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Modified Vector 4000
- Thread starter bob85
- Start date
Matching a full wave version of this antenna is not that difficult. Keeping the radiation pattern on the horizon once the top section is longer than 5/8 wave is another story altogether.
I believe it's basically a Vector 4K, a half wave very efficiently matched and elevated 1/4 wave by the 1/4 wave matching system at the base, consisting of a 1/4 wave down and a 1/4 wave up which, when added together, the 1/2 wave radiator and the two 1/4 waves comprising the base cone area, you have 1/2+2/4=1
or 1 full wavelength
lol
or 1 full wavelength
lol
I think there is more to the Vector than just being an efficiently matched half wave antenna. For example, Bob85 and Shockwave have both talked about the ability to steer where the radiation from the antenna is directed, at least as far as line of sight is concerned. This is something I have duplicated in modeling, and this allowed for a fairly wide range of "steering". You could, for instance, put this antenna on a mountain top, and steer the RF down to a town in the valley below. Aside from this antenna, I have seen no other antenna that allows this type of control over where you can put the RF. And when this type of steering is done they normally use two antennas in a collinear configuration, and out of phase with each other. The next closest antenna was the astroplane, where you could control the angle of RF to a small degree (only about 5 degrees maximum), but not nearly to the degree that, at least as far as modeling shows, you can manipulate the angle of the Vector. This is just one oddity I have noticed with modeling this antenna. I would also ascribe one of HomerBB's claims of this antenna to this same effect. He has stated that, even when mounted at the same tip height as the other antennas he has built, he was able to talk to local distance people further away than any other antenna design, and their are others who have reported this antenna as very good at local distance communications.
The dimensions you are giving for the various parts of the antenna aren't necessarily correct. For example, in the current version of the vector the vertical element is not .75 wavelengths, but closer to .8 or .82 wavelengths in length. Now I'm not saying that what you are talking about (such as cancellation) in general isn't happening to some (or even a large) extent, I'm just saying that their is more going on than the nice cut and dry figures people like to post about this antenna. I would personally put it at "1/2 wavelength +" as the cancellation is, at the very least, not complete. This being said, over an earth, I think you will notice more of an effect out of the RF steering ability mentioned above than this "half wavelength +" effect.
The DB
The dimensions you are giving for the various parts of the antenna aren't necessarily correct. For example, in the current version of the vector the vertical element is not .75 wavelengths, but closer to .8 or .82 wavelengths in length. Now I'm not saying that what you are talking about (such as cancellation) in general isn't happening to some (or even a large) extent, I'm just saying that their is more going on than the nice cut and dry figures people like to post about this antenna. I would personally put it at "1/2 wavelength +" as the cancellation is, at the very least, not complete. This being said, over an earth, I think you will notice more of an effect out of the RF steering ability mentioned above than this "half wavelength +" effect.
The DB
Since this thread began, there are over a hundred more FCC licenses for broadcast stations and commercial translators using this antenna design. The licensed Effective Radiated Power, Transmitter Power Output and coverage area all show noticeable gain over a 1/2 wave.
DB, I modeled a Vector changing the radial length 5" then 5" again for a total of 10" inches added. I did the models in Free Space and I see the following gain and angle results.
My stock Vector with 107" radials.
2.48 dBi maximum gain at +2* degrees to the horizon.
Vector with 5" added to the radial length and the height of the hoop increased.
2.55 dBi maximum gain at -179* degrees to the horizon.
Vector with 10" added to the radial length and the height of the hoop increased.
2.70 dBi maximum gain at -176* degrees to the horizon.
However, when I add the Earth back to these models the gain and angle remain virtually the same as the stock model.
DB, I recall you saying something similar to this sometime in the past and I figured those dimensions were the ones you used based on Homer's homebrew, but I could be wrong on that.
I also do not agree with JAFO that the Vector is a full wavelength antenna.
I have the New Vector 4K dimensions that Bob posted long ago, and his dimensions work out pretty close to 317" - 319" at 27.205 MHz.
I also found about the same with my model of the A/P...no matter what I did there just wasn't much difference noted in the maximum angle.
Considering this idea of RF Steering, my models over Real Earth did not show any effects on angle. That said however, I only made changes to the radial lengths in my models noted above. If you made other changes in your model...maybe you could tip me on that?
I tend to agree with Master Chief (I think he said it) saying the primary effects on radiation angle is, to a point, the height of the antenna.
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How about an example situation where RF steering is commonly used both in ham radio and broadcast radio in the (so called) real world. You have a mountain with an antenna on top, and a town/city in the valley below. A high gain omni-directional antenna on top of the mountain will get no signal to the town/city below as it is pushing the signal out to the horizon, not down below. What do they do to solve this issue? The put two antennas in a colinear configuration (one right above the other in line), and feed them out of phase. They adjust the phasing so the RF is steered down towards the town/city below, hence where the term RF Steering comes from. You are steering the RF in the nearby environment.
Now we take EZNec (or 4Nec2 or whatever modeling program we happen to have) and we model this antenna, both with and without the phasing. The peak angle of radiation with an earth looks the same with both of them.
In one case, (no phasing) people in the town/city cannot pick op said signal, and in the other case (with the phasing) the signal comes in loud and clear. Yet our modeling software shows no change in angle between these two antennas when they are over an earth. So Eddie, why do you think that is?
The DB
Now we take EZNec (or 4Nec2 or whatever modeling program we happen to have) and we model this antenna, both with and without the phasing. The peak angle of radiation with an earth looks the same with both of them.
In one case, (no phasing) people in the town/city cannot pick op said signal, and in the other case (with the phasing) the signal comes in loud and clear. Yet our modeling software shows no change in angle between these two antennas when they are over an earth. So Eddie, why do you think that is?
The DB
I can imagine where such a scenario might happen similar to what you describe DB, but I don't think this is what Bob was talking about when he described his idea that he was steering the RF with his vertical Vector antenna years ago. I can only assume he felt his results were due to some modifications he made to his design and that is what showed him some increased gain in the far field.
I could be wrong, but I seem to recall back then Bob was telling us about his idea that the Vector was some sort of non-apparent colinear, and that the 1/4 wave cone radiated equally well, in magnitude and phase, with the top 1/2 wave radiator.
I think we have learned a thing or two about cancellation between the cone and the base of the radiator inside the cone...and that pretty much rules out any possible colinear response with the Vector design.
DB, when you told us you had modeled this idea...I figured you were using a Vector design and that by modifying the radial length and cone height your models showed a nice range of change in the angle of the maximum gain lobe to the horizon.
Sorry, I know little about ideas for a colinear antenna on a mountain top and the phasing required to transmit a good signal to a city below in a valley.
The conclusions I reached in my simple effort to modify my New Vector 4K model showed me that the FS model lowering the RF angle down by a few degrees, as I've noted above. This model also shows a modest increase in the gain simply by making the radials a bit longer than specified earlier.
I find there is one simple limitation in my results, however, the model has to be a free space model. I can't tell you why, however.
Maybe Henry or others have some thoughts on this subject.
If I'm up to the work I might post some details for my Vector models.
Thanks for your reply.
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I wasn't referring to the vector being a collinear antenna of any kind in that post, I was just using a collinear antenna as a known example that exists in reality of an antenna with similar capability and is used by both hams and the commercial industry in certain parts of the world. To me, the Vector being (or not being) a "non-apparent collinear" is mutually exclusive to weather the RF from a Vector is steerable, so please don't make the assumption that I am making this leap, I am not.
I have also talked to Bob about this in the past. All I am saying is that modeling is saying that what he describes seeing is feasable, that is all. What does it matter if the RF is being steered down the side of the mountain, or out to the horizon, it is still steering, so in both cases effectively the same thing is happening, just towards different targets.
When it comes to the models of what is happening in free space, and over an earth, this is as expected for me. I never expected the models with the earth to change the angle of radiation simply because of a change in the antenna, or hell, even swapping it out for another antenna mounted at the same current node height. That being said, models with an earth tell us very little, if anything at all, about what is happening between the antenna and the horizon. All they are really doing is showing us what is happening from a DX perspective. If looking for information on local contacts, a model with an earth is mostly, if not completely useless.
You should go back to Henry's report on the Vector, I recall him referring to RF Steering in said report (although I could be remembering that wrong). Weather or not it was in his report, however, it was discussed between him and myself in the public thread on this forum about said report. I, personally, thought it was an interesting aspect of this antenna that I have yet to duplicate with any other antenna design except to a very small degree (aka the Astroplane antenna), but apparently no one else cared.
The DB
I have also talked to Bob about this in the past. All I am saying is that modeling is saying that what he describes seeing is feasable, that is all. What does it matter if the RF is being steered down the side of the mountain, or out to the horizon, it is still steering, so in both cases effectively the same thing is happening, just towards different targets.
When it comes to the models of what is happening in free space, and over an earth, this is as expected for me. I never expected the models with the earth to change the angle of radiation simply because of a change in the antenna, or hell, even swapping it out for another antenna mounted at the same current node height. That being said, models with an earth tell us very little, if anything at all, about what is happening between the antenna and the horizon. All they are really doing is showing us what is happening from a DX perspective. If looking for information on local contacts, a model with an earth is mostly, if not completely useless.
You should go back to Henry's report on the Vector, I recall him referring to RF Steering in said report (although I could be remembering that wrong). Weather or not it was in his report, however, it was discussed between him and myself in the public thread on this forum about said report. I, personally, thought it was an interesting aspect of this antenna that I have yet to duplicate with any other antenna design except to a very small degree (aka the Astroplane antenna), but apparently no one else cared.
The DB
Who ever needs it. You can down load the Victor 4000 manual straight from Sirio Italy
http://www.sirioantenne.it/en/products/hf/new-vector-4000
http://www.sirioantenne.it/en/products/hf/new-vector-4000
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Since the cone also drives the top section of the vector, changing its length not only changes the wavelength on the outside of the cone, it changes the delay feeding the top section of the main radiator too. Adjusting the length of both can focus the radiation beam above or below the horizon. That "non apparent collinear effect" can also compress the beam directly on the horizon.
Jeff, check out Henry's comprehensive revealations of the modeling aspect of the Sigma IV design in the link below.
http://cb-antennas.com/wp-content/uploads/2013/12/Sigma-IV-1.01-Jan-2015.pdf
http://cb-antennas.com/wp-content/uploads/2013/12/Sigma-IV-1.01-Jan-2015.pdf