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SIGMA IV Details

kt4ye

Member
Aug 18, 2012
27
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Matthews, NC
I'm interested in this antenna. But all the online documentation that I can find just shows pictures or photos of the assembled device or various bits and pieces.

Can someone please direct me to a sketch or diagram that shows how this antenna is connected? I don't need/want dimensions (though it might be useful if I model it in EZNEC) but for now, all I want is to understand what is connected to what.

Thanks!
 

I'm interested in this antenna. But all the online documentation that I can find just shows pictures or photos of the assembled device or various bits and pieces.

Can someone please direct me to a sketch or diagram that shows how this antenna is connected? I don't need/want dimensions (though it might be useful if I model it in EZNEC) but for now, all I want is to understand what is connected to what.

Thanks!

Kt4ye, let me know if you have Eznec 5 or greater. The Demo version will not handle my model...set to the physical specifications.

PM me your email address, and I'll send you the Eznec file. I think you can get all the info you need for the model I have.

View attachment Sigma4 in and out of phase..pdf
 
I'm interested in this antenna. But all the online documentation that I can find just shows pictures or photos of the assembled device or various bits and pieces.

Can someone please direct me to a sketch or diagram that shows how this antenna is connected? I don't need/want dimensions (though it might be useful if I model it in EZNEC) but for now, all I want is to understand what is connected to what.

Thanks!

heres some of the 3 element basket sigma 4

DSC07270.jpg


DSC07267.jpg


DSC07268.jpg


simple SS nuts and bolts . i like #8 hardware better .

everything is connected together physically (basket loop/basket elements and vertical) but is shows as open circuit at the coax connector because of the insulator in the gamma .
 
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Sigma IV

THANK YOU! I followed the links and also admired the nicely made look-alike! Also, Marconi kindly shared his EZNEC model. And THAT sparked an interesting (to us) off-list exchange.

His model *appears" to be properly done. (I've made quite a few EZNEC models so have a bit of experience with this program.)

However, EZNEC has a feature called "average gain." This allows a modeler to do a "sanity check" on the overall validity of the model. A "perfect" model will "score" an average gain of 1.0 = 0dB. Small variations are usually OK and provide the modeler with an adjustment factor.

But Marconi's model had a fairly high figure. So... (like the "smarty pants" that I am) I "fixed" his model by moving the feed point about a foot. The average gain with my adjustment was now 0.995 (a good thing) BUT the entire shape of the radiation pattern -- as modeled -- changed DRAMATICALLY.

I've never seen that happen before and we are both very puzzled. (At least, I am, and I'm puzzled enough for at least two people!)

Brilliant ideas welcomed!:confused:
 
THANK YOU! I followed the links and also admired the nicely made look-alike! Also, Marconi kindly shared his EZNEC model. And THAT sparked an interesting (to us) off-list exchange.

His model *appears" to be properly done. (I've made quite a few EZNEC models so have a bit of experience with this program.)

However, EZNEC has a feature called "average gain." This allows a modeler to do a "sanity check" on the overall validity of the model. A "perfect" model will "score" an average gain of 1.0 = 0dB. Small variations are usually OK and provide the modeler with an adjustment factor.

But Marconi's model had a fairly high figure. So... (like the "smarty pants" that I am) I "fixed" his model by moving the feed point about a foot. The average gain with my adjustment was now 0.995 (a good thing) BUT the entire shape of the radiation pattern -- as modeled -- changed DRAMATICALLY.

I've never seen that happen before and we are both very puzzled. (At least, I am, and I'm puzzled enough for at least two people!)

Brilliant ideas welcomed!:confused:

Hey Bill, can you reset the S4 model back to "default" and run an Eznec+ Far Field Plot, and email or post the pattern results. I would like to see if they're different than my Eznec model shows...compared to your Eznec+ program.

I still have a question why we see a pattern difference after we set both our models to the same settings moving the source down to the bottom of the antenna mount instead of up about 33" high on the radiator above the hub.

Then if you would, set the "default" model up to read AG, and tell me what values you get for AG using your Eznec+ vs. my Eznec for the antenna just as I sent it to you without any changes? I would like to see your results using Eznec+ in case it changes compared to my results with the AG too, OK?

Maybe I didn't tell you that this S4 model, "Sigma4 Per Manual," was setup as close as I could get the dimensions for my Antenna Specialists version of the Sigma 4. I did not tweak anything from the specs, trying to improve gain, angle, match, resonance, or Average Gain. The model, is what it is.
 
you may find this interesting too .

FMBroadcastAntenna.com | FM Broadcast Antenna's

Dominator NWE-34 radiation currents displayed in CST model.

Dominator_NWE-34_CST_S.jpg

Hey Booty or anybody else, how would you describe what we are seeing in this image?

Thank goodness we're off that page that BM messed up with his multi-meg images. Hey BM, can't you figure out how to edit your images so we don't have to use the elevators to read the pages that have to wrap around your images.

Isn't this big enough.

Booty Monster's V4000.jpg
 
"Hey Booty or anybody else, how would you describe what we are seeing in this image?"

FWICT it's " ...... CST Microwave Studio is an exceptionally accurate software tool that provides 3D Electro-Magnetic simulation of antennas. The image displays both the magnitude and phase of all radiation currents along the antenna at a driven phase angle that produces maximum current. Clicking on the image above will open a GIF video that shows the currents at all driven phase angles throughout the 360 degree RF sinewave.

Magnitude is displayed with color intensity and referenced to the chart on the right. This chart shows the magnitude in amps per meter for the corresponding colors. Phase is also indicated by opposing colors at the positive top and negative bottom of the chart. The Dominator has obvious characteristics not typically found in antennas other then collinear types. It has 3 separate radiation currents with two allowed to radiate freely in a phase that is constructively combined in the far field. The third current is in a deconstructive phase with respect to the other two and has been confined within the tapered coaxial skeleton cone.

It is the tapered 1/4 wave coaxial cone that sets this antenna apart from others. It allows the longer top section of the main radiator to radiate freely while the deconstructively phased radiation on the lower 1/4 wave of the main radiator is confined within the cone. Since the base of the cone and the base of the main radiator are excited by opposite phase polarities, the currents allowed to radiate on the outside of the shielding cone combine constructively with the longer main radiator extending above the cone. Total currents radiated by the cone are divided into its four vertically tapered radials. This provides noticeable gain over a dipole on the distant horizon. ...... "


Dominator%20NWE-34%20in%20CST.gif


"Thank goodness we're off that page that BM messed up with his multi-meg images. Hey BM, can't you figure out how to edit your images so we don't have to use the elevators to read the pages that have to wrap around your images.

Isn't this big enough."

i just posted the url to the photo icon . its not wider than my monitor and scrolling down a page is necessary for almost every thread . didn't mean to cause you problems .
 
Well Booty as usual, you missed my point about the image being too big, and it is a lame excuse to say that we all use the elevator to scroll down the page, while I'm complaining about having to also scroll across the page.

You obviously don't have an opinion on what you see in the image, you have to post a response from someone else. Boy?

I'm just trying to get an idea from someone else on this forum what this graphic shows us.

You also don't realize that some of us don't have a 3' wide monitors too. You are the only one I know that does this frequently. It use to really be bad when you added such images to your signature and that was a real nuisance. You mean well BM, but that's all I can call it.

I have to scroll up and down and that's fine. I just prefer not to have to scroll across the page too.

Did you see the image I left instead of the one you posted? Was it big enough on your end?

Hey Shockwave, do your have a tabular currents list for this antenna that you could share with me. I see what I see, but I believe the data would be of more meaning to me. my email is: edromans@comcast.net
 
jesus frickin christ , if you have nothing better to complain about than the size of a pic you have a wonderful life .

"Hey Booty or anybody else, how would you describe what we are seeing in this image?"


i certainly don't understand all of it , but you asked a question , i just posted the information given with the image telling what it is . hopefully shockwave will see this post and make a personalized answer just for you since you don't like the one from the link that tells what the pic is showing . forgive me for not thinking you would rather have a answer with my guesstimate of what is going on rather than the answer given by the article .

what do you think is going on marconi ?


Newegg.com - Monitors, LCD Monitors, LED Monitors
 
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I'll pipe up.
This graphic is what it is.
As with anything posted on the www, this one has to be taken in trust.
What the explanation BM posted says, and what has been said about it in other places is all we have, and so we can neither prove nor disprove the validity of any claims regarding it.
It is the same with any kind of information, modeling or otherwise. It is the integrity of the persons posting that has to be considered. Lacking that, there is nothing more that can be considered.
I know a simple graphics program that can be used to produce animated gifs could duplicate this image.
What I think it is has already been said. How that is achieved by the program that produced the image I have no idea. But it is cool.
 
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jesus frickin christ , if you have nothing better to complain about than the size of a pic you have a wonderful life .

"Hey Booty or anybody else, how would you describe what we are seeing in this image?"


i certainly don't understand all of it , but you asked a question , i just posted the information given with the image telling what it is . hopefully shockwave will see this post and make a personalized answer just for you since you don't like the one from the link that tells what the pic is showing . forgive me for not thinking you would rather have a answer with my guesstimate of what is going on rather than the answer given by the article .

what do you think is going on marconi ?


Newegg.com - Monitors, LCD Monitors, LED Monitors

BM, what we are looking at may be right on the mark accurate, I don't know for sure. This is why I asked Shockwave if he could provide the real current and phase data that supports this graphic.

My new model of the New Vector 4000, does not indicate that the currents in the bottom radial cage are in-phase between the radiator and the radials, as others have suggested, or as I have suggested, saying earlier that everything on this antenna is in phase and thus is radiating. According to my Vector model, I was wrong.

As a result I have change my mind and I see cancellation in the area of the bottom of this antenna. I missed this in my Sigma4 model I made earlier, because the Vector, with its longer radials, shows to be far more effective in its work, and if asked I can demonstrate that too.

The radials are all noted to be in a + phase condition with each other, and their magnitudes are about equal, so they radiate as antenna currents. However, the portion of the radiator inside the radials shows a - phase condition, with an equal magnitude to the combined magnitude for the radials...so we see cancellation due to the phase difference.

The data follows and indicates how I made the comparisons: I summed the magnitudes of currents for the 1st segment in each radial. They are in a + phased condition, and when their currents are combined they = 1.0217 Amps.

The I did the same with the 1st segment of the currents in the radiator, which is in a - phase condition = 1.1326 Amps.

These five parallel elements show us magnitudes that are all about equal...which fits one aspect for the rule on radiating currents. However, when we consider the phase, we find there is a difference, and this fits the rule for cancellation. Thus there is little to no effective RF generated.

That said, there may be a little RF generated however, due to the very small difference in magnitudes, and we would refer to that as common mode currents.

All I have as evidence is my model. It is available for display, and is more descriptive for what I see than the graphic model that Shockwave produced.

I will post the tabular currents log and make some notes explaining things as I see them...depicting further what is going on in my model and in the bottom of the Vector.

Again, I have requested Shockwave to consider to show me a similar data set from the software he used to produce his graphic.

Now, since Shockwave has already declared that Eznec cannot model the Sigma4 design, without indicating an off-the-wall maximum high angle pattern, then all I have to counter that is...does my model display what SW suggested will happen when we try to use Eznec to model the Vector.

IMO, this model does not indicate what Shockwave claims, that Eznec will show a very high angle for the maximum signal at about 43* degrees which is undesirable for CB work. He further claims that this is due to the fact that Eznec cannot model the radials at sharp angles to the radiator, because Eznec does not recognize the radials in that position, while other's claim that Eznec limitations will not allow for radials that are close together. Don't you see the radials are close together on this model, and don't you see the model is working? If an Eznec model does not work due to its critical limitations the program will stop and produce a warning pop-up message, and you cannot proceed until the issue is resolved. I have a work around for this close radial condition in the Vector model, and I will share the info.

That said, how do we answer this question without further information, which I'm willing to produce for us to consider. Plus I add the question, why don't we see my model showing a very high angle of radiation in the 43* degree area of the pattern...instead of what we see with this model?

Booty Monster, here we are dealing with the rules that apply to radiating elements, or conversely with the rule for non-radiating elements that are due to cancellation. I am referencing antenna mode, transmissionline mode, and common mode currents to be sure.

Since the question I've asked, regarding what Shockwave's image is showing us, appears to be too difficult for anyone to speculate on, maybe we could have a discussion on what the definition for the rules on radiating elements as noted above.

Thus we see magnitudes that are about equal, but phase is different. Thus we see cancellation. If Shockwave can show me his current data, and it shows to be to the contrary to the Eznec currents, then I will concede that the Sirio antenna software shows the correct data, and without doubt the Sigma4/Vector works just as he and others state.

I will post the model and the currents log soon.

View attachment New Vector 4000 model..pdf

Bill, also note that this model shows very little currents on the mast in the tabular currents list and the red indicator on the antenna view as well. Shouldn't have any common mode currents problems with this model at 36' high to the hub and feed point.
 
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Marconi,
I looked at the pdf. I get lost in all the rows of data, so I probably miss a lot.
What I notice in your post is that you refer to the cancellation of the cone against the vertical radiator, but make no mention of the in phase currents on the outside of the cone we have all discussed before.

If those currents are not revealed by the Eznec model, then it could be true that Eznec fails to model all the activity going on with the Sigma/Vector antennas. The animated model supplied by SW shows the cancelling currents inside the cone, but also shows a radiating in phase current on the outside of the cone.
I see why you'd like to know whether there is any further data to go along with the graphical model he has provided, but again, I'm not so sure Sirio gave him more than the graphic we've been looking at.

There seems to be evidence in your model to support the in phase radiation of the cone and the vertical on the V4k. Your model shows an 8° cursor elevation, and no outstanding lobe at 43° as you pointed out. We all know that a 3/4ƛ antenna will have a predominant lobe at a very high degree of angle, so something is bringing the TOA down toward the horizon and reducing the typical high angle TOA of the 3/4ƛ antenna in your model. I think it is owed to the work of the in phase radiation of the outside of the cone at best, or of the ability of the cone to shield and cancel the the negative effect of the lowest 1/4ƛ of this antenna. Then there id=s the question of whether, and why, the antenna shows more gain on the horizon. Might this not be because of the booster effect the in phase radiating of the cone?

This kind of puts me in mind of how NASA used the gravitational force of both the Earth and the Moon to get the spacecraft to travel to the moon and back. Without the calculated use of these gravitational bodies there would have been no way to power the craft that distance. Maybe the lower radiation helps to slingshot the RF toward the horizon . . ? Oh, well, not likely. But it does seem to help pull it downward toward the horizon.

Perhaps more could be learned by modeling other wavelength antennas with an without a cone shaped set of radials, as well as producing a model of the 3/4ƛ antenna with a typical set of radials and a variety of angles upward and look closely at the data Eznec supplies.

Just thinking out loud . . .
 
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