Booty Monster's Vector 40000 thread on Eham

[Shockwave]

So Henry, what is the purpose of adding a value other than a 0 to that Source field, and when might we use a value other than 0?

The most useful purpose for this is when dealing with multi bay arrays (stacking or combining more than one antenna). In this case each antenna will have its own source. Depending on the installation configuration, changing the phase on the source of the antenna independently can allow us to do very useful things.

If the antennas are stacked vertically, changing the source phase between them can allow us to tilt the beam down on the horizon or fill in nulls in the pattern. For horizontally spaced arrays, changing the phase angle between them can electrically "steer" the pattern into different directions.

 

[Shockwave]

@ Marconi,
Pse see my new post to you at the end of page 11..



@ Shockwave:

.....when you say...."i have to admit"..."it's making little sences...
Would that be: you understand a litlle...Or not ?

If not...
Of course phase changes along the length of the radiator....
And thats why the angle is expressed along the (in this case) vertical and thus heigth...segmentations.

However the single angle provided is given from a "above" view".

I understand its difficult to see....but one has to "think" 3d...instead of just looking in 2d against that vertical wire.

So its more or less a vector....
At first we have the "heigth" of that wave. (along the radiator)
At that height there is a certain current with a magnitude...
And that maximum magnitude at that point can be pointed in a specific direction (under a horizontal angle).
At thats the current phase angle.
Its "cruled"...twisted...

So, yes it is logical that with heigth the angle changes.

However the angle provided is not given with a magnitude point of view.
Most people look to much at the magnitude of that line...and "see" it going through the ax of the antenna.
But that says nothing about the ANGLE...it only shows there is no magnitude.
THe angle could be a lot of things.

It is provided at a "single" segment heigth...and therefor horizontal (in this case)

take for example the radials under the antenna.
there are 4 radials they are at a 90 degree angle in reference to the antenna.
But the radials are 45 degrees seperated from each other.
Now, that last one is how the phase is given the angle between them...not from the vertical antenna...

Thats how the angle is and should be given.

Regards, H>

I'm still confused but I have a question about how this may relate to the CST models. If you look at the CST model, the phase appears to be different from the left side of the antenna to the right. Do you feel this has anything to do with what you're trying to explain or could it be completely unrelated?

 

[Marconi]

I'm glad you got it fixed.
I have no idea what you did, but I see you found what you were looking for.

Thanks Homer. I wasn't sure I could ever show such results, even if I find the results are ultimately wrong due to changing the phase angle for the model.

I'm not yet sure what to think in light of Henry's last post, but the results I posted finally do look exactly like what I was expecting.

However, now I also see what Henry was trying to describe. Other than the sign differences noted, the data for the first 5 to 6 segments in both models shows to be exactly the same magnitude, segment by segment.

Henry also mentioned the word vectors. I'm sure that is a big factor in his thinking about this issue, but I don't specifically understand the vector idea as it applies here, but I think it does apply in the way phase and current magnitude are manifested.

 

[Marconi]

Donald, do you recall telling me a while back that a previous Vector model I posted did not look right at the phase shift area? You said it looked to be noticeably higher than the top of the radials, and that should not happen if the dimensions are setup correctly.

I think you also mentioned that I needed to make the radiator longer or shorter in order to make the current cross over point at the hoop line up better.

Well when I fix the phase angle in the Source dialog box it also looks to fix that problem as well. I hope the new Vector model will show this issue has improved well.

 

[Henry HPSD]

Hello guys,

Attached is another drawing.
Im afraid im not that good with drawings hihi...but you will get the idea.
Just hoping that at some point it will all "come to place"....


@ Watson:
Shockwave is of course accurate when he is refering to the broadcast application
(the use of the source angle that is)
But for our "antenna enthousiasts" it is also commenly used for..
All the different phased antennas out there..w8jk, phased verticals etc.
Or it can also be of use with "circulair polarisation".
And i know exactly what you are thinking....."of course...i knew that" ....hihi..

Please do read again marconi, it is vital to understand what is going on.
Especially if you are looking into antennas a bit deeper...

And i cant say it enough....but dont look at the phase current line at the side of the antenna. It is then not showing the angle. And stop doing the "change" of angle of the source. By now you will have noticed "nothing" else has change...so there is probarbly some truth in what im saying.
...you will get mixed up.
Look from above....(enlarge currents if needed)

@ shockwave,
All i did so far was trying to explain how the phase angle is expressed.
But so far it seems difficult to understand and i perfectly get that...
I havnt (yet) related it to cst.
Ofcourse i have seen your cst plot..so I know what you are talking about.
i have actually already tried to find it...but all i could find now was the "single" plot.
Thougth you had a small movie somewhere..Ill enhance my search hihi.

But upfront...without "additional" data it can be interpertated in many ways.
(as with eznec of course)

Kind regards,

Henry


Hmm...just noticed i made an error in the drawing...
Who ever spots the error ....understands ...
(Dont worry if you dont...the pic is still oke to get an idea...)

 

[Henry HPSD]

ah found it shockwave...
(it was at your site of course hihi)

Welll yes it does relate.
If you take a look at the "o" ampere point (green)
You will see that moving along the radiator.....upwards.

Now just think of the antenna and a curled thing around it.
(that round fire escape or tornado figure)
that thing is rotating...and presenting your "o amp" spot.
Presenting a radio wave moving up the antenna.

It is current magnitude that changes... (and displayed)
(A/m it says...)

So if we "concentrate" on the 0 amp thingy
We see that single "o amp" spot moving...
And because of that vertical change in "heigth" we can realise there are different
angles...nothing else is capable of "indicating" that.

If that "0" amp spot wouldnt move...there was only "magnitude" and a single angle...
Now, because of there are different angles (phase angles...and thus going....around the antenna and because we are looking in time (hence the radio wave is moving upwards) we see that 0 amper spot going upwards.

And ill bet the "speed" of the wave moving is telling us indirect how the phase is.
Taking a look at any "current- phase log" we see the phase difference getting large really fast...and remaining rather "equal" for a period of time.
That remaining rather equal....is presenting the phase "peak" .
And that going "fast" the phase "shift".

But the above is substraction from the cst plot is just....probarbly...it would be (more than) logical....
However we will never be 100 percent sure...simply cause the data is not provided.


regards, H>

 

[Marconi]

Well guys, I think it is probably futile for me to continue with this Vector model, but I do see it indicating a similar far field pattern at the base like the CST model is suggesting.

IMO however, the radial cone shows a lot of current flowing out of phase, and thus we would expect a lot of cancellation if the current magnitudes in the area are about equal, which is the case. However, the is a small difference favoring the in phase radial currents, and IMO this small current difference is the current adding constructively with the top 1/2 wave element.

Thus we do have some radiation, and it does likely contribute to far field radiation like Bob and Shockwave tell us. But IMO the contribution is very small. This is due to the small difference in current magnitude as a result of the cancellation, and the currents being almost equal between the radiator and the the radials.

It is true that the current in the bottom segment of the 4 radials are summed together, and in this model the numbers are 4 x .2909 (a) = 1.1636 (a). The current flowing in the base segment of the radiator is 1.1365 (a). Thus we have 1.1636 - 1.1365 = .0271 (A) left over which can radiate.

The following suggest what this amount of current means. Again, this value of .0271 is left over current that can radiate from the very bottom of the in phase radials compared to the top segment in the radiator, which shows a current of .0278. I think it goes without saying that the tip of antenna radiators do not contribute much to far field radiation...and in this case the current is small and does not radiate much.

Note: this model does not look to model well with the radiator tapered as Eznec limitations suggest. So, I made the radiator a single wire, I made the radials wires the same diameter as the radiator, and all segments are as close to equal lengths as possible.

I also added screen shots to show the Average Gain and Source set at 0* degrees and set at 33* degrees in order to indicate how the tabular currents log responds. You have told me this setting is using it in error, but this is what it is.

Donald, you have told us what you did to test for the error that Eznec showed you early on, but can you tell me what Eznec did that alerted you there was a problem you saw using Eznec for your Dominator? Was it a phase problem similar to what I describe here...cropping up in the tabular currents log, or was it something else?

View attachment New Vector 4000.pdf

 

[W5LZ]

The 'problem' is that EZNEC isn't able to handle everything, as the author has said before. It's limited to the users understanding of the programs abilities and what the user is trying to do with it. EZNEC isn't the absolute best/comprehensive thing going and has never pretended to be.
Marconi, I think you've taken it about as far as possible (maybe a bit too far).
- 'Doc

(Now, if you could tell me why this @#$ computer seems to have eaten all of the EZNEC files, or where the #3// I put them, I'd almost be happy! Sort of...)

 

[Marconi]

The 'problem' is that EZNEC isn't able to handle everything, as the author has said before. It's limited to the users understanding of the programs abilities and what the user is trying to do with it. EZNEC isn't the absolute best/comprehensive thing going and has never pretended to be.
Marconi, I think you've taken it about as far as possible (maybe a bit too far).
- 'Doc

(Now, if you could tell me why this @#$ computer seems to have eaten all of the EZNEC files, or where the #3// I put them, I'd almost be happy! Sort of...)

Thanks 'Doc, but I'll wait until the good Lord tells me to hang it up. Besides all I have now is time, so why not do something besides sitting an drooling on myself.

Open Eznec and tell me exactly what you see in the path field at the top of the "Open" screen as noted below. You should see the following path.

C:\ProgramFiles(x86)\EZW\Ant
or something similar to what is shown in the image below.

Eznec files its stuff in a hidden folder, so I think it is called. You have to have the systems switch turned on to show hidden files in order to see the folder. However, I don't think you need to see the folder for Eznec to work, you just have to have the path correct. Try clicking on the down arrow button at the right of the path field. A dialog window should open and maybe you can figure out how to get to Program Files (x86), then select EZW, then select Ant and your file index should open up.

Then exit Eznec via the Main Menu, and when you open it again, your path should be fixed until you physically change it, which you should not have a need to do, unless you wish to save a file in another folder outside of the hidden area.

This is an example of going "...a bit too far," but I do it all the time for my buddies if I can.

View attachment Eznec path to index..pdf

Sorry the image is not too clear, you may have to zoom in a bit.

 

[BOOTY MONSTER]

Thanks 'Doc, but I'll wait until the good Lord tells me to hang it up. Besides all I have now is time, so why not do something besides sitting an drooling on myself.

..........

makes perfect sense to me

just out of curosity ...........
how does the toa of a 3/4 wgp with drooped ground elements compare to a 1/4 wgp with sloped ground elements at the same feed-point ? say ..... 18 - 27 ft. .

 

[W5LZ]

Marconi,
I appreciate it but due to a number of problems I find that the program and it's files are just no longer on this @#$ computer. I've given up on resurrecting the thing and will see about getting it again. Naturally the 'key' is gone too. I love computers!
- 'Doc

 

[Marconi]

makes perfect sense to me

just out of curosity ...........
how does the toa of a 3/4 wgp with drooped ground elements compare to a 1/4 wgp with sloped ground elements at the same feed-point ? say ..... 18 - 27 ft. .

I don't know for sure, but I have a 3/4 wave model with slanted down radials. I think I was seeing how it handled the match compared to radials being horizontal.

It probably works at very high angles like the regular 3/4 with a horizontal ground plane.

 

[Marconi]

Marconi,
I appreciate it but due to a number of problems I find that the program and it's files are just no longer on this @#$ computer. I've given up on resurrecting the thing and will see about getting it again. Naturally the 'key' is gone too. I love computers!
- 'Doc

Like I told you, the folder that Eznec uses for the indexed .ez files are hidden, and you will not see them even at "dos" level...unless you set the switch to show hidden files.

You may find a "ProgramsFiles(x86)" folder if you list files/folders in C: drive. Do you have Vista or later version of Windows.

There are two such folders on my computer (Vista), one is on C:/ drive for regular use, and the other is in a hidden folder. That is where Eznec Ant files are kept.

This is all documented in the Eznec manual. You have to read every word, all the way to the end of the manual to really understand the limitations. You could also call Roy about your problem, he may have a solution for paying customers. Did you buy his systems disc? If so, at the very least you could reinstall it. You wouldn't save any files you added in the past, but you would be up a working again.

Do a Google search on "hidden files/folders." Look for turning the switch on or check with Microsoft help.

 

[Henry HPSD]

Marconi,

Again...it strikes me that you are showing the view antenna plot and expecting phase to be at the "side" of the antenna.
You provide a "plot" ...and write down "phase on" ...
But all one can subrtract with a amount of certaincy is current magnitude.
Of course you can have a good "guess" about the phase along, but it is not the way to provide it.

AND Again...you have pointed out that the "phase shift" happens at 0 degrees.
BUt...well...you do realise thats not the "center" of your phase shift ?
That "0" degree number has NOTHING TO DO WITH IT.

Im afraid you still dont understand
I strongly suggest you go back to where we started and try again.

@W5LZ
The only limitation NEC2 i see regarding this antennna is:
1- closed spaced wires.
2- those closed spaced wires under a angle.
However, it is clearly desribed in the manual how to handle this.
And while NEC4 would be a better approach, nec2 should provide a good indication.

It is 99 percent of the time the opperator behind it who doesnt understand and makes errors. A good example is how things are "interpertated" in this thread..

Regards,

Henry.

 

[Shockwave]

Marconi, I've tried to explain the inaccuracy I see with EZNEC and the Sigma design many times. It comes down to exactly what you see each time you experiment. The programs complete inability to identify significant radiation currents combining from the cone.

If you still think EZNEC is right, go build a collinear version with an additional 1/2 wave radiator on top. When the design peaks its gain in EZNEC, build the prototype and field test it. You will find there is no improvement in gain whatsoever. How can that be if we have added another 1/2 wave of in phase radiation?

It cannot be and the problem is EZNEC peaks its gain on the horizon when the phasing section is 100% too long. Not 10 or 20% off but 100%. EZNEC will guide you to construct a 180 degree phase delay between sections because it sees the cone as nothing more than transmission line.

The proof that the radiation from the cone is significant comes from understanding that EZNEC's phasing section places 50% of the added collinear 1/2 wave in a phase that is bucking the constructive radiation from the cone. If that radiation on the cone was weak, the entire top half wave would absolutely become dominant and there would be gain in the field using the 180 degree delay.

For there to be no improvement in gain with a 180 degree delay is very strong evidence that the cone radiates nearly as much energy as if it were a free standing 1/4 wave.

Henry, Thank you for your explanation after looking at the CST video. I think I'm now understanding what you mean as this crossover point in phase changes in step with the phase the antenna is driven in. I can see this effect in CST.