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Homemade Sigma 4 11 meter base antenna
- Thread starter Lil'Yeshua
- Start date
no eddie i got it from cebik, the arrl open sleeve article, and reading about transmission-lines, we talked in emails about where i thought transmission-line and antenna mode currents were flowing in the open sleeve sigma astroplane and in gamma sections well before shockwave obtained the cst plot,
my opinion of how it likely operates has not changed since a week or so after i last corresponded with cebik, im pretty sure you know that,
cst does not show what im trying to show,
the first one was for the extended version,
i tried to show the same thing first time around not well so i did another one for the 3/4wave, i remember you pulling me over about the same thing in my other drawings, i have not changed those either even though you were right, ezbob gui needs some work with sign of phase,
i still missed at least one current on this one, i hope i got them in the correct relative phase.
my opinion of how it likely operates has not changed since a week or so after i last corresponded with cebik, im pretty sure you know that,
cst does not show what im trying to show,
the first one was for the extended version,
i tried to show the same thing first time around not well so i did another one for the 3/4wave, i remember you pulling me over about the same thing in my other drawings, i have not changed those either even though you were right, ezbob gui needs some work with sign of phase,
i still missed at least one current on this one, i hope i got them in the correct relative phase.
Phase is determined by the length of the vertical radiator. Anything longer than 1/2 wave will cause phase inversion at the base over the exact length this radiator extends past 1/2 wave. In the case of the Sigma, that's 1/4 wavelength. Remember, this is an unbalanced antenna with CMC flowing on the cone. Cancellation requires equal and opposite currents and that is not what we have in the Sigma.
Depends on where you begin listening to the discussion and at what point you jump out.
Dam! Sounds remarkably like a 'J'-pole, doesn't it??
- 'Doc
The J-pole is simply a 1/2 wave monopole with a very large 1/4 wave matching stub.
The Sigma differentiates itself by having a Gamma Match for impedance matching instead of what is arguably the largest matching network relative to antenna size out there, and a 1/4 wave lower cage that contains phase inversion within it while producing in-phase currents on the outside of the cage/cone that contributes to the at-the-horizon RF radiation.
The J-pole is a 1/2 wave monopole.
The V4k is a 3/4, or longer, end fed monopole based on the iteration employed without the out-of-phase lower end currents characteristic of other end fed monopole antennas that exceed 1/2 wavelength long.
As far as additional gain is concerned, that would be simply the function of the additional overall length of the V4k if nothing else. Perhaps it is simply that there is more of what matters down there where folks live - on the horizon.
Whether one chooses to accept the CST plot or not is the privilege of the individual. I have seen similar resistance to Eznec modeling, and Ezbob modeling on this forum no matter the antennas in question.
Good questions are being asked, and I am watching to see if the answers supplied awaken any additional understanding in my middle-aged brain.
What I do accept is my personal experience with this antenna.
Something accounts for the improved performance of theV4k over other antennas set to both the same bottom and top heights. We look to technological data, ie science, for explanations, yet resist the available explanations when they coincide with the experiences of those who've gone the additional step of mounting the antenna and proving the data empirically.
What I have learned along the way with many other things is if someone dislikes a thing and your experience supports their predisposition, you are right, however, when your experience does not support the predisposition of others, then you are wrong.
I have had some tell me the 6' radials on the A99 were the cat's meow. When I added them they provided absolutely no detectable difference for me. I don't see them as anything more than an unnecessary expense. On the other hand, I believe all verticals benefit from a good GP system. Now, whichever way you see it I have either just been affirmed, or disallowed as ignorant.
So, in fairness, I promise that if you agree with me I'll like you when you say something I agree with. . .
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Dam! Sounds remarkably like a 'J'-pole, doesn't it??
- 'Doc
I simply ask when was the last time you saw a 1/2 wave J-Pole sitting on top of another 1/4 wave in phase radiator with no insulator between them??
this
"Allowing the longer top section above the cone to radiate constructively with the currents on the outside of the cone."
and this link
http://fmbroadcastantenna.com/images/Dominator NWE-34 in CST.gif
are helping me to "see" what is happening, you really have to look at the cst model...
"Allowing the longer top section above the cone to radiate constructively with the currents on the outside of the cone."
and this link
http://fmbroadcastantenna.com/images/Dominator NWE-34 in CST.gif
are helping me to "see" what is happening, you really have to look at the cst model...
B
BOOTY MONSTER
Guest
Dam! Sounds remarkably like a 'J'-pole, doesn't it??
- 'Doc
i very strongly suspect that if someone swaps a J-pole for a vector that they will easily learn that they are not so similar .
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B
BOOTY MONSTER
Guest
you mean the one found on this page?
Gain-Master - Vs. conventional Antenna
so you think they are one and the same?
i was thinking the sigma iv would have a 1dbd gain! oops i just answered my own question.
ok thanks marconi
Gain-Master - Vs. conventional Antenna
so you think they are one and the same?
i was thinking the sigma iv would have a 1dbd gain! oops i just answered my own question.
ok thanks marconi