See what happens, you miss one "J-Pole" post and you get harassed on the forums! Even from across the pond! 8)
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Jo-Gunn: Son of a Gunn
- Thread starter Master Chief
- Start date
i know your a busy guy chief but are you holding out on us with this antenna,
did you use my rivets to fix it back together ?
sorry you know how it is i could not resist :twisted:
I was looking back at this very old thread, and was reminded of some old discussions we've had over time.
Well Bob, even though I currently pretty much agree with Master Chief's idea that the base of the Sigma4 design does not radiate, or it does not radiate very much........
I'm reminded that we seldom saw our buddy MC...hardly ever followed thru on his promises.
I guess the issues raised about the JoGunn Son of a Gunn were never followed up on either.
I think I'll re-check my old model of the JG Son of a Gunn, and see how it compares to some of the ideas noted here.
I understand there may still be temptation to assume the cone does not radiate. One simple collinear test proves this idea is as outdated as the world being flat. While my test may not be understood by everyone, the results prove the cone radiates significantly enough that it absolutely cannot be ignored when constructing a collinear version. If you choose to ignore the cones radiation (as EZNEC does) during the construction of a collinear model, you will quickly find that the added collinear section will buck the phase of the radiation emitting from the cone in the field.
One must grasp several different aspects before they can follow how this complex design works. Most revealing is how the radiation currents and phase are distributed on the original antenna before any attempt at making a working collinear version is possible. You must account for ALL radiation emitting from the original antenna before you can choose the correct phase delay to drive an added collinear section. Take the time to research and investigate that last sentence before sharing myths about non radiating Sigma cones.
The basic facts are as follows: If the cone did not radiate a significant in phase signal, the Sigma would function like an end fed 1/2 wave, case closed. All end fed 1/2 wave antennas can be expanded into a 1/2 wave over a 1/2 wave with the use of a 180 degree phase shift placed in between the two 1/2 wave sections. If by some "non apparent" miracle the Sigma managed to display in phase radiation that was significantly longer than 1/2 wavelength, the 180 degree phase shift will fail miserably when adding another 1/2 wave collinear section.
I'd bet my life there is not a person in the world that will ever make a 1/2 wave over a 1/2 wave collinear Sigma work with the suggested 180 degree phase shift between sections, even though EZNEC based models assure you it would work. It also suggests no one has ever seen a working model of the Sigma in EZNEC. The errors it displays are related to the cone, not just a collinear version. The collinear version just makes it impossible to trust EZNEC on the Sigma since it clearly shows a physical discrepancy in the length of the phase shift element that is 100% longer in the program than what works in the field.
One must grasp several different aspects before they can follow how this complex design works. Most revealing is how the radiation currents and phase are distributed on the original antenna before any attempt at making a working collinear version is possible. You must account for ALL radiation emitting from the original antenna before you can choose the correct phase delay to drive an added collinear section. Take the time to research and investigate that last sentence before sharing myths about non radiating Sigma cones.
The basic facts are as follows: If the cone did not radiate a significant in phase signal, the Sigma would function like an end fed 1/2 wave, case closed. All end fed 1/2 wave antennas can be expanded into a 1/2 wave over a 1/2 wave with the use of a 180 degree phase shift placed in between the two 1/2 wave sections. If by some "non apparent" miracle the Sigma managed to display in phase radiation that was significantly longer than 1/2 wavelength, the 180 degree phase shift will fail miserably when adding another 1/2 wave collinear section.
I'd bet my life there is not a person in the world that will ever make a 1/2 wave over a 1/2 wave collinear Sigma work with the suggested 180 degree phase shift between sections, even though EZNEC based models assure you it would work. It also suggests no one has ever seen a working model of the Sigma in EZNEC. The errors it displays are related to the cone, not just a collinear version. The collinear version just makes it impossible to trust EZNEC on the Sigma since it clearly shows a physical discrepancy in the length of the phase shift element that is 100% longer in the program than what works in the field.