Modified Vector 4000

[bob85]

Donald,

over a short time i see no change at all but over a longer time period i did see a change,

first test tonight was opposite results to the test i did before on different days exactly 3.6dBm, very strange,

im sat thinking i can't post this, they will think i have got the antennas mixed up,
i have to do it again, so we did & that's how we found out the signals change over time,

we had the same 3.6dBm difference between antennas but stronger signals,

I do see the much wider vswr bandwidth with the 3/8wave cone,

i don't see how getting the vswr down a little lower is going to change which one wins in this test,

maybe the 3/8 will have better luck higher above ground.

 

[Shockwave]

Donald,

over a short time i see no change at all but over a longer time period i did see a change,

first test tonight was opposite results to the test i did before on different days exactly 3.6dBm, very strange,

im sat thinking i can't post this, they will think i have got the antennas mixed up,
i have to do it again, so we did & that's how we found out the signals change over time,

we had the same 3.6dBm difference between antennas but stronger signals,

I do see the much wider vswr bandwidth with the 3/8wave cone,

i don't see how getting the vswr down a little lower is going to change which one wins in this test,

maybe the 3/8 will have better luck higher above ground.

I'm just curious if any of the issues you had to address with the gamma match on the 3/8 wave cone, required making it larger in order to add more capacitance? As I recall, when the cone covered more than the first 1/4 wavelength of the main radiator inside, it required more capacitance in the gamma match to tune out the reactance. The stock gamma failed to be enough to reach a good match.

 

[bob85]

Of the combinations of gamma tube & rod i have tried the shortest tube with longer rod gives the best match on the 3/8 version,

That does not mean its using less capacitance as i don't know the overlaps,

It means im using a thinner gamma that's more rod than tube where the 1/4wave cone tunes no problem with the stock gamma tube & a short rod,

The Vortex also looks to use a longer rod with a proportionally shorter tube,

The Vortex gamma comes preset & sealed.

 

[Marconi]

The Vortex also looks to use a longer rod with a proportionally shorter tube,

The Vortex gamma comes preset & sealed.

Bob, now I think your EzBob software is showing you apples and oranges.

This comment is a bit similar to long ago when you first saw my old CB vertical antenna video comparisons, and advice me, "...I had it all wrong."

After a long while of talking about such issues, you finally explained what you meant in such a way as I could finally understand. Then I agreed with you...my old tests were no-way-no. Then I started to see the flaws in my original idea to try and test the CB claims I was hearing on my radio and later on hearing the same on the Internet. I bought one of Jay's I-10 K antennas to start the process of my testing ideas.

I think you're likely to find that your extended 3/8 wavelength Vortex Q82 Mark 2 will not work like you expect...using the much smaller Vector parts at the base, say nothing about the overstated claims by Vortex.

When you told me that my Exnec model could never duplicate the match or performance unless I made the model exactly like the Vortex antenna, I attempted to not only model the dimensions, within the limitations in not knowing what the dimensions really are, but to also add taper to the radiator, but so far I have not been able to use my tools to make the radials with taper. That seems to require additional Geometry skills beyond me.

Maybe DB could add something here.

So, I'm just waiting to hear form the peanut gallery saying, "...that won't work Eddie, because we all know that your version of Eznec cannot work using taper. It is also said that Eznec does not handle close wire spacing, and I think I know what that really means too.

When I modeled my Vortex with the extended cone, I found the gamma tap point worked best at 60" inches above the feed point, but I didn't press the point because I could have never explained what or why. There is more I could say here, but it would not get us back to the task of trying to compare these two antennas, and also consider if the Vortex performs like it's reported.

Do you remember seeing a Your Tube video recently of a young man that was installing his new Vortex Q82 Mark 2? I also checked on Viemo and it does not seem to be there either. I can't be sure how I found that Video, but it could have been linked on the Vortex Website, and now it is gone like the Vortex Website is gone. I would sure like to look closer at that video.

I also cannot find a contact for M0ogy Dave either. He never responded to my questions about dimensions that I posted on several of his recent videos. Bob, do you know Dave or have any contact info?

So, in light of what I think you have suggested to me about my Eznec models, and not
having good dimensions, the question is, how can you test using dbm procedures and really expect to get reliable results, if you don't have all the correct dimensions either?

I know you told me you could give me the dimensions when you got it tuned, but I don't think you were expecting a problem either.

Probably said too much already, but that's it.

 

[The DB]

When you told me that my Exnec model could never duplicate the match or performance unless I made the model exactly like the Vortex antenna, I attempted to not only model the dimensions, within the limitations in not knowing what the dimensions really are, but to also add taper to the radiator, but so far I have not been able to use my tools to make the radials with taper. That seems to require additional Geometry skills beyond me.

Maybe DB could add something here.

When it comes to taper, mininec is much better at handling it than the nec2 programs out there. That being said, most nec2 based programs have a function designed to compensate for taper, although with eznec specifically I am not sure how they handle it. I can tell you that taper doesn't make much of a difference when it comes to 4nec2. Testing on various antennas with and without taper I have yet to see a model that using taper makes even a 0.1 dB difference in gain, or any real difference when it comes to tuning. In fact, I'm so not worried about it I don't bother using taper most of the time, instead using an average of the diameters that the elements would have for the entire antenna...

I think taper makes much more of a difference on lower frequencies, and their competitively much longer antennas. As the length of the tubing doesn't change much, they have many more tubes, which by extension means much more taper. On some low band antennas you might start with a 2 or even 3+ inch diameter, and end up with 1/4 inch or less diameter. I think taper would have much more of an effect on these than CB antennas, where even 5/8, and even the longer vector type antennas will only have so many tubes in comparison.


The DB

 

[Marconi]

DB, thanks for your comments.

I agree. I have not seen much performance difference either, as long as I take a simple approach to my models. This means without including a matching device, and showing a good match, my model can still show reasonable performance as long as the model shows a good Average Gain results.

So, when I got the radiator set to specs, so-to-speak, with a few guesstimates, using taper, and adding a physical gamma match device, I began to see what I've attempted to describe below.

This may be confusing to some folks, but IMO this is the way it is.

As DB told us, averaging the tapered radiator and radial length serves us well ordinarily, but when I add a physical gamma match in this case, the averaged diameter of approximately 0.84" - 1" inches, failed to match well no matter what I did. I attribute a lot of this whacky understanding to one fact...this model is not a multiple of a 1/4 wavelength.

Bob, the spacing from the feed point to the dog bone (the connector part of the gamma at the top (for you guys in Reo Linda), also needed to be made longer to get close to a 50 ohm match for this Vortex antenna with a 3/8 wavelength extended radial cone.

I could have adjusted the radiator length and maybe found a better resistive match, where the gamma would work better, but that would be defeating the specs for the antenna. @ FreeCell.

In this modified Sigma4 design with an extended radial cone section, the changes seem to me to be more critical to the matching using a Physical Gamma in my model.

I may be repeating here, so to recap. In this case the gamma wire lengths and diameters relative to the radiator diameter (not averaged) appear to me to be much more critical as to the specified relationship of wire to wire and maybe that is why Bob is having an issue with the match.

This may also account for why Dave told us in his review video that the gamma came preset, secured, and weather proofed by the manufacture. This would suggest to me this antenna is not intended to be tuned at some other frequency other than 27.500 in this case.

So, Bob this is all I have to say about this antenna, right or wrong.

 

[bob85]

I don't have contact details for oggy, i know & talk to people who do know him including the guy at the other end of the mk2 test,

oggy was taken seriously ill & pulled back from radio & doing reviews for a while,
maybe you can contact him through his youtube videos,

relative to wavelength i am using larger tube & gamma diameters than any 27mhz version of that antenna including the vortex,

i should increase spacing because i am using relatively fatter tubes but i can only do that at the gamma strap with stock gamma tubes,

im not finished tuning the last gamma i put on it yet.

 

[Shockwave]

When I modeled my Vortex with the extended cone, I found the gamma tap point worked best at 60" inches above the feed point, but I didn't press the point because I could have never explained what or why.

As DB told us, averaging the tapered radiator and radial length serves us well ordinarily, but when I add a physical gamma match in this case, the averaged diameter of approximately 0.84" - 1" inches, failed to match well no matter what I did. I attribute a lot of this whacky understanding to one fact...this model is not a multiple of a 1/4 wavelength.

When you move the gamma tap point up to 60 inches from the base, haven't you also moved the source on the antenna? This may get us closer to a 1/4 wave multiple in terms of resonance but you still have to tune out the reactance this shunt feed presents.

 

[Marconi]

When you move the gamma tap point up to 60 inches from the base, haven't you also moved the source on the antenna? This may get us closer to a 1/4 wave multiple in terms of resonance but you still have to tune out the reactance this shunt feed presents.

No Donald, I don't think you don't understand my point.

The feed point on this antenna only changes with height.

I know you just made a mistake, because I remember you telling me categorically that you modeled a Sigma 4 or a Vector 4K design, six ways from Sunday, and it was definitely a collinear antenna, not a J-Pole, and for sure was not an elevated 1/2 wave, but instead is a non-apparent collinear, whatever that means.

Do you remember what the feed point symbol in Eznec looks like? I'll give you a clue (O)

So, take a look at my model below for this antenna and see if it reminds you where the feed point actually is...on the Sigma4 design idea.

 

[Shockwave]

No Donald, I don't think you don't understand my point.

The feed point on this antenna only changes with height.

I know you just made a mistake, because I remember you telling me categorically that you modeled a Sigma 4 or a Vector 4K design, six ways from Sunday, and it was definitely a collinear antenna, not a J-Pole, and for sure was not an elevated 1/2 wave, but instead is a non-apparent collinear, whatever that means.

Do you remember what the feed point symbol in Eznec looks like? I'll give you a clue (O)

So, take a look at my model below for this antenna and see if it reminds you where the feed point actually is...on the Sigma4 design idea.

You know the tap point from the "dog bone" on the main radiator is the RF feed to the element in question. If you raise this tap higher on the radiator, it raises the resonant frequency by making the element appear shorter electrically.

 

[bob85]

Eddie,

I said the Nv4k & mk1 Vortex are so close in cone & monopole length that the only things making them different are the tube taper schedule & diameters,

if you don't include what makes them different they are the same antenna in nec.

you will never see the claimed 2 s-units increase over the Nv4k in any same pole same timeframe test,
its nonesense & anybody that ever tested different 27mhz antennas on the same mast knows it,

something other than the antennas themself screwed the test up,


looking at oggy's video you can see the gamma is closer to the monopole than the 1/4wave cone versions,

You said you had to use a longer dogbone & the models look to have the gamma spaced further from the monopole,
one model has a long gamma strap putting the gamma out near or past the radials,

relative tube diameters & spacing determine the characteristic impedance of the gamma section,

My antennas are using about the same angle as the 27mhz version & that's no problem with the 1/4wave cone,
it tunes ok with more than one combination of gamma tube/rod

The Q82mk2 gamma is not wide spaced like your models
it looks to start about the same as the radials at the bottom & sits parallel to the monopole,

I have turned gamma rod clamp over so the gamma sits more parallel to the monopole but i have not tried tuning it yet.

 

[Marconi]

I said the Nv4k & mk1 Vortex are so close in cone & monopole length that the only things making them different are the tube taper schedule & diameters,

Bob I agree that the NV4K and the Q82Mark1 are almost identical, and my models show hardly any difference in the performance. I have even less of the dimensions for the Mark1. This thread has a lot of words in the posts, so maybe you were talking about the Mark 1, but I was thinking Mark 2, so forgive me.

I sent you some modeling images of my model with several view of the antennas. At the bottom of the images were noted the details and dimensions for several of the most important wires. I was wondering how these dimensions line up with your dimensions, but you got hung up on the fact that the scaling tool I use in Eznec did not show the right diameters. I was only curious how the lengths compared to you 6 meter version of the Vortex Mark2 in that case, and I wasn't real clear about that.

 

[bob85]

Eddie,

1/4wave cone version,
37mm x 965mm
33.5mm x 1245mm
30.5mm x 950mm
24mm x 950mm
20mm x 410mm

radials 13mm x 1400mm & 10mm x 48mm

diameters matter because your not modeling a dipole

The radials form transmission-lines,

the gamma section is a 2 wire transmission-line shorted at its far end,

anytime you change the spacing or diameters of the conductors in a transmission-line you change the characteristic impedance of the line,

anytime you change the spacing or diameter of the conductors within the gamma section you change the range of step up ratio for r ,

narrower spacing & thinner gamma gives a wider range of stepup,

Here's what Cebik says about NEC & gammas

"It is possible to construct a series of antenna models to serve as a surrogate for the physical antennas. However, we cannot do the job in NEC-2 or even NEC-4. As suggested in Fig. 5, the gamma assembly presents NEC with two problems. First, unless the gamma and main elements are the same diameter, we encounter angular junctions of wires with dissimilar diameters. Although NEC-4 improves on the performance of NEC-2 under these circumstances, the results are insufficiently accurate for use as a comparator to the calculated values. In addition, gamma spacing is rather narrow for most beams that use relatively fat element diameters. Under these conditions, NEC tends to yield less than precise results. The relative unreliability appears in the average gain test (AGT) scores, which generally are no better than 0.92 when a perfect score would be 1.00. Since arriving at a feedpoint impedance of 50 Ohms is critical to the comparisons, AGT values in the range of 0.92 are too far from ideal to be useful. Values of 0.98 to about 1.02 are more valuable to the task of comparison"

more on modeling gammas & using calculators

https://ea5nd.com/wp-content/uploads/2017/11/Gamma-Match.pdf

 

[The DB]

The radials form transmission-lines,

the gamma section is a 2 wire transmission-line shorted at its far end,

In your mind, what are the minimum requirements for radials angled upwards to "form transmission lines"?


The DB

 

[bob85]

Im not sure what you mean by minimum requirements DB