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New thread to debate V-4000
- Thread starter nosepc
- Start date
Can you use a Vector to pick up the satellite signal to watch Myth Busters in Argentina? According to you, it should work for that
I found what he thinks supports his high angle gain claim. It is the mistake of modeling this antenna over a theoretical "perfect" ground plane. That is a mistake that he was informed about already (in the astroplane thread). I refuse to post such a model here as he will likely dismiss all other models and take it as proof he is correct... I have been unable to duplicate the strong 30 degree lobe using any "real" ground options that I have tried in the 4NEC2 software...
The DB
http://www.worldwidedx.com/attachme...vector-40000-thread-eham-collinear-vector.pdf The WorldWide Radio Forum[/url] More can be learned from the model posted here. The model would lead you to believe this antenna has good gain over the stock one. Field tests reveal there is indeed gain to be had but not nearly the difference EZNEC shows in this example. Care to guess why? It looks to me like EZNEC shows no added gain coming from the cones in phase radiation. That means the reference to beat here is a simple 1/2 wave. EZNEC thinks you've now doubled the amount of in phase currents.
The proof that EZNEC is totally wrong is that field tests confirm not one bit of extra in phase currents will radiate in the model above as compared to the stock antenna. The phase has been shifted too far so that 50% of the extra 1/2 wave will buck the phase on the outside of the cone. It takes the other 50% of the added 1/2 wave to bring the gain back up to the level of the stock antenna.
The reality is even my 90 degree phase shift that works the best in the field can't approach a 3db increase over the stock antenna. It only has 66% more in phase radiation length than the stock antenna and the current nodes are too close together. Vertically stacking separate antennas and properly spacing them is the only way to approach the full gain.
The proof that EZNEC is totally wrong is that field tests confirm not one bit of extra in phase currents will radiate in the model above as compared to the stock antenna. The phase has been shifted too far so that 50% of the extra 1/2 wave will buck the phase on the outside of the cone. It takes the other 50% of the added 1/2 wave to bring the gain back up to the level of the stock antenna.
The reality is even my 90 degree phase shift that works the best in the field can't approach a 3db increase over the stock antenna. It only has 66% more in phase radiation length than the stock antenna and the current nodes are too close together. Vertically stacking separate antennas and properly spacing them is the only way to approach the full gain.
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DB, this is what I've been talking about for some time now. Just a while back I asked GHZ24, to do the same and tell me what changed in his 4nec2 model. He came back with an inverted V on one side, first saying that the wire connections mattered to the model, but did not explain beyond that.
I asked him to explain what difference he saw, and then he came back and said it changed the gain and angle. I told him the only difference I saw was the currents noted on the currents log changed, but the gain, angle, and match all remained the same.
He came back later and said he was wrong, that nothing changed. I don't think I've heard from him since, so I'm not sure what he is thinking now.
When you saw this, did you realize this is what I've been trying describe for a long time...thinking maybe this was why Donald originally saw phasing issues using Eznec in the past.
Apparently nec2 will allow wires to be connected either way out of convenience. Noting that this difference does not change any results except how the currents are reported out:
wire 1 end 1 to wire 2 end 1 wrong
wire 1 end 2 to wire 2 end 1 right
IMO, if we wish to consider phase and currents with our models it looks to me we need to make sure that all wires connect the way that nec2 is expecting the wires to be connected.
Roy Lewallen personally told me on the phone when I asked him questions about currents saying: Eddie always keep your eyes on the currents. This statement is also noted in italics in his manual, but there is no elaboration on the issue. That is also the way he handled that issue on the phone...just a caution without elaboration.
I can tell you why I think this works this way, but see if you can first reason why on your own. Donald might already know why, but I'm not sure he would remember. I've given him my ideas for why.
DB this said however, does not explain the collinear effect that Donald describes, nor does it explain why 4nec2 and Eznec does not report 4.15 dbi in a free space model.
This is why I questioned what Sirio has reported, and when I asked them this specific question...they have not responded.
I asked him to explain what difference he saw, and then he came back and said it changed the gain and angle. I told him the only difference I saw was the currents noted on the currents log changed, but the gain, angle, and match all remained the same.
He came back later and said he was wrong, that nothing changed. I don't think I've heard from him since, so I'm not sure what he is thinking now.
When you saw this, did you realize this is what I've been trying describe for a long time...thinking maybe this was why Donald originally saw phasing issues using Eznec in the past.
Apparently nec2 will allow wires to be connected either way out of convenience. Noting that this difference does not change any results except how the currents are reported out:
wire 1 end 1 to wire 2 end 1 wrong
wire 1 end 2 to wire 2 end 1 right
IMO, if we wish to consider phase and currents with our models it looks to me we need to make sure that all wires connect the way that nec2 is expecting the wires to be connected.
Roy Lewallen personally told me on the phone when I asked him questions about currents saying: Eddie always keep your eyes on the currents. This statement is also noted in italics in his manual, but there is no elaboration on the issue. That is also the way he handled that issue on the phone...just a caution without elaboration.
I can tell you why I think this works this way, but see if you can first reason why on your own. Donald might already know why, but I'm not sure he would remember. I've given him my ideas for why.
DB this said however, does not explain the collinear effect that Donald describes, nor does it explain why 4nec2 and Eznec does not report 4.15 dbi in a free space model.
This is why I questioned what Sirio has reported, and when I asked them this specific question...they have not responded.
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Sigma V4000 Antena Sirio V4 irradiation pattern 4NEC2 .NEC
Here I made a pretty complete with cone and feed point.
What I see is that the radiation efficiency is very low, which makes "my myth" is quite real??.
The cone does not help, hinders the gain and the performance is not helped, unlike their presence is very negative.
Obviously not perfect, but what software is allowed to do and see.Is an imaginary antenna Besides, in the real world yield less because the antennas are connected to masts, brackets, cables, coaxial etc.
4nec2 Sigma V4000 Antena Sirio V4 irradiation pattern
Here I made a pretty complete with cone and feed point.
What I see is that the radiation efficiency is very low, which makes "my myth" is quite real??.
The cone does not help, hinders the gain and the performance is not helped, unlike their presence is very negative.
Obviously not perfect, but what software is allowed to do and see.Is an imaginary antenna Besides, in the real world yield less because the antennas are connected to masts, brackets, cables, coaxial etc.
4nec2 Sigma V4000 Antena Sirio V4 irradiation pattern
I'm still working my way around it. Have some thinking to do for sure. I was definitely not expecting the direction of the wire to change how a modeling program determines its phase. I was also not expecting for a modeling program that shows different phases for the same wire to have the exact same radiation pattern and gain figures. My first thought in either case is it is obviously in error as I know in the real world neither of those would be the case. My guess is when NEC looks as the wire it sees currents traveling from the first endpoint data, whatever that may be, to the far endpoint data. This would explain why reversing the endpoint data the phase would be shown inverted.
In any case it has opened my eyes. I will have to do some research in to how NEC calculates all of its data. That may shed some light on some of this...
I don't see any comparison between NEC and CST, however. One of which is a cheap program that has in one form or another been around for decades, the other is the most advanced modeling program today, and its price shows it. At this point I am satisfied with the fact that I have found errors in this cheap and free modeling program, and will be careful to stay within its limits. Further, it will help me to potentially find other errors in other models, even those I didn't create myself... One of the errors I have found will be demonstrated in a post below...
The DB
Here I made a pretty complete with cone and feed point.
What I see is that the radiation efficiency is very low, which makes "my myth" is quite real??.
The cone does not help, hinders the gain and the performance is not helped, unlike their presence is very negative.
Obviously not perfect, but what software is allowed to do and see.Is an imaginary antenna Besides, in the real world yield less because the antennas are connected to masts, brackets, cables, coaxial etc.
4nec2 Sigma V4000 Antena Sirio V4 irradiation pattern
I did notice yesterday that as I raised the radials from a horizontal to an upward pointing position that yes the radiation efficiency as reported by NEC does indeed go down, but the gain also went up, as well as the pattern dropped down to a lower angle, namely the you see in my plots above.
That being said, I'm not convinced about NEC's ability to accurately display efficiency or gain in all cases. For example the following two images...
21 dB gain from a Vector? Wow, I wish it were true. That model also showes...
Over 3000% radiation efficiency in an omni? Wow... I want that antenna!!!
Because of this data I simply don't trust NEC's ability to accurately calculate efficiency or gain for these antennas.
I haven't found a specific problem with this model of yours as of yet, aside from the fact that, as was said before, it (and all other Vector models from NEC based software) don't match up with real world measurements taken by people here on this forum as well as others. This is where understanding the limits of modeling comes into play, and further, taking its data in context.
I don't have absolute scientific proof here to say the data is wrong, but then you have no more scientific proof backing your data up either. All I have to go on is my ever growing knowledge of antenna theory to make a judgement call.
Just remember, NEC is a tool, and as a tool it can be manipulated, as was shown by me above in this and a previous post. As I'm knew to modeling my next step is to figure out why it can give incorrect, even blatently wrong information...
The DB
I did notice yesterday that as I raised the radials from a horizontal to an upward pointing position that yes the radiation efficiency as reported by NEC does indeed go down, but the gain also went up, as well as the pattern dropped down to a lower angle, namely the you see in my plots above.
That being said, I'm not convinced about NEC's ability to accurately display efficiency or gain in all cases. For example the following two images...
21 dB gain from a Vector? Wow, I wish it were true. That model also showes...
Over 3000% radiation efficiency in an omni? Wow... I want that antenna!!!
Because of this data I simply don't trust NEC's ability to accurately calculate efficiency or gain for these antennas.
I haven't found a specific problem with this model of yours as of yet, aside from the fact that, as was said before, it (and all other Vector models from NEC based software) don't match up with real world measurements taken by people here on this forum as well as others. This is where understanding the limits of modeling comes into play, and further, taking its data in context.
I don't have absolute scientific proof here to say the data is wrong, but then you have no more scientific proof backing your data up either. All I have to go on is my ever growing knowledge of antenna theory to make a judgement call.
Just remember, NEC is a tool, and as a tool it can be manipulated, as was shown by me above in this and a previous post. As I'm knew to modeling my next step is to figure out why it can give incorrect, even blatently wrong information...
The DB
DB, check your impedance is very small and you have very high SWR and that makes the gain look real nice...if you believe it.
Maybe you changed the wire directions and forgot to change the source location.
Thanks fellows for coming to my defense. Those intelligent enough to realize I was merely using the tailwind to demonstrate the idea of how a lesser force working in concert with a greater force can have a disproportionate impact on the overall result will not need an explanation beyond what I posted, however, I do appreciate the respect I got from you.
I quoted and responded to Marconi's post.
I have no truck with nosepc as I find him to be highly narcissistic, deeply disrespectful of others, and beneath serious consideration as either a student, a teacher, or just as a real practitioner of antenna experimentation with a yen to discuss such things.
Those of you who regard his language limitations as a barrier to better understanding are kinder than I presently am. I believe his behavior to be calculated.
"There was once a fellow who passed by a farmers fields daily. One daily he saw the farmer in the field and stopped to engage him in conversation. Immediately, this fellow began to ridicule the farmers plowing. He mocked with irreverence the crookedness of his rows, and berated the foolishness of the direction the farmer had chosen to lay out the fields for planting. Patiently the farmer waited until the self-opinionated passerby wound down. The farmer asked this fellow, "Sir, where are your fields?" The fool answered, "I haven't any fields"
As I have said, "A man with an experience is never the servant of one with only an argument"
They could show a single model that shows it is more than an antenna 5/8, or even a simple dipole.
The only thing that made a real-world test was -wavrider- and went they said that the team that used the Sigma IV had no power, had a headwind or coax was shorter, perhaps a lobe that will was negative, it was SSB audio, etc, when 5/8 crushed to V 4 for over 6DB!
Only words, evidence of anything ever. Only words like a preacher.
When I do the test and the Sigma IV walk not going to tell me he was on an anthill, maybe a cloud hid it, I had a headwind, etc.. I made a Slim Jim with flat cable-TV of that size, antenna very noisy and very inefficient..
The only thing that made a real-world test was -wavrider- and went they said that the team that used the Sigma IV had no power, had a headwind or coax was shorter, perhaps a lobe that will was negative, it was SSB audio, etc, when 5/8 crushed to V 4 for over 6DB!
Only words, evidence of anything ever. Only words like a preacher.
When I do the test and the Sigma IV walk not going to tell me he was on an anthill, maybe a cloud hid it, I had a headwind, etc.. I made a Slim Jim with flat cable-TV of that size, antenna very noisy and very inefficient..
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So..... you told us it was a j-pole then made a j-pole out of 300 ohm flat TV cable to prove it??? Makes no sense whatsoever. Not to mention you've already seen the only accurate model of the Vector that has been published. You also mean that the only person's tests you think you're able to get away with manipulating right now may be Wavriders.
Don't forget that inefficient Slim Jim is exactly what you were recommending yesterday in favor of this design. Because yesterday it was efficient and economical. The laws of physics must have changed in the last 24 hours, or you need a new lie to cover your old lie.
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What I did is attach a single wire of a single segment with a z location of 5.45 to 5.5 where 5.5 is the bottom of the model. I was just seeing what positioning the feedpoint under the cone would do to the model. I can further adjust the gain and efficiency figures by changing the overall length of this 1 segment wire...
You sure like talking about yourself a lot. To say that the only person on the forum that actually tested this antenna in the real world is Wavrider is just plain fooling yourself.
You are allowed to believe what you wish, but that doesn't mean what you believe is in fact correct. So keep on talking like the "preacher" you are... In spite of your words being meaningless, they also clearly show you for what you actually are...
The DB