Avanti Sigma4: An alternative view point

[CDX-007]

CDX, if you agree that adding one radial increases gain slightly, then you must connect that with the fact the additional radial combines in the far field. Therefore it is not true that only a radial facing the direction of signal will increase the signal.

With respect to the "bloom" we've gone over this before. It is in "full bloom" as you put it. I have not guessed at this. I've asked the question to the right person and at this point I even have the complete CST video version to confirm it. It shows exactly what I said. The field collapsing in on itself and reforming the same peak in the opposite phase.

To me it's self explanatory where this antenna get's it gain from. We have about 27 feet of in phase radiation surface area. It contains two independent current nodes. The CST image is as near field as it gets and does not show the combined effect of the four radials.

If you think it's possible for the bottom 1/4 wave to reach it's "full bloom" point at any other phase angle then the top 1/2 wave, you're not understanding this has nothing to do with antenna design and everything to do with the RF source.

The source is a sign wave. As with any sign wave there will be two phase angles where there is no energy into the load (0 degrees and 180 degrees) and two phase angles with maximum energy (90 degrees and 270 degrees). The Vector image is for sure shown with the source applying energy at the 90 degree phase angle.

Wow, I'm not only feeling baffled, :blink: - I'm dazzled! ...

...some nice long responses but still no explanation for why the Vector CST model shows so little energy in one area compared to another, other than the obvious. Thank you Mr CST for showing us what's really going on.

For the lower ¼λ cone to operate in a non-apparent collinear fashion it would have to radiate as efficiently as the upper ½λ. If this were so, it would then show a current bloom equally as wide but only ½ as long.

It doesn't.

I believe I've now seen, and read, enough evidence for me to side with the 'negligible' radiation camp, (as per the patent explanation) accepting the entire antenna as radiating including the lower ¼λ cone, but only enough from the lower ¼λ cone to cancel the undesirable out of phase main element current, (as shown in the CST model) lowering the TOA as it elevates the upper ½λ.

Apparently the Vector is achieving a lower TOA over a conventional end-fed 5/8λ, providing the associated far-field gain but merely equaling the SGM, not providing enough gain to be a true fully radiating collinear, which is typically closer to 2-3 S-units far-field gain, a perceived gain figure I and others have witnessed on multiple occasions from the introduction of a collinear element and which I simply won't waste time debating.

...and I'd like to see that full Vector CST.

Movin' on...

 

[Shockwave]

Wow, I'm not only feeling baffled, :blink: - I'm dazzled! ...

...some nice long responses but still no explanation for why the Vector CST model shows so little energy in one area compared to another, other than the obvious. Thank you Mr CST for showing us what's really going on.

For the lower ¼λ cone to operate in a non-apparent collinear fashion it would have to radiate as efficiently as the upper ½λ. If this were so, it would then show a current bloom equally as wide but only ½ as long.

It doesn't.

I believe I've now seen, and read, enough evidence for me to side with the 'negligible' radiation camp, (as per the patent explanation) accepting the entire antenna as radiating including the lower ¼λ cone, but only enough from the lower ¼λ cone to cancel the undesirable out of phase main element current, (as shown in the CST model) lowering the TOA as it elevates the upper ½λ.

Apparently the Vector is achieving a lower TOA over a conventional end-fed 5/8λ, providing the associated far-field gain but merely equaling the SGM, not providing enough gain to be a true fully radiating collinear, which is typically closer to 2-3 S-units far-field gain, a perceived gain figure I and others have witnessed on multiple occasions from the introduction of a collinear element and which I simply won't waste time debating.

...and I'd like to see that full Vector CST.

Movin' on...

Again, I can only present you with the facts. It is your option to close your eyes and ignore them. If you feel you know more then the engineers who have worked on this project and assume the base radiation is negligible, then you are drawing the conclusion it's a simple half wave with unity gain. Completely wrong but you are entitled to your opinion.

It has been fully explained that this is an extremely near field model that will not show how the four radials combine their currents constructively in the far field. Had the design only used one radial with all currents applied to this radial, you might see the magnitude you would expect from a 1/4 wave radiator rather then one that is four times less.

Your comment on the antenna needing to have 2 or 3 db gain to be functioning anything like a colinear, oddly enough is the exact gain the antenna has and is advertised at. With respect to the complete active Vector file, I will be posting the information on my website soon. I see no point in posting it here.

I've already been open enough to share the best information ever produced on this antenna only to have it ridiculed by people who don't understand what they are looking at. When you become familiar with the modeling images this program produces, you will see there is nothing to be gained seeing the pattern at any other phase angle then 90 or 270 degrees that produce the current maxima.

 

[Shockwave]

I believe I've now seen, and read, enough evidence for me to side with the 'negligible' radiation camp, (as per the patent explanation) accepting the entire antenna as radiating including the lower ¼λ cone, but only enough from the lower ¼λ cone to cancel the undesirable out of phase main element current, (as shown in the CST model) lowering the TOA as it elevates the upper ½λ.

This deserves a specific response. I apologize if it sounds like I'm picking on you but this is ridiculous. Are you saying the engineers who worked on this antenna decided to add another 40 feet of tubing (4 radials and radiator length) plus a loop just to place a unity gain 1/2 wave 8 feet higher in the air? Why not just buy a 10 foot pole and the A99 and be ahead of the game with this logic? I can see the ads now. Buy our special 8 foot pole for use with the A99 and add 2 db as it lowers your TOA and elevates the 1/2 wave. Please make sense.

 

[CDX-007]

Again, I can only present you with the facts. [No, you are presenting me with your theory. The evidence supports facts not in your favor as there is almost no radiation bloom from the bottom ¼λ showing it isn't enough to be more than marginally additive, as your conjecture demands it must be.] It is your option to close your eyes and ignore them. [Or to open my eyes to see clearly that which is plainly visible] If you feel you know more then the engineers who have worked on this project and assume the base radiation is negligible, then you are drawing the conclusion it's a simple half wave with unity gain.[No, I could be simply accepting what's written on the Sirio website, you know, a '¾ wave J-pole'.
- Actually I haven't given a moments consideration to imagining I know any amount more or less than any "engineers", though I have read the patent information which was written by these "engineers" describing it to be as the CST image clearly shows, making your presumption of imaginary radiation which isn't there but miraculously shows up somewhere 'out there', wrong. I have also stated that I believe this to be an ingenious ½λ with an elevated and efficient feeding system and a lowered TOA providing gain over a conventional end-fed 5/8λ. This is me repeating basically what I wrote in the last post in order to clarify the inaccurate words you are attempting to imply I stated, that it is a simple ½λ with unity gain, which would be wrong] Completely wrong but you are entitled to your opinion.

It has been fully explained that this is an extremely near field model that will not show how the four radials combine their currents constructively in the far field. [Really? I haven't read that specific claim, nor do I believe the CST was designed or programmed to be in error, nor that some mysterious magic RF dust somehow accumulates way out there somewhere as it travels along an invisible path which no program could possibly hope to capture or display, only to reform somewhere out there like something sent through the Starship Enterprise transporter beam] Had the design only used one radial with all currents applied to this radial, you might see the magnitude you would expect from a 1/4 wave radiator rather then one that is four times less. [You sound like you're confusing this with eznec. They have a program here which I believe has been written and programmed with the necessary information to show all radiation emanating from the antenna in a manner also showing it's energy field at any given point around it's circumference, including taking into consideration the current split between the cone radials.
Which, by the way, is also diluted across a 360° field of radiation. Any "combining" this program is too supposedly kindergarten-level to consider showing will be more than offset by the amount of 360° radiation area it is energizing.

I am certain we see an accurate visual representation of the current bloom emanating from the antenna, though calling the program wrong or inaccurate does help your position.]

Your comment on the antenna needing to have 2 or 3 db gain to be functioning anything like a colinear, oddly enough is the exact gain the antenna has and is advertised at. [Gain? Gain over what? What's your point without a reference? I used the SGM as my reference based on your statement that it keeps up with the Vector, and Sirio claim 1.5-2dB over a conventional end-fed 5/8λ, nowhere near the 2-3 S-units increase I have seen by adding a collinear element] With respect to the complete active Vector file, I will be posting the information on my website soon.[ A day? Month? Year?] I see no point in posting it here. [You see no point in posting it here? Well, gee, I guess there's no relative discussion going on here about this antenna is there? WTF?? OK, well then, as long as you say it I guess that means I'm forced to simply accept it.
Shame on me for wanting to see it with my own eyes.]

I've already been open enough to share the best information ever produced on this antenna only to have it ridiculed [Why is a difference of opinion always spoken of as some negative action like "ridicule" by those who argue an unsupported position?] by people who don't understand what they are looking at. [Oh, you mean people who look at a program designed to show what's going on with the currents emanating from a given antenna and then accept it's visual representation of such?] When you become familiar with the modeling images this program produces,[Yes? You mean showing high current bloom only where high current bloom exists?] you will see there is nothing to be gained seeing the pattern at any other phase angle then 90 or 270 degrees that produce the current maxima.

But I'd still love to see it, and that should be enough.

 

[CDX-007]

This deserves a specific response. I apologize if it sounds like I'm picking on you but this is ridiculous. Are you saying the engineers who worked on this antenna decided to add another 40 feet of tubing (4 radials and radiator length) plus a loop just to place a unity gain 1/2 wave 8 feet higher in the air? [No.] Why not just buy a 10 foot pole and the A99 and be ahead of the game with this logic? I can see the ads now. Buy our special 8 foot pole for use with the A99 and add 2 db as it lowers your TOA and elevates the 1/2 wave. Please make sense.

"Please make sense".

 

[Shockwave]

CDX, all I can say is you assume many things not founded in a bit of RF theory. Now implying that the matching network or feed system is responsible for 2 db. Sirio told you all the information you needed to determine it's gain. 2 db without an "i" at the end or a specific reference such as "over a 5/8 wave" means 2 db over a dipole. Basic antenna theory. The 1/2 wave dipole needs no matching or fancy feed system. Adding one will surely not increase it's gain.

Your insistency to see the active file on this antenna amounts to nothing more then implying I've been untruthful. Something I'm not even willing to entertain if the real goal is to have a relative discussion about how this antenna works. No offense intended but to me this is like casting more pearls to swine. If you assume you have more knowledge about this antenna you are asking questions about then the people who make a living working to perfect it's design, my time is wasted.

 

[CDX-007]

CDX, all I can say is you assume many things not founded in a bit of RF theory. Now implying that the matching network or feed system is responsible for 2 db. [No, I believe the entire design is offering the ~2dBEF5/8 gain, would you offer the determination that elevating a ½λ above ground & the feed point while increasing it's matching network efficiency will absolutely change nothing in comparison to a standard end-fed ½λ?] Sirio told you all the information you needed to determine it's gain. 2 db without an "i" at the end or a specific reference such as "over a 5/8 wave" means 2 db over a dipole. Basic antenna theory. The 1/2 wave dipole needs no matching or fancy feed system. Adding one will surely not increase it's gain.[Actually, I believe Sirio claim the SGM provides 1.5-2dB over a conventional end-fed 5/8λ 1.5-2dBEF5/8]
Your insistency to see the active file on this antenna amounts to nothing more then implying I've been untruthful. Something I'm not even willing to entertain if the real goal is to have a relative discussion about how this antenna works.[I believe that's what we're doing] No offense intended but to me this is like casting more pearls to swine. If you assume you have more knowledge about this antenna [No, just reading the available information given under both the patent and the marketing company's website] you are asking questions about then the people who make a living working to perfect it's design, my time is wasted.

I believe you're mistaken about your inference regarding my motivation.

I would just simply like to see it.

Is there a problem loading it, or some other reason you have chosen to keep it from being viewed here by me and the countless number of readers who peruse this forum and whom I'm sure would also love to see it?

Is this like dangling a carrot?

 

[Shockwave]

[No, I believe the entire design is offering the ~2dBEF5/8 gain, would you offer the determination that elevating a ½λ above ground & the feed point while increasing it's matching network efficiency will absolutely change nothing in comparison to a standard end-fed ½λ?]

Elevating any antenna will usually help performance. However, there is nothing you can do with matching or feeding the end fed half wave that will increase it's gain beyond unity. The center fed dipole that requires no matching is the standard of reference. Increasing matching efficiency in the end fed half wave can only get it closer to unity gain, not more.

[Actually, I believe Sirio claim the SGM provides 1.5-2dB over a conventional end-fed 5/8λ 1.5-2dBEF5/8]

This is hardly a good argument to support your idea that an end fed 1/2 wave can have gain. The SGM is neither an end fed or a half wave.

[No, just reading the available information given under both the patent and the marketing company's website]

The available information on the Avanti patent clearly claims 1 db over a 5/8 wave and 30 years later Sirio's specification of 2 db over a dipole is within two tenths of a db difference.

I believe you're mistaken about your inference regarding my motivation.

I would just simply like to see it.

Is there a problem loading it, or some other reason you have chosen to keep it from being viewed here by me and the countless number of readers who peruse this forum and whom I'm sure would also love to see it?

Is this like dangling a carrot?

I'm really not sure what your motivation is but many of your ideas on this antenna are not accurate and do not help others to understand it's function.

While I don't usually mind sharing information about my products, I also have business interests to protect. Since I begin posting information about this design, my competition has both stolen the information I posted and attempted to clone my product. Sirio is having a similar problem with their models. At this point I will no longer be posting technical information of this nature online before it is branded with my company logo to prevent theft.

Another issue is that it has become clear you don't take my word on many of the things I've explained relating to this image. Please explain to me what you hope to gain from seeing the complete file? When you understand the image you will also understand you cannot learn a single thing more about how the antenna works seeing it at any other phase angle then 90 degrees. It just looks pretty.

 

[CDX-007]

Elevating any antenna will usually help performance. [Ah, yes, so it does help performance, providing gain...] However, there is nothing you can do with matching or feeding the end fed half wave that will increase it's gain beyond unity.The center fed dipole that requires no matching is the standard of reference. Increasing matching efficiency in the end fed half wave can only get it closer to unity gain, not more. [So, you put them together and instead of a simple end-fed ½λ, you have a ¾λ acting as a more efficiently fed elevated ½λ with a lower TOA providing gain on the horizon.]


This is hardly a good argument to support your idea that an end fed 1/2 wave can have gain. [Sorry, but that is not my argument. The Vector design is NOT a simple ½λ antenna, but an ingenious ¾λ design which ACTS as an elevated ½λ with gain on the horizon. You have attempted a Straw-man argument.] The SGM is neither an end fed or a half wave. [Though we agree on this point, the SGM design is not in question.]




The available information on the Avanti patent clearly claims 1 db over a 5/8 wave and 30 years later Sirio's specification of 2 db over a dipole is within two tenths of a db difference. [Even a crappy end-fed ¾λ shows gain over a 5/8λ in the near field but the TOA is so high it provides loss, not gain, on the horizon.]



I'm really not sure what your motivation is but many of your ideas on this antenna are not accurate and do not help others to understand it's function. [So you believe you speak for what does or does not help all others reading this forum?
Your ideas are not accurate when compared to both the patent information written by it's engineers, and the Sirio website here which claim it is a coaxial J-pole]

While I don't usually mind sharing information about my products, I also have business interests to protect. [Interesting, I thought we were discussing the Sirio Vector 4000, not your "business interests".] Since I begin posting information about this design, my competition has both stolen the information I posted and attempted to clone my product.[This design has been around since the early '80s, I had one in the late '80s, a ¾λ like the Sirio] Sirio is having a similar problem with their models. At this point I will no longer be posting technical information of this nature online before it is branded with my company logo to prevent theft. [Is there something in the information I have offered, (information which you state is inaccurate BTW) which is so different from that within MANY long-going older posts on this forum and other forums regarding this design which for some reason now threatens your profit? Have you changed your story and now feel you're being cornered to reveal something other than the same information found in the many other posts you have made about this 30+ year old antenna design?

- Or is this merely your excuse as to why you won't post the entire Vector 4000 CST?
Hmmmm.

]

Another issue is that it has become clear you don't take my word on many of the things I've explained relating to this image.[Image? You mean the single image, or slice, in debate from the beginning of this discussion? I'm still awaiting your release of the entire Vector CST you seem to need to keep hidden.] Please explain to me what you hope to gain from seeing the complete file? [So now you interrogate before you share information shared with you, information which you state won't make a difference, though you've been asked to do so on several occasions and when you obviously must know that many others would also like to see it?

Will you also be interrogating each of them before you privately release it to only certain interested parties who 'qualify'? ] When you understand the image you will also understand you cannot learn a single thing more about how the antenna works seeing it at any other phase angle then 90 degrees.[Wonderful, then there's no reason not to share it with the rest of us, is there? - Unless...

] It just looks pretty.

Oh! - OK, I like "Pretty".

Is that sufficient reason yet?

 

[Shockwave]

[Ah, yes, so it does help performance, providing gain...]

There is a significant difference between actual antenna gain and the increase in performance associated with height and TOA.

[So, you put them together and instead of a simple end-fed ½λ, you have a ¾λ acting as a more efficiently fed elevated ½λ with a lower TOA providing gain on the horizon.]

Lets try and break this down in ways that are easy to understand. Completely forget about this idea of any single 1/2 wave radiator having any db gain whatsoever. This is completely impossible regardless of how you feed it. Unless of course the 1/4 wave underneath it contributes to the in phase radiation.

[Sorry, but that is not my argument. The Vector design is NOT a simple ½λ antenna, but an ingenious ¾λ design which ACTS as an elevated ½λ with gain on the horizon. You have attempted a Straw-man argument.]

Elevate the 1/2 wave and use any matching network you like the end result is still unity gain at best. Please show me any application that implies it's possible to have omni directional gain in any half wave radiator.

[Even a crappy end-fed ¾λ shows gain over a 5/8λ in the near field but the TOA is so high it provides loss, not gain, on the horizon.]

At least here you make some sense. However, you fail to understand the reasons behind the effect. Eight feet of elevation and the worlds best feeding system is never going to remove the approximate 45 degree lobe on a 3/4 wave ground plane or give a 1/2 wave gain. On the other hand, shielding that lower 1/4 wave of the main radiator does remove most of this lobe and improves field strength on the horizon. Radiation from the cone also constructively reinforces this. Now we have far field gain where it counts.

[So you believe you speak for what does or does not help all others reading this forum?
Your ideas are not accurate when compared to both the patent information written by it's engineers, and the Sirio website here which claim it is a coaxial J-pole]

I can certainly determine the difference between what is useful to understand this antenna and what Cebik referred to as the meaningless pages of nonsense that discussion of this non apparent colinear would generate. The Avanti team that built the first ones never once called it anything like a J-Pole. In an effort to name a nameless design it was Sirio that used the term "Coaxial J-Pole". I assure you the word coaxial makes a huge difference in the J-Pole.

[Interesting, I thought we were discussing the Sirio Vector 4000, not your "business interests".] [This design has been around since the early '80s, I had one in the late '80s, a ¾λ like the Sirio] [Is there something in the information I have offered, (information which you state is inaccurate BTW) which is so different from that within MANY long-going older posts on this forum and other forums regarding this design which for some reason now threatens your profit? Have you changed your story and now feel you're being cornered to reveal something other than the same information found in the many other posts you have made about this 30+ year old antenna design?

- Or is this merely your excuse as to why you won't post the entire Vector 4000 CST?
Hmmmm. ] [Image? You mean the single image, or slice, in debate from the beginning of this discussion? I'm still awaiting your release of the entire Vector CST you seem to need to keep hidden.] [So now you interrogate before you share information shared with you, information which you state won't make a difference, though you've been asked to do so on several occasions and when you obviously must know that many others would also like to see it?

Will you also be interrogating each of them before you privately release it to only certain interested parties who 'qualify'? ] [Wonderful, then there's no reason not to share it with the rest of us, is there? - Unless... ] It just looks pretty. Oh! - OK, I like "Pretty".

Is that sufficient reason yet?

For the most part I avoid discussing my credentials or business in this forum. It does take priority over the fun I have here sharing with others. I've spent over 15 years perfecting this design for Broadcast use. Learning from the brightest minds in this specific area. I don't make a dime of profit on any CB antenna and none of my customer base is here. I've logged over 1000 hours on the test range regardless of weather. Back in the day I use to weld each antenna together by hand. The results of this work and information produced is my property.

Before you could buy a Vector, I contacted the company with my specifications to arrange for them to mass produce the broadcast antenna exclusively for my company. Their expert staff was fully capable and more then willing to work with me. This provided me with access to information no one else has ever seen on this design. What did I do with it? I shared it with you guys before I even used it for it's intended marketing purpose.

What has it gotten me in return? Endless speculation from those who still can't think beyond the 1/2 wave J-Pole even when you prove the concept is false in the most tangible way possible. Tons of wasted time explaining it's concept of operation over and over. Technical data and my exact wording has been copied online and used to market other products. The few that truly understand antenna design here, expressed considerable appreciation for the one picture that was worth a million words.

You on the other hand claim I make excuses up for not sharing some hidden information with one who does not appreciate the material in the first place. Misleading others to think it's not shown at current maxima ("full bloom") or that some magic must be happening to allow the radials to reach current maxima at some other phase angle. It's been a long time since I played the game of "you must not have it or must be wrong if you don't show it". Please don't expect me to regress now.

 

[jazzsinger]

Before you could buy a Vector, I contacted the company with my specifications to arrange for them to mass produce the broadcast antenna exclusively for my company. Their expert staff was fully capable and more then willing to work with me. This provided me with access to information no one else has ever seen on this design. What did I do with it? I shared it with you guys before I even used it for it's intended marketing purpose.

For that alone i salute you Donald, very few businessmen would be willing to share information of that nature for the obvious reason it can be easily ripped off and plagerised by the unscrupulous, but never ever think some of us don't appreciate the expertise you and those in manufacturing you do personal business with have offered us, no other manufacturer that i know of has ever gave the hobbyist such insight into such technically hard to understand material as you and lorenzo have recently provided.

in a cut throat business world sharing information like this is very very rare.
i disagree with sirio on the "j pole" discription, but as you correctly say the word coaxial preceeding it makes one hell of a difference, as the word coaxial basically describes what the basket is, if i'm not mistaken the basket around the radiator imitates the way coaxial cable works,ideally cancellation on the inside, but cleverly manipulating a kind of cmc effect radiation (albeit not exactly the same) on the outside of the basket to add to the farfield gain.

in much the same way as common mode current on a coaxial cable CAN be beneficial to certain antenna designs whilst at the same time being very destructive to other designs.


keep it coming as i just love to read your posts,

 

[bob85]

im waiting for the 1/2wave endfed j-pole camp to post ANYTHING that makes sense,

lets look at some of the things they have claimed over the years of posting nonesense without ever showing us where this info came from,

1/2wave endfed
radials that restrict radiation to make it act like a 5/8wave
radials that solve the problem of feeding a high end impedance 1/2wave
lossy gamma feed
sigmas are difficult to tune for a low vswr compared to the i10k
raising a sigma higher causes the vswr to go through the roof
sigma4's are weak antennas that need drilling and bolting together
the sigma works like a slot antenna
aperture is a slot or opening not related to antennas,

Effective Aperture


where are the links to anything factual,
a book to go look at, an alternative method of operation??

i am keen to learn IF what is been claimed can be shown to be true or even possible from a respected source,

speculation and personal none factual ideas mean absolutely nothing

jazz,
antennas such as the sigma do have two current modes,
some call them transmissionline mode and antenna mode ( arrl ) while others call them transmissionline and common mode.

 

[Shockwave]

Thank you Jazz. For certain there is more then one key function in the tapered coaxial basket. It's not 8 feet of elevation or magically increasing efficiency to some point beyond 100%. It is part transmission line, part radiator, part shield, tapered with a changing velocity factor and impedance. Sure are a lot of things to juggle in an attempt to reach maximum gain.

I also agree that this basket cleverly manipulates the use of CMC to produce it's second point of in phase, correctly polarized radiation. It is also important that this basket maintain it's electrical 1/4 wavelength properties to effectively radiate this energy without causing undesired coax radiation.

 

[ericcson]

ham international big mac 7/8ths picture in the flesh.

 

[MrSuburban]