Modified Vector 4000

[HomerBB]

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.

What he said.

 

[Marconi]

Earlier, I posted a very good report about the Sigma 4 design that was done by Henry HPSD, a notable member of this forum.

Modified Vector 4000

To save you extra reading or having to search for the interesting topics that continue to be discussed of late...check the following:
Pg. 6 paragraphs 3-4
Pg. 27 whole page
Pg. 34 Conclusions at the bottom of page
Pg. 42 paragraph 4

 

[Shockwave]

I've seen the ability to steer the angle of radiation in this design on 11 meters, 10, 6, 2 and the FM band by simply adjusting the wavelength of the top and bottom sections. The interesting thing is you have to make relatively large changes in wavelength to see any difference locally and the advantage is virtually indistinguishable.

Get 50 miles out and the entire situation changes. Subtle changes in wavelength here can make a 2 to 3 db difference at the targeted take off angle. I can't see any other logical explanation for the pronounced characteristic seen in this design other than this shift in wavelength and delay to the top section does have the ability to effectively steer the TOA. Otherwise known as "electronic beam tilt".

 

[HomerBB]

I appreciate the loyalty to Henry for the detailed work he put into the report. I really have enjoyed some clarity from it However, his work falls short of the greater potential the antenna seems to be capable of.
As a metaphorical example;
If I were to test a light that some have reported could cast illumination many miles away, and confine the test to a room, or even a forest, I would never see it's potential.
Also, if I wish to prove my Buick gets 16 MPG, I can. Yet, I have also seen my Buick get 99.9+ MPG. Some would argue it can not do it, drawing upon the manufacturer's reports to prove it. Wouldn't change my experiences.

Henry does admit there could be more beyond the limits of his report that may be possible with this antenna. At least that's how I read it. Also, he appears to be attempting to describe the exact nature of the antenna, settling on "it is a half wave vertical mounted above a quarter wave impedance matching section".
Personally, I believe that fails to describe the potential of the antenna beyond the limited, or should I say, the confined, parameters of the report.
I am not the scientists some are, but in the simplicity of my experience, the cone is NOT a 1/4 wave matching section. If that were it's only function then we would not require a gamma match capacitor to tune, ie match, it. Whether that was or was not the intention of it's designers is beside the point. What is relevant to the discussion at this late date is whether the antenna is capable of producing the kind of far field results many have seen with it.
As I've long time said, "A person with an experience is never the servant to a person with an argument." Or, no one's argument can change my experience.

 

[AudioShockwav]

It is a very interesting antenna.
Henry's report has good points in there about the cone radiating and adding to the far field even if only slightly.
And removing the gamma match and "tapping " the 50 ohm feed point would get away from any losses caused by the gamma.
The choke and ground radials are other suggested improvements. I see that as all positive input about the antenna.

This Antenna has made me change my mind about it more than once.

It is amazing that it has generated this kind of discussion and is still ongoing.

I need to take my time to read all of the report.
Thanks Eddie.
73
Jeff

 

[Marconi]

I've seen the ability to steer the angle of radiation in this design on 11 meters, 10, 6, 2 and the FM band by simply adjusting the wavelength of the top and bottom sections.

I and other folks asked Bob what adjustments he made back in the days before he started this thread. But all I recall him saying was something similar to this, "...Eddie the results you get at your location will be different than what I get here, so my mods won't work for you."

Donald, I think you talk about actually seeing some interesting evidence that supports RF steering effects using the Sigma4 design at several frequencies. Could you give me a link or some viable reference so I can try and model this antenna and the effects you saw?

Get 50 miles out and the entire situation changes. Subtle changes in wavelength here can make a 2 to 3 db difference at the targeted take off angle.

I've taken many signal reports over the years, some in error by using a switch box, and others more correctly using the same mount, coax, and radio. In my experienceds, if and when I happened to see such differences in signals like you describ...I figured it was just as likely that skip was working or an amp or a beam was making the difference vs. your claim that RF steering and/or a non apparent collinear effects was going on.

I admit that what you claim about RF steering, in general, could be possible. We hear stories of RF steering in the commercial broadcast and possibly among some ham operations. However, I have never seen any evidence that steering was going on with my Sigma 4 or for sure that is was ever 2-3 db stronger than my other CB verticals at close to the same tip height.

I've heard these claims from you, Bob, DB, Homer, and possibly some others...but I've never heard anybody try and explain how this effect was implemented, except in broad terms like you suggest.

Another question. Can you duplicate this effect whenever you wish on your Vector 4K?

I can't see any other logical explanation for the pronounced characteristic seen in this design other than this shift in wavelength and delay to the top section does have the ability to effectively steer the TOA. Otherwise known as "electronic beam tilt".

I understand what you are telling us, and I too cannot explain the effects using a Sigma4 design. With your help, maybe I could model the idea along the lines your talk about when modified. Maybe my model could show similar results to the claims you guys talk about...if I knew exactly what you did to modify.

A'm I right to assume you are telling us the S4/V4K will NOT work as you describe, unless they are modified somehow?

If you have a Vector that shows 2 - 3 db better gain at 50 miles vs, the stock version, could you give me the basic dimensions used...so I could try and model the idea?

I would like to learn something new today.

Thanks for responding.

 

[AudioShockwav]

Eddie,
Can you model the Vector with a Choke at the bottom and ground radials as Henry described in his report?
He did say that improvements could be made.
Also he talked about removing the gamma match and direct feeding, it is it possible with modeling to determine where you could find a 50 ohm feed point on the cone?

73
Jeff

 

[Marconi]

Henry does admit there could be more beyond the limits of his report that may be possible with this antenna. At least that's how I read it.

Hey Homer. I agree this is what Henry said, but he also said there would be an additional report at the bottom of Pg 40. I think that meant he would try and address the lingering questions left by his original report...which was intended to address the 7 claims that Henry listed on Pg 6.

Also, he appears to be attempting to describe the exact nature of the antenna, settling on "it is a half wave vertical mounted above a quarter wave impedance matching section".

Personally, I believe that fails to describe the potential of the antenna beyond the limited, or should I say, the confined, parameters of the report.

Homer, I agree with his limited description of the design. Maybe he will have some new thoughts on the potential as you suggest. And, maybe he can also demonstrate using some convincing science. I hope one day he has the time and the will to continue.

I'll post on the rest later if I still have anything to add.

 

[Marconi]

Can you model the Vector with a Choke at the bottom and ground radials as Henry described in his report?

Jeff here is my model of the V4K with and without a choke to stop current from flowing on the feed line and/or mast. This model of the V4K is made using what I call a "Simulated Feed Point." This means I simply placed the FP at a point on the model's mast near the bottom where I find 50 OHM's. This is similar to how the gamma taps into the radiator and IMO this is not direct feeding the antenna.

PDF #1
1. this model is in Free Space (FS). 1st page shows the Main Control screen which indicates, at the bottom, the Average Gain Report for this model. It shows AG = 0.999, which indicates the model is reliably accurate. The other 3 images are the antenna view in FS, the free space pattern with the max gain & angle noted, and the feed point match condition for the model. I add this version of the model as a control to help maintain accuracy when I finally place this model over Exnec's idea of Real Earth, which simply adds back the losses and the mast to the real Earth model.

2. I added the mast connected directly to the base of the antenna. This model is the V4K with the mast 4" inches below the base of the antenna to add CMC isolation (ISO). The model has no choke, and instead requires an insulator to deal with the current on the radiator like Henry discusses. The model shows an image in the antenna view. I also add a close up view of the cone area including the location of the feed point (O) up above the base of the antenna where I found 50 OHMs. Next image shows the pattern and the max gain/angle, next is the image of the wires used to make the model, and last shows the feed point impedance values and SWR.

3. shows the same model as #2 with no isolation (ISO) and instead uses a simulated choke at the top of the mast to deal with the CMC currents.

PDF #2
1. shows the V4K antenna with out ISO or a choke. I forgot to include this model above. It shows how bad the CMC can be for this model. IMO, this is what Henry was talking about when he discussed the CMC issues.
2. is an unrelated V4K model I had on file. Jeff, per your request I added 4 horizontal 109" radials about 12" inches below the base of the antenna. This model also has the feed point located at a 50 OHM point near the bottom of the radiator, but the model is a bit different in other minor ways, even though the matching results are similar. Jeff, I also added overlays of the various patterns in the PDF files, so you can more easily compare these effects.

Thus far I don't see any of these modifications to the models making a notable difference, one way or another. IMO, I don't think these variations are the same mods as Donald is suggesting, mods that will make a big difference 50 miles away. I'm hopeful that maybe he and/or Homer can give me some dimensions that supports their observations and experience.

 

[Marconi]

Also he talked about removing the gamma match and direct feeding, it is it possible with modeling to determine where you could find a 50 ohm feed point on the cone?

My models for both the Vector and the S4 show the feed point impedance at the very bottom of the radiator is about 22 - 27 ohms with very low reactance at resonance for 27.205 MHz.

I haven't tested an idea for making the bottom offset legs for the radial longer at the mounting hub, but IMO that could change the resistance and the reactance too. These radial mounting legs are currently about 2.5" inches long in a model I just checked.

I find the natural 50 OHM resistance tap point for both the S4 and the V4K are higher up the radiator, rather than near the bottom. My models with a physical gamma included place the gamma tap point very close to the specs for both the S4/V4K, at about <>28" inches up to the dog bone connector,

Tomorrow I will post my model with this physical gamma included. You probably haven't seen this model, however DB and I both posted such models sometime back. The difference I note in adding physical matching devices to my models show a bit more gain and some skewing of the radiation pattern. IMO, this is due to the physical matching device being added to the model. That said, they don't seem to hurt the model...if I can get it working right. In fact, I usually see an improvement in the models in spite of the possible skewing.

I'll mention another example of how adding an element to a model that actually exists on a real antenna and how adding the element can make noticable differences in pattern and performance. Did you happen to see what happened to the pattern for the Imax model...when DB and I added a 42 pF capacitor to the middle element of our Imax models a while back?

 

[Marconi]

Also he talked about removing the gamma match and direct feeding, it is it possible with modeling to determine where you could find a 50 ohm feed point on the cone?

Jeff, below is my Sigma 4 model in Free Space that shows what the match looks like at the very bottom of the radiator right above the radial hub.

PDF file below
1, is the front page of my manual showing the length of the radiator and radials I used.
2. is the Antenna View.
3. is a close up of the cone/feed point (O) on wire #2, and right above top of wire #1.
4. is the total field view of the pattern showing the maximum gain and angle.
5. is the Source Data view of the match, SWR, and a perfect reactance.

IMO, I don't see any way we can directly-end feed this design.

Sorry these PDF file images are so faint and I should have made the red (O) FP black (O) rather than red.

 

[Marconi]

Jeff below is the End Fed Sigma4 model over Real Earth.

I included overlays of the patterns for comparison of my gamma matched model over Real Earth vs. this End Fed model. I also added the Source Data report to show the match is still mismatched at resonance.

 

[Shadetree Mechanic]

It would seem to me that direct feeding at the 50 ohm point on the radiator would change the phase of the radiated signal at the location of the basket. It seems that the balance would be upset and cause the basket not to contribute as much to the far field?

 

[Marconi]

Shadetree, basically I tend to agree.

Currents and phase are difficult topics and for me they are even harder to talk about.

Maybe DB can help.

 

[AudioShockwav]

I have been working a lot Eddie.
I will try to make time to go over all you have posted in the next day or so.
Thank you for all your hard work.

73
Jeff