Marconi's Eznec5 model - Imax with radials at various angles.

[Marconi]

I read a thread on another forum discussing different angles that were best for the Imax Ground Plane Kit (GPK), so I modeled several configurations to compare what Eznec might indicate. Below are the Imax with horizontal radials, at 45* degrees, at 30* degrees, and at 20* degrees. Tech 833, on this other forum peg this right in his remarks, and in his article, "Imax Ground Plane Kit Reviewed."

Interesting results.

View attachment Imax radials at various angles..pdf

 

[wavrider]

Interesting thanks for posting the models.

 

[Mic Snatcher]

Why are you including the mast as part of the antenna in your model?

 

[Marconi]

Why are you including the mast as part of the antenna in your model?

Good question.

These models are over real Earth, so I use a mast. Reason is the mast has some effects that probably should be considered for how an antenna might respond. With the mast included the model also shows how the mast currents tend to affect the pattern over real Earth.

Personally, I prefer free space models and in most of those cases I remove the mast.

How do you see the use of the mast in the model?

 

[BOOTY MONSTER]

looks like macos boomer ground plane kit would be a far better performer with the imax than the sloped one commonly sold/recommended for it .

Maco GPKR Boomer - Palco Electronics



but the much revered and often quoted Cebik might not agree with the software results

http://www.worldwidedx.com/cb-antennas/81989-workman-w-58-help-needed-please-9.html#post367508

 

[Marconi]

looks like macos boomer ground plane kit would be a far better performer with the imax than the sloped one commonly sold/recommended for it .

Maco GPKR Boomer - Palco Electronics

but the much revered and often quoted Cebik might not agree with the software results

http://www.worldwidedx.com/cb-antennas/81989-workman-w-58-help-needed-please-9.html#post367508

BM, I don't know what maco's boomer GPK predicts in better performance, but my models where I changed the angles for the slanted down radials seemed to make a notable difference in gain. The difference was not Earth shattering, but the horizontal radials appeared to be better.

Can you be more specific about what you think Bob posted. I read that saying in quotes as Bob telling us what Cebik told him on the issue of slanted radials not making much difference until we slanted them up..... Here is the full quote:

he said that in the real world of earth masts and feedlines as opposed to freespace models, the radial angle makes little practical difference to the angle of radiation, that is untill we fold the radials up towards the radiator,
then a none aparent colinear array is possiblle that will outperform any conventional groundplane,
he said my test results were very much possible but was reluctant to get involved with the pages of meaningless arguments that such misunderstood antennas can generate ...

I didn't see Cebik's quote as saying anything on my specific issue, about the Imax GPK radial angles. I'm interested though, and I will go back and re-read the thread. These were just models of a 5/8 wave un-matched, end fed radiator, with radials that I had on file. I just changed the angle from very steep at 20*, then to 45*, then to 30*, and then finally to horizontal at 0* degrees toward the horizon. I was surprised at the results too.

You might remember I was trying to justify what Tech 833, reported in his field testing of the Imax GPK, and I was very surprised to find he was right.

Let me try and explain this to clear up any confusion you might have on what I said compared to what Bob posted for us, that Cebik told him. I thought Bob was quite clear in what he posted, and I just read Cebik's quote differently than you.

So, go back and look at what exactly my recap below indicates, at 40', 65', 36' feet. I did the recap to help the reader better understand what I was trying to do, and what I saw in the models, not trying to mislead them.

Bob told us that Cebik told him there was little difference in the angle of radiation. I highlited that in his quote above.

BM, in my report I was talking about the gain difference that Tech 833, reported. I said nothing about the maximum angle of radiation, in fact my recap shows, with the exception of one report which was probably a mistake on my part in selecting the angle for the model, there were no changes in the maximum angle of radiation, just like Bob posted to us that Cebik reported to him.


See again BM, it's as I've said before, it is usually a problem when folks just look at the pictures, and don't bother to read the captions.

But not to worry, I do it too. I make my remarks about looking at pictures in order to help make a point about what we look at on the Internet sometimes.

Here is my recap:

View attachment Imax radials height angle.pdf

 

[BOOTY MONSTER]

i could certainly be misunderstanding the pretty pics , but it looked to me like there was a great deal more gain on the lower lobes with the horizontal ground elements than on the other pretty pics . it also looks (to me) like the lower the angle of the elements the more of a "cloud warmer" effect it has . hopefully someone has used a imax with both sloped and horizontal ground elements and can share any differences they noticed in their actual results using them .

 

[Marconi]

i could certainly be misunderstanding the pretty pics , but it looked to me like there was a great deal more gain on the lower lobes with the horizontal ground elements than on the other pretty pics . it also looks (to me) like the lower the angle of the elements the more of a "cloud warmer" effect it has . hopefully someone has used a imax with both sloped and horizontal ground elements and can share any differences they noticed in their actual results using them .

Nope, you didn't misunderstand the pictures, the high angle lobes do tend to show something that I often find unpredictable in models, you saw that right. I suspect that most often it is the presence of radials that tends to push up the higher lobes or make make them more pronounced. At other times this might do something totally different to the model. I haven't figured out yet, what controls such situations, but I think it has mostly has to do with the current results in the antenna, than it does with a particular physical arrangement of the elements. You see that right I think, but your are trying to change the subject, those lobes don't help us much working our radios.

What you got confused was that Cebik was talking about changing the radiation angles close to the horizon where they are most important, and I was talking about a change in gain for the models when changing the angle for the radials.

I'll have to admit however, that sometimes the gain changes for the good and sometimes for the bad, when the mast is radiating big currents like the image with 4 radials I posted, and the image with 4 radials at 20* degree slant. In this case the models went bad, but with other heights maybe or possibly with other radial lengths...such changes in gain could go the other way. I didn't test for height and compare different radials lengths for the Imax, so there is more to consider. I know you don't trust modeling, but don't come back later and try to tell me I didn't consider this or that in this thread, because you would be right, I didn't do it...YET!

If these models tend to even be close to the facts, and that is real hard to say, then hopefully the guys designing the antennas we use are considering such things in their design. Hopefully when we install these antennas we're lucky, and do it at a beneficial height. Plus, even the soil under the antenna and it pattern maybe for a long way off from the base, can effect performance in good ways and then maybe not so much.

This is why I try not to be categorical in my claims, but you just missed the important word distinctions between what I posted about, and what Cebik meant in the quote that Bob gave us.<gotproof>

Well Tech 833, reported his results, but if his total claim was true, then he was on a Field Test Range, and he may have been able to tell. IMO, this is not enough difference that I could tell using my radio maybe, and I think most claims from other guys probably suggest the same no difference in results...might also be true.

 

[BOOTY MONSTER]

i was talking about the angle on the horizon also ... or so i thought . what do you think is more beneficial to the typical user ... more gain going up to the clouds ? or a stronger lobe on the horizon .

IIRC ..... somewhere here there's a thread whee someone said something about the imax/antron matching network negating or not making as much use of ground elements as other matching networks , and i think i recall you were in the conversation . does that sound familiar to you ? i think it might have been jazz or shockwave ....... but i could be wrong .

 

[Marconi]

i was talking about the angle on the horizon also ... or so i thought . what do you thing is more beneficial to the typical user ... more gain going up to the clouds ? or a stronger lobe on the horizon .

IIRC ..... somewhere here there's a thread whee someone said something about the imax/antron matching network negating or not making as much use of ground elements as other matching networks , and i think i recall you were in the conversation . does that sound familiar to you ? i think it might have been jazz or shockwave ....... but i could be wrong .

I think that Shockwave is of the opinion, like me, that both the Imax/A99's matching section provides enough control for that antenna to work flawlessly with out the need for radials, and that is likely due to the matching scheme.

Personally, I go a step further, I don't believe a 1/2 wave radiator needs radials at the tip of the antenna's voltage node, simply because there just ain't much current there for the radials to use.

Now I'll admit that my models do show radials at the bottom of a 1/2 wave vertical, end fed 1/2 wave do tend to decouple the antenna from the mast somewhat, but when looking at the results real close, and not just looking at the pictures, I see there is not enough difference to make the modification worth the effort.

That leads me to my next "Marconism." When someone tell us this or that will make a difference, "...I always ask, how much difference are you talking about."

Then we usually have a lot of silence to follow, or the thread just stops dead, even when <gotproof>.

 

[BOOTY MONSTER]

I think that Shockwave is of the opinion, like me, that both the Imax/A99's matching section provides enough control for that antenna to work flawlessly with out the need for radials, and that is likely due to the matching scheme.

Personally, I go a step further, I don't believe a 1/2 wave radiator needs radials at the tip of the antenna's voltage node, simply because there just ain't much current there for the radials to use.

Now I'll admit that my models do show radials at the bottom of a 1/2 wave vertical, end fed 1/2 wave do tend to decouple the antenna from the mast somewhat, but when looking at the results real close, and not just looking at the pictures, I see there is not enough difference to make the modification worth the effort.

That leads me to my next "Marconism." When someone tell us this or that will make a difference, "...I always ask, how much difference are you talking about."

Then we usually have a lot of silence to follow, or the thread just stops dead.

"both the Imax/A99's matching section provides enough control for that antenna to work flawlessly with out the need for radials, and that is likely due to the matching scheme. "

then why do some folks get better results with GP's added ? and of course some folks say theirs worked better without them .

i agree %100 about how much difference depending on who's doing the talking . one persons whole lot can be another persons "so what" . when i see folks talk about one thing being better than another because of a needles width of difference and that they will make more contacts , i just figure they're a fan boy for the product . no biggie to me . but when huge across the board claims are made about something laying waste to all other similar products ...... it inspires questions .

 

[Marconi]

"both the Imax/A99's matching section provides enough control for that antenna to work flawlessly with out the need for radials, and that is likely due to the matching scheme. "

then why do some folks get better results with GP's added ? and of course some folks say theirs worked better without them .

i agree %100 about how much difference depending on who's doing the talking . one persons whole lot can be another persons "so what" . when i see folks talk about one thing being better than another because of a needles width of difference and that they will make more contacts , i just figure they're a fan boy for the product . no biggie to me . but when huge across the board claims are made about something laying waste to all other similar products ...... it inspires questions .

BM, when you hear this spoken or see it written, try asking a few questions, they generally run away or it starts a fight.

All humans, are by nature given to a reprobate mind, and the only way to understand and guard against it a little bit...is from the wisdom in the Holy Bible.

We all have a reprobate mind, so my saying I understand does not make me any better than the next, but I understand a bit of why I am what I am, a man with a reprobate mind. Thus we will and can do just about anything our mind tells us, both good, bad, and in between. So, I try the best I can, to avoid this nature I am given.

You didn't expect this, did you?

 

[BOOTY MONSTER]

LOL , you may have noticed i'm not shy about asking questions .
and i know you're a fan of casper , but i don't hold it against you

 

[Marconi]

LOL , you may have noticed i'm not shy about asking questions .
and i know you're a fan of casper , but i don't hold it against you

Me neither, I pray for your soul and salvation.

 

[Marconi]

I believe that guys who might think to put radials on their Imax might be better off with the maco GPK with horizontal radials, but you would have to remove the mounting plate and that is another issue to consider. Plus it looks like it could even be dubious to use 1/4 wave radails, rather than the shorter 72" radials Solarcon makes.

I think these models suggest that horizontal radials might just be the way to go using radials, or don't use radials at all. It looks like the kit, the way it comes in the box, is no-way-no.

But, on-the-other-hand, it just don't look like folks are interested in anything having to do with modeling, and I guess I'm not really surprised, modeling can be difficult for most CB'rs to even get started using.