Base Jay's I-10K - 5/8 wave model using taper

[Marconi]

Here is my Free Space model of the Jay in the Mojave I-10K 5/8 wave ground plane.

I used Ezenc 5 which is reported NOT to handle tapered construction well in the models using my version of the software. This is a comparison of the model using taper. I will post my no taper model later.

This tapered model of the I-10K shows an Average Gain result for accuracy that is near perfect at a value of (1.002). This is determined by the Eznec software...and is noted on the image of the Control Center for the Eznec software at the bottom line on the 1st page in the PDF file below.

PDF file #1

1. is the Control Center image showing the Average Gain results.
2. is an image of the antenna showing the segments in green dots, the connections as blue squares, and the wire numbers for each wire. The model uses 17 wires as noted in the tabular wires report near the end of the file.
3. is a close up image of the antenna's physical trombone matching device noted in red segments, and indicating the location of the feed point (O) a red circle on wire #9
4. is the free space pattern.
5. is the SWR bandwidth curve indicating the Return Loss value at 14.8 db at resonance...which IMO is very low.
6. is the wires table that is the data entry point using Eznec. It includes the wire dimensions for X,Y, Z at end 1 and end 2 of each wire, in inches. Near the end of the data table it shows the wire diameter, and the number of segments assigned to each wire. There are also two data fields to handle insulation covering wires.
7. is the Source Data report that shows the matching and SWR information for the model.

PDF file #2

Is a free space overlay comparing the patterns for this I-10K vs. Sirio's New Vector 4000...set to the specs provided by Bob85. The Return Loss for the Vector model only shows 13 db vs. the I-10K with 14.8 db. Neither model shows a good Return Loss. However, I'll have to check, maybe all of these high gain antennas might tend to show low Return Loss.

Check out the gain differences at 0 zero degrees, it might amaze you. It amazed me!

 

[Marconi]

Here is my model of the I-10K with NO taper in the radiator. This model is also not tuned perfectly but the Average Gain result is very good at (1.018 db). The Return Loss on this model is 15.7 db.

 

[bob85]

What do you think is causing the i-10k's skewed freespace pattern Eddie,
it looks more than id expect from the asymmetric radials & trombone match but i don't see anything else that could cause it,

how do they compare at your often used & fairly typical 36ft over average ground ?

 

[Marconi]

Bob, I haven't done the real Earth models for the I-10K models yet.

I did a search and apparently I never created a thread showing the I-10K model. Maybe some of the files have gone missing that far back due to an update or two.

I remember a few folks saying my model of this antenna, that included my idea of the trombone tuner, showed a terrible pattern. It didn't looked like other 5/8 wave, so the pattern was different. I thought in spite of that fact, the pattern was very good. So, at some point I just stopped messing with the model.

That was back before I started using Free Space Average Gain and folks didn't like FS models either, so I didn't model in Free Space much until a few years ago.

I suspect the model might do the same over real Earth, but I could be wrong Bob. I know the pattern will not look like a FS pattern for sure.

Maybe later today after a nap...right now I'm feeling low, out of energy, and I'm seeing floaters. Click the link:
https://www.google.com/imgres?imgurl=https://edc2.healthtap.com/ht-staging/user_answer/avatars/1802990/large/open-uri20140602-25229-6whx56.jpeg?1401736209&imgrefurl=https://www.healthtap.com/topics/eye-floater-small-dot-in-vision&h=450&w=600&tbnid=BMdfUCvU0ruj-M:&tbnh=160&tbnw=213&usg=__xnLh9MrW81hquBEbDVa3_nIxR_I=&vet=10ahUKEwiQh9_5iojZAhXHzlkKHZPADqsQ9QEILTAA..i&docid=GwKzq3xCap2_dM&sa=X&ved=0ahUKEwiQh9_5iojZAhXHzlkKHZPADqsQ9QEILTAA

 

[Marconi]

Bob, here is the I-10K model over Real Earth.

All I did to the Free Space model, posted above, is to add a grounded mast with a 4" space to simulate isolation (ISO) and add back the loss characteristics for the model. It is also set over Average Soil at (0.005, 13).

I also set the pattern to show both horizontal and vertical polarization because IMO this antenna produces some horizontal RF at low angles. IMO this is probably due to the strong RF produced by two of the radials that are in parallel with this very large trombone tuning device, as noted in the antenna view with the currents displayed as a red line along the wires.

 

[Marconi]

Here is an overlay over Real Earth comparing this I-10K vs. Vector that I posted earlier when they were set in Free Space.

 

[bob85]

Have you nailed down that it is the trombone causing the skewing Eddie ?
i don't recall other models of 5/8wave that have conventional matching or no matching showing a pattern like your free space model,

i remember years ago somebody claiming the trombone will cause a skewed pattern,
strange that it almost goes away when you add the isolated mast over real ground,

The Shockwave 5/8 has symmetrical radials & the trombone is not aligned with the radials.

 

[Marconi]

Have you nailed down that it is the trombone causing the skewing Eddie ?

Bob, I more or less see skewing in all my models when a physical matching device is add to the simple construction of these CB antennas I've modeled. A model over real Earth with a circular tuning coil also makes some horizontal RF and it to shows up in the pattern if I turn on both vertical and horizontal polarization for a model. The difference seems to be the smaller the tuner is the less horizontal RF shows up in the pattern.

i don't recall other models of 5/8wave that have conventional matching or no matching showing a pattern like your free space model,

Well, it is possible something else is going on here and this model is in error, but the first free space model of the I-10K I ever did to specs and including my idea for the trombone tuner...showed very similar results. Earlier I tried to explain why IMO you haven't seen similar patterns. It's basically because nobody is modeling this way. I don't believe this, but some error could be the culprit causing this skewing...if it is not the tuning device.

I tried to engage in constructive conversations going on back then, but the critics of modeling simply drowned out my ideas, and it left me discouraged in following up with this particular model. Besides that...I never saw anything of a particular advantage for the I-10K...except that the antenna is was very sturdy and I thought it made a good pattern over Real Earth.

I was excited when I got my new I-10K and I gave it some praise, but over the long haul the antenna did not impress me in performance.

Plus I recall you and I talking about the strange matching effects we both saw, and that topic too fell on deaf ears, beyond our conversations.

i remember years ago somebody claiming the trombone will cause a skewed pattern,
strange that it almost goes away when you add the isolated mast over real ground,

I made plenty of such claims about the I-10K, but nobody wanted to hear it. They probably thought I was nothing but a trouble maker. I even tried to talk to Jay about what I was seeing in a model of his antenna. I don't remember him responding at all. This was on Mauldroppers.

Bob, just adding back the mast is not all that causes the model to make a real Earth pattern look different than a free space model. In fact my mast in this case is isolated (ISO) from the antenna...so it has very little effect at all.

The Shockwave 5/8 has symmetrical radials & the trombone is not aligned with the radials.

Bob, you are correct. But, for simple convenience in modeling...I model the I-10K with symmetrical radials, so that is not the problem in skewing we see here. In fact, I did a model of the antenna making the radials asymmetrical and I saw very little to no difference.

I could do a bunch of models trying to describe the difference between these free space models and the effects we've seen so far. Then I would have to do the same for real world models as in this case, but I won't. I stopped modeling this antenna once before.

Besides, this would get very detailed and confusing for everybody including me. Modeling is not always easy work.

I know the differences I see, and my words on the subject will not change anybodies thinking and I'm not sure if models help either. Probably most folks that model...think I'm going down a rabbit hole making this model with a physical matching device, and I don't want to try and convince them either. That said however, so of the models with such a physical matching device do work.

I see the real world pattern I get for the I-10K as a plus, but the antenna does not seem to make the gain I was expecting. I have old models for the antenna that showed >5.00 dbi gain at 1 wavelength...but those models were not tested against a good Free Space model showing a good Average Gain.

 

[Marconi]

I see the real world pattern I get for the I-10K as a plus, but the antenna does not seem to make the gain I was expecting. I have old models for the antenna that showed >5.00 dbi gain at 1 wavelength...but those models were not tested against a good Free Space model showing a good Average Gain.

I rechecked my I-10K model and I found the radials were short. I fixed that and it improved the gain over Average Earth and at 36' feet. That is much better at 4.23 dbi vs. 3.71 dbi that I posted earlier. Now the model is very close to my Vector model, however the pattern for the I-10K still looks much better to me...even with a 2* degree rise in the maximum angle.

 

[bob85]

I prefer the pattern with most gain at the lowest angles Eddie,

from what i have read the high angle lobe dominance of a 5/8 gets worse the lower its mounted which fits with my own experience swapping from vector hybrid to i-10k not very far above ground,

Im not sure yet but i may like the isolated astroplane mounted at the same tip height better than any of them.

 

[Marconi]

I prefer the pattern with most gain at the lowest angles Eddie,

Well we do see a difference here and the Vector does make a lower stronger signal.

Im not sure yet but i may like the isolated astroplane mounted at the same tip height better than any of them.

Well keep us posted.

Remind me how high your A/P is to the feed point?

My Sirio Top One is mounted outside my radio room only 22' feet to the feed point. The bottom of the hoop is 3' feet below the roof ridge on on the south side of my house...and that cuts down my signals to the North noticeably. This antenna survived Hurricane Harvey that hit here in August, 2017 and it still works...just a little low on signals to the North for sure. I let it down lower for the storm, but before that it was about 30' feet and worked great. IMO this one does a lot better with some height and to be well into the clear.

 

[bob85]

At the moment my astroplane is 33ft or 35ft to feedpoint give or take a foot,
there is a 2ft step in ground level at the base of the mast to the north,

When the weather picks up we are putting up a makeshift tilt over mast further from the house & 21ft higher so i can swap & change antennas without needing help.

 

[Marconi]

When the weather picks up we are putting up a makeshift tilt over mast further from the house & 21ft higher so i can swap & change antennas without needing help.

When my Old Top One was at or near your current height, the antenna worked great. If raising works out good...you might even think you have a NV4K up there.

I may have asked this already, but what do you figure is the cause of your match not being lower that 1.50:1?

Again, I've heard reports for the Avanti version as being very low in the US CB band, similar to what I see with my Old Top One. That said, my model using the specs for the Avanti version shows +10.4 ohms if reactance, so the model is inductive. It is not much, but I can't explain that either. Thus the SWR is a little higher and the match is a bit lower in frequency, at resonance, than my OTO. I can fix the model to show better results, but it will require shortening the top hat and a change in the specs.

I think you told us earlier your A/P only showed 1.50:1 SWR pretty much the CB band. Do you see better resonance anywhere?

Sorry Bob, for getting off track in this thread and talking about the AstroPlane, but I did ask you the question.

 

[bob85]

I am very happy you did get off track talking about the astroplane Eddie, you made my evening

when i first put it up vswr on my kenwood sw200 meter with the coupler screwed to the radio was as i reported,
i was not happy with the vswr put performance was very good at such a low height,

you asking about vswr made me remove my old dentron supertuner to see where vswr was lowest,
vswr is very low all across your band, minimum vswr point is 27.025,
the 1.5:1 vswr points are 26.0mhz & 27.500,

what changed apart from my vswr been much lower than before,
nothing on the antenna system changed at all, but the radio did change,

my FT100D was playing up oscillating & occasionally showing high vswr on the radio, it was a simple lack of any grounding connection between case & chassis,

some dumbasses at yaesu coated the case with a none conductive coating then in a lame attempt at fixing the oscillation added farty little strips of copper tape that do nothing at all & ground & shield things that don't need it.

 

[Marconi]

That's great news Bob.