Question on the Vector

[The DB]

But, I have claimed this is all a mute point now...because DB's new 4Nec2 model has shown us the kind of gain that Sirio reports for their NV4K, Donald claims in his real world testing, and we see the model suggesting the gain noted as CMC's.

No it does not...

As previously mentioned.

Eddie, I agree with Henry, I think your description and what you were trying to say was actually 35% to 40% correct. I think what Donald was talking about was also partially correct. How could your descriptions both be largely correct especially when they are contradictory in nature? I think Donald's two source idea is a good way to explaining it, and the open sleeve article Bob found is even better. What we have is essentially two different antennas wrapped up in one design. I have evidence from early in the process of designing the model presented above that has not been released publicly yet to draw on.

To set this up a bit, assuming that the radials acted partially like radials, and partially like a transmission line, we get both antenna mode currents and transmission mode currents on the same radials at the same time. This is something Bob has been talking about for years. In this case we have two different feedpoints. The antenna mode currents feedpoint, (below I'm going to call this the apparent feedpoint) at the base of the antenna. For this feedpoint, the vertical element is longer than 1/2 wavelength long, so there is a phase change along the vertical element.

Now the transmission line mode currents on the radial section will push their feedpoint, I'm going to call it the non-apparent feedpoint, to the top the the radial section, and equivalent electrical length up the central vertical element. Now lets assume the vertical element above this point is not longer than 1/2 wavelength long, so this non-apparent feedpoint does not have the same phase change between the non-apparent feedpoint and the tip that the apparent feedpoint has.

What would happen is, at least in theory, the two feedpoints would cause currents that are out of phase to appear on the same vertical element in the same location. This would have the effect of a cancellation of currents. I have a model that I think shows this very thing happening...

Note the central vertical element has very few currents on it compared to the radials section. I will also point out that the currents in the radials are also divided by four, as there are four identical radials. This should drive home how few currents are actually on the central vertical element in this model. When I made the vertical section long enough that both the apparent and non-apparent feedpoints had more than 1/2 wavelength of antenna above them the model very quickly showed a significant amount of currents on that same element that above has virtually none.

This evidence appears to agree, at least in principle, with the open sleeve articles explanation of the currents, and its multi-mode currents, if you will, explanation Bob has brought up multiple times in the past. This also agrees in principle with the open sleeve data in the current ARRL Antenna Book, 23'rd Edition, Chapter 10, which I think draws heavily on the same article.

Unless someone has another explanation...

Eddie, I think your description was very close to what the antenna mode currents in the radials are doing, although I also think there are some differences from your description as well. That is why I said I think you were 35% to 40% correct above, and not 50%.


The DB

 

[bob85]

henry
if he looked me in the eyes i would be asking him to explain the 3dbd, where he got the .82wave idea from and how the slimjim does what is claimed

eddie,
what i meant was each side of the dipole be 3/4wave with 1/4wave sleeve each side.

 

[Marconi]

DB, I stepped back from my ideas, because after you posted your model IMO I was getting the impression I was doing nothing but creating a distraction. I'm counting on your efforts in your model...that looks to be supporting the group think.

I do wish I could figure out how to use your 4Nec2 text file of your Vector and get it into Eznec. Thus far I have imported it into Eznec, but the model does not look like an antenna. I can see the cone however and it looks like the radials have the added wires you talked about. For some reason I was thinking the model was your regular Vector model.

This model also looks to have a source at the top of the radiator, but I can't be sure, this imported model is that bad. Right now it has so many errors that I can't even print an image to post...so you can see what I've got.

That said, I think that Henry had success importing your antenna descriptions, but mine is not working so well...so I must be doing something wrong.

Thanks for the information.

Could you post for me the headings above each column in the link to your model on page 10?

 

[The DB]

DB, I stepped back from my ideas, because after you posted your model IMO I was getting the impression I was doing nothing but creating a distraction. I'm counting on your efforts in your model...that looks to be supporting the group think.

I do wish I could figure out how to use your 4Nec2 text file of your Vector and get it into Eznec. Thus far I have imported it into Eznec, but the model does not look like an antenna. I can see the cone however and it looks like the radials have the added wires you talked about. For some reason I was thinking the model was your regular Vector model.

This model also looks to have a source at the top of the radiator, but I can't be sure, this imported model is that bad. Right now it has so many errors that I can't even print an image to post...so you can see what I've got.

That said, I think that Henry had success importing your antenna descriptions, but mine is not working so well...so I must be doing something wrong.

Thanks for the information.

Could you post for me the headings above each column in the link to your model on page 10?

I made some the elements backwards from what most people, including myself, normally do when making models. I forget the reason why I did that. As long as I followed convention it won't make a difference. Segment 1 on that element is at the top, not the bottom. That is why the source is at a high segment count.

It doesn't directly give me what is what. I'll sit down and figure them out for ya when I get a chance, but that will have to wait until next week, I'm going camping...


The DB

 

[Marconi]

I made some the elements backwards from what most people, including myself, normally do when making models. I forget the reason why I did that. As long as I followed convention it won't make a difference. Segment 1 on that element is at the top, not the bottom. That is why the source is at a high segment count.

It doesn't directly give me what is what. I'll sit down and figure them out for ya when I get a chance, but that will have to wait until next week, I'm going camping...

The DB

DB, I just want to know what each column title in the text file you posted. I figure the first data column is the wire number, and the first column with GW is a wire description, right?

 

[Marconi]

What would happen is, at least in theory, the two feedpoints would cause currents that are out of phase to appear on the same vertical element in the same location. This would have the effect of a cancellation of currents. I have a model that I think shows this very thing happening...

Note the central vertical element has very few currents on it compared to the radials section. I will also point out that the currents in the radials are also divided by four, as there are four identical radials. This should drive home how few currents are actually on the central vertical element in this model. When I made the vertical section long enough that both the apparent and non-apparent feedpoints had more than 1/2 wavelength of antenna above them the model very quickly showed a significant amount of currents on that same element that above has virtually none.

DB, I have never seen one of my models showing 13.3 amps unless maybe I set the power at 5000 watts. BTW when I imported your model on page #10, it came in to Eznec horizontal...laying down on its side relative to the ground.

What does the match for this model look like?

Is the model you posted above the model you posted on page #10, or has it changed?

 

[Marconi]

DB, I found the headers for the text file you posted on page #10, and now I understand what the data in each column means. You don't need to go to the trouble to get the info for me when you get back from camping.

Tomorrow I will add the 26 line descriptions into Eznec by hand...so I can at least see what you did with your model. You have painted a pret

 

[Marconi]

eddie,
what i meant was each side of the dipole be 3/4wave with 1/4wave sleeve each
side.

Bob, I posted above my model of your idea of a 3/4 wave dipole for each leg of my previous CFSD 1/2 wave model. I'm not sure what this is meant to tells us, so I await your comments.

I could have guessed wrong again exactly what you described.

 

[bob85]

just curious what the pattern looks like in nec eddie, thanks.

 

[Marconi]

DB, I finally got your model working, or at least close enough to see what you did.

I found the 4Nec2 editor scheme for the NEC Editor wires on YouTube and it was a little different configuration than Eznec, but it showed the headers for each column.So I was able to add your wire descriptions by hand instead of importing your file. I still have that to try and figure out.

I was very surprised to see that you added a wire, but you connected the wire to the radial at both ends and made the radials into skinny quads or folded dipole shaped radials. I just imagined the idea that you and Bob came up with, at best, more like parasitic wires and that is what I did in my model. I was really surprised to see such a difference in ideas.

BTW, where did I get the idea you did you model in mm's? Was it in the model that came across to Eznec that did not look like an antenna?

See both our models below. As a note the radiator on my model is 27+' feet tall and your model's radiator looks to be nearly 36' tall??????????????

 

[The DB]

DB, I just want to know what each column title in the text file you posted. I figure the first data column is the wire number, and the first column with GW is a wire description, right?

4NEC2 doesn't give me that data. The file I posted is what I got. I would have to line up columns and compare to the data in the software. You seem to have figured that out below though.

DB, I have never seen one of my models showing 13.3 amps unless maybe I set the power at 5000 watts. BTW when I imported your model on page #10, it came in to Eznec horizontal...laying down on its side relative to the ground.

What does the match for this model look like?

Is the model you posted above the model you posted on page #10, or has it changed?

I don't still have that specific model anymore, I only have that picture because it was posted in a private discussion, where I mentioned the lack of currents on the vertical radiator and how that surprised me. It shouldn't be to difficult to recreate if you need me to. It is a *very* early version of the model that, after a lot of additional work, eventually became the model on page 10.

DB, I finally got your model working, or at least close enough to see what you did.

I found the 4Nec2 editor scheme for the NEC Editor wires on YouTube and it was a little different configuration than Eznec, but it showed the headers for each column.So I was able to add your wire descriptions by hand instead of importing your file. I still have that to try and figure out.

I was very surprised to see that you added a wire, but you connected the wire to the radial at both ends and made the radials into skinny quads or folded dipole shaped radials. I just imagined the idea that you and Bob came up with, at best, more like parasitic wires and that is what I did in my model. I was really surprised to see such a difference in ideas.

BTW, where did I get the idea you did you model in mm's? Was it in the model that came across to Eznec that did not look like an antenna?

See both our models below. As a note the radiator on my model is 27+' feet tall and your model's radiator looks to be nearly 36' tall??????????????

I use meters. I think that came about when you tried to import one of my models into EZNEC and it was in mm's there. My segments in that model are actually 10 mm's long.

Glad you seem to have gotten everything worked out. The idea to simulate common mode currents necessitated a connection on the tip of the radials. That was the model that 4NEC2 gave me an error on, although I did address that error any why I though it wasn't relevant in the text above, how many pages ago now? Does EZNEC give you an error when running it?

In post 190 on page 13 I converted the model to aluminum and adjusted for maximum gain again. The data is there for you to play with if you are interested.

If you want to post the data files to make it easier for users of EZNEC to import the files go for it. I have no problem with that.


The DB

 

[Marconi]

4NEC2 doesn't give me that data. The file I posted is what I got. I would have to line up columns and compare to the data in the software. You seem to have figured that out below though.

Yes I figured it out.

DB here is the text .txt file you posted with the headers I found on YouTube noted at the top of each column.

 

[Marconi]

I don't still have that specific model anymore, I only have that picture because it was posted in a private discussion, where I mentioned the lack of currents on the vertical radiator and how that surprised me. It shouldn't be to difficult to recreate if you need me to. It is a *very* early version of the model that, after a lot of additional work, eventually became the model on page 10.

DB, I asked you earlier what kind of match you got with the model on page 10. I had to change your model to Meters where it belonged. I did that by leaving the data numbers the same and changing the units. Then I think the model presented without errors. I guess you also set the element diameters to .0001 mm in order to help eliminate segment errors, but this is just a guess, because I have no idea what you were thinking or doing.

I have your model in Eznec now, and it looks like what you might have intended at the time. I posted it compared to what I thought you guys were talking about...adding wires. I was wrong again...that is what happens when we try and guess what others mean.

All I recall you posting earlier was some results that showed the model's gain compared to a dipole and the gain (6.00+dbi) was about what Sirio reported for their NV4K. This was the bases of my concession. I still can't be sure I have your model correct as noted on your computer however. Can you show me a model with an antenna view that shows the gain results you described earlier?

I use meters. I think that came about when you tried to import one of my models into EZNEC and it was in mm's there. My segments in that model are actually 10 mm's long.

Glad you seem to have gotten everything worked out. The idea to simulate common mode currents necessitated a connection on the tip of the radials. That was the model that 4NEC2 gave me an error on, although I did address that error any why I though it wasn't relevant in the text above, how many pages ago now? Does EZNEC give you an error when running it?

In post 190 on page 13 I converted the model to aluminum and adjusted for maximum gain again. The data is there for you to play with if you are interested.

If you want to post the data files to make it easier for users of EZNEC to import the files go for it. I have no problem with that.

The DB

I also think that is where I first saw the model had units set to mm's too.

I figured out that your model's units were really set at Meters and not mm's, but I wasn't sure that I didn't use a model of mine to enter in the data by hand...that was already set using mm's, even though I never use mm or Meters as units in my models. I also try and set my antenna in the CB range so maybe some can easily compare any dimensions noted...to what they might already understand like 102"-108" inches as a 1/4 wave length at CB frequencies.

I'm sure you had some idea about the use of adding a feed line and seeing if it too would show CMC's by adding the wire idea from the Eznec Manual that I posted for Bob a while back. I just imagined such an idea as the wires being parasitic and not a physical part of the antenna.

We can see the results in the pattern you got, it does not look right, and your radiator is almost a wavelength long at 9.1 meters...just like Henry noted earlier. But I can wait for you to post the other results that shows us a good match, gain, and angle from your Vector model with wires added that you, Donald, and Bob came up with.

You can't be seriously thinking that Eznec's...add a feed line feature to a model, mucks the model up like we see here...just trying to show currents flowing on the outside of the cone area.

I will now try your other model posted on page 13.

No DB I won't be posting any more of my results, but I do appreciate your work in this discussion. This is your model to prove by showing all of your results that coincide with the comparative results you showed us earlier...with a pattern of a 1/2 wave dipole compared to your Vector model with wires added showing CMC's flowing on the radials.

I've just been trying to guess what you guys were thinking and doing here, like I did earlier, and I don't wish to get caught up trying to guess or change what may be proving 4Nec2 is able to predict how the S4 design works according to your model.

You got upset with me before in a PM I sent you...when I tried to predict what you may be doing wrong, my asking questions, and me making assertions without really knowing. I don't want to get me and you in that position again. I'm trying to be helpful.

 

[Marconi]

DB, I looked at the model descriptions you posted on page 13. The dimensions look to have gotten shorter a bit and there is some new code added to the .txt file that has a line descriptor noted by "LD".

Can you tell me what this LD descriptor means?

Is it part of the antenna or does LD describe something else like a setting?

I can look it up in the manual.

Let me know if I did not make myself clear.

 

[Marconi]

DB, I added the new wire descriptions from your .txt file on page 13 in a new Eznec model. It looks similar to the other model on page 10, but it is a little shorter in the radiator at nearly 35' feet instead of 36' feet tall.

The Eznec pattern over real Earth shows the gain, the match, and the currents are all terrible.

However, the Eznec model in Free Space reports an Average Gain = .03 dbi. This is similar to what you indicate, and that is because the feed point is down close to the base of the antenna where the complex impedance is low. This FS models also shows a 4.74 dbi gain at zero "0" angle, which is good, but this is misleading. If we add losses the gain goes to heck in a hand basket. Your model is desperately outside of any reasonable limitations. Sorry, but when i saw the good reports of gain compared to a dipole that you posted earlier, I decided to concede to your better model, but after you gave us some detail...I can't overlook what I see now.

Like Henry suggests...as soon as you added losses to the model it falls apart and now I understand his point.

I set your model to meters instead of mm's, leaving the data values as they were, and that fixed all the segment errors your model showed at first scan.

For the life of me I cannot explain how this 4Nec2 model can show me -65.08 dbi gain using Eznec over real Earth. Yet you claimed good results similar to what Sirio publishes in the specs. Then you posted a good gain and pattern when you compared a 1/2 wave in an overlay of the two patterns.

If my Eznec model of your model is correct, then no wonder the 4Nec2 currents image you showed earlier in the antenna view indicated hardly any currents flowing on the top 1/2 wave radiator. The model is in error.

My Eznec model of your wire descriptions shows a match for R=529300 - J 28720 OHMs, and SWR >100, which is similar to your first model I posted above.

I will also note that in every case before where you or I compared our models...we noted that the results were always very similar.

DB, if I'm wrong on any of this...please work with me to figure this out.