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#1
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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 |
#2
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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 |
#3
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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 |
#4
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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 |
#5
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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 |
#6
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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 |
#7
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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. |
#8
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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 |
#9
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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. |
#10
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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 |
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