Modified Vector 4000

[Marconi]

OK Bob, this is Mikey with his new Vortex Q82M1 at 27.500.

I haven't scaled the model yet, so I used the dimensions I had on a Vector. I made the radiator 338.6" and the radials 107.029" inches. I had to fiddle with the bottom radial off-set to get a match, but that is not important to know unless you want a model to match.

You know I don't have to match the antenna using Eznec, as long as the Average Gain for the Free Space model is good enough to be considered as accurate. With that said, no matching is sometimes difficult to impossible to produce any bandwidth info because the SWR is out of whack.

I'll continue with this model and maybe get it to be more in line with all the specs you have provided above, and I will also do it as an end fed antenna...like Vortex has done. I doubt I can get it to match however, but I could be wrong.

Does this sound like a plan until you get the conditions to do your test?

 

[bob85]

Rain all day, i already turned the lawn into a mud bath

Eddie
if the advantage is still there when i do another test with 2 antennas im happy are working as they should and higher above ground & you still feel like trying to model them it will be easier as they are the same antenna,

the only thing that changes is how far out i pull the upper radial tubes & maybe shorten the monopole top section a littlle, then find a good match with the gamma,

tapers & diameters are identical so any difference i see is not down to the details that make a Vortex different,

it could be due to other factors im not aware of & more tests with different people would be nice but not doable right now.

 

[Marconi]

since the hoop cone & monopole are so similar in length to a Nv4k i will list the things that are different,
it won't help you make a good model,

The tube diameters for the mk1 radials are 16mm & 12.7mm
mk2 radials version 1 & 2 use 20mm 16mm & 12.7mm,

vector uses 13mm & 10mm,

you can see from oggy's video review on the Q82 mk2 version1 that they did not use equal length sections,

we also know that on the mk2 version 2 they extended the 38 & 30mm lower tubes so that the spreader clamped to the 2nd section & not the 3rd section shown in oggy's video,



The lowest part of the monopole inside the cone is 2" / 50.8mm box section stepping down to 38.1mm tube, & 30mm tube
vector uses 33.5mm & 30.5mm lower tubes

Vortex gamma is 16mm & 9mm
vector gamma is 13mm & 6mm,

these seemingly small details are what makes the a Vortex Q82 mk1 different to a vector & all the other sigma4 clones sold in cb shops,

i don't believe those differences make a Q82 mk1 consistently 2 s-units up on a vector 4000 unless other factors were screwing the tests up in a major way.

Bob, I also am not sure that my getting the tubing diameters as close as possible to the Vortex Q82M1 will make a difference, but I had used my earlier models and made 1 with a physical gamma, 1 that has a simulate match somewhere above the base of the radiator, and 1 with the feed point at the base as in End Fed...similar to what Vortex apparently did in their ads. There is not much difference and their reported gain of 4.41 dbi at 8* degrees, and my models showing close to <> 4.30 dbi at 8* degrees.

The 1st model of a Vector I ever made with a real gamma match was back in 10/2016, and it showed 4.15 dbi gain at 8* degrees. That was before you posted your dimensions for the New Vector 4K, but you did not say what frequency, so I always used 27.205 with those same dimensions and my gamma tuned setup took care of the length and the frequency difference, if any.

Since I made assumptions about what I saw of the antenna back then and knowing it was suggested to be 3/4 wavelength at some frequency...I just guessed and I posted that guess on the forum. A few folks sent me dimensions, mostly without frequency and diameters, and they all varied in size. They just got the antenna to working an the gamma made the match, with the dimensions within reason.

If this is all we've talked about for the last 4 years re: the Vortex...then we've been wasting our time. That is unless we finally learn about how to use a term you coined long ago, "...tuning the matching and length for the maximum gain at a long distance."

However, now we have a claim from Vortex saying the Q82 Mark 2, when accurate produces 5.82 dbi at 8* degrees...then we have a horse of a different color. www.youtube.com/watch?v=YGAPKnHcGDM

Can you give me any ideas for the tube lengths and diameters for this 6 wire "Vertical Radiator Stock," they talk about in their ads?

Again, while we are waiting on the weather, I want to at least try the real dimensions using taper (TPr) on the Q82 Mark2.

TPr == Taper
EF = End Fed
PhyGa = Physical gamma
SG = Simulated gamma

 

[bob85]

We don't have the section lengths Eddie,

you could work the diameters out using wall thickness but they use unequal lengths as seen in the video & the mk2 version 2 uses longer 38.1 & 30mm tubes,

I won't be doing any tuning for signal strength, I will tune for a low vswr,

Vortex claim 4.41dbi @8degrees for the mk1 & 5.82dbi @7.5 degrees for the mk2,

they used 10mtrs above average to good ground on 27mhz & you use about 1 wavelength above ground in models, I will test at about 1 wavelength above ground on 50mhz.

 

[freecell]

"I won't be doing any tuning for signal strength, I will tune for a low vswr,"

swr on the feedline has nothing to do with whether or not the antenna is in a "tuned" condition. regardless of the match between the feedline and the load, an antenna is in a "tuned" condition when reactance is equal to 0 at any given frequency. the total absence of all reactance, both inductive and capacitive, (X=0) is the absolute indicator of the "tuned" condition known as resonance.

 

[bob85]

When the rain stops & it drys up a little i can take the laptop out & put the analyzer at the feedpoint,
i don't tune for resonance through my coax,

i can't see how the 3/8 version or the longer than 3/4wave monopole versions can be self resonant,
but does it have a very wide swr bandwidth & produce stronger signals than the circa 1/4wave cone versions that everybody else but Vortex has used over the last 40+ years.

 

[freecell]

"i can take the laptop out & put the analyzer at the feedpoint,
i don't tune for resonance through my coax."

are you and your laptop also going to be present in the near field of the antenna along with your analyzer while you're reading / taking the measurements?

 

[bob85]

Not close enough to effect the tuning, antennas will be up in the air,
i can see on the laptop if me moving around changes the readings,

its not scientific, nor are the tests any cb antenna maker i ever came across does,

what i am doing reflects what people will typically do with their antennas expecting to see the gains claimed in the advertising,

i have had a few suggestions on how a test should be conducted including dummy antennas to absorb ground reflections,

im sure there are much better methods using better equipment out in the middle of nowhere in flatland but none of that was done with the Vortex tests,
no mast isolation & i see no choke in the test setup,

my test is to find out if what Vortex say is true,

i will also test isolated from mast & choke the coax because that's how i use my antennas.

 

[Marconi]

i can't see how the 3/8 version or the longer than 3/4wave monopole versions can be self resonant,

Bob, I think somebody suggested that idea for a 7/8 wavelength Vortex with the extended cone basket.

Did you see that in one of my models? If I posted such a model it would not be matched with the feed point at the bottom end. At best I might try and get the Average Gain to show = 1, but it would not be matched without some matching device added.

 

[The DB]

swr on the feedline has nothing to do with whether or not the antenna is in a "tuned" condition. regardless of the match between the feedline and the load, an antenna is in a "tuned" condition when reactance is equal to 0 at any given frequency. the total absence of all reactance, both inductive and capacitive, (X=0) is the absolute indicator of the "tuned" condition known as resonance.

Interesting opinion. The reality is, just because someone chooses to use SWR when tuning an antenna does not mean the antenna is not tuned, it is simply tuned to a different point. Seriously, does it really even matter if you choose one or the other?

Do you know how much of a performance difference there is between the low SWR point and the resonant point? You will never notice this difference in the real world, which leads to the question again, why does it matter which you choose to tune the antenna to? If you claim resonance because you think it will give the absolute best possible performance, well...

Do you know where peak signal strength lines up? It doesn't necessarily line up with either SWR or resonance. Sometimes it is close to one, sometimes it is close to the other. Something that is often not even considered can have more of an effect on this than tuning to either of these tuning points, namely the coax. The more losses in the coax the closer peak gain lines up with the low SWR point and it doesn't take much, 1 dB is more than enough, to cause a shift in where peak gain for an antenna system is. There is a very good reason for this.

I am saying this as someone who has used several methods to measure field strength over the years, starting with a field strength meter, then using a spectrum analyzer, and now I am experimenting with a second antenna attached to the s21 (in short second) port of a VNA, and so far the results of measuring antennas with all of these devices agree with what I posted above.

are you and your laptop also going to be present in the near field of the antenna along with your analyzer while you're reading / taking the measurements?

There are multiple VNA's out there that can calibrate out the effects of a feed line, so you don't necessarily have to measure at the feed point of the antenna to get accurate measurements. One of them costs around $50 so its also not like they are prohibitively expensive. The only real issue is if common mode currents exist they will affect the readings, however, it is not difficult to tell if they are present after using one of these devices a few times...

I'm sorry if this sounds mean but seriously, freecell, its like you think you are talking to newbies, but in reality you are making yourself appear to be the newbie...


The DB

 

[bob85]

Eddie,
it was Donald that asked if Vortex tested a longer monopole with the extended cone,
i have not seen Vortex talk about such an antenna.

 

[bob85]

Twins ready for tuning,

 

[Shockwave]

Twins ready for tuning,

Nice work Bob. If trading radiator length for more cone length increases signal, it does seem to change the idea that cone radiation is far weaker than the monopole. Or, it changes the situation, so that much more current flows on the cone. Thanks for sharing your progress.

 

[bob85]

If the 3/8 cone does outperform the 1/4wave cone i will certainly be looking for answers on how that could be,

Iooks like a 3/8wave transmission-line feeding a 3/8wave radiator which is more unbalanced than the standard setup & we don't want to upset Kirchhoff,

i imagine more radiation from outside of cone & coax braid/mast,

Here's something from Cebik on none standard j-poles that explains why you can extend the cone feeding the upper monopole,

"If we hold the matching-section open end length constant and change only the length of the radiator upward, then the feedpoint resistance decreases while the feedpoint reactance increases.
If we hold the total antenna length constant and increase only the length of the matching-section open-end leg, then both resistance and reactance increase at the feedpoint.
The common reactance response to length increases together with the opposing resistance response to length increases permits one to find a purely resistive 50 Ohms for the feedpoint.
However, since the currents on either side of the feedpoint are not balanced, a choke balun is mandatory to suppress unwanted currents on the feedline"

 

[Marconi]

Bob, here is my model of the Vortex Q82 M2 scaled to 50 MHz.

Here are my dimensions for wire #1 thru #47 in meters. For me to be sure we're on the same page, see how close these are to your antenna with the extended radial basket?

My model here is intended to have no mast, like Vortex showed on their Website but I added an image to indicate the antenna height only.

I also set the feed point at the very bottom of the model...just like they did and I know you are using a gamma.

I did not try and match this model. The Average Gain shows 1.152 = 0.62 db and that indicates the gain reported is overstated a little (+0.62) to indicate a unreliable model. With that said, when I scan the SWR the antenna shows resonance at 44.8 MHz and IMO that is not right either.

No doubt I have some dimensions wrong in my 27 mhz model or I did something wrong to the scaled model.