whether you want to make it an antenna system that just hooks onto an existing rig and PA, essentially hanging off a single feedline, or whether a higher level of integration is desirable or feasible. (for instance, rather than power combining a bunch of solid state amp modules like the current kilowatt class SSPAs do, put a power module on each antenna) "the magic box in the center of the array" is more the former model, and while simple conceptually, in the long run probably isn't the best way to solve the problem in a system context. For instance, a multi channel receiver, which can do all the phasing, very precisely, at low levels, either with analog or digital processing, can give you the nice deep nulls and adaptation.For TX, though, null depth isn't as important as maximizing the power squirted in the right direction. Hardware wise, the design isn't particularly complicated (any of the current crop of automatic antenna tuners can serve as the building block). Hard to control is mostly a matter of calibration and the right algorithms (and, yes, non trivial, but so is building a tetrode or FET power amp that's stable from 10 to 160, etc.). Expensive is more a matter of "compared to what".. You can buy a kilowatt autotuner for $500, so, assuming you needed 8 of them to control 4 elements (a single L network can only give you 90 degrees of phase shift, and you need 180).. that's $4K. Probably need some relays and transformers, as well as controller. I'd figure $6K, today.. But that's "off the shelf" assemblies. and not purpose designed. Start comparing that to the $10K to put up a tower and a Yagi (comparing new prices to new prices, plus building permits, etc.) and the phased array starts to be competive. So.. not today, but I'd figure that in 10 years, you'll start to see real broadband phased arrays (not just 4-8 switched beams in a single band like a 4 square). They provide a real solution to restricted space installations, if nothing else, because you can make effective use of the "volume" of space within a small suburban lot (i.e. the max theoretical gain from an antenna that fits in a box that's say, 15x30x10 meters is pretty high). Jim, W6RMK |
phased array practicality was Gaussian antenna aunwin
On 28 Feb, 23:20, wrote:
On Feb 28, 12:29 am, Ian White GM3SEK wrote: Jim wrote: I'll bet the hardware cost of a electronically steered phased array for HF suitable for ham use is comparable to the hardware cost of a big tower, rotator, and Yagi.. the phased array just isn't available as an off the shelf product yet. The fully steerable phased array that can also handle 1.5kW TX power is not available as a HAM product off the shelf yet... but we can already see where the future is headed. --------- snip ---------- snipe). They provide a real solution to restricted space installations, if nothing else, because you can make effective use of the "volume" of space within a small suburban lot (i.e. the max theoretical gain from an antenna that fits in a box that's say, 15x30x10 meters is pretty high). Jim, W6RMK Jim, this volume approach to gain versus linear length comparison sounds very interesting but I have not seen any reference to it anywhere. Basically a gaussian array say for a single feed point makes full use of volume where other antennas which are of planar form lose out. With a planar design one can extrapolate gain by number of elements combined with length e.t.c but I have not seen any such gain calculation for a volume,can you help me there? I have found that the number of elements with respect to contained volume is a good measurement where the array is contained within the 1/2 wave length cubed beyond which it appears to have reached its maximum. This means having covered a real estate area of half that of a yagi but with equivalent gain. Ofcourse one can gang arrays together if one uses multiple feeds but I haven't personaly pursued that approach as yet. Glad to see you posting, most informative Best regards Art |
phased array practicality was Gaussian antenna aunwin
Jim wrote:
On Feb 28, 12:29 am, Ian White GM3SEK wrote: Jim wrote: I'll bet the hardware cost of a electronically steered phased array for HF suitable for ham use is comparable to the hardware cost of a big tower, rotator, and Yagi.. the phased array just isn't available as an off the shelf product yet. The fully steerable phased array that can also handle 1.5kW TX power is not available as a HAM product off the shelf yet... but we can already see where the future is headed. --------- snip ---------- It's all down to the magic phasing box at the centre of the array. Whatever goes into that box will be hard to design, complicated to control, and expensive to build... but most four-square owners would be happy to have even a fraction of those extra capabilities. I think it might be a bit of time before it's an off the shelf product (lack of demand is part of the reason). It also depends a bit on just how good you want the performance to be (null depth, primarily.. forward gain is not very sensitive to phasing and amplitude accuracy), and whether you want to make it an antenna system that just hooks onto an existing rig and PA, essentially hanging off a single feedline, or whether a higher level of integration is desirable or feasible. (for instance, rather than power combining a bunch of solid state amp modules like the current kilowatt class SSPAs do, put a power module on each antenna) "the magic box in the center of the array" is more the former model, and while simple conceptually, in the long run probably isn't the best way to solve the problem in a system context. That is very true. Unfortunately, the ham market is divided up into physically separate compartments of transceivers, power amplifiers and antennas. That is a severe restriction which makes all the technical challenges much more difficult. However, we can try to pare the problem down a little. Another important point is that the concept of 'market demand' is beginning to break down in ham radio. The big manufacturers are increasingly challenged by new products that pay no attention to the market - they spring directly from some individual or small team deciding they're going to do it. Then maybe the design is produced as a kit, or manufacturing is taken up by some lower-tier company that is faster on its feet. Seems good to me... For instance, a multi channel receiver, which can do all the phasing, very precisely, at low levels, either with analog or digital processing, can give you the nice deep nulls and adaptation.For TX, though, null depth isn't as important as maximizing the power squirted in the right direction. That seems a good place to cut the problem down to size. By all means continue to use the existing phasing networks for TX, with 4 or 8 switchable directions and fixed phasing; but switch the antennas over to a totally separate network for RX. At the lower power levels, the RX network could be much more complex and versatile, combining the signals from the four (say) antennas with amplitudes and phasing that could be varied on the fly. Another way to scale down the problem is not to be too ambitious about automatic null steering. In ham operating it is often difficult for a computer to identify which is the wanted signal and which is the QRM, so maybe let's not try. Semi-automatic null steering definitely would be within reach, where the user has a control to steer the null direction manually for the best audible results, and the computer does the math to select the required network parameters. So.. not today, but I'd figure that in 10 years, you'll start to see real broadband phased arrays (not just 4-8 switched beams in a single band like a 4 square). Yes, I think maybe so. We already have most of the technology for an advanced manually steerable RX array, so it's mainly a matter of integrating the separate parts of it to make a practical design. Someone just has to decide to do it... and maybe they already have. -- 73 from Ian GM3SEK |
phased array practicality was Gaussian antenna aunwin
On Mar 1, 11:58 am, Ian White GM3SEK wrote:
"the magic box in the center of the array" is more the former model, and while simple conceptually, in the long run probably isn't the best way to solve the problem in a system context. That is very true. Unfortunately, the ham market is divided up into physically separate compartments of transceivers, power amplifiers and antennas. That is a severe restriction which makes all the technical challenges much more difficult. Dare I say that what is needed is that much overworked phrase "paradigm shift"? It used to be that a "transceiver" was a radical new thing, because everyone knew that you needed a separate Tx and Rx. Oddly, with phased arrays, perhaps the transceiver becomes passe. However, we can try to pare the problem down a little. Another important point is that the concept of 'market demand' is beginning to break down in ham radio. The big manufacturers are increasingly challenged by new products that pay no attention to the market - they spring directly from some individual or small team deciding they're going to do it. I think this has actually been the case for decades. I doubt, for instance, that the KWM-1 was motivated by some massive pentup demand for an integrated SSB transceiver. Then maybe the design is produced as a kit, or manufacturing is taken up by some lower-tier company that is faster on its feet. Seems good to me... This would be true of many things.. the SDR1000 might be an example. A variety of TAPR kits might be another. For instance, a multi channel receiver, which can do all the phasing, very precisely, at low levels, either with analog or digital processing, can give you the nice deep nulls and adaptation.For TX, though, null depth isn't as important as maximizing the power squirted in the right direction. That seems a good place to cut the problem down to size. By all means continue to use the existing phasing networks for TX, with 4 or 8 switchable directions and fixed phasing; but switch the antennas over to a totally separate network for RX. In fact, for HF, you can probably get away with smaller active antennas for receive. There's no particular reason why the Tx antennas and the Rx antennas have to be the same, since you're not typically receiver noise figure limited. There IS a strong signal IM problem..so maybe active receive antennas aren't the right solution. But, there's a lot of convenience possible if your receive antennas are all something like 6 foot whips. At the lower power levels, the RX network could be much more complex and versatile, combining the signals from the four (say) antennas with amplitudes and phasing that could be varied on the fly. You can use nifty things like the 4 quadrant vector multipliers from Maxim, for instance. Another way to scale down the problem is not to be too ambitious about automatic null steering. In ham operating it is often difficult for a computer to identify which is the wanted signal and which is the QRM, so maybe let's not try. Semi-automatic null steering definitely would be within reach, where the user has a control to steer the null direction manually for the best audible results, and the computer does the math to select the required network parameters. That would be where I would start. Adaptive nulling is a bit weird to work with as a user, especially if you expect to control it. And, for hams, they want a bit more control. What would be cool is to have a 3D panoramic display that somehow indicates not only the frequency spectrum, but the angle of arrival. So.. not today, but I'd figure that in 10 years, you'll start to see real broadband phased arrays (not just 4-8 switched beams in a single band like a 4 square). Yes, I think maybe so. We already have most of the technology for an advanced manually steerable RX array, so it's mainly a matter of integrating the separate parts of it to make a practical design. Someone just has to decide to do it... and maybe they already have. I've got most of both halves (steerable Tx array and steerable Rx array) in pieces, but there's a lot of practical usability and integration issues. Sure would be nice to have a wealthy patron and have lots of free time and a big budget to work on itgrin. I developed the in-situ calibration algorithms as part of a R&D effort at JPL, but the resources eventually ran out. Too many projects and too little time. Jim, W6RMK |
phased array practicality was Gaussian antenna aunwin
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phased array practicality was Gaussian antenna aunwin
In fact, for HF, you can probably get away with smaller active
antennas for receive. There's no particular reason why the Tx antennas and the Rx antennas have to be the same, since you're not typically receiver noise figure limited. Adaptive nulling is a bit weird to work with as a user, especially if you expect to control it. And, for hams, they want a bit more control. Using this kind of technology is about the only reason I would trash my current rigs and go for a custom driver (but it would have to inhabit each array antenna's amp and thus render it a complete transmitter. This would in turn cast all the features (like SSB generation) into each of those elements. The unit cost of this would climb because of feature creep, not component pricing. What would be cool is to have a 3D panoramic display that somehow indicates not only the frequency spectrum, but the angle of arrival. When living in a residential area, as I do, canceling or reducing local qrm and man made noise is your first interest! Using an array is may be the only way to go. Either by using analog means (phasers) or using digital signal processing. In DSP a lot more is possible. I use an array of 2 small active loop antennas. The two phase coherent receivers are made using the front-ends of two Elecraft K2īs and a Delta 44 soundcard in the PC. The software makes the rest of the dual (SDR) receiver. No expensive hardware needed. See: http://www.pa0sim.nl/Software.htm (one of the windows shows the phase difference (TDOA), which helps eg. selecting the correct phase for the phaser) Even two antennas can be very effective against local qrm and even non local qrm. I sure would like to try four antennas HI. It is easy to scale it to four antennas/receivers, but I still have my qrl ..... 73 de Jan PA0SIM |
phased array practicality was Gaussian antenna aunwin
On Mar 1, 10:32 pm, Richard Clark wrote:
I can sense that this discussion is leading back to a separation of driver from amplifier. You could still use a power divider to feed the remote amps at the various array locations. Say 10W at 10 active antennas, each with a 100W rating. This probably the most practical thing.. and in fact what I'm working on prototyping. The challenge is in the amplifiers (although the recent FCC ruling doing away with the anti-CB amplifier rules will help) Most inexpensive amplifiers do not have "well behaved" properties at RF (i.e. they change all their parameters as they heat up).. this makes dealing with phasing and mutual coupling a bit challenging If the output Z changes, then the network matching it to the element needs to change..if the gain and phase through the amp changes, then the drive needs to be adjusted. Fortunately, the problems are solvable, at least in a theoretical sense. This would preserve investment, and create and alternative to the Henry market. Hams would have two purchase paths instead of discarding their introductory base station and opting in for N number of active arrays driven by a specialty item that looks like their old rig gathering dust in the corner. Yes.. this is exactly the growth path I would envision. There's no reason to expect you need a large transmit antenna for solid state amps either. The native source resistance of a transistor is quite low, and has to be transformed UP to match 50 Ohms. If you had a radiation resistance of only several ohms (a very short radiator) all you have to pay attention to is cutting Ohmic loss and providing flexible inductance. Unfortunately, this may be a performance killer - but if you are demanding multiband performance, you will have to answer for this for any size array element. Indeed, yes.. fortunately, you already need to have an adjustable impedance transformer (because the feed point Zs change with frequency/ steering), and even more fortunately, you don't need a broadband match.. All you need is a few kHz, so a single L and C might do it, "good enough". There IS a strong signal IM problem..so maybe active receive antennas aren't the right solution. The same transceiver that survives IM would still handle it from several phase active array elements. As you can see, redesigning a new driver eventually leads you back to the gear you have. If you now demand a separate receiver, separate driver, and separate active array antennas, costs rise faster by the number of connections. But it turns out that you want a different kind of phasing for receive than for transmit (not only a different pattern, but it turns out you'd like to do it a different way... null formation being one reason).. that pushes you away from a simple adjustable LC phasing network for the receive array. For receive, you'd also like it fast (and, potentially, multiple beams at once). Adaptive nulling is a bit weird to work with as a user, especially if you expect to control it. And, for hams, they want a bit more control. Programmable oscillators that shift immediately and start at any point in the cycle (absolute phase AND frequency control) would be miles further down the road. That's available now.. it's a DDS. And you can buy a radio off the shelf that has these capabilities (the FlexRadio SDR1000), although, there are a couple difficulties with the flex (for one, they didn't bring the sync input to the DDS out to the connector). You can buy a eval board from Analog Devices for $200. ordered to a single frequency. You still have the elemental clock osc XTAL for processor and driver, but those litter the world for pennies. Interestingly, in a very much higher budget arena (deep space comms and ranging), they're also doing this. Until recently, you had to special order the crystal for your spacecraft radio (with 18+ month lead time!!), so if you had a channel reassignment, it was a real problem. (One of the Mars Rovers and the Mars Reconnaissance Orbiter are on the same channel.. wasn't supposed to be a problem because the rover was not planned to survive long enough) Using this kind of technology is about the only reason I would trash my current rigs and go for a custom driver (but it would have to inhabit each array antenna's amp and thus render it a complete transmitter. This would in turn cast all the features (like SSB generation) into each of those elements. The unit cost of this would climb because of feature creep, not component pricing. Kind of depends where you divide up the building blocks. The raw exciter cost (DDS plus mod plus D/A converter for modulation) is quite low. Jim |
phased array practicality was Gaussian antenna aunwin
On 2 Mar, 10:41, "Jan Simons PA0SIM"
wrote: In fact, for HF, you can probably get away with smaller active antennas for receive. There's no particular reason why the Tx antennas and the Rx antennas have to be the same, since you're not typically receiver noise figure limited. Adaptive nulling is a bit weird to work with as a user, especially if you expect to control it. And, for hams, they want a bit more control. Using this kind of technology is about the only reason I would trash my current rigs and go for a custom driver (but it would have to inhabit each array antenna's amp and thus render it a complete transmitter. This would in turn cast all the features (like SSB generation) into each of those elements. The unit cost of this would climb because of feature creep, not component pricing. What would be cool is to have a 3D panoramic display that somehow indicates not only the frequency spectrum, but the angle of arrival. When living in a residential area, as I do, canceling or reducing local qrm and man made noise is your first interest! Using an array is may be the only way to go. Either by using analog means (phasers) or using digital signal processing. In DSP a lot more is possible. I use an array of 2 small active loop antennas. The two phase coherent receivers are made using the front-ends of two Elecraft K2īs and a Delta 44 soundcard in the PC. The software makes the rest of the dual (SDR) receiver. No expensive hardware needed. See:http://www.pa0sim.nl/Software.htm (one of the windows shows the phase difference (TDOA), which helps eg. selecting the correct phase for the phaser) Even two antennas can be very effective against local qrm and even non local qrm. I sure would like to try four antennas HI. It is easy to scale it to four antennas/receivers, but I still have my qrl ..... 73 de Jan PA0SIM- Hide quoted text - - Show quoted text - Jan, the above is beyond me. I see it as an ideal addition to a Gaussian array where you have two receive points or more on the antenna such that the receiver could make the best choice which is polarity of choice. At the same time allows you to disconnect two feed points to concentrate on the desired feed. Of course all feeds can be connected for recieve anyway to counteract fade. I believe that there is a niche in ham radio for what you have there. Thanks for sharing Cheers and beers Art |
phased array practicality was Gaussian antenna aunwin
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phased array practicality was Gaussian antenna aunwin
On Mar 2, 12:15 pm, Richard Clark wrote:
If you are interested in a design for yourself, and maybe a production run of a few hundred, then look to the HF/10M/6M/2M surplus repeater market from Motorola and RCA designs of the 70s and 80s. Dirt cheap decks with enough elbow room to make mods. Or, perhaps the HF Superpacker Pro.. 100+Watts..20dB or so gain. Fortunately, the problems are solvable, at least in a theoretical sense. One doesn't usually see fortunately paired with theoretical. ironically this is how this thread started - was with a pig in the poke explanation passing for science A heck of a lot better than "theoretically there is NO solution..." girn All you need is a few kHz, so a single L and C might do it, "good enough". So, this daydream is on one band only? 1 adjustable L, 1 adjustable C.. covers all bands. For ham applications, you only need to have the match and phase adjust at one frequency at a time, and over a fairly small bandwidth, so the Q of the matching circuit can be high. Not like a generic wideband phased array where you need to have a wideband match, and do something like true-time-delay processing. OK, Analog Devices is a star performer. I built a tube version of this DDS back in '68 when it was called a coherent detector (could have been called many names depending on where you developed the audio output). However, this is NOT what I was referring to, as that is distinctly different. This is a software controlled oscillator whose frequency and phase is immediately settable (within on clock, this is in the nanosecondS range). That is precisly what a DDS does.. It has a phase accumulator where you can adjust the phase increment per clock. The output of the phase accumulator goes to a sine lookup table and then to a DAC. A typical part might have a 48 bit phase accumulator and a 12 bit DAC. Check out, for instance, the AD9858.. You might not be able to update the phase increment or absolute phase in a nanosecond, but it's pretty fast (there's some pipeline delay too.).. I'd say you could clock in a new configuration and have the new RF appear no more than 100ns later. If you need to phase each array element independently to phase steer the combined system (also to take care of phase matching through mutual coupling), the software solution spring immediately to the front for a solution. Well, software for the calculations, but perhaps not for all the RF processing. You still need to adjust Ls and Cs for the match, unless you're willing to design a fairly unusual amplifier: ideally, it would act like a current source with a lot of voltage compliance that can tolerate a very reactive load.. so you're essentially synthesizing the L and/or C with an active device.. doable, but not too hot on power efficiency these days. Interestingly, in a very much higher budget arena (deep space comms and ranging), they're also doing this. Until recently, you had to special order the crystal for your spacecraft radio (with 18+ month lead time!!), so if you had a channel reassignment, it was a real problem. (One of the Mars Rovers and the Mars Reconnaissance Orbiter are on the same channel.. wasn't supposed to be a problem because the rover was not planned to survive long enough) The software oscillator I described in the previous post would solve that for the same cost as the custom XTAL. Well.. not the same cost as a custom rock. The rock may have a long delivery time, but it's not particularly more expensive than a standard frequency. The DDS doesn't come for zero power, either, so you have a tradeoff of more DC power for flexibility (power consumption is a very big deal in deep space exploration). And, then, there's also the whole radiation tolerance issue. If you are looking for a design and a market, I cannot think for the life of me why that hasn't happened yet. Systems like this exist, but not in the ham market. Oddly, it seems that hams balk at forking out more than $100K for a system that does all this. The challenge is in getting it in a ham friendly format. The hardware's not expensive, it's all that software and system integration. But, 10 years from now, when the early adopters have cobbled together their systems from bits and pieces, and some of the concepts become more familiar, I think you'll see someone make the investment to do the development to create an off the shelf product. Clearly, there is SOME market for $10K ham widgets or things like IC7800s and big towers with arrays of SteppIRs wouldn't exist. 73's Richard Clark, KB7QHC |
phased array practicality was Gaussian antenna aunwin
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