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Made a Moxon

you don't really believe jo-gunns claims ..... do you ?

So, you got the connection that I think Henry was trying to make, except maybe he was trying to ascribe it a Vector.

I would not have said it, but I think he was describing a list of CB BS at the time.

BM, if anybody knows all the CB BS, you would be counted among that group. It has been your claim to fame to fight against CB BS ever since I've known you.
 
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i have a claim to fame ? (y)
i thought i was just another butt-hole not afraid to give my opinion . :LOL:
 
Well Homer, I could be wrong about what Henry was referring to, but I doubt it. Audio gain is just one of the many stories we hear regarding JoGunn Antennas and have for years. You may be too young.

What are you doing to your second Moxon? Are you building a vertical, or a dual polarity? That will be interesting.
 
Hello Guys,

Let me try to make my point a bit more clearer.

If you understand how beams work (phase shifts ,elements)
You also understand that any "metal" object in the same field will cause this to alter.

Now, this can be to your benefit
Adding elements, longer boom, more gain....

And we can "deal" with it like:
Interlaced multiband yagi's,

But we can not "get away" with it.
It is not easy to design a good yagi.
And all beams are designed in such a way they will work in "most" situations.
The manufacturer hasnt thougth of all those different masts sizes and lengths beeing in the same plane as the antenna.

In aspect to the moxon, as mentioned in this thread.
Yes, there migth be situations where the lack of performance due to a mast in the same plane as the elements is minimized.
But without a doubt there will be situations (most of the time) where performance drops significant.

Everybody always worries about a additional 0,1 dB...i cant see why anyone would write down its "oke" if the SWR rises the FB drops and the gain drops.

Perhaps im answering here a bit too much with a manufacturer point of view...
Can you imagine all the calls i would get: if i told the people that a vertical moxon is no problem ?

All im saying: It is not wise to put up a moxon vertical between a metal mast, performance will drop, it is difficutlt to predicut how much as each situation will be different.
There are much better solutions for a vertical beam: the cubical quad for instance.

Kind regards,

Henry
 
Well Homer, I could be wrong about what Henry was referring to, but I doubt it. Audio gain is just one of the many stories we hear regarding JoGunn Antennas and have for years. You may be too young.

What are you doing to your second Moxon? Are you building a vertical, or a dual polarity? That will be interesting.

Sort of on the same topic, and sort of not, but..........

Suppose you built two Moxons, oriented them vertically, and fed them in phase. It would resemble a two element quad, but would be "side firing" instead of an end-fire array like the quad. I'm wondering if you would gain the "usual" 3dB of gain and still retain the high F/B ratio of the single Moxon.

Do-able? Thoughts?
 
The Moxon I was working on was an attempt to make it of coax to see whether it would actually be around 20% smaller or not. Until i get my analyzer calibrated it is just on standby.

@PA629 I have been considering doing just that. It would be a fairly easy thing to do, I believe.
 
@Homer BB
opposite to what a lot of people think..
The coax cable when used for elements doesnt make the element length really shorter
At least not in the way most people would think.
(the electrical velocity factor which is roughly between 0,6 and 0,8).

There is a small "detail".
Cause the coax has a coat on (the plastic) it is about 3-4 percent shorter in comparisment to a "bare" copper wire.

@PA629.
Yes you can easily stack two moxon's in a vertical polarisation you will overcome many problems. You will "gain" about 3 dB and it is possible to maintain a relative high FB.
Though (as always with stacking) a litlle retuning is probarbly needed.

Kind regards,

H.
 
Well, Henry, I've not been successful with it, yet. The tune ends up way too low.
I haven't worked on it much. Thee 11 meters Moxon is small enough already.
 
Well guys, here are the models I have been trying to describe. It is easy on this forum to discredit what my models show, but it is all I have on the subject. Maybe Henry can see some issue that I missed and help us understand.

The first model is Homer's Horizontal Moxon based on his first calculator dimensions at 36' feet. The other two models are the model set to vertical, one with a mast and one without as I have described.

As a note there is a 6' difference in height of the feed point between the vertical and horizontal, because I did not try and adjust them to be equal, so the results would be a bit different in a true side by side comparison.

View attachment Homer's Moxon compared.pdf
 
Marconi,

The way i look at your model:

The SWR at 27,275, its equal to 2:1.
Higher in the band your model shows it is lower, but that will mean you will need to extend length.
That will influence other things like gain/fb as well.

Looking at your Model it is 1: 1.4 at 27.9 Mhz
but the gain there has dropped to 3,19 dBI. (azi plot)
(less than a standard 5/8 wave) any dipole will outperform the antenna.


Think I have said it before, but one can not do too often..
You have to bare in mind the program.

People question NEC if it is accurate, but it the operator which makes it accurate or not.
As soon as I “input” your data, I get a warning from Eznec…segmentation warning !
Its not there to ignore.
Besides that, I always say…be aware of the average gain figure which is around 0,95 …not that accurate.

You think you have a nice elevation pattern provided, but please do reconsider if it is accurate or not.
No…perhaps dont reconsider but better try a few different segmentations and you will find out the pattern will change.
While fixing the segmentations keep an eye on what the SWR does.
Indeed, the provided SWR by your initial model is a bit optimistic isnt it ?
the antenna is higher in the band resonant, it will probarbly go in the direction of 27,9 but more like 29 Mhz.

Because of the above reasons I haven’t looked further into the model.
From this initial point of view it looks like the simple groundplane or ½ wave vertical will be a better option.

The advice, if im allowed to provide..please take a closer look to the segmentations and the average gain figure.
With that said, you migth wanna look up what the NEC manual tells you about "bends" and keep that in mind as soon as you "publish" data.

I hope it was of use...if not pse do let me know where to be of assitance.


Kind regards,

H.
 
Marconi,

The way i look at your model:

The SWR at 27,275, its equal to 2:1.
Higher in the band your model shows it is lower, but that will mean you will need to extend length.
That will influence other things like gain/fb as well.

Looking at your Model it is 1: 1.4 at 27.9 Mhz
but the gain there has dropped to 3,19 dBI. (azi plot)
(less than a standard 5/8 wave) any dipole will outperform the antenna.


Think I have said it before, but one can not do too often..
You have to bare in mind the program.

People question NEC if it is accurate, but it the operator which makes it accurate or not.
As soon as I “input” your data, I get a warning from Eznec…segmentation warning !
Its not there to ignore.
Besides that, I always say…be aware of the average gain figure which is around 0,95 …not that accurate.

You think you have a nice elevation pattern provided, but please do reconsider if it is accurate or not.
No…perhaps dont reconsider but better try a few different segmentations and you will find out the pattern will change.
While fixing the segmentations keep an eye on what the SWR does.
Indeed, the provided SWR by your initial model is a bit optimistic isnt it ?
the antenna is higher in the band resonant, it will probarbly go in the direction of 27,9 but more like 29 Mhz.

Because of the above reasons I haven’t looked further into the model.
From this initial point of view it looks like the simple groundplane or ½ wave vertical will be a better option.

The advice, if im allowed to provide..please take a closer look to the segmentations and the average gain figure.
With that said, you migth wanna look up what the NEC manual tells you about "bends" and keep that in mind as soon as you "publish" data.

I hope it was of use...if not pse do let me know where to be of assitance.


Kind regards,

H.

Henry, I have more to say here, but right off these models were done this way on purpose. Assualter and maybe Homer only have the Demo version, so I modeled this project with no more than 20 segments so they might be encouraged to and try using Eznec.

Since I have already posted the models earlier, it would be rather confusing now to change the segments all around, but I understand your point.

I try to be constructive in my discussions, and sometimes instructive, but I never wish to be destructive. I think you intend to do the same, but I had a time trying to understand what your point was in you first comment above.

I hope I got your second comment right however. I had to scratch my head a bit.

This is for those that didn't get what Henry was referring too. I took my model with a mast and reset the frequency to 27.9 just for you Henry. Then I did an overlay comparing the difference as if I fixed the original dimensions Homer gave us to the 27.9 higher frequency. The problem with us having this discussion, here and now, will be the difficulty it will cause for these other guys understanding. Using Eznec to demonstrate an idea is already difficult enough without you and I discussing protocols and procedures, and for sure considering that it probably makes so little difference in the end results or the trends we might like to try and communicate and understand.

As you can see by the following overlay, there is a difference just like you suggest, but I doubt anyone would ever know the difference just using their radio.

View attachment overlay.pdf

Homer has a radar like sense for signals and audio from his radio, so he might be able to perceive this small a difference in rejection, and maybe to a little less degree with the gain, but most would never realize this kind of value difference. This is why I use the words "likely" and "OK" when I posted above.

These results weren't perfect and would not be what I preferred, but they were good enough and maybe better than just words.

I was surprised that the model based on Homer's calculator came out with such a good SWR too. I did not tweak the model to get it there, I just used the dimensions he referred to. Why would I change the specs, if I was trying to duplicate what Homer described?

I didn't go further into the model either, and for the same reasons, but I didn't say anything hoping to avoid confusion and upsetting folks and see the thread stop, which I venture a wild guess will happen soon.
 
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Well Henry, I fixed the segmentations and I saw a little difference in gain, and reflection like you suggest, but no where near as much of a difference as some reading this thread might imagine...based on your words above.

I also did an Average Gain calculation on the Moxon with the mast, and it shows to be perfect...even before I fixed the segments. You should have seen that already when you duplicated my data entry. If you didn't, your model is different from mine.

You did my model from the Wires View I provided, why don't you fix your model and show the guys the big difference in results you find. I think at this point they don't believe me I'm sure.

What Average Gain value did you get with your model that duplicated my data, again mine shows to be perfect and =1?
 

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