Modified Vector 4000

[Marconi]

Bob, here is my model of the Vortex Q82 Mark2.

I added taper to the radiator, but I don't understand the geometry well enough to taper the radials...unless the radial is a single wire.

With single wires I use an Eznec elevation rotation tool the sets the radials slanted up or down at a <>180* degree angle of choice. Multiple wires look to be allowed using the tool, but so far the process does not seem to work for me.

I have thought about this, but I don't think I can explain why except to say, if I use the Average diameter for the radiator, the gamma is looking for a diameter for the radiator to the gamma ratio to be at or near specs. And averaging is not working when I use an Average diameter between 0.75" - 0.84" inches for 11 meters and the specs call for the radiator to be about 1.50" inches or more at the base.

Once i got the radiator tapered as to lengths and diameters, by guessing, I checked the bandwidth curve to see what happened. Then I was able to see the wide band width noted for this design. So, that suggest to me the model needs to be pretty close to the real specs.

I was tweaking very small dimensions here and the model would fail due to errors being reported. This tells me this antenna is working right on the edge.

Maybe that is why the video some young man made while installing his new Vortex is no longer anywhere that I've looked. I might try and look thru my YouTube history file...I think I saw his video recently.

Did you ever see this video of a young guy installing his Vortex?

Also note the two bandwidth curves. I tweaked the antenna and I changed the length to start with but that did not work right, probably because I had a capacitor on the gamma match at the tap point. In such cases I find the models do not respond to the physical change like a normal model without a load of some kind. IMO this is a Eznec issue. I was also trying hard to keep to the 0.75 wavelength what ever that is and I did not want to change the specified 3/4 WL if I could avoid it. It looks like the bottom may be producing more currents that the top, and they both show to be in phase. So the radial loop is doing its job here.

Could this possibly be similar you were seeing in your thread on a "Different Viewpoint?"

Could this be what you were seeing when you commented, "...did these guys at Vortex solve the problems with stacked 1/2 waves?" No, but it looks like they did produce a set of stacked 3/8 wave radiators at about 161'' inches per element.

 

[Marconi]

1/4wave cone version,

Bob, I will compare these dimensions to my Vortex Q82 Mark 1, but I was just curious what your dimensions were for your 6 meter version of the Vortex Q82 Mark 2 with 3/8 wave extended radials.

Maybe you don't want your dimensions to be published, I get it.

Did you notice that I didn't post my dimensions above either.

 

[bob85]

I don't recall saying anything about vortex & stacked 1/2 or 3/8waves Eddie,

i have wanted to see a model of a 3/4wave center fed dipole 10mtrs above average ground to the bottom of the dipole (not feed-point) for a while,

that's the best i imagine is possible from a 3/4wavelength tall single element antenna at that height,

My antennas are identical apart from cone length,

the tip on the 3/8 version may end up a little shorter but not much,
i don't want to change the length ratios Vortex used on the mk2.

radials are the same apart from the 10mm top tubes are exposed further to make the cone about 2275mm

same size hoop,

im not done tuning it yet, just need it to stop raining & snowing,

if im too close at the base of the cone i can change the the radial bolts & put spacer nuts on,

if the gamma spacing is too close at the base i can fold another tube with a longer flap to space it off,

the shorter gamma strap should give me more range of adjustment.

i look at your gamma situation like this Eddie,
if the diameters & spacing effect real world gammas they must also effect eznec gammas,

im not saying that averaging tapers ruins the gain & pattern,

only that diameters and spacing between the monopole & radials,
and in the gamma section effect the match.

 

[The DB]

Im not sure what you mean by minimum requirements DB

You have been talking about this since when it comes to these antennas since before I became a member of this forum, and while I have always had a general idea about this, I guess now I am more interested in the specifics. I'm sure you talked about this in the past, but I don't know which threads, or in some cases how deep said descriptions are.

So, does being coaxial specifically refer to the shape of the cone on these antennas, and other antennas like a sleeve dipole? Is this all that is required, or do certain electrical lengths come into play, or is there also a certain voltage/current distribution needed as well? Do you see a lack of radiation from cancellation or some other means being required as well?

What does it take in your mind to consider a part of this type of antenna coaxial?


The DB

 

[bob85]

DB
I would say anytime two or more conductors occupy a similar place in space & carry energy from one place to another in a somewhat confined manner its a transmission-line,

length does not matter & current & voltage phase need not be equal & opposite,
it can be unbalanced, its still a transmission-line,

3/4wave coaxial j-pole is what sirio called the vector, they also call the solid stub CX series 3/4wave coaxial j-poles, the CX is just like a fat 1/4wave section of air spaced coax,
i think they mean having a common central axis,

to my eyes the skeleton sleeve fed monopole is the closest antenna to a vector & looks like 4 parallel 1/4wave j-pole stubs with the diameters length & spacing set for a good match to 50ohm coax,

I see the vector as a shorted variant of the ssfm in the same way the shorted stub j-pole is a variant of bottom fed j-pole,

I would say even though the vector radials look nothing like a solid tube or piece of coax
the spacing & roughly parallel position relative to the monopole are enough for it to act much like the CX series of 3/4wave coaxial j-poles.

I see two sources of radiation from the cone, the radials are not very close and not parallel,
I think Henry's model of the cone terminated with resistors shows this radiation,

radiation due to the unbalance at the top of the stub just like a j-pole stub
with current divided between the radials eliminating the j-poles front to back ratio.

 

[Marconi]

I don't recall saying anything about vortex & stacked 1/2 or 3/8waves Eddie,

Bob, as I was writing my post I had a thought about your comment as I recalled it. We were discussing the 3/8 wave Vortex and my memory just failed me.

I also remembered making a stacked 3/8 dipole and I checked the pattern and was surprised that it looked very similar to the Vortex. Also, the stacked dipole showed more gain and the top element shows more currents, and I see the opposite situation with the Vortex.

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

I saw that also.

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,

I think I said the space from the feed point to the dog bone was 60" inches. I could have posted some models that had a 5" - 7" inch dog bone in the process of trying to get my models to match too. If I modeled and antenna that I don't own or the manual does not show the DB dimensions...then I now days I would rather guess than ask.

When I model I sometimes changing several wires to get the match, and sometimes I make a mistake or forget to fix something.

I saw Dave's video, and I think he also suggested the gamma was almost parallel with the radiator.

 

[bob85]

That's why i said it will be easier to model my versions,
we have the dimensions & no big steps in diameter around the cone area,

you can make a model look great by cheating or leaving mast & coax out of the model as you demonstrated,

cheating does not work when you build real antennas connected to coax & masts.

We have a bit of sun today Eddie,

first scan with the gamma set parallel looks much better, 1.7:1 with a flatter looking curve between 45 & 55mhz before i start tuning,

im thinking i will have this dialed in in no time ,

then the stiff coax flipped over & the plug & adaptor landed in the dogs water bowl which would have been ok had the sun not melted the ice,

its the only spare coax i have with plugs on so im drying it before testing it with a good dummyload,

weather is not good enough to be taking the laptop outside & hooking the analyser to the feed-point.

 

[bob85]

Eddie
i think the video you are asking about was a guy called Nick Parker 2E0POS,
he did the first comparisons against the vector 4000,

I put some plugs on a longer length of new rg213 & tuned it for 50mhz,

measured vswr dropped from 1.7:1 to 1.58:1 before i started tuning due to the extra loss in the longer coax,

tuning with the closer spaced gamma is much easier, i used a shorter tube & longer rod than i used on the 1/4wave cone,

50mhz
3/8 cone 1.04:1 very wide banded can get it lower
1/4 cone 1.02:1 fair bandwidth

Then it started raining & vswr has gone up a little,

I just did another test with Nav on the short tuning pole,

3/8wave cone -90.5dBm
1/4wave cone -87.9dBm

tuning the 3/8 cone has improved it by about 1dBm but its still behind the 1/4wave cone at this height above ground,

neither of us can see any difference on our radio meters.

 

[Marconi]

Parker 2E0POS

The video I saw was showing a guy installing a Vortex Q82 Mark2. He never showed the antenna installed, he was just holding it up sitting on the ground, and the radiator was not installed yet. He was raving about how good it was and acting like a Parrott, telling us the claims that Vortex has made. I probably saw this on their Website as a link, and I had the thought that it was likely just an advertising stunt.

Eddie
i think the video you are asking about was a guy called Nick Parker 2E0POS,
he did the first comparisons against the vector 4000,

Bob, I don't find anything about Parker 2E0POS on YouTube, a lot of images about fountain pens etc., in the IMAGES.

tuning with the closer spaced gamma is much easier, i used a shorter tube & longer rod than i used on the 1/4wave cone,

50mhz 3/8 cone 1.04:1 very wide banded can get it lower
1/4 cone 1.02:1 fair bandwidth

Bob, I make a gamma as follows and thus far it hasn't been far off in use with other models...if I'm able to tweak into a good match.

I just use a wire that is close in length and diameter to the rod used and the distance the manual shows for the gamma off-set (at the hub) at the base...up to the gamma dog bone. So, I have 4 wires to consider and to help tune. Then I add a capacitor to a segment close to where the rod typically is exposed on the real gamma. Then I move the tap point around until I get close to 50 ohms. Then I tweak the capacitor value until I get a good match.

Sometimes I have made a model using what I call a simulated gamma feed point. This is where I move the feed point up and down on the base of the radiator until I find a spot close to 50 ohms.
Then set the source there to start. I also determine where this point is and if I use a gamma I set the dog bone at this point and see if it will works there.

Sometimes this process seems easy and other times it is difficult. Sometimes I find myself chasing my tail. Then I figure the rod length or the spacing is off and I start tweaking for a good spot close to 50 ohms again. I use several wires that effect the tune, and this is where I can get confused and possibly get stuff wrong. I have failing short term memory so I forget what I was doing sometimes, when I have to eat, go take a leak, let the dog out, or go to bed...among others.

I just did another test with Nav on the short tuning pole,

3/8wave cone -90.5dBm
1/4wave cone -87.9dBm

tuning the 3/8 cone has improved it by about 1dBm but its still behind the 1/4wave cone at this height above ground,

neither of us can see any difference on our radio meters.

I thought the 3/8 wave cone antenna was showing the best gain earlier.

So, what is the difference in db vs. dbm in the case above.

My models tend to show 1.51> dbi less gain for the VM2 version, meaning more gain for the NV4K.

How do you think the lack of being linear is affected by being close vs., farther away?

I checked some of my old Signal Reports for some of my regulars over a 2 month period of time in the Fall of 2011, at 16 miles and less, and at 40 miles and more. I had a few closer in and they were all, at or less than a 1/4 of an Sunit mark difference on my meter as I recorded. Over time I used several radios that were also noted on the reports and they to checked out to be pretty much the same.

The 16 mile range seemed pretty steady and the longer distances showed a tad more difference at times. That said a lot of things could have effected my results as you have brought to my attentions.

How do you think more distance would effect your results? I think Henry saw that distance made more difference in the antennas he reported on page 41.

Good work Bob. Now try and get a hold of your old Fish Munger buddy on the coast 90 miles away and give him the test as he traveled down the coast road in his huptie mobile.

 

[bob85]

The 3/8 was further behind in the last test Eddie,
lets see what happens when i raise them higher above ground,

dB is relative to something such as dBi or dBd,
dBm is relative to 1milliwatt of power,

i don't know what effect further distance would make, there's nobody to test with further away that i know of,
Nav builds more antennas than all of my hammy mates combined, none of them have 6mtr antennas up,

we know we can't test with long times between tests, swapping fast seems to take care of signals changing with time,
i don't see any change with 0.1dBm resolution, signals from both antennas settle on the same numbers,

it would be nice to have somebody further away to test with, even some hams using 6mtrs to talk instead of bsgatewaydigifusioncrapola would be nice.

 

[HomerBB]

Bob, I'm in Arkansas. Would that help?

 

[bob85]

If Arkansas was about 20 miles east of me you would be ideal Homer ,

I don't want to jump to conclusions about the 3/8wave cone too soon,

I have only compared them 1/4wave from the ground & only with Nav on his modified sirio tornado 5/8,

Vortex tested about 1 wavelength above ground not isolated from the mast,
I will do the same, then isolate the antennas & repeat.

 

[Shockwave]

Bob, You've probably thought about it, but I'm guessing there are no six meter repeaters in the distance you can tune against?

 

[Marconi]

I started a new medicine on Thursday Bob. The Dr. thinks I may have had some Mini-Strokes. I think the med is giving me headaches and making me get dizzy at times. It is hard to concentrate and I'm seeing floaters. She is trying to wean me onto this miracle drug for a week, using an old anti-depressant drug that has been found to be effective at healing the damage from such strokes. I've not had a major stroke, so I'm going for and MRI Monday.

I'm going to try and take a break today, and get some rest.

Keep up the good work.

Assuming you are using the Vector hub I need the diameter and the mast diameter.

I'm converting the M1 model to your dimensions. What is the space (length) from the feed point to the dog bone, and what is the off-set at both top and bottom of the gamma for this space? What is the exposed length and diameter of the rod and the length of the tube part - to where the rod goes into the tube?

I will 1st try this point for the cap I add checking for get a match.

 

[bob85]

Eddie,

The hubs are 70mm wide where the radials bolt, monopole is 37mm diameter at the bottom,
mast 48.3mm diameter,

gamma tube 13mm x 225mm
gamma rod 6mm x 540mm exposed to center of dogbone

gap between gamma & monopole
bottom 32mm
top 55mm

tapped 765mm from hub to center of dogbone



Good luck with the new medication.