Modified Vector 4000

[Marconi]

Here is my current model of the NV4K with a physical gamma match included before and after scaling to 50 MHz. I also included the scaled model and noted some dimensions it shows...so you can make a comparison.

These dimensions all scaled in the process and I need you actual lengths and diameters Bob including all the dimensions for the gamma setup, including the dog bone L", and the offset L" at the radial hub from the center of the radiator to the center of the radial.

I will have to guess at the average element diameters for the radiator, radials, and the loop, because I will not be using taper. If you can estimate these values that might help me get closer too.

 

[Marconi]

Bob, I've been checking the difference in these 2 model dimensions.

1. I see the length of the radiators is 1" longer on the model Homer posted, but it has a top hat too, and the physical gamma model has no top hat.

2.The model Homer posted has the average radiator diameter set at 0.75" inches and the model with the physical gamma is set at 0.80" inches.

3. The loop diameters are identical at 29.97" inches.

4. The radials lengths are also identical at 106.259" inches.

5. The radial off-set at the hub bracket for both is set at 2.50" inches and I've had to guess at this dimension. I forgot to check the off-set for the wire to the feed point, but I think it is close to < 2" inches...but I used my Sigma 4 model for this measurement, so it is just a guess too regarding the NV4K.

6. The real gamma model uses 313 segments and Homer's model has 453 segments. That could have the effect of the difference in gain reported.

So IMO, with these dimension being so close, it appears that the difference in reported gain has to do with the matching differences or the segments difference.

This leaves me to at least consider, that we can't just take some dimensions and make a model that looks like some antenna we saw somewhere at a distance, and expect to see really good results.

 

[Marconi]

Bob, I'm not sure exactly what you've said here recently, per your new project. But, I may have just jumped into the middle of you business. Sorry!

But, I'm curious at to what specific lengths for the radials you plan to consider when checking or comparing your results?

Or, are you talking about Henry's and W8JI's ideas about radials being necessary and thus interested in adding more radials below the NV4K/Sigma4 that will make for improved performance?

What happened to the idea old ideas of making the loop bigger or making the radiator longer to get better results?

I recall modeling the Vortex M2 I think...and I found them likely puffing about those results being well overstated at 4.50 dbi or more...as best I can recall.

 

[bob85]

The radials are from a sirio 827, 8mm diameter x 1400mm long,
I can add tuning tips using a few inches of gamma rod if i need to,

Making the hoop bigger is an idea from the patent, it claims .6db more gain if you make the radial tips 9 feet apart where the radials are about 30 degrees from the monopole,

To me the mechanical issues outweigh the small gain advantage they claim and i don't like the look of the big ring,

I may experiment with monopole length at some point but for now i want it 3/4wave with a 1/4wave sleeve,

I can test Vortex's claim about the mk2's 3/8wave sleeve giving more gain and wider low vswr bandwidth.

 

[Marconi]

I can test Vortex's claim about the mk2's 3/8wave sleeve giving more gain and wider low vswr bandwidth.

Bob, I sure hope you get a chance to test the Vortex idea.

When I made those models I did see the extra bandwidth over the NV4K for sure, but I found their gain in Eznec appeared to me to be overstated.

I figured nobody would believe a model over the claims from Vortex, so I think I lost interest in that idea. Their M2 antenna looked funny anyway with the radials about 140" inches long.

I also see they are shutting down operations as of this month.

 

[bob85]

Eddie its snowing here, not much but its not antenna weather,
my buddy is in the same boat waitng for a break in the weather to put his 6mtrs modified 5/8 tornado up,

Vortex make some BIG claims about the q82 mk2,
if theres no radiation from the outside of the sleeve then its just an unusual 3/8wave,

Cebik wrote some info on modeling j-poles with unconventional construction
http://on5au.be/content/a10/vhf/jp1.html

 

[Marconi]

Vortex make some BIG claims about the q82 mk2,
if theres no radiation from the outside of the sleeve then its just an unusual 3/8wave,

Bob, I noticed the antenna patterns show the currents in the at the bottom of the top 1/2 wave radiator where the phase change happens is well above the loop. IMO this effect is similar to the bottom 1/8 wave on a 5/8 wave. This out of phase portion pushed the high angle lobe higher.

I'd think that if Vortex did discover something to help solve this distortion in the pattern issue and they were using Eznec+...that would be enough. IMO however, it looks like that was not enough of a benefit just to improve the pattern...they had to boost the gain to cater to the CB world.

If you look back at the older thread on the M2 you can see my models look very close to the model, item for item, that they posted. As best I recall, I ran a free space models to check the Average Gain results and I fixed my model accordingly...in order to show a more accurate model. Vortex didn't show us that and left the overstated gain as a sales pitch. Looks to me like a lot of folks believe that hype.

Did I post that Vortex is out of business?

 

[bob85]

You did mention they were shutting down Eddie,
I won't lose any sleep over that, I don't like the way they build antennas with few sections of stupid heavy thick wall tube,

My buddy has the Q82 mk2 but he has not put it up yet & seems to be in no rush to try it,
when i asked him what his first impressions were, "fcking heavy" was his reply.

 

[bob85]

Eddie

i did a quick rx test between me and Nav with & without the 1/4wave radials ,
the antenna is only 5ft or so off the ground,
its not tuned perfect without the radials & i have not tested vswr with the radials installed,

i had him key multiple times each way to make sure signal readings were stable on 50mhz, they are, i got the same numbers every time

without radials
-89.7dbm snr 13.4db

with radials
-90.2dbm snr 13.3db

so as the vector is setup now at that height & not retuned for the radials im losing .5db @ 4.5miles when i add the radials.

 

[Marconi]

Homer we have conflicting models of what effect radials have on the vector,

Eddies model shows radials cause a drop in gain & radiation wasted at high angles,
Donald claims radials spoil the cake too,

Henry's model shows radials give an increase in signal strength that becomes less of an advantage the higher the antenna is above ground,
w8ji also says this type of antenna needs radials,

Best way to find out is put 1/4wave radials on a vector & make them quick/easy to add & remove,

My buddy 6 miles away has chopped a sirio tornado for 50mhz so i will have somebody for signal checks,

Here is another series of models trying to show how my models predict how the NV4K responds with various lengths of horizontal radials set at 3" inches below the Feed Point.

I only added the antenna model of my best NV4K and for Henry's idea that 1/4 wave horizontal radials added to the Vector...might help produce more gain, and W8Ji saying this type of antenna needs radials.

 

[Marconi]

Thank God, I tested clear of China Covid 19 again.

 

[HomerBB]

If W8JI said this antenna could benefit by having radials my guess is it would be with reference to common mode currents. He has been very vocal about the CMC issues for jpoles, and considers the V4k a jpole antenna type.
Your models do not suggest any gain improvement toward the horizon.

 

[Marconi]

If W8JI said this antenna could benefit by having radials my guess is it would be with reference to common mode currents. He has been very vocal about the CMC issues for jpoles, and considers the V4k a jpole antenna type.
Your models do not suggest any gain improvement toward the horizon.

Thanks for your comments Homer.

Here are my comparison models. I don't include Feed Lines, so that will be next. This shows how models can show to be overstated or understated and how it effect the reported gain.

This is where Free Space models come in handy by reporting what Eznec determines is an accurate model or not. I use them, but I see very little use otherwise. This is what I think folks like, Vortex and JoGunn, and some others might be reporting when their gain looks to be overstated or unbelievable.

1. My comments on this issue.

2. The Control Center for Eznec is showing Free Space where the Average Gain results for the model is showing to be overstated gain of +1.12 db in this case. When this happens we subtracted the error value noted from the gain that is reported for the model. 3.02 - 1.12 = 1.19 dbi gain. This doesn't look like a good model right off the bat...and all I did was add 4 x 109" x 0.625" radials 3" inches below the Feed Point at the bottom of the antenna.

3. is the Real Earth version of this model. I show several view of the antenna and this notes the dimensions for several important measurements for the radiator, radials, mast, and the gamma section area. It also reports 4.71 dbi gain at 8* degrees. This value is noted to be overstated by the Free Space model #2 above.

4. Again this model's results Is considered accurate by the Free Space model results being equal 1. Since this model with 4 horizontal radials added to the antenna is not showing me what others say will increase the gain...I decided not to try and tune this to a better match...plus the model should be workable at 1.419 SWR at 27.205 MHz.

 

[bob85]

Eddie,
Henry's models don't claim incresed free space gain, its claiming an increase in signal strength @ 30kilometers when you isolate the mast & coax & add radials,

I think i posted it ass backwards, the improvement with radials is claimed to increase the further away from ground the antenna is,

My test vector is only about 1/4wave from the frozen ground at the moment & i think the cone is too long,

from me to Nav is 4.5miles as the crow flies,
at that distance & antenna height adding the radials & doing no retuning consistently loses me .5dbm or 1/12 s-unit,

its not lab standard measurements but it is a measurement of power at the rx port & not just a relative guesstimate based on agc line voltage in a radio & displayed on a very low resolution s-meter,

HF s-meters are not calibrated the same as vhf/uhf meters,

on HF my 90.2dbm reading equates to a little under s-6, the same 90.2dbm on vhf where im experimenting is 2db over s-9

 

[Marconi]

Eddie,
Henry's models don't claim incresed free space gain, its claiming an increase in signal strength @ 30kilometers when you isolate the mast & coax & add radials,

Bob, I can't argue the merits of this new idea for measuring signal strength, at least for Me. I don't see where Henry mentions Free Space in this area on page #41 of his report either.

However, I do see a fallacy with the idea that ground is a factor in Free Space modeling in your comments above. Height is also NOT factored in a Free Space models either. All losses have been removed and that is simply what a Free Space model is.

I would like to understand more about this new process for measuring signal strength. I see the chart that Henry reported to us, but I don't see how a Free Space model could be effected by changes in height. Plus, everything that Henry says about this topic on page #41 is referring to height above Earth at 10m and up to 30kM away.

I do remember Henry giving The DB a caution in his application of this feature in his modeling with 4NEC2 back around the time you posted Henry's report. However, I do not know if they discussed the idea further. Those 2 are the only folks I've ever heard discuss whatever this signal measurement feature is called.

I do seem to recall asking about the # values being reported as db's in the left side of the chart. I think I heard the higher the numbers that represent the db's, the lower the value, and thus the lower the signal and that was said because the values are (-) values.

If true, then these results in Henry chart shows the Sigma 4, without radials is stronger than the Sigma4, with radials added.

I think I right and I know, little to nothing, about this idea.

How say you?