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VORTEX Q82 mk2

When it comes to the tapering discussion above. I know how to use it with 4nec2, but I really don't. The results when it comes to gain and SWR bandwidth will be somewhere in between the two diameters depending on where the current peak happens on said wire. In most cases the two diameters in question produce results that are very close to each other to begin with.

You can also use tapering to actually vary the length of segments along a wire as well, essentially more segments on one side and less on the other side of a given wire. While I can see the potential in this, I don't need it as I use enough segments in general to account for this to begin with. If I had a segment limit I would likely use this feature.

The DB

DB, I didn't know that about taper, but its nice to understand the real nitty-gritty.

I started out using taper trying to make my simple CB antenna models more like the real antennas, but that was before I learned that Eznec5 did not handle taper very well.

I'm glad Henry used a better versions of Eznec...since he set taper in his model of the Maco M103C. This way we all can see the difference in results it makes. DB I want to be clear, that was my only reason for making the comparison that I posted above.

Now that I don't use taper anymore...I do it for pure convenience and understanding is not required. So you guys don't worry about not seeing taper used in the models you might see on the Internet...if you're lucky enough to run across one, now and then, that uses taper.

When my model of the Maco 103C shows the same results that Henry got for his Maco 103C using taper, I figure that's about all I needed to know about taper working with simple CB antennas. BTW. Henry used 99 segments and I used 76, so I'm well within my 500 segment limit.

I don't use taper with few exceptions, and I hope I made it clear.
 
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Eddie,
i will take the 8.9db version, when will mine be ready ?

If its that easy to fake models what do we look for to check the model has been done correctly,
if there's no indicator its been fudged people can claim anything they like.
 
Eddie,
i will take the 8.9db version, when will mine be ready ?

If its that easy to fake models what do we look for to check the model has been done correctly,
if there's no indicator its been fudged people can claim anything they like.

Bob I'm working on a J-Pole model right now.

I don't know Bob. I reported what I saw that looked questionable earlier that got my attention...but no body responded, so I did not elaborate further. I just kept on trying to get the model to show better results, but it was no-way-no. Ask yourself..."...self what is my opinion on the words, about performance, from folks that manufacture, promote, and sell the CB antennas?"
 
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DB
i think the article was W4RNL "some j-poles that i have known"
for some reason i can't post a link

Bob, I have a hard copy, but it will take some big money to shoot you a copy...it might be copyright protected.
 
it likely is copyright protected Eddie, i think the folk that took over the website said as much when they started charging for access,
many of the articles are available online.
 
Bob, I got and email notice from WWDX and it showed "embedded media." There was nothing on the thread but it was from you.
 
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If its that easy to fake models what do we look for to check the model has been done correctly,
if there's no indicator its been fudged people can claim anything they like.

Here is an example of an accurate model, and two manipulated counterparts. One has an AGT of 1 which is accurate (green line below). An AGT of 2 which is far outside of being accurate (red line). The software is also telling me for the AGT 2 output that it is over reporting gain by 3.01 dB, and in this case that number appears to be dead on. Also, I created a model with an AGT of 3, (blue line) which is even further outside of being accurate. The software is telling me that it is over reporting gain by 4.77 dB, and if you look below you will see it has 4.77 dB of gain over the accurate model. I can go on here and further skew the results, but I think this is far enough to show what I, and Marconi are talking about when it comes to AGT and manipulating models to show whatever I want it to show.

model.jpg


I want to point out that I made only one change between these models, and that is a trick that ghz24 taught me to control AGT. Like I stated above it is easy to show whatever gain result I want to show. The elements and such are the same length, and except for one 2 inch segment, are all the same diameter as well. Seriously, changing only the diameter of a 2 inch length portion of the antenna model was able to cause this much of a change in the output of the model, and I didn't even push it to its limit.

So how can you, the person sitting at home in front of a computer screen, tell how accurate a model is? Unfortunately, just by looking at the model you really can't. The only thing you have to rely on is the saying "if it looks to good to be true it probably is". If it is on a forum like this one, ask the modeler questions. For example, don't be afraid to ask what the AGT of a model is, that in and of itself should tell you if the software considers the model accurate. If the modeler doesn't know what AGT is they are either inexperienced, or they don't care to check, or they know and are hiding it from you. I'll have to dig up the numbers for what the range that is considered accurate is, unless Marconi knows off the top of his head. With my models you can assume that they all have an AGT of 1, which is perfect accuracy, unless I tell you otherwise and that is something I will tell you when I post such a model (I've only had one model since I started using this method that I couldn't get the AGT to 1). Marconi's models aren't always 1, but I am pretty sure he keeps them in the accurate range that I mentioned above, so his models should be reliable.

AGT isn't the be all and end all to this. Ground types can also affect reported gain, although it is pretty easy to tell if they pushed a model to its extreme by using "perfect ground" as for those models, for the most part, peak gain is at the 90 degree mark (or 0 or 1 degree radiation angle) or very close to it. Modeling the antenna at excessive heights will also show a higher gain and a lower angle of radiation, although if you have some experience, those are fairly easy to pick out as every half wavelength of height to the antennas current node adds another lobe to the radiation pattern, so as we can see with the models I posted above, with the second lobe formed we are about 1/2 wavelength in height to said current node, which is 1/4 wavelength below the antennas tip.

Aside from that, ask to have someone you trust model the antenna for you and compare, or even sometimes just look at the model and get a second opinion. After playing with literally hundreds of models in all types of conditions, I will generally be able to pick out more from a given model than someone who hasn't done the same.

I wish I had more to tell you, and I wish their was an easy way, but in some cases their really isn't...

DB
i think the article was W4RNL "some j-poles that i have known"
for some reason i can't post a link

I've read that article before.


The DB
 
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Regarding my Maco 103C post with taper included and without. I didn't intend to step on anyone's toes, due to my curiosity and wanting to see if taper made an obvious difference.

There are claims out there that tell us using taper in the version of Eznec that I use...does not work well. I repeat, when I found out about this I just stopped using taper, and I never tested the idea to see such ill-effects if any.

My words here are not intended to claim that the use of taper doesn't matter, but to try and be more informative on the issue as I see it right now. That said however, I continue to see little to no difference in my models...whether I use taper or not.

When I did the model with Henry's link I posted the other day, I had no idea what the comparative results would be. I thought maybe my model would not show similar results or maybe just fail due to geometry errors. However, I was surprised that the results were almost identical. That post is now worthless for comparison purposes, because Henry's link stopped working and there is no longer a model for comparison.

So Bob, no models this time, you'll just have to take my word for it. I just did a model of the Maco 103C, using Eznec 5, and I still get similar results whether I use taper or not. They'll probably deny it, but I fear I've upset DB and Henry already and I don't want anybody to get upset at my posting a model...if that is possible.

I plan to check some of my old vertical ground plan models to see if taper will produces similar results again. I'll be using my version of Eznec5, and that might tell me more...concerning this issue. I could be surprised again however. I think there is still something going on with issues around the AVG that we have not discussed here, (I could be wrong though.)

Bob I've said this before. Back when I did models, whether I used taper or not, most of them could have shown an unacceptable Free Space Average Gain results and I regret posting those flawed models. I really didn't understand much about Average Gain until late in 2012...and I think that was when you guys were taking privately about Henry's Sigma 4 report. I was also, at about that time right before he published his report, talking to Henry privately...and we had our disagreements...which we don't seem to be able to forget.

And, it was the last couple of years before I started to seriously check the AGR on all of my models. That said however and until then, I seldom checked and published the Free Space - Average Gain results for my models. I've heard folks claim, many times, that FS models are not worthy of consideration, and do not exist in or out of this world...but IMO these folks are unaware of the real purpose for Free Space models.

Also note in Henry's Sigma 4 report...that he talks about sure signs of issues concerning dissimilar segment lengths in parallel or near parallel wires and at narrow angle connections for sure. See page 10.

Another sign is, you'll also see this dissimilar segment condition in the Vortek published reports for their Mark 2 antenna on their Website if you look close and check the segment dots on the wires in the antenna view. IMO, this potential error in modeling published by Vortek shows a segment length difference of about 50% between the radials and the main radiator. Does this dissimilar segment length matter? I think this can be tested to see if it makes a difference for an antenna that also shows a perfect or near perfect AVG result in Free Space.

Until we hear or see more on-air results for the Q82 M2 from reliable operators, I would like to think Vortex could have come up with their modeling results the same way, unknowingly. DB told us, when he did a model of the Vortex Mark2, a while back, he saw similar results to my Eznec model.


I didn't see it, but I believe him.

 
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but I fear I've upset DB

You didn't. I was just posting my experiences using taper, and they seem to line up with yours, even if we got to that point differently. I was just trying to add my 2 cents to that conversation.

I've heard folks claim, many times, that FS models are not worthy of consideration, and do not exist in or out of this world...but IMO these folks are unaware of the real purpose for Free Space models.

I also agree with you here. Freespace has it place, and its uses. Their are things that you will only see with a free space model, so to rule said models out so easily without knowing what you might learn from them is only holding yourself back. Its the kind of mistake an amateur will make.


The DB
 
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I picked on a hard model to match, a old 5/8 wave model I did for Homer back in 12/31/2012. It is probably posted here on the antenna section.

The model includes taper in the radiator, a physical matching coil, and was done in Free Space, so I had and old model that showed the Average Gain and I did not have to create a new model.

Then I took the model and changed the radiator to a single element with (noT) no taper...which is noted as a difference in the titles below, one wT and one nT.

I added 2 overlays for the models and the highlighted the titles using the (*) indicating the active model. If you check out the number of segments for both radiators...you will see they both have 57 segments and I got the segment lengths for the radiators as close to the same length as possible for both models.

I was lucky on this one...the matches were effected only to the extent noted in the Source Data reports as indicated on the last page for each model.

The difference in these model overlays speaks for themselves.
 

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  • Homer's 5_8 wave with taper and no taper..pdf
    3.2 MB · Views: 10
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You didn't. I was just posting my experiences using taper, and they seem to line up with yours, even if we got to that point differently. I was just trying to add my 2 cents to that conversation.

DB, I was referring to the models that I posted with inflated gain due to a very high Average Gain result. Again I did that as an example of what a model can show and to warn folks not to be persuaded simply by seeing a model with big gains...without some inquiry or questions, just like I think you suggested in your post above.

I'm just a simple man and I don't understand everything in the books, but I will check things out if I can.

I have been accused of being an overly curious guys since I was a kid over 70 years ago when I was in the 4th grade. It's just my nature.
 
@ Marconi... which model u need online .?
@ Marconi... Yes you have, and i will not forgive or forget.
@ Marconi..(and u guys:)) .. im on now...but not that often ..
I do read from time to time, wont answer due to several reasons.
one would be: i simply wont read all atm... and im not willing to spend that much time. with that said..if i can help any of u guys.. (not that i can ..or am better etc u get what im feeling/ saying)... but if u have a few issues.. feel free to "hint" me.. if u wish.. perhaps i know someone who can..

Keep up the good work,

Kind regards,
H.
 
Oke..catching up...and found an example...

like this:

What i would like to ask.... whats the "fuzz" about tappering ?

Nec2 is known to provide less accurate results regarding tappering
(ps : says who ? With what accuracy?)
yes, ! with large diameter differences if tappered elements are used
(for instance the hairpin rod in reference to the main radiator).
But....
That difference will be neglible ...
(in this case.. not with delta loops.. what the heck r people thinking providing "accurate" data from eznec by modeling a inch thick radiator to a 12 awg .wire ?)
If u compare figures to specs on ch1 versus ch 40.

for that example.. for that answer... i dont think thats what ur after...hihi.

73 h>
 
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