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Dish reflector
I made a helical end fed antenna that is inside a cone shaped
reflector The reflector is made from 1/2" mesh steel with an aluminum foil liner and connected to the braid of the feed coax. No baluns are used, just direct connections. I was surprised to hear signals from the rear! I thought that a dish reflector prevented such signals getting to the receiver. So what can be wrong with the reflector or can signals get reflected back from the frontal area? Antenna is at a 40 foot height Any ideas as to what the fault could be? Regards Art I have no experience with dishes thus the question Note, the helical antenna does not protrude beyond the dish envelope. Art |
Dish reflector
On Thu, 9 Apr 2009 20:05:20 -0700 (PDT), Art Unwin
wrote: No baluns are used That alone is at least one thing wrong with the design. Ignoring the obvious, the design suffers from the basic disregard for scale and wavelength. There are probably other issues beyond these violations of first principles. 73's Richard Clark, KB7QHC |
Dish reflector
In message
, Art Unwin writes I made a helical end fed antenna that is inside a cone shaped reflector The reflector is made from 1/2" mesh steel with an aluminum foil liner and connected to the braid of the feed coax. No baluns are used, just direct connections. I was surprised to hear signals from the rear! I thought that a dish reflector prevented such signals getting to the receiver. So what can be wrong with the reflector or can signals get reflected back from the frontal area? Antenna is at a 40 foot height Any ideas as to what the fault could be? Diffraction off the edge of the reflector. It causes backlobes. It's not a fault. Brian GM4DIJ -- Brian Howie |
Dish reflector
On Apr 9, 11:59*pm, Richard Clark wrote:
On Thu, 9 Apr 2009 20:05:20 -0700 (PDT), Art Unwin wrote: No baluns are used That alone is at least one thing wrong with the design. Ignoring the obvious, the design suffers from the basic disregard for scale and wavelength. There are probably other issues beyond these violations of first principles. 73's Richard Clark, KB7QHC The radiator is totally within the reflector envelope ! It is possible that the transmission line is picking up some signal but a brief scan of the books show that dishes do some how obtain some signals from the rear.. "Ignoring the obvious" is a nonsense aproach, as is scale and wavelength. I was hoping for somebody who is familiar with dish design and not from one who is a talking head bent on agitation and slander |
Dish reflector
In message , Richard Clark
writes On Thu, 9 Apr 2009 20:05:20 -0700 (PDT), Art Unwin wrote: No baluns are used That alone is at least one thing wrong with the design. Do you use a balun with a helix and a dish reflector? Surely that bit at least is right! -- Ian |
Dish reflector
"Art Unwin" wrote in message ... I made a helical end fed antenna that is inside a cone shaped reflector The reflector is made from 1/2" mesh steel with an aluminum foil liner and connected to the braid of the feed coax. No baluns are used, just direct connections. I was surprised to hear signals from the rear! I thought that a dish reflector prevented such signals getting to the receiver. So what can be wrong with the reflector or can signals get reflected back from the frontal area? Antenna is at a 40 foot height Any ideas as to what the fault could be? Regards Art I have no experience with dishes thus the question Note, the helical antenna does not protrude beyond the dish envelope. Art There is a lot of very important information missing here. What frequency are we talking about and what is the dish diameter? Do you have any idea as to what your edge taper is or sidelobes? Dale W4OP |
Dish reflector
Brian Howie wrote:
In message , Art Unwin writes I made a helical end fed antenna that is inside a cone shaped reflector The reflector is made from 1/2" mesh steel with an aluminum foil liner and connected to the braid of the feed coax. No baluns are used, just direct connections. I was surprised to hear signals from the rear! I thought that a dish reflector prevented such signals getting to the receiver. So what can be wrong with the reflector or can signals get reflected back from the frontal area? Antenna is at a 40 foot height Any ideas as to what the fault could be? Diffraction off the edge of the reflector. It causes backlobes. It's not a fault. Brian GM4DIJ Ask him the working frequency and dimensions of his "dish reflector". Don't be drinking anything when you read his answer. -- Jim Pennino Remove .spam.sux to reply. |
Dish reflector
Dale Parfitt wrote:
"Art Unwin" wrote in message ... I made a helical end fed antenna that is inside a cone shaped reflector The reflector is made from 1/2" mesh steel with an aluminum foil liner and connected to the braid of the feed coax. No baluns are used, just direct connections. I was surprised to hear signals from the rear! I thought that a dish reflector prevented such signals getting to the receiver. So what can be wrong with the reflector or can signals get reflected back from the frontal area? Antenna is at a 40 foot height Any ideas as to what the fault could be? Regards Art I have no experience with dishes thus the question Note, the helical antenna does not protrude beyond the dish envelope. Art There is a lot of very important information missing here. What frequency are we talking about and what is the dish diameter? Do you have any idea as to what your edge taper is or sidelobes? Dale W4OP The last time he talked about it, it was "designed" to operate on the 160 meter band and the "reflector" was 3 meters in diameter. No, those numbers are not typos. -- Jim Pennino Remove .spam.sux to reply. |
Dish reflector
On Apr 10, 9:50*am, "Dale Parfitt" wrote:
"Art Unwin" wrote in message ... I made a helical end fed antenna that is inside a cone shaped reflector The reflector is made from 1/2" mesh steel with an aluminum foil liner and connected to the braid of the feed coax. No baluns are used, just direct connections. I was surprised to hear signals from the rear! I thought that a dish reflector prevented such signals getting to the receiver. So what can be wrong with the reflector or can signals get reflected back from the frontal area? Antenna is at a 40 foot height Any ideas as to what the fault could be? Regards Art I have no experience with dishes thus the question Note, the helical antenna does not protrude beyond the dish envelope. Art There is a lot of very important information missing here. What frequency are we talking about and what is the dish diameter? Do you have any idea as to what your edge taper is or sidelobes? Dale W4OP Dale I thought that if the radiator was in the reflector envelope, that is the radiator is below the top of the cone then there should be no radiation from the rear though possibly a little edge refraction. I know little regarding dish reflectors thus the question. I am of the opinion that radio is a matter of particles and not waves so I can easily visualize impregnation of the shield at the center as per Rutherford foil and particle experiments, but I am not ready to jump because of edge taper and other things that I am not aware of What is very clear from dish radiation patterns in the books that there is a localised radiation congregation at the dish axis rear which appears unexplainable. at the rear at the dishes axis tho it is in the area of direct impact I appreciate the comments and thoughts applied but not the nonsensicle writings of Richard who is wired so differently from the rest of us. These signals appear at all frequencies though I fail to see what the impact of frequency is because of the reflector envelope or umbrella. |
Dish reflector
Art Unwin wrote:
On Apr 10, 9:50 am, "Dale Parfitt" wrote: "Art Unwin" wrote in message ... I made a helical end fed antenna that is inside a cone shaped reflector The reflector is made from 1/2" mesh steel with an aluminum foil liner and connected to the braid of the feed coax. No baluns are used, just direct connections. I was surprised to hear signals from the rear! I thought that a dish reflector prevented such signals getting to the receiver. So what can be wrong with the reflector or can signals get reflected back from the frontal area? Antenna is at a 40 foot height Any ideas as to what the fault could be? Regards Art I have no experience with dishes thus the question Note, the helical antenna does not protrude beyond the dish envelope. Art There is a lot of very important information missing here. What frequency are we talking about and what is the dish diameter? Do you have any idea as to what your edge taper is or sidelobes? Dale W4OP Dale I thought that if the radiator was in the reflector envelope, that is snip These signals appear at all frequencies though I fail to see what the impact of frequency is because of the reflector envelope or umbrella. Dale You will, of course, have noted that he hasn't given a couple of the important items that you requested. Based upon some of his earlier babblings, I suspect that this is a helical antenna of perhaps UHF dimensions that he is attempting to use on 160 or 80. tom K0TAR |
Dish reflector
On Fri, 10 Apr 2009 06:29:24 -0700 (PDT), Art Unwin
wrote: "Ignoring the obvious" is a nonsense aproach, as is scale and wavelength. This is a curious defense of poor practice. The results fully follow the obvious problem of ignoring scale and wavelength. Fundamentals have been violated - it doesn't take a PhD nor a research grant to figure that out. No models are necessary, but they would show the failure too. 73's Richard Clark, KB7QHC |
Dish reflector
On Fri, 10 Apr 2009 14:35:26 +0100, Ian Jackson
wrote: No baluns are used That alone is at least one thing wrong with the design. Do you use a balun with a helix and a dish reflector? Surely that bit at least is right! Hi Ian, What has been done right is arguable in the face of failure. The simple testimony easily reveals very simple problems of a fundamental nature. Hoisting the design 40 feet only added to the inefficiency of the exercise (use common sense before muscles - much in the sense of "measure twice, cut once"). 73's Richard Clark, KB7QHC |
Dish reflector
On Fri, 10 Apr 2009 07:54:41 +0100, Brian Howie
wrote: Diffraction off the edge of the reflector. It causes backlobes. It's not a fault. Hi Brian, You have hit the nail on the head. More, you have pushed in the tack with a 10# sledge. This design we are talking about suffers immensely from the violation of observing what you comment upon. It is very much a fault. 73's Richard Clark, KB7QHC |
Dish reflector
Maybe the coax ground is insufficent and a seperate ground from mother earth
is required.....Maybe "Art Unwin" wrote in message ... I made a helical end fed antenna that is inside a cone shaped reflector The reflector is made from 1/2" mesh steel with an aluminum foil liner and connected to the braid of the feed coax. No baluns are used, just direct connections. I was surprised to hear signals from the rear! I thought that a dish reflector prevented such signals getting to the receiver. So what can be wrong with the reflector or can signals get reflected back from the frontal area? Antenna is at a 40 foot height Any ideas as to what the fault could be? Regards Art I have no experience with dishes thus the question Note, the helical antenna does not protrude beyond the dish envelope. Art |
Dish reflector
On Apr 10, 1:07*pm, "Rollie" wrote:
Maybe the coax ground is insufficent and a seperate ground from mother earth is required.....Maybe "Art Unwin" wrote in message ... I made a helical end fed antenna that is inside a cone shaped reflector The reflector is made from 1/2" mesh steel with an aluminum foil liner and connected to the braid of the feed coax. No baluns are used, just direct connections. I was surprised to hear signals from the rear! I thought that a dish reflector prevented such signals getting to the receiver. So what can be wrong with the reflector or can signals get reflected back from the frontal area? Antenna is at a 40 foot height Any ideas as to what the fault could be? Regards Art I have no experience with dishes thus the question Note, the helical antenna does not protrude beyond the dish envelope. Art Rollie I checked. The coax ground and the reflector is grounded at the same place at the top of the tower. All horizontal coax is buried. Seems like the dish reflector does not get a lot of attention from ham operators ! Art |
Dish reflector
Art Unwin wrote:
On Apr 10, 1:07Â*pm, "Rollie" wrote: Maybe the coax ground is insufficent and a seperate ground from mother earth is required.....Maybe "Art Unwin" wrote in message ... I made a helical end fed antenna that is inside a cone shaped reflector The reflector is made from 1/2" mesh steel with an aluminum foil liner and connected to the braid of the feed coax. No baluns are used, just direct connections. I was surprised to hear signals from the rear! I thought that a dish reflector prevented such signals getting to the receiver. So what can be wrong with the reflector or can signals get reflected back from the frontal area? Antenna is at a 40 foot height Any ideas as to what the fault could be? Regards Art I have no experience with dishes thus the question Note, the helical antenna does not protrude beyond the dish envelope. Art Rollie I checked. The coax ground and the reflector is grounded at the same place at the top of the tower. All horizontal coax is buried. Seems like the dish reflector does not get a lot of attention from ham operators ! Art Hmmm, I guess this guy just talks to himself. http://www.signalone.com/kb2ah/KB2AHantennas.html -- Jim Pennino Remove .spam.sux to reply. |
Dish reflector
On Apr 10, 10:15*am, wrote:
Dale Parfitt wrote: "Art Unwin" wrote in message ... I made a helical end fed antenna that is inside a cone shaped reflector The reflector is made from 1/2" mesh steel with an aluminum foil liner and connected to the braid of the feed coax. No baluns are used, just direct connections. I was surprised to hear signals from the rear! I thought that a dish reflector prevented such signals getting to the receiver. So what can be wrong with the reflector or can signals get reflected back from the frontal area? Antenna is at a 40 foot height Any ideas as to what the fault could be? Regards Art I have no experience with dishes thus the question Note, the helical antenna does not protrude beyond the dish envelope. Art There is a lot of very important information missing here. What frequency are we talking about and what is the dish diameter? Do you have any idea as to what your edge taper is or sidelobes? Dale W4OP The last time he talked about it, it was "designed" to operate on the 160 meter band and the "reflector" was 3 meters in diameter. No, those numbers are not typos. -- Jim Pennino Remove .spam.sux to reply. That antenna was when I used an old parabolic satellite dish which was unsuitable. Scanning past antenna papers point to the use of a cone shape similar to a horn of 2 metres diameter produces better results. The antenna needs a longer mast so at the moment I can't compare F/R. Either way, with the radiator within the reflector envelope it is difficult to understand what creates a rearward lobe regardles of scale or frequency of use with respect to receive. At the moment I see nothing that points away from the Rutherford particle experiments with foil .ie penetration when at right angles , deflection at other angles. |
Dish reflector
On Apr 10, 8:35*am, Ian Jackson
wrote: In message , Richard Clark writesOn Thu, 9 Apr 2009 20:05:20 -0700 (PDT), Art Unwin wrote: No baluns are used That alone is at least one thing wrong with the design. Do you use a balun with a helix and a dish reflector? Surely that bit at least is right! -- Ian Ian; I specifically mentioned the absence of a balun. I stated that since it doesn't seem relevent, especially when one reviews published patterns. In a way I knew that Richard would pile up his postings of olde english prose in the shape of riddles that provide nothing, But one has to get used to him and his pals kb9....and others who smear this group with a foul smell as they are wired very differently from the rest of us. |
Dish reflector
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Dish reflector
That antenna was when I used an old parabolic satellite dish which was unsuitable. Scanning past antenna papers point to the use of a cone shape similar to a horn of 2 metres diameter produces better results. The antenna needs a longer mast so at the moment I can't compare F/R. Either way, with the radiator within the reflector envelope it is difficult to understand what creates a rearward lobe regardles of scale or frequency of use with respect to receive. At the moment I see nothing that points away from the Rutherford particle experiments with foil .ie penetration when at right angles , deflection at other angles. As usual Art you are avoiding answering the questions and choose to confuse the issues with you own preconceived ideas and terminology. The fact that the feed is totally within the "reflector envelope" tells you or us nothing about sidelobes and edge taper. I really don't think you want answers, but I'll try once mo 1. What frequency 2. What is the dish diameter 3. What is the dish focal length to diameter ratio (F/D) Dale W4OP |
Dish reflector
On Apr 10, 6:00*pm, "Dale Parfitt" wrote:
*That antenna was when I used an old parabolic satellite dish which was unsuitable. Scanning past antenna papers point to the use of a cone shape similar to a horn of 2 metres diameter produces better results. The antenna needs a longer mast so at the moment I can't compare F/R. Either way, with the radiator within the reflector envelope it is difficult to understand what creates a rearward lobe regardles of scale or frequency of use with respect to receive. At the moment I see nothing that points away from the Rutherford particle experiments with foil .ie penetration when at right angles , deflection at other angles. As usual Art you are avoiding answering the questions and choose to confuse the issues with you own preconceived ideas and terminology. The fact that the feed is totally within the "reflector envelope" tells you or us nothing about sidelobes and edge taper. I really don't think you want answers, but I'll try once mo 1. What frequency 2. What is the dish diameter 3. What is the dish focal length to diameter ratio (F/D) Dale W4OP I am not avoiding questions, just those that appear irrelevant, but here goes Anything to make you happy, this should be interesting how you use these answers with respect to the posted question 1 160 metres upto 2 metres, tunable 2 2 metres 3 Doesn't have a focal length, it is an end fed ( series connection) helix antenna. At least to the best of my knowledge which is why I posed the question Hopefully we will all stay on subject and not get side tracked. I will leave it to others to respond to Richard when they determine what he is talking about. |
Dish reflector
On Fri, 10 Apr 2009 16:49:31 -0700 (PDT), Art Unwin
wrote: 1. What frequency 2. What is the dish diameter 3. What is the dish focal length to diameter ratio (F/D) I am not avoiding questions, just those that appear irrelevant, 20 postings to get to the point (not unanticipated, however) which Art calls "irrelevant." As for those answers? 1 160 metres upto 2 metres, tunable 2 2 metres Hence the wholesale disregard for first principles in size vs. wavelength. Elementary analysis need not go any further when failure is so obviously designed in. 3 Doesn't have a focal length, it is an end fed ( series connection) helix antenna. -Well, maybe not obvious to everyone.- But why don't we chalk this design up to S U C C E S S and call it a thread? If this bier gets anymore wreaths tossed onto it, it will kill the pallbearers. 73's Richard Clark, KB7QHC |
Dish reflector
"Art Unwin" wrote: -drivel snip- In a way I knew that Richard would pile up his postings of olde english prose in the shape of riddles that provide nothing, But one has to get used to him and his pals kb9....and others who smear this group with a foul smell as they are wired very differently from the rest of us. Art-let me point out the obvious.... unless your license has expired, then you ARE a kb9!!!!! Have a nice weekend, glad to see you back posting on the NG. Things were dull without you. Mike W5CHR Memphis |
Dish reflector
On Apr 10, 7:19*pm, Richard Clark wrote:
On Fri, 10 Apr 2009 16:49:31 -0700 (PDT), Art Unwin wrote: 1. What frequency 2. What is the dish diameter 3. What is the dish focal length to diameter ratio (F/D) I am not avoiding questions, just those that appear irrelevant, 20 postings to get to the point (not unanticipated, however) which Art calls "irrelevant." As for those answers? 1 160 metres upto 2 metres, tunable 2 2 metres Hence the wholesale disregard for first principles in size vs. wavelength. *Elementary analysis need not go any further when failure is so obviously designed in. * 3 Doesn't have a focal length, it is an end fed ( series connection) helix antenna. -Well, maybe not obvious to everyone.- But why don't we chalk this design up to S U C C E S S and call it a thread? *If this bier gets anymore wreaths tossed onto it, it will kill the pallbearers. 73's Richard Clark, KB7QHC The posting is about dishes not antennas. I have not read about a dish that does not emit signals to the rear. Now I have built one and find to my surprize that it does accept signals from the rear ! All very simple, the radiator is resting at the bottom of a cone and the top of the radiator does not stick out beyond the reflector. Since you do not know what you are talking about and intent is to disrupt this thread why on earth are you muttering about nothing at length? Simple question has been posed and obviously you do not know the answers that antenna engineering knowledge would provide as you are not an engineer but a actor or actress by day and by night. My question remains unanswered after all these posts.How do signals arrive or depart from the rear of a dish or horn? We all know that you don't know the answer but there are qualified engineers in this group who possibly doand willing to share. |
Dish reflector
The posting is about dishes not antennas. I have not read about a dish
that does not emit signals to the rear. Now I have built one and find to my surprize that it does accept signals from the rear ! All very simple, the radiator is resting at the bottom of a cone and the top of the radiator does not stick out beyond the reflector. Since you do not know what you are talking about and intent is to disrupt this thread why on earth are you muttering about nothing at length? Simple question has been posed and obviously you do not know the answers that antenna engineering knowledge would provide as you are not an engineer but a actor or actress by day and by night. My question remains unanswered after all these posts.How do signals arrive or depart from the rear of a dish or horn? We all know that you don't know the answer but there are qualified engineers in this group who possibly doand willing to share. Your antenna has nothing to do with dish antennas, bu rather plane reflectors (of which yours is way too small as Richard pointed out). I know we cannot change your opinion or teach you anything- so I am out of here. Dale W4OP |
Dish reflector
Art Unwin wrote:
The posting is about dishes not antennas. I have not read about a dish that does not emit signals to the rear. Now I have built one and find to my surprize that it does accept signals from the rear ! All very simple, the radiator is resting at the bottom of a cone and the top of the radiator does not stick out beyond the reflector. Since you do not Well, to start with Art, a cone reflector doesn't meet the definition of a dish antenna. I'm sorry, but they just aren't the same thing. I surprizzzed you missed the difference. tom K0TAR |
Dish reflector
Tom Ring wrote:
Art Unwin wrote: snip tom K0TAR Jimmie I just couldn't resist, just this once. :) tom K0TAR |
Dish reflector
On Apr 10, 7:38*pm, "Mike Lucas" wrote:
"Art Unwin" wrote: -drivel snip- *In a way I knew that Richard would pile up his postings of olde english prose in the shape of riddles that provide nothing, But one has to get used to him and his pals kb9....and others who smear this group with a foul smell as they are wired very differently from the rest of us. Art-let me point out the obvious.... unless your license has expired, then you ARE a kb9!!!!! Have a nice weekend, glad to see you back posting on the NG. Things were dull without you. Mike W5CHR Memphis Oh, I have just popped in and saw Richard up to to his old tricks with Cecil. I don't really expect a satisfactory answer. All on this group denied it was possible to expand Gaussian law of statics to the laws of Maxwell so there is nobody with a real feel with respect to radiation, and of course it shows! Same goes for the nature of Richard no matter how he tries to hide things. The KB9 station and his foul mouth friends are what I was referring to and is why they are pleading for a moderator for this newsgroup. Not really the type I wish to associate with. When the group deviate from the question at hand is when I leave as they all eventually do. Within the next few hours they will want to ask questions about you know what to cover their ignorance and Richard will come prancing in again with his long leg mesh underware acting out a shakespere scene . A few years on a ship tends to change how you look at life so that he walks in the snow with his foot prints in a straight line so that the torso wobbles and then there is the way that he acts and speak. My question is still there and regardles of the number of postings made I doubt that it will be answered. This newsgroup becomes dull when radio goes out the window and personal attacks begin so one really gets what he wishes for when they hang around. |
Dish reflector
On Apr 10, 8:13*pm, "Dale Parfitt" wrote:
*The posting is about dishes not antennas. I have not read about a dish that does not emit signals to the rear. Now I have built one and find to my surprize that it does accept signals from the rear ! All very simple, the radiator is resting at the bottom of a cone and the top of the radiator does not stick out beyond the reflector. Since you do not know what you are talking about and intent is to disrupt this thread why on earth are you muttering about nothing at length? Simple question has been posed and obviously you do not know the answers that antenna engineering knowledge would provide as you are not an engineer but a actor or actress by day and by night. *My question remains unanswered after all these posts.How do signals arrive or depart from the rear of a dish or horn? We all know that you don't know the answer but there are qualified engineers in this group who possibly doand willing to share. Your antenna has nothing to do with dish antennas, bu rather plane reflectors (of which yours is way too small as Richard pointed out). I know we cannot change your opinion or teach you anything- so I am out of here. Dale W4OP Dale, my response above was with respect to Richard not you, but I did know you would run eventually. Study the math of Maxwell and Gauss before you decide to take up teaching. |
Dish reflector
On Apr 10, 8:45*pm, Tom Ring wrote:
Art Unwin wrote: The posting is about dishes not antennas. I have not read about a dish that does not emit signals to the rear. Now I have built one and find to my surprize that it does accept signals from the rear ! All very simple, the radiator is resting at the bottom of a cone and the top of the radiator does not stick out beyond the reflector. Since you do not Well, to start with Art, a cone reflector doesn't meet the definition of a dish antenna. I'm sorry, but they just aren't the same thing. I surprizzzed you missed the difference. tom K0TAR Tom I asked the question as I am not personly knowledgable about dish style reflectors. I do read a lot and I read a paper once where it was found that a cone shaped reflector produced increased gain when used with a helix antenna, so I made one to try it out. Personaly I see it more as a horn and not as a dish with a radiator at a phase control difference from the reflector? Either way I do not understand how that I can hear signals to the rear if the reflector envelope encloses the radiator thus the question. Note that a helix radiates differently from the normal dish radiator such that phasing does not enter the design which is why you see planar dishes or "cups". Thus questions with respect to reflector diameter are not pertinentwhen the radiator is enclosed. |
Dish reflector
Art Unwin wrote:\
Tom I asked the question as I am not personly knowledgable about dish style reflectors. I do read a lot and I read a paper once where it was found that a cone shaped reflector produced increased gain when used with a helix antenna, so I made one to try it out. Personaly I see it more as a horn and not as a dish with a radiator at a phase control difference from the reflector? Either way I do not understand how that I can hear signals to the rear if the reflector envelope encloses the radiator thus the question. Note that a helix radiates differently from the normal dish radiator such that phasing does not enter the design which is why you see planar dishes or "cups". Thus questions with respect to reflector diameter are not pertinentwhen the radiator is enclosed. He is _awfully_ funny, isn't he? tom K0TAR |
Dish reflector
On Apr 10, 9:30*pm, Art Unwin wrote:
On Apr 10, 8:45*pm, Tom Ring wrote: Art Unwin wrote: The posting is about dishes not antennas. I have not read about a dish that does not emit signals to the rear. Now I have built one and find to my surprize that it does accept signals from the rear ! All very simple, the radiator is resting at the bottom of a cone and the top of the radiator does not stick out beyond the reflector. Since you do not Well, to start with Art, a cone reflector doesn't meet the definition of a dish antenna. I'm sorry, but they just aren't the same thing. I surprizzzed you missed the difference. tom K0TAR Tom I asked the question as I am not personly knowledgable about dish style reflectors. I do read a lot and I read a paper once where it was found that a cone shaped reflector produced increased gain when used with a helix antenna, so I made one to try it out. Personaly I see it more as a horn and not as a dish with a radiator at a phase control difference from the reflector? Either way I do not understand how that I can hear signals to the rear if the reflector envelope encloses the radiator thus the question. Note that a helix radiates differently from the normal dish radiator such that phasing does not enter the design which is why you see planar dishes or "cups". Thus questions with respect to reflector diameter are not pertinentwhen the radiator is enclosed. Guys In the absence of a explanation I will provide a possible alternative. Maxwell added a specific portion to his mathematical laws that refer to mass and the speed of light thus verifying the existance of particles. This addition brought statics laws into the radiation sphere. Rutherford of the UK ( Manchester)showed that particles could piece a foil of gold because of the relative size of the particle with respect to the latice make up of the foil when viewed head on. Thus in the same way a particle or mass ejected at the speed of light from a radiator could possibly pierce a reflector when met head on. If so this would explain the rear signals. In the case of a radiator that is not enclosed by the envelope of a reflector head on deflection/ interaction is quite possible and well understood and there are designs to avoid it. With respect to dish edges one can see in the radio handbook what happens to a signal grazing a sharp edge, but that seems hard to swallow when hams cling to the idea of radio "waves" when their actions has not been satisfactorily explained with respect to radiation by physicists. I suggest that you all pick up the Gaussian equations and add the presence of a time varying field such that it is mathematically the same as one of Maxwell's laws ie look for mass and light speed signatures. We are past the times when one could suppress ideas such as the World is not flat. When you finally arrive at the point of understanding of Maxwell you only then gain an understanding of radiation. With the denial of this mathematical evidence by all you have zero understanding of radiation and therefore redundant. Bye |
Dish reflector
On Fri, 10 Apr 2009 20:05:34 -0700 (PDT), Art Unwin
wrote: In the absence of a explanation I will provide a possible alternative. ... such as the World is not flat. Which would, of course, mean that the dish (cone?) antenna?)) radiator?))) is not listening to signals from the back, but those that have gone all the way around the World to the front to be heard now with 3dB gain. Nothing is broken, it is a S U C C E S S. Modern theory has proven Alfred E Newton right! Blimey-what. Me Worry, guv? (non Shakespeare, modern English). 73's Richard Clark, KB7QHC |
Dish reflector
On Fri, 10 Apr 2009 18:01:17 -0700 (PDT), Art Unwin
wrote: The posting is about dishes not antennas. Are you offering recipes now? How to fill a 3 quart mixing bowl with an imperial gallon of secret-sauce? I can anticipate the amazed posting of how surprised you would be to find you need a mop there too. 73's Richard Clark, KB7QHC |
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Dish reflector
I don't see Art's postings except as they're quoted by others. But from
what I'm seeing here, it looks like he's done a great experiment which graphically shows that radio waves don't act like particles. More experiments along this line weren't really necessary, since it's been known at least since Hertz's experiments in the 19th century. And anyone who took high school physics and watched the ripples in the ripple tank should be able to immediately predict what Art is describing. But I suppose the experiment and its results might prove enlightening for those readers who didn't take high school physics and who are nearly completely unacquainted with electromagnetics. Roy Lewallen, W7EL |
Dish reflector
Roy Lewallen wrote:
I don't see Art's postings except as they're quoted by others. But from what I'm seeing here, it looks like he's done a great experiment which graphically shows that radio waves don't act like particles. More experiments along this line weren't really necessary, since it's been known at least since Hertz's experiments in the 19th century. And anyone who took high school physics and watched the ripples in the ripple tank should be able to immediately predict what Art is describing. But I suppose the experiment and its results might prove enlightening for those readers who didn't take high school physics and who are nearly completely unacquainted with electromagnetics. Sorry, Roy, that experiment won't be possible. The bathtub is permanently occupied by the wannabee Archimedes. -- 73 from Ian GM3SEK |
Dish reflector
On Thu, 9 Apr 2009 20:05:20 -0700 (PDT), Art Unwin
wrote: I made a helical end fed antenna that is inside a cone shaped reflector The reflector is made from 1/2" mesh steel with an aluminum foil liner and connected to the braid of the feed coax. No baluns are used, just direct connections. I was surprised to hear signals from the rear! I thought that a dish reflector prevented such signals getting to the receiver. So what can be wrong with the reflector or can signals get reflected back from the frontal area? Antenna is at a 40 foot height Any ideas as to what the fault could be? Regards Art I have no experience with dishes thus the question Note, the helical antenna does not protrude beyond the dish envelope. Art How do you know? The "rear" signals may come from the front side actually, having been reflected by your neighbours house, or distant mountains, or anything in between. w. |
Dish reflector
"Art Unwin" wrote in message ... Seems like the dish reflector does not get a lot of attention from ham operators ! certainly not by 160m ham operators! welcome back art, needed something to brighten up a dreary saturday morning! |
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