Base New Vector 4K radiator at 0.75 - 0.82 - 0.875 wavelength.

[Marconi]

Bob, I didn't think modeling and a few other technologies would ever develop and be available for the hobbyists. I'm just a CB operator that was determined to learn, from hard knocks, what I could about antennas.

The reason I mention this is to indicate to folks complaining about Eznec limitations and maybe modeling in general...that they didn't know what they were talking about in this regard.

 

[Marconi]

I can model using AN-SOF 100 if you want colors. I think DB's 4Nec2 also produces some color images, but IMO none of that really makes a model better and some of those graphic design reports are difficult to get a grip on, and for sure with nobody around to explain or even talk about this stuff.

Remember the misunderstandings we were getting when we were told about the Sirio CST model results, and the three wire test that proved col-linear results from the Sigma4/NV4K designs.

Thanks to Henry, he got us all straight on that boondoggle.

 

[bob85]

That's what i mean Eddie,
me & Donald fell into the trap of seeing what we wanted to see because its not clear to the untrained eye what the cst image is showing, we don't have that problem with eznec,

my up graded sigma will be close to 3/4wave with 108" radials Eddie, mainly to increase wind survival,

is it safe to say that the 3/4wave version with the 107" radials when installed at the same tip height as the extended versions with either 90" or 107" radials gives the best performance at low angles ?

 

[Marconi]

my up graded sigma will be close to 3/4wave with 108" radials Eddie, mainly to increase wind survival,

If it was me Bob, I too would 1st modify my S4 model with 107"-108" inch radials and use a 3./4 wavelength radiator. Get it to work right and then maybe make the radiator longer and see if the gamma is able to make a match and possibly get more gain. Then you can report to use if you still see increased gain at a distance...like you did with your Vector Hybrid.

is it safe to say that the 3/4wave version with the 107" radials when installed at the same tip height as the extended versions with either 90" or 107" radials gives the best performance at low angles ?

I have not done that comparison yet, but I will post it soon.

BTW, have I posted something about using Eznec's Average Gain Test and using the "gain correction factor" it also provides for models that get into trouble and need a fix like Steve and I have been doing recently...to make some models show AGT = 1 and get the match looking good at resonance too.

I found the 1st "old" Vector model that ever I did with taper and without taper. I checked the Free Space Average Gain on both, and the one with taper was off a bit showing a 0.83 db correction factor. The Real Earth model reported a gain of 5.13 dbi and was overstated due to the AG error reported. So, I did the math and got: 5.13 - .83 = 4.30 dbi.

I did the same for the model without taper. It had a perfect AG, so there was NO correction needed. However, the match was of at 1.453 SWR (not so bad) but off. This model reported a gain of 4.34 dbi.

Again this shows that taper does not report as bad a model as some folks report.

Then I took my most recent Vector model at 323" inches and it reports a perfect 1 AGT, and reports 1.048 SWR with a gain of 4.33 dbi.

With this I figure my older Vector models were fine, because this shows us the gain for these old model with/without taper vs. the more recent model all produce almost identical gain results at about 4.30-4.34 dbi.

me & Donald fell into the trap of seeing what we wanted to see because its not clear to the untrained eye what the cst image is showing, we don't have that problem with eznec,

So, all this time Eznec could have been reporting accurate gain results had Steve and I just made a Free Space model and used the error correction to fix the gain and made it clear what was going on.

Big difference would have been...asking folks to believe any gain results reported from a model with a bad match and maybe showing currents on the mast. In such cases they would be inclined to get the eye-candy factor...that is common in human perspectives on many things. Plus we all tend to believe what we believe...come hell or high water.

 

[Marconi]

Bob here is the 323" model raised to the same tip height as the 380" model. Both tips are at 380" inches. The shorter Vector shows a 1* degree lower maximum angle however. However if I lower the 380" antenna to 7* degrees like the 323" model shows the gain only drops from 4.78 to 4.72. This is better than 4.52 dbi. I think you predicted that earlier...that the longer radiator my go up a bit in angle.

I know you remember these are only models and need to be verified in the real world.

 

[bob85]

i don't know when we started seeing reasonably accurate vector models Eddie,
i guess when they were telling us the sigma style antennas out perform a 5/8wave on the same mast,

i will experiment a little with length because i have 4 x 108" radials,
we don't know what length is electrically 1/2wave when we add the radials
i won't be making all the iterations i did in the past,

if it works like my old hybrids & survives the weather like my i-10k i will be happy.

 

[Marconi]

i don't know when we started seeing reasonably accurate vector models Eddie,

I was trying to suggest that my Eznec model of the Vector was pretty accurate as far back as my Eznec index file goes to 2/4/2013.

No big deal folks...I was just curious how accurate that old New Vector 4K model really was. So, I checked and reported what I found 5 years later...when I was more confident in the accuracy of my models.

Bob, I don't know when we started seeing reasonably accurate Vector models either.

i guess when they were telling us the sigma style antennas out perform a 5/8wave on the same mast,

If you know, who is they?

i will experiment a little with length because i have 4 x 108" radials,
we don't know what length is electrically 1/2wave when we add the radials
i won't be making all the iterations i did in the past,

Experimenting is good.

if it works like my old hybrids & survives the weather like my i-10k i will be happy.

Maybe you should incorporate similar radiator construction ideas in Jay's I-10K for your new hybrid, but it will add weight. I can't be sure but may Booty Monster found out his homebrew Vector was pretty heavy too.

I think he said he is moving to a place where he can mount his antenna soon. Maybe then we will get some performance results on his new Vector design and I can ask him how tall he made the antenna.

 

[bob85]

They meaning the models Eddie, not anyone in particular,

I am happy enough with the construction of my sigma,
its stronger than a stock sigma4 or my i-10k without been as heavy as the Vortex.

 

[HomerBB]

@Marconi
About the 7/8^ on the vertical I spoke of trying...
What occurred was I managed to successfully homebrew a SigmaIV clone that worked. I had used dimensions that I obtained off the net. It had three cone radials and they developed straight away from the vertical without any offset. I don't think I had good info on the gamma dimensions so went through about 3 different combinations of of gamma sleeve and rod length before getting it to match to a good SWR. As I recall, at that time I had not purchased an analyzer, yet, and was only working with an SWR meter and a Galaxy 88.
By the time I got around to trying a V4k I had gotten the analyzer and began using an electrical 1/2^ jumper centered on 27.385 to tune antennas. At the beginning of the V4k effort I had been following online discussions regarding these type antennas and got swept into excitement about a 7/8^ vertical. I took my SigmaIV and redid the 3el cone into a 4el cone, set the vertical length to 7/8^ at 27.385 Mhz, left the radials without offset to the vertical as the S4 had been, used the same gamma, and hooked up my new analyzer. The MFJ-259B did not like this antenna at all. Period.
I expressed my frustration on the forum and, as I recall, Bob and Donald advised some actions to try. They suggested the NV4k version - 3/4^ vertical and 106.5" radials length. It was at this point that my memory tells me that you, Eddie, noticed my cone radials had no offset as the production models did. You urged both Booty and me to stay as near original as we could to best represent any results that might be expected from the production antennas. What I did now was change the vertical length to 3/4^, and restructure the cone mount to have offset. I wasn't sure about the length of the dog bone and had assumed it should take the same angle as the radials. You helped me with that based on the S4 you owned, so I lengthened my dog bone, too. I kept the same gamma match on the modified NV4k as I'd had success with on the S4. The MFJ-259B still disliked the antenna and would not tune it out. I was impatient to get an answer from anyone about the exact dimensions of the gamma match. Who had one had it in the air. I just made a new one increasing the tube length and diameter as well as the rod diameter. I used the 6" dog bone taking your advice to keep it centered directly between two radials. This time the antenna and the analyzer made up and were friends until the NV4k went on to a new home. I later built another NV4k exactly as I had done, but all at once. The analyzer liked this one from the beginning.

 

[Marconi]

About the 7/8^ on the vertical I spoke of trying...
What occurred was I managed to successfully homebrew a SigmaIV clone that worked. I had used dimensions that I obtained off the net. It had three cone radials and they developed straight away from the vertical without any offset.

IMO, the Sigma4 with shorter radials tends to create a little wider angle for the radials/radiator at the hub. Maybe there is a tipping point for this angle at play.

At the beginning of the V4k effort I had been following online discussions regarding these type antennas and got swept into excitement about a 7/8^ vertical. I took my SigmaIV and redid the 3el cone into a 4el cone, set the vertical length to 7/8^ at 27.385 Mhz, left the radials without offset to the vertical as the S4 had been, used the same gamma, and hooked up my new analyzer. The MFJ-259B did not like this antenna at all. Period.

I expressed my frustration on the forum and, as I recall, Bob and Donald advised some actions to try. They suggested the NV4k version - 3/4^ vertical and 106.5" radials length.

I never got any idea that you made a V4K without making the radials longer as noted in the specs. Sirio added another radial, shortened the radiator, and made the radials longer. IMO making the radials longer was the big question "why" in my mind at the time.

I also seem to recall that Booty Monster made his radials connect directly to the radiator in the beginning of his construction. That said, I recall him making a post showing his new offset radial brackets. Do you recall talking to him about the issue of using an offset for the radials?

So, when you attempted your first V4K you did not use the 107" radials, you just added another radial at about 90" inches? If this is the case, the idea I posted above is no-way-no.

So, do you think the issue that caused the problem on the V4K was due to adding the other radial and not the angel? Sorry Homer, the only reason I gave you the suggestion back then "...to try using a radial offset like we see on the real antenna" was because I saw an Eznec error message stating this angle was too narrow.

Thanks for the story Homer. I always had a feeling I didn't quite know the full story on both builds by you and Booty. I figured I missed something in the reading.

 

[Marconi]

wasn't sure about the length of the dog bone and had assumed it should take the same angle as the radials.

Did you see my response the other day, saying that the gamma on my S4 lays a good 2"-3" outside of the plan created by the radials. I could not reach the dog bone on my Sigma in storage, but it looks ever bit of 6" inches or more as installed on the radiator. I also could not reach the area to measure the space for the radials from the radiator at the point of the gamma either.

I have a feeling this spacing is also important to consider.

Shad tree mechanic has a NV4k he is going to install. I'm sure he would be glad to tell you how the Vector's gamma is situated as installed relative to the radials. He has a thread on his new antenna install.

 

[Marconi]

i don't know when we started seeing reasonably accurate vector models Eddie,
i guess when they were telling us the sigma style antennas out perform a 5/8wave on the same mast,

Bob, I've already responded to your comments above, but I was re-reading Henry's article on "The Avanti Sigma4" and I read his section at the bottom of page #41, under the heading of "6-Room for Improvement." This is where he suggests that direct feeding is a possible improvement that would eliminate the gamma. So, I made some models of that to see what my models indicate.

These models are Free Space showing the Average Gain = 1 in both cases. These models do not include an Eznec matching device, the difference is the location of the feed point only.

Henry I mentioned you here, so any comments you wish to make are welcome. I get the same results as you reported, but the difference in free space is small. I have not done models for these two over real Earth yet.

1. The main thing I noticed between the models is the number of segments used and the difference in segment lengths. I was not aware of that until this writing. IMO, this difference has to do with my getting a good match for the model with the feed point at the bottom of the radiator.

2. The overlay at the end belongs to another idea I was working on about CMC, but it is a variety of 5/8 wave models compared to my idea of Henry's S4 model noted on page #39 of his report where he compared a 5/8 wave to a Sigma4.

 

[HomerBB]

IMO, the Sigma4 with shorter radials tends to create a little wider angle for the radials/radiator at the hub. Maybe there is a tipping point for this angle at play.

It does. It's like sliding the hoop down the longer 107" radials which would push the upper ends of the cone radials outward.

I never got any idea that you made a V4K without making the radials longer as noted in the specs. Sirio added another radial, shortened the radiator, and made the radials longer. IMO making the radials longer was the big question "why" in my mind at the time.

I can't answer that unless it was to capture more of the opposing current at the lower area of the vertical. The TOA would then improve.

I also seem to recall that Booty Monster made his radials connect directly to the radiator in the beginning of his construction. That said, I recall him making a post showing his new offset radial brackets. Do you recall talking to him about the issue of using an offset for the radials?

I did not, but I did think it improved the looks of his antenna.

So, when you attempted your first V4K you did not use the 107" radials, you just added another radial at about 90" inches?

That is correct.

If this is the case, the idea I posted above is no-way-no.

I wouldn't read too much into why I did it. I was scrambling for a good tune on this antenna so changed multiple details in a very brief time - length of vertical, length of radials, and offset of radials mount point. I can not attest to which of any one of them determined the most impact on the antenna performance and tuning.

So, do you think the issue that caused the problem on the V4K was due to adding the other radial and not the angle?

My impression at the time was a combination of factors. My leaning, or reasoning was that if the distance between a gamma and driven element of a yagi was critical then these spacings were also critical.

Sorry Homer, the only reason I gave you the suggestion back then "...to try using a radial offset like we see on the real antenna" was because I saw an Eznec error message stating this angle was too narrow.

I think it was critical if for no other reason that I build as close to specs as possible in order to speak to the performance attributes of that particular antenna.

Thanks for the story Homer. I always had a feeling I didn't quite know the full story on both builds by you and Booty. I figured I missed something in the reading.

 

[HomerBB]

Marconi, can you model this thing with a cap hat instead of a gamma?
Probably silly...

 

[Marconi]

Marconi, can you model this thing with a cap hat instead of a gamma?
Probably silly...

Homer, can you describe a little more what thing you have in mind?