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How bad does a J-Pole look in an Eznec model?
- Thread starter Marconi
- Start date
Here is my Marconi JPole ISO over real Earth at 36' feet and in Free Space.
ISO = isolated mast
I'll post my NV4K or my S4 in a bit. The FS model shows the max gain cursor located to both sides of this skewed pattern so as to indicate the big problem with J-Poles that many complain about not making a good omni directional pattern. Judge for your self guys.
I can even steer this model to show a little gain of the outside of the good side or the stub, so it is like a collinear too and nobody knows except you guys now. It is not so good on the inside however, but I'm working on that as we speak. Stay tuned I'm working on a 5.00> gain JPole too.
ISO = isolated mast
I'll post my NV4K or my S4 in a bit. The FS model shows the max gain cursor located to both sides of this skewed pattern so as to indicate the big problem with J-Poles that many complain about not making a good omni directional pattern. Judge for your self guys.
I can even steer this model to show a little gain of the outside of the good side or the stub, so it is like a collinear too and nobody knows except you guys now. It is not so good on the inside however, but I'm working on that as we speak. Stay tuned I'm working on a 5.00> gain JPole too.
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Here are the latest versions the med and the max. These babies don't shot around corners though. This is my new and improved dial-a-matic, but it is only in the developmental stage, soon to be fully electronic Inverse current switching from the shack.
The med and max models in post #3 above have been tricked, so to speak, with Eznec program switches that have the effects of maximizing a model for gain and angle. These switches can also be used to mislead, as a result.
This is not good procedures for modeler unless these features are noted as being used, and a purpose is given for that use.
I was trying be bit provocative in my approach to rasing attention to some of the misinformation about J-Pole antenna. IMO, they are not without potential issues, but they can also be effective and they are more efficient than their bad reputation suggests. I don't believe many folks realize how they compare to other antennas designs and this is trying to demonstrate the issue.
The med model has the ground type switch turned on and it is set to the worst soil condition noted in the table of soil conditions.
The max model has the model also set over the perfect ground condition instead or Earth.
This is not good procedures for modeler unless these features are noted as being used, and a purpose is given for that use.
I was trying be bit provocative in my approach to rasing attention to some of the misinformation about J-Pole antenna. IMO, they are not without potential issues, but they can also be effective and they are more efficient than their bad reputation suggests. I don't believe many folks realize how they compare to other antennas designs and this is trying to demonstrate the issue.
The med model has the ground type switch turned on and it is set to the worst soil condition noted in the table of soil conditions.
The max model has the model also set over the perfect ground condition instead or Earth.
Here is my overlay of my J-Pole vs. my Vector and I don't see much difference between the patterns over Real Earth. What do you think?
I know there are disputes out there that claim the S4/NV4K are not similar to the J-Pole, say nothing about being based on the idea. Look at these patterns, and ask yourself can you see the difference that might explain these concerns?
This surprised me how similar these antennas look here.
I know there are disputes out there that claim the S4/NV4K are not similar to the J-Pole, say nothing about being based on the idea. Look at these patterns, and ask yourself can you see the difference that might explain these concerns?
This surprised me how similar these antennas look here.
I can't vouch for the accuracy of your models Eddie but i have seen enough j-pole models from respected sources to know they don't have 2.14dbi when mounted over real earth,
Henry has a good article on his website with full instructions on how to build a j-pole,
His models and real life measurements using a vector 4000 indicate the vector and j-pole produce similar results,
Give or take a few dbi depending on height above real avg ground id say you are not far from the truth.
Henry has a good article on his website with full instructions on how to build a j-pole,
His models and real life measurements using a vector 4000 indicate the vector and j-pole produce similar results,
Give or take a few dbi depending on height above real avg ground id say you are not far from the truth.
I have said for a long time Bob, I could not get my Vector to work as good as my S4, so I never fixed it...with the little things I found improving my S4 over time either.
When I finally did that...the Vector model started showing the same or better results as my S4. I was surprised. I suspect that it must surprise you too...that I was surprised.
Modeling in my approach, I never know what will happen ahead of time. Even when I have a expectation of what might or should happen...I am still surprised. I know this is not normal in your experiences, but that is what happens to me and this is why I sometimes might change my mind/thinking.
I can't pin this down to any particular thing that I did, but I was amazed at the results recently...when I took some time and did a few adjustments to the Vector model. It was probably just little stupid thing, like setting the length of a radial hub wire at different length from the others, so the base was not symmetrical. You know little things.
Therefore I don't try and push a model to the limits of my imagination without first trying to get the model right and working near expectations first.
I first noticed these new effects, for me, on my FS version of the Vector, and the angle dropped. Just so you will know this will likely never have any similar effect on a model over real Earth.
Just to be clear we don't want to mix FS results with RE model results without, at least, an understanding of the difference.
I had the though that this was due to the difference in the length of the radials, but I did not have to fix the length of the radials. I also tried to reverse my steps in what I had done, a nice feature available in Eznec, but I must have made a misstep in the process, because the model was no longer tracking with the same results in each change..as I backed up.
Right now I don't even know if I'm making any sense, and I don't know why I'm trying to tell you any of this. You may not understand, but here goes.
I think I'm A-fib again, but I don't feel bad yet.
I think my point is, I can't tell you if the best J-Pole made will make gain or not, I have no way of telling about gain, except by maybe considering signals, but I don't have a setup like you Bob...so that is not possible for me. I see lots of my ham buddies running repeater stations using a two meter> J-pole antenna at the top of their stacks...and they claim they work fine. Maybe you don't need so much watts or gain to work 2 meters, so I have to believe you, the real world a J-Pole is not on par with these Sigma design.
If so, we are seeing here that modeling must be measured in conjunction with real world testing, and RW testing must prevail.
So, what does that tell us about Donald's testing, since this model is so far off?
Bob, I don't mind the "straight skinny" and getting something right...that is always my goal. But this is just like the issue with Henry's Vector model reporting 2.27 dbi @ 23* degrees, that I asked about.
From what you say, Henry model agrees with what I just reported.
I set out to show these guys that are interested...that the J-Pole is not that bad of an antenna. So can you tell us why you think we see the big difference in your report for how a real world J-Pole really works, compared to what the models show?
Here is an overlay of my Vector vs my S4 in Free Space and even though the cursor is set for the S4, you can easily see the Vector pattern is really max at or near 0* degrees to the horizon in the image and you can check the gain difference in the details to the right hand bottom data block where it shows gain at 2.49dbi @ 3* degrees for the Vector.
When I finally did that...the Vector model started showing the same or better results as my S4. I was surprised. I suspect that it must surprise you too...that I was surprised.
Modeling in my approach, I never know what will happen ahead of time. Even when I have a expectation of what might or should happen...I am still surprised. I know this is not normal in your experiences, but that is what happens to me and this is why I sometimes might change my mind/thinking.
I can't pin this down to any particular thing that I did, but I was amazed at the results recently...when I took some time and did a few adjustments to the Vector model. It was probably just little stupid thing, like setting the length of a radial hub wire at different length from the others, so the base was not symmetrical. You know little things.
Therefore I don't try and push a model to the limits of my imagination without first trying to get the model right and working near expectations first.
I first noticed these new effects, for me, on my FS version of the Vector, and the angle dropped. Just so you will know this will likely never have any similar effect on a model over real Earth.
Just to be clear we don't want to mix FS results with RE model results without, at least, an understanding of the difference.
I had the though that this was due to the difference in the length of the radials, but I did not have to fix the length of the radials. I also tried to reverse my steps in what I had done, a nice feature available in Eznec, but I must have made a misstep in the process, because the model was no longer tracking with the same results in each change..as I backed up.
Right now I don't even know if I'm making any sense, and I don't know why I'm trying to tell you any of this. You may not understand, but here goes.
I think I'm A-fib again, but I don't feel bad yet.
I think my point is, I can't tell you if the best J-Pole made will make gain or not, I have no way of telling about gain, except by maybe considering signals, but I don't have a setup like you Bob...so that is not possible for me. I see lots of my ham buddies running repeater stations using a two meter> J-pole antenna at the top of their stacks...and they claim they work fine. Maybe you don't need so much watts or gain to work 2 meters, so I have to believe you, the real world a J-Pole is not on par with these Sigma design.
If so, we are seeing here that modeling must be measured in conjunction with real world testing, and RW testing must prevail.
So, what does that tell us about Donald's testing, since this model is so far off?
Bob, I don't mind the "straight skinny" and getting something right...that is always my goal. But this is just like the issue with Henry's Vector model reporting 2.27 dbi @ 23* degrees, that I asked about.
From what you say, Henry model agrees with what I just reported.
I set out to show these guys that are interested...that the J-Pole is not that bad of an antenna. So can you tell us why you think we see the big difference in your report for how a real world J-Pole really works, compared to what the models show?
Here is an overlay of my Vector vs my S4 in Free Space and even though the cursor is set for the S4, you can easily see the Vector pattern is really max at or near 0* degrees to the horizon in the image and you can check the gain difference in the details to the right hand bottom data block where it shows gain at 2.49dbi @ 3* degrees for the Vector.
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Eddie,
I can only assume ( i can't prove ) that some have good results from j-poles and some have bad results like i did way back when built them that they were not adjusted for best performance and not decoupled from any mast i used and no choke or balun on the feedline,
Many articles don't explain the potential common mode issue with J-poles, some even claim that because the base is a voltage minima there is no issue but that's far from the truth,
There is so much misinformation about antennas on the www that getting at the truth is more difficult than shoving butter up a porcupine's ass with a red hot needle,
They clearly don't need any physics defying field confinement explanation to provide a fairly symmetrical pattern so long as the stub spacing is not large.
The extra height of current maxima over other antennas is enough to make a well constructed and installed j-pole a good performer.
Does that sound reasonable Eddie?
I can only assume ( i can't prove ) that some have good results from j-poles and some have bad results like i did way back when built them that they were not adjusted for best performance and not decoupled from any mast i used and no choke or balun on the feedline,
Many articles don't explain the potential common mode issue with J-poles, some even claim that because the base is a voltage minima there is no issue but that's far from the truth,
There is so much misinformation about antennas on the www that getting at the truth is more difficult than shoving butter up a porcupine's ass with a red hot needle,
They clearly don't need any physics defying field confinement explanation to provide a fairly symmetrical pattern so long as the stub spacing is not large.
The extra height of current maxima over other antennas is enough to make a well constructed and installed j-pole a good performer.
Does that sound reasonable Eddie?
Bob, I'm not the expert here on J-Poles. I've heard guy's complain that their old Vector and their V-58's that don't work worth a hoot also. I just discount those from the get go.Their complaining about a lack of performance for any of these CB antennas we talk about...just doesn't make sense to me, I know they can work.
I didn't become aware of such problems as you note above...until I read the attached 1980's article below.
Me and my partner in crime and the radio hobby conspired together to see if we could figure out how to cut down on near field issues when using our radios in congested neighborhoods.
The article talked about issues noted in the report, and how the practical good results were mitigated somewhat by the TX energy even though the effects on the patter seemed profound and destructive. So we were not expecting to see any benefits in our TX and thus maybe no benefits in improved signals on the receiving end either.
However, being young and full of optimism, ego, and spunk...we always talked up our enterprise in this regard anyway. It was about how the discussion on the S4 use to go.
In later years, working with multi-element horizontal beams, I felt I could sense a difference...due to good balance in design and maybe when using a ferret choke, but I could not prove anything. I was getting good results with my homemade horizontal 4 element yagi where reducing any vertical radiation might help more. I never could figure out how radiation on a vertical mast under a vertical antenna could be a disadvantage. However, today and with modeling I think I see this manifest as possibly being destructive to the pattern in some cases...just like you have always told us. I just never noticed the big differences that you talk about...but we did see a reduction in TVI at our stations and with the neighbors.
We were talking where we wanted on our StarDusters either way, and messing up of our patterns did not matter, and only God and the FCC (a government lie) could see our patterns anyway.
I don't know why it is not discussed more, but maybe it is just a relative new idea and ideas tend to take time to go thru all the meaningless chatter first. That said, I have never sensed a problem with transmit without using something that was supposed to stop such currents in their tracks.
And it might of benefit to at least consider the conclusions made in the article above.
I have done a little Eznec work on that subject Bob, at least in the way I think might reveal something to also consider. But, with my Goose being cooked...I don't think anybody cares what I do.
Bob, I don't believe you believe that, but just in case I'm wrong and with that kind of comment from you Bob...I'm not quite sure I have the answer you want.
If you're expecting the typical high tech kind of results that seems to the hot topic of the day with the big time guru types, and you are not talking about 100's of feet in the air installations, then the answer is YES!
Bob, don't you know by now that this idea is my trade mark idea on these forums, and that the idea is based in MY real world experiences and MY modeling?
What do you think is important for us to know in this regard?
Bob, I don't believe you believe that, but just in case I'm wrong and with that kind of comment from you Bob...I'm not quite sure I have the answer you want.
If you're expecting the typical high tech kind of results that seems to the hot topic of the day with the big time guru types, and you are not talking about 100's of feet in the air installations, then the answer is YES!
Bob, don't you know by now that this idea is my trade mark idea on these forums, and that the idea is based in MY real world experiences and MY modeling?
What do you think is important for us to know in this regard?
Bob, I reservedly said above YES above, but I got to thinking...words are still not enough.
Below is an overlay patterns from:
Starduster with a tip height @ 58.5' feet
Vector ISO with tip height @ 63' feet
The gain for the SD'r is in the data block at the bottom left of the image under the words Elevation Plot, with both antennas maximum TOA at 8* degrees.
Assuming the models are close to correct...see what I mean.
Does that look reasonable?
That's all I've got Bob to support my words...my models.
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Eddie,
Yes i do believe a well constructed j-pole can be a good performer,
i was friends with an old timer ex RAF comms guy that used homebrew j-poles, lovely guy to talk to,
I built a few over the early years, I knew nothing about them back then, I had no arrl book no www just an ex RAF guy and some story's,
I can't say if your starduster vs vector model is correct, I don't recall testing either my m400 or m800 or my astroplane at a similar tip height as my other antennas, maybe i did but i forgot,
i know the m400 can perform well in its own right if its well above its surroundings, id take one over a shaki big stick or cheap endfed 1/2wave at the same tip height given the choice,
All this talk about field strength reminded me i had an old meter my mate gave me a few years ago buried in the shack so dug it out ,
Its no HP not even close but it seems much better than any of my vhf/uhf radio's s- meters,
Been playing with it yesterday using a short telescopic whip antenna listening to FM vhf radio,
I can see signal strength changes waving my arms around in the air close to the antenna a couple of tenths of a db,
Its a 45 - 2150mhz unaohm ep314, This ep300 looks the same,
http://www.dxsatcs.com/sites/defaul...asurement receiver with QPSK and NIT card.jpg,
Can't say if i will get around to trying it or not, i wish it covered 27mhz.
Yes i do believe a well constructed j-pole can be a good performer,
i was friends with an old timer ex RAF comms guy that used homebrew j-poles, lovely guy to talk to,
I built a few over the early years, I knew nothing about them back then, I had no arrl book no www just an ex RAF guy and some story's,
I can't say if your starduster vs vector model is correct, I don't recall testing either my m400 or m800 or my astroplane at a similar tip height as my other antennas, maybe i did but i forgot,
i know the m400 can perform well in its own right if its well above its surroundings, id take one over a shaki big stick or cheap endfed 1/2wave at the same tip height given the choice,
All this talk about field strength reminded me i had an old meter my mate gave me a few years ago buried in the shack so dug it out ,
Its no HP not even close but it seems much better than any of my vhf/uhf radio's s- meters,
Been playing with it yesterday using a short telescopic whip antenna listening to FM vhf radio,
I can see signal strength changes waving my arms around in the air close to the antenna a couple of tenths of a db,
Its a 45 - 2150mhz unaohm ep314, This ep300 looks the same,
http://www.dxsatcs.com/sites/defaul...asurement receiver with QPSK and NIT card.jpg,
Can't say if i will get around to trying it or not, i wish it covered 27mhz.
That sounds like my experiences with my old buddy and mentor, retired US Army. He was in communications training in Japan after WW2 and until he retired. We met in 1965, on The Texas City Dike fishing at night. For over 30 years I spent most Wednesday with him fishing, shooting, hunting, or something to do with radios. Most of that was before computers, and the Internet for sure. He was a plane Jane sort of instructor however. He knew the technical side of communications, but he had to teach kids out of HS how to do stuff the Army way.
I don't know for sure either, but IMO...I'm not far off. If guys don't see that...then they don't even know or want to know how to judge simple modeling results.I give more information on the models I post than anybody. I might not do it well sometimes and that is my fault, I get it.
You made a correct comment to Homer the other day, and it was 100x more effective at setting him straight than it would have been...had I said the exact same words. There is a little friction between us, and I'm not sure I understand why. But I do think about it at times. He has told me his neighbor is a Ham of some class and they talk. Maybe some of my ideas were discounted by his mentor.
I can't think of one idea I posed to Homer that has ever failed to result in his seeing things the same way I have. My excitement about the A/P is one example, and another is my fascination with the end fed 1/2 wave, and AA5TB's ideas. Even though Yates says he doesn't have a good idea about the A99, I've tested ideas on the A99 more than any other real CB antenna I have. In a fit of rage or depression one time I destroyed over 10 years of notes on that one, along with all of my antenna work sheets.
The only reason I ever got into the study of CB antennas was because of hearing and seeing everything claimed in the hobby being blown unbelievably out of any common sense proportions.
So, I set out to see if I could duplicate all that, and that has always put me on the opposite side of the claims.
I was searching for "WHAT IF" while you were figuring out "WHY."
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Bob hinted at some of the common problems that can detract from the J-Pole performance: common mode currents and not installing it on a non-conductive mast. The non-conductive mast is critical. Without using a choke at the feed point, you will have common mode currents that cause pattern degradation; whether or not that is an issue is up to the individual operator.
I agree Mr M. I'm glad you pointed that out. I really wasn't trying to show the bad or worst case effects for a bad design or bad construction. I was hoping that a keen observer might see, besides the remarkably similar pattern, gain, and angle results compared to my New Vector 4K model, how a good model of a J-Pole might look.
IMO this was my way of suggesting both of these antennas might be very effective.
We've heard all about the bad ideas in design and function that bad press, CB world, and the "non-apparent collinear" guys have always claimed in the S4/NV4K discussion that has gone on for years. I also understand that there have been plenty of guys, out there in the real world, that have tried to make these antennas and failed...only to get terrible results.
I know the J-Pole is not a popular idea and models don't always pan out to suggest accurate real world results, but I was just trying to present another Point of View and a picture idea to consider in the defense of the J-Pole antenna...if a model could show good results.