The Skeleton Sleeve Fed Monopole

[Marconi]

Here is the link to one of the references used by Bob and Shockwave to help us try and understand the Sigma4 design. The currents appear to me to be just as Bob tells us, but again I see primarily cancellation in the base with a very small advantage difference in currents of .05291 Amp on the radials which show to be in phase with the top 1/2 wave.

http://k6mhe.com/files/ssfm.pdf

Here is an Eznec model of that project at 146 mhz. I show the model with currents turned on and without. I also show an image of the base plate assembly for the model and dimensions are noted, and the tabular currents log with notes.

The article does not discuss gain or angle in the pattern images, so I did not include this information with my model either. However my pattern is almost identical to those presented in free space and over real Earth.

Note that Eznec does not indicate a good match however and the resonance for the model as dimensioned is closer to 139 mhz. The factors do not agree with the author's words and I can't explain that.

View attachment The Skeleton Sleeve Fed Monopole.pdf

In my opinion Eznec does present problems at times, but this model seems to support just what Bob is suggesting. However, I see only a very small magnitude of current possibly flowing from the bottom radials section that is in phase with the top part when the radiator to radials ratio is set to 3.03 to 1.

In the current log I compared the first segments for the radiator and the sum of the first segments for the radials only...to find the difference in currents flowing of .05291 Amp from the base area.

 

[Marconi]

Here is how An-SOF shows the gain and gain dbi pattern for the Skeleton Sleeve at 146 mhz.

View attachment An-SOF Skeleton antenna..pdf

Producing images using this product is not easy. I wanted to see how clear they show up after all the maneuvering to get them printed and scanned.

 

[bob85]

the arrl open sleeve antenna eddie,
the article shows the pattern and gain over a perfect groundplane and mentions that the measured impedance of the monopole was high probably because of a very poor groundplane under the antenna,
i presume you would only see the claimed gain over a perfect groundplane, take your pic,

the ansoft image looks pretty but i don't know what im looking at,

can you answer my question eddie ?

why does feedpoint impedance drop and current increase when the sleeve elements are brought closer to the monopole ?,
what is changing ?

 

[Marconi]

Bob, I sent you this link of an old thread that is very short with only two posts, and I made both of the post. It is entitled: "The Skeleton Sleeve Fed Monopole." No body ever responded to this thread, but I did do the model and posted my results back in 2013.

You missed at least two links I wanted you to look at that I posted in my post #1. You will have to check the text close to see these two links above, because they don't stand out for us like the old forum use to do.

I did not do a model on this ARRL article, because there are no dimensions to be noted. I didn't want to waste my time doing a model, get it wrong, and you tell me I got it wrong.

The Open Sleeve model I have on file is a sample model that Roy provided with his Eznec software.

Then, instead of you going back to the actual thread to respond, you replied in this old thread without realizing it.

Bob, this confusion is not about you. The problem has to do with this new forum look, and the way it shows things. So, things can get confusing at times for folks that use these features. I often spend wasted time just trying to find my cursor and that is not right, and you will note that I now try to highlight all of the links I post that are imbeded in the text.

I pity anybody trying to follow this thread. This thing is not user friendly.

I've already posted about such stuff in the Help Area.

 

[bob85]

i did see this post yesterday eddie, it does not answer my question,

if you use eznec you should be able to explain what is going on when the sleeve spacing is reduced ,

the article tells us the antenna is easy to model in eznec,
it gives dimensions for a 1/2wave monopole with 1/4wave sleeve,
the spacings and tube diameters and aproximate impedance & resonant frequency with 8" and 6" spacing.

its not about you getting it wrong eddie, i don't know enough about eznec to know if you got it right or not but theres no harm in seeing if you get the results they claim over a perfect groundplane.

 

[Marconi]

Bob, I'll read the Open Sleeve article again, and refresh my memory.

I don't think, just because I can use Eznec that I should automatically understand and be able to answer your questions on the details of the article, I don't remember much about the article.

Bob, are you suggesting that the author of the article used Eznec to prove some principals that you believe are true, and that might give us some explanation for how the S4 design works...while in another breath you would likely claim Eznec is fraught with limitations and errors, can't produce good results on the S4 design, and that the Vector is no J-Pole?

This sounds like a trick question Bob, but I'll try and play the game.

I do remember when trying to make a point some time back on an issue in the article. That is why I posted the link noted above. At that time I found that the antenna length of your Hybrid Vector >30'...looked to be too long. I based this idea on 3 conditions I noted at the end of the article. So, I posted that maybe your antenna was beyond those length limitations in the article, but I don't remember all the details. So, give me a little time to refresh my recollections and I get back.

I just turned 76, and sometimes I don't remember details too well, so I'll have to go back and check that article closer.

 

[bob85]

yes read the article again eddie,

im not saying anything about eznec other than the article says the open sleeve antenna is easy to model,
cebik said the vector would be very difficult to model in eznec,

my hybrid was the correct length for its surroundings eddie,

 

[Marconi]

yes read the article again eddie,

im not saying anything about eznec other than the article says the open sleeve antenna is easy to model,
cebik said the vector would be very difficult to model in eznec,

my hybrid was the correct length for its surroundings eddie,

I understand Bob, and I've been tweaking my S4 model every time I think I've learned something new about modeling.

I just recently found that the radials were not symmetrical between the base radial mount and the top hoop. I fixed that, but it made little to no difference to the performance factors. It did make some difference to the currents distribution however. That said, the difference was minor.

When I did that analysis based on the 3 limitation considerations at the end of the Open Sleeve article and posted the results you shot down...I did not consider wire diameter at all in the mix.

As I recall, the article did not consider element diameter either, or I would have taken that into consideration. Back then I could have also been using tapper in my Eznec models, and it could have been raining that day too.

It is a shame we didn't get together and talk when that post was fresh in our minds. Like I said, nobody responded to that thread, and I have lost memory of what I was doing, and I'm not going back trying to rehash what I saw. If I understood the ideas presented in the Open Sleeve article better, maybe I would.

Bob, I do not deny what you reported. I think you recounted what you saw.

If you guys read the first post in this old thread you will see I'm saying the same then as now.

 

[Marconi]

i did see this post yesterday eddie, it does not answer my question,

if you use eznec you should be able to explain what is going on when the sleeve spacing is reduced ,

the article tells us the antenna is easy to model in eznec,
it gives dimensions for a 1/2wave monopole with 1/4wave sleeve,
the spacings and tube diameters and approximate impedance & resonant frequency with 8" and 6" spacing.

its not about you getting it wrong eddie, i don't know enough about eznec to know if you got it right or not but theres no harm in seeing if you get the results they claim over a perfect groundplane.

Bob, sorry to be dragging my feet, but this recent conversation has gotten complicated for me to follow. The nature of having out of control diabetes, and all of the $2000/mo drugs...takes away my working hours for some of my days.

This article "The Open-Sleeve Antenna" is complicated by addressing several frequencies. I did miss some of the dimensions, because after a while wondering around the article I began to concentrate only on the last section starting with "Current Distribution," and ending with "Radiation Pattern and Gain." This is when I wrote my post to you about the three ratio considerations noted at the end. I've read it again and I'm sure I probably missed some points in my conclusions back then.

I note this OSA article does claim that a 3:1 ratio does produce a 3 db gain more than a 1/4 wave. But, if we think about this claim it is no more that the standard idea that a 5/8 wave has approximately 3 db gain over a 1/4 wave...and we all should know that idea is debatable. See the article by Donald K. Reynolds, "5/8 Wave Mystique," if you can still find it free on the Internet.

I'll post the gain part of the article below as an attachment, but you may not believe this graph either.

The big difference to be noted here is, the claim that a 5/8 wave is 3db gain over a 1/4 wave only happens over a perfect ground plane...an important point in the theory that everyone seems to ignore.

Bob, I didn't get to the rest of your remarks, but maybe later. I'm still trying to refresh my understanding of "The Open-Sleeve Antenna" article. I hope I'm not repeating myself here.

 

[bob85]

i agree we dont see the claimed gain of a 5/8wave over real earth eddie,
me and donald see better performance than the 3/4wave version in our tests.

 

[Marconi]

i agree we dont see the claimed gain of a 5/8wave over real earth eddie,
me and donald see better performance than the 3/4wave version in our tests.

Bob, I only posted the 5/8 wave idea into the mix, because the reference (The 5/8 Wave Antenna Mystique, by Donald K. Reynolds K7DBA), only compares 1/4, 1/2, 5/8 wavelength antennas.

It would seem plausible to me that Reynold's may have at least updated the idea for a 3/4 wave antenna like the Avanti S4 idea, but he didn't. Maybe the S4-3/4 wavelength idea was not so spectacular in the Amateur world of radio. The fact is...that nobody has ever updated this old standard chart for antenna gain that I know of, to add the 3/4 wave S4 design or the Skeleton Sleeve Antenna. I wonder why that is, since in the old days they probably only found that the .625 wavelength was the maximum possible length for low angle radiation, just like we have all heard for years.

Recall that Richardson wrote in his article on "The Skeleton Sleeve Fed Monopole" that the mount lowered the Q, and thus made the SWR to show to be perfect, but the performance sucked. I wondered why a guy claiming to understand all of this business of antennas he talks about in his published article...did not question buying a cheap mount in the first place. Plus he did not even bother to suggest a fix for the problem, and that is strange too me.

I'm not too sure the Q problem has that much to do with the mount I see in the picture...but the problem may be more to do with the antenna design itself.

It is strange that you and other's seem to see this better gain performance in the CST image of Sirio's New Vector 4K too, saying the S4 will not produce such gains, and then you use the CST image to show us an example of added performance, all while the NV4K is a bit shorter than my S4. I don't get the rational.

I will state that the small difference that I see in my Eznec models for both the S4, and the NV4K, favors the S4 in gain a little, but the pattern on the NV4K with longer radials, shows a bit better looking pattern. I don't see as much high angle RF in the NV4K.

I really don't know if this difference has to do with the increased length of the radials on the NV4K, or the fact that the S4 has only three radials. If the Average Gain indicator is truly any indication of the accuracy of the Eznec models...both of my models report an AG=1.00, as good as it gets.

Can you tell me how you can see such added gain results in the CST image, and it is nothing but a 3/4 wave antenna like my S4?

Earlier, I posted a picture of a CST FS pattern and noted how that image also shows details, including the FS gain, but Donald's image of the NV4K does not show this important data field. Would that information have been of help to our better understanding, and possibly showing us the 2 db gain over a FS dipole that is claimed.

When I questioned Sirio about this issue, they did not even bother to respond.

 

[bob85]

theres a lot you don't get eddie,
why would reynolds update that article?

i can't see any extra gain in the cst animation eddie, i cant see any gain at all, can you ?
the cst animation does not look like the nv4k to me eddie,
looks more like the old vector, longer than your sigma4,

yes the full cst info would have been very nice, and some info on how the model was constructed,
we could have spent houres studying the images and argued about them for years eddie,

since when did saying i get better results with the 4 radial vector mean the sigma is no good,
i said your tests were no good eddie, i told you that again a couple of days back.

 

[Marconi]

theres a lot you don't get eddie,
why would reynolds update that article?

i can't see any extra gain in the cst animation eddie, i cant see any gain at all, can you ?
the cst animation does not look like the nv4k to me eddie,
looks more like the old vector, longer than your sigma4,

yes the full cst info would have been very nice, and some info on how the model was constructed,
we could have spent houres studying the images and argued about them for years eddie,

since when did saying i get better results with the 4 radial vector mean the sigma is no good,
i said your tests were no good eddie, i told you that again a couple of days back.

Bob, it is true there is a lot I don't get. I apologize if it is a thorn in your side, because I don't agree with you on this matter. I have my opinions too.

You have to ask, why would Reynolds' update the article? You must have missed my comments as to why I might consider it appropriate, after all these years since Ballentine did his definitive work, to bring up a new discovery...if this S4 design had any merit. The answer you seek is right there in my words, and I didn't stutter.

Some swear that the .64 wave is the highest gain monopole too, but the standard maker's in this business apparently don't support this idea either.

No Bob, the only gain figures Sirio posts for the NV4K are in the advertising of their specs. Could this possibly be a reason not to show the gain values on the pattern, because it does not match their claims? Just look at some of the other antenna images on the Sirio site, and you will see that same data block like I posted earlier of another CST model of a dipole. Was it conveniently left out in Donald's image so we would not see and know the truth?

In most cases Sirio looks to have selected this little side-show of the scanning phase counter at the bottom instead of the antenna gain value. They know most guys will get their jollies looking at an animation...rather than the important details about a model. IMO this is possibly the same reason that Donald will not send me one of his Eznec models where he claims shows that Eznec is not worthy to consider using.

Well it's a shame the CST' model doesn't look like the Vector we know. My Vector model looks just like the Vector, yet you put your faith in some model that doesn't even look to you like the antenna we all recognize. Again I don't get the rational, and me being somewhat sceptical...I will question what I see. Am I wrong?

Take a closer look at the .625 model below and you will see, it too does not look like the antenna. The animation make the base of the antenna look to balloon up into a full 1/4 wave pattern, and I don't get that either.
http://www.gain-master.it/vsconventional.php

In the link below, look close at the image of the GM behind the pattern. You will see the antenna set cock-eyed to the top of a mast? Is it photo-shopped in this CST model? You may have to open the free space image of the GM to the right of the screen to see a GM pattern with a picture of the GM attached to a mast.
http://www.gain-master.it/technologies.php

Have you ever considered that Sirio only shows us what they want? Companies seem to have that privilege in this world and it seems to have no rules. Just like what Solarcon tells us regarding their A99? I know there is a doubt in your mind on that claim of >9db gain. Regardless of your minds idea of the truth here...this image from Donald was revealed to us all, and it was claimed to be the Sirio's NV4K, but otherwise we don't know for sure, because even the antenna name is missing. You can see some of the antenna however, and it could be said to be close if you use your imagination.

So Bob, you see an old long Vector in that image that Donald posted? Do you also see the dimensions that tell you it is an old Vector about 30' feet tall? How convenient that is what you see. Is that also what convinces you this model is the real thing...that shows us exactly what is going on with the Vector design?

I disagree, this model is exactly why...we have never really been able to definitively come to any common decision for how the S4 design might work. It just confuses the issue, and the image is useless for any real information. The ideas and articles that you have presented over the years have more meaning to me...even if I don't fully understand everything like you do.

You never said to me the S4 was no good, because it only had 3 radials. I don't think I ever suggested you said that either. I agree my testing was less than professional.

Well just have to agree that we disagree.

 

[bob85]

you are going off into one of your long boring posts again eddie.

 

[Marconi]

Yep, it pleases me when I'm feeling up to saying what I think.