Base Jay's I-10K Eznec Model at 59' feet to the tip.

[Marconi]

I found a lot of little errors in my old model with a physical trombone matcher included.

The matcher does work to make a fair match, but this antenna is very sensitive to tune in the real world and with my model.

Bob, I started with the specs noted in the manual on the first page or two with a range chart for dimensions.

Later I used the math calculators that Jay gave us that allows me to be more specific with the frequency. I modeled at 27.205 MHz. The math is close for V7 the tip length, but the the range chart is not nearly as close and it takes a lot of trial and error to get it right. The match dimension for H3 is very close using the math and the range chart is pretty close too. That said the radials don't seem to change that much. I used the math for the radiator and the 257.328" inches I got is what I used. The math is the only way to go. I did not use the radials or the radiator to tune...if was all tweaking the trombone tuner.

I also noticed that every dimension for T1 and T2 in the range chart, with the exception of the range 27 to 28 MHz, shows T1 longer and T2 shorter. All the other ranges are the opposite for the 27 to 28 range. When I tuned my real antenna this is the range I used, 27 to 28 MHz I never did think I had it tuned right and I think this range could be backward in the manual. I even tried it today and no-way-no.

The first model I did, sometime back, was using the range chart for 27.205 and it was no-way-no. I used that model to start with Eznec again today. I was trying to get the model to perform and show a perfect AGT result = 1.

I did not use taper, so that could make a difference...if I did not use a good average radiator diameter over the full length...which was just a guess. I did not try and test the 0.875" average diameter for the radiator I used here and the 0.50" diameter for the radials was a guess too. That said, my model shows resonance at 27.300 MHz with an SWR = 1.19:1 and that is another good sign.

I was surprised the model looks so good. My earlier models, with all the errors, I posted here on the forum several years ago...looked even better...maybe too good.

I posted the dimensions in my Eznec antenna notes included in the PDF file.

Seeing as I just posted some comparison models at 705" inches to the tips for various models in my thread "Bob's Avanti AstroPlane model," I set this model at 705" inches to the tip as well.

Bob, if this model is even close...don't sell your I-10K.

 

[bob85]

I can't explain why this model shows the 10k having higher gain than a 1/2wave at the same tip height and all the others too Eddie,

afaik an efficient 1/2wave has a little more low angle gain than a 5/8, do you think the i-10k's hat is giving it an advantage raising current further up the radiator ?

or is some other aspect of the model having an effect.

 

[Marconi]

I can't explain why this model shows the 10k having higher gain than a 1/2wave at the same tip height and all the others too Eddie,

afaik an efficient 1/2wave has a little more low angle gain than a 5/8, do you think the i-10k's hat is giving it an advantage raising current further up the radiator ?

or is some other aspect of the model having an effect.

I have an idea, Bob, but I can't factually tell you why. I know when I first modeled the I-10K I saw a similar pattern with gain over 4.00 dbi and I posted it here on WWDX. I didn't get much response, so I dropped my idea for adding the trombone tuner for a long time...thinking the model was faulty somehow and nobody seemed to care about details anyway.

I also posted the model on Mauldroppers. I posted it for Jay over there and I deliberately did not show him the full model, I knew he would be defense when questioned. However, my words were telling him if this model was even close to accurate...then it looks to at least support his claims for better performance and possibly shows us why. Again, I deliberately did not reveal the results for my model.

1. The PDF file shows the AGT results = 1.027 db well within the limits for accuracy and I did not understand how to control the AGT results back then...even though I knew it was an issue if the model's results were in the bad range.
2. Shows the old model I made posted here in late 2014.
3. Shows my models side by side and it is the same one I posted on Mauldroppers. Responses by Master Chef and Jay seemed troublesome to me as noted in #4 below.
4. Comments to Homer about this model that maybe sets the tone for what I saw going on over there, right after posting my idea. Jay did respond, but did not seem happy. Opinions are always a battle on MDr's.

If this model is even close to how this design works...then it might prove my point about why I see all my CB antennas showing the same response. Even with this nice gain over my Starduster...which is obviously less of a performer...these differences are difficult to measure just using a radio.

Bob I don't recall, but have you actually compared your I-10K to another 5/8 wave?

Back in the days when I got my I-10K all I had to compare it too at the time was my SD'r and an old Top One...I reported I could see very little difference just working my radio. I got my I-10K because it was a new high gain antenna and I wanted to compare it to myself and see if the stories I was hearing had any merit.

I think the I-10K with the big trombone tuner is what makes the difference I see here. Maybe Steve and I are the only ones to suggest this idea...regarding adding the physical matching device to antenna models.

 

[Marconi]

afaik an efficient 1/2wave has a little more low angle gain than a 5/8, do you think the i-10k's hat is giving it an advantage raising current further up the radiator ?

Of course I think the top hat tends to make the current distribution a little more concentrated (increased current per segment in my models) for a shortened radiator. However, I'm not sure how much difference it makes without modeling the idea for that specifically in mind.

I think the difference is the trombone tuner...just like Jay preached, but I doubt he ever saw a model that showed him this pattern...I don't care how many folks he had model his I-10K. AFAIK, Jay never once produced a model of his antenna...and I would think if he had something at hand to show evidence to support his words...he would have jumped on it like a chicken on a June Bug.

There is another issue that shows up in these models with a physical matching device added...that is the horizontal pattern that also develops. I've also shown and talked about this too.

Later I may post the the tabular data for currents on the matching device and the currents on the radiator and radials. I suspect that might be revealing.

How say you Bob or anybody else, if you care to comment?

 

[The DB]

Recently I have seen models with a matching section actually increase gain over the same antenna with no matching section. That happened with the gamma on a v4k lately, as well as a few other antennas I added a gamma to. This doesn't happen to all antenna designs I add a gamma to, a 5/8 for instance, a gamma made the overall antenna efficiency, as measured in the far field, better, although the gain went in a non-beneficial direction.

I wish I could post images on-line at the moment to show you guys what I am talking about... Perhaps I should make a video, although I've said that a few times and have yet to do it...


The DB

 

[HomerBB]

On Facebook people who don't post videos post pictures of spaghetti. Or pizza...

 

[Marconi]

That happened with the gamma on a v4k lately, as well as a few other antennas I added a gamma to.

Steve at some point I posted a model of the S4/NV4K with a gamma match, but it was only an image that did nothing for the model. That was because I made the 3 wires for the gamma = 0.0000001" and then connected the wires to nothing at the far ends.

I often can locate the source at or very near the dimensions of the tap point for the real antenna radiator...where-in at that location the model produces a modestly good match and a good AGT result, if the segments were right and I was lucky.

You showed me another way to control the AGT by making a short wire with only 1 segment and then place the source on this wire and by adjusting this short wire's diameter the model may report a good AGT result.

Said another way...if the tap point location is close to 50 OHMs, as far as the model is concerned, it can show AGT = 1 or very close.

Could you share with me this gamma you describe above and how to model same? It sounds very interesting.

Is it like a real gamma...a physical part of the model or is it added as a utility in 4NEC2?

I once inserted an object into the tip of an (ISO) isolated mast and I was very surprised that the match for the model dipped to a near perfect match.

Steve, I'm always here to encourage you to make a video on modeling...those you done in the past are far better than you will admit.

 

[bob85]

Yes Eddie my i-10k has been A/B tested on the same pole & coax against multiple antennas including end fed 5/8 with & without radials and a gainmaster,
i had two locals bring their new antennas to compare on their way home from the shop they bought them from,

the 10k did have a small advantage over them all but only a needlewidth or two over the gainmaster,

bear in mind they were not isolated for the test & the mast was about 1/2wave & connected to ground so far from ideal,
which is why i think the imax did so poorly against the i-10k,
its not possible that the imax is so far behind unless something other than the antenna was skewing the result.

 

[Marconi]

A while back when you had your I-10K up was it ISO'ed and choked well?

What did them old boys say when you tested their new antenna and they didn't see better results?

Why didn't you test with good ISO?

 

[Marconi]

bear in mind they were not isolated for the test & the mast was about 1/2wave & connected to ground so far from ideal,
which is why i think the imax did so poorly against the i-10k,
its not possible that the imax is so far behind unless something other than the antenna was skewing the result.

Bob, the overlays in my post #4 was the I-10K pattern showing the Vertical, Horizontal, and Far Field patterns. No Imax there, but maybe you're saying the Imax was one of the antennas you tested.

I agree you probably tested in a possible worst case situation and the Imax/A99 have bad reputations with regards to CMC. Since your test showed very little difference compared to your I-10K what does that suggest to you Bob, or am I just confused?

 

[bob85]

Under the conditions i compared my imax to 10k the 10k wiped the floor with the imax,
to one friend i was s-7 on imax, s9+ on the 10k,
to another friend in the opposite direction 1.5 s-units drop then back up when i swapped back to the 10k,

neither knew what antennas i was comparing,

the gainmaster on the same setup was very close to the 10k with most locals which means gainmaster whoops the imax under those test conditions,

other tests we have done on longer masts with the same and other imax with and without radials show much less difference between imax and gainmaster,

i think i had close to a worst case scenario for the imax & the 10k & gainmaster patterns are not as upset by the same mast.

my locals don't say much, their antennas cost 1/4 the price and don't have 1/4wave radials.

 

[Marconi]

Under the conditions i compared my imax to 10k the 10k wiped the floor with the imax,
to one friend i was s-7 on imax, s9+ on the 10k,
to another friend in the opposite direction 1.5 s-units drop then back up when i swapped back to the 10k,

Maybe my comments above were poorly made. I sure didn't mean to suggest your I-10K was setup in a worst case condition. My question was intended to ask why would you compare these buddies new antennas by setting them up in worst case condition and comparing them to your I-10K?

 

[Marconi]

the gainmaster on the same setup was very close to the 10k with most locals which means gainmaster whoops the imax under those test conditions,

If you didn't use the best solutions for installing the Imax...no wonder it acted so bad. Even I understand that.

I recently sold my Imax to an old ham buddy of mine we call DB. He had an A99 up and the SWR went bad. I told him what I would do about his A99, but he was not convinced. I told him I would trade him my Imax + a few dollars for his A99. I told him I bought mine new and it still had the high gloss look about it. I just used it for testing. I never did any of the tricks for the Imax like you've talked about for years now.

My grandson put his A99 up for me, and the next time I talked to DB on it...I told him I had his A99 up on a 40' pushup pole, and he was amazed.

Neither of us did a thing to mitigate CMC in our installation in this case.

During the month or so he had his A99 down...I figure the water inside probably drained out or evaporated. I tried to talk him into buying a new 50' foot Times Microwave LM4R400 I had, since he told me his feed line was old. He is a mudduck and his signal wasn't worth a wit. His neighbor walked=on=him several times while we all talked and he was using an A99 too.
.

 

[bob85]

That's how they use them Eddie, none of the antennas were isolated from the mast for the test,
that setup seemed to hurt the no radial imax more than the others.

 

[Marconi]

On Facebook people who don't post videos post pictures of spaghetti. Or pizza...

Homer, the folks on FB you are describing here are probably using those images as code in their speech.