What does Exnec say about a couple of Moxon Calculators?

[Marconi]

Homer I think the following is your 1st thread on your Moxon project. It shows it was back in September 2012 and the title "Made a Moxon." Here is the link: http://www.worldwidedx.com/cb-antennas/145068-made-moxon.html

In your opening post you tell us that you use a Moxon Calculator. Can you be more specific as to which software you used?

I don't think it was Moxgen.

I want to see what Eznec shows me using a couple of these different calculators, and in particular the frequency etc., which is currently being discussed in another thread.

So, I need some info from you since you have made your Moxons based on these software calculators, then tested them in the real world, and sometimes you reported your analyzer scan results, which maybe I can use to compare.

Note: Until recently I thought your results using the Moxon software always got you real close, but I think the guys talking in another thread were saying they see their results showing them 1 mhz higher in frequency, and that is the opposite of what you and I have reported.

Again, I think your thread below was for your wire model. I also think it was your first Moxon, and that is where I will start. I will recheck my model's for accurate dimensions to get them just like you posted, but I'm not sure which software you used...so I asked the question above.

I decided to finally put together a Moxon for 11 meters. I ran out of time today to tune it up a bit more, but I did get it together and in the air. A few preliminary transmissions confirm it works. I will not be able to confirm the fabled back door until tomorrow, or perhaps later depending on the weather. I used the Moxon Generator to determine the dimensions and went forward with them. The only analyzer readings I got were at 10' off the ground and without any fine tuning.

Parts:

I didn't realize I had not snapped a photo of the top of the finished spreader plate until now. I'll get it done as soon as I can.

In the air, at 10' to check it out, and at 36':

Analyzer reading at 10':

As can be seen, it is a bit low on the frequency at ten feet.

 

[Marconi]

Homer, below are my 2 Moxon models. They are over real Earth, in Free Space, and I show them with and without a mast. I did this to show the mast effects also.

I generated the dimensions using the AB1JX version of "Moxon Rectangle Generator" (MRC) at: Moxon Rectangle Calculator

I think this is the same (MRC) version that AC6LA published at: AC6LA Software.

I'm thinking you might have used the later AC6LA version however, because I get the same exact dimensions as you have published. Thus I figure these two versions are the same. Plus they both claim to be using the Cebik algorithm. This surprises me, because since the time in 2012, I thought you first used another Moxon calculator at first...and then later you switched to Moxgen.

I would not get so detailed here, but I am trying to determine which calculators get us the closest to producing a good resonance. That said, I can only base this on how Eznec sees things. So, if these models are correct...then my Eznec model is producing what you reported in the real world...saying Moxgen produces element that are a bit long, but it is nothing to really worry about.

Some time back I got discourage at this point with modeling the Moxon, it is hard to modify, and this is my first re-try at attempting to confirm what I saw back in 2012...when you first posted your Moxon project. I see my Eznec results below...showing very close to what I got back in 2012.

I know there is still some problems out there, because I think both Bow and 711 are seeing their Moxons showing to be high in frequency rather that low...like you and I have reported. Bow and 711, please let me know if you are seeing different from what I've said here, OK?

How say you?

View attachment Moxon MRC 16g wire 27.4 mast vs. no mast.pdf

 

[Marconi]

Homer here is a calculator published by W4/VP9KF. I used the same settings as you did above. Frequency = 27.4 mhz, wire gauge #16.

I had to convert feet to inches. I did that by hand.

View attachment W4_VP9KF's calculator.pdf

I have not modeled this one yet, so I'm just guessing, but since these dimensions are so much shorter, this might be the calculator that 711, and Bow used...where their results was very high in frequency around 28 mhz.

 

[Marconi]

Like the other models above that claim to use the Cebik algorithm,
N3WWN published this one and it is off a little, but it is very very close.

View attachment N3WWN's calculator..pdf

 

[Marconi]

Here is the last one I'll post. It was published by KG4ZOW. I will also show the frequency higher.

View attachment KG4ZOW calculator.pdf

 

[Crawdad]

Hello Marconi,

Old thread I know, but I am planning an 11 meter Moxon and I have a question about the two that you modeled for Homer. I believe that you used 27.4 MHz for the frequency, but is the Z axis dimension 27.4 feet in the model w/ mast? I have modeled mine using EZNEC demo but my EZNEC skills haven't progressed enough yet to add a mast. The elevation plot in your model is quite different from mine and I feel like I'm probably missing something. I used MoxGen for the dimensions.

Thanks and

73

 

[Marconi]

Crawdad, did you notice that Homer never responded to this thread?

Here is a link I think that works; https://www.worldwidedx.com/threads/mfj-moxon.194919/#post-539329

Also the link I provided in my original post to the thread is a dead link now. So, I can't reconstruct what happened back then, but the best I can recall is we were probably disagreeing with each other about the Internet being full of Moxon generators.

I was probably suggesting some worked and some did not. I don't have any interest is the Moxon, and I don't care to go back and rehash these old threads.

But Cradad, I would like to help you along with your wanting to get into modeling. Just not enough folks want to try and learn a new tool, and many others don't have any confidence in Eznec...even while they will recommend references by Notable folks on the Internet: that almost always produce Eznec models in support of their articles and reports.

About the 27.4 Mhz, I think that might have been a default frequency the some Generator program you saw. Homer could have also been discussing a model at 27.4 MHz, that is another possibility.

Can you post your wires descriptions report, found on Eznec front page...I call it the Control Center (CC)?

Click on "Outputs" at the top of the CC page.
Click on "Show Description."

This shows all the wire descriptions used in you model including all the features added to the model, as needed.

I can then see what you have done and try an explain how to add a mast so you can understand the process.

 

[HomerBB]

@Marconi, I am not sure how I missed this thread except to say the dates may have been about the time I had gotten very involved in the furniture restoring I have been doing over the last 7 years, now. My apologies, old friend.

Working from memory the 27.4 was the top of the CB band near my usual 27.385 roost but not far off from the 27.555 that a lot of freeband dx calling is done. I think you figured things out accurately as far as the first Moxon was wire, and identified the calculator I used. Correctly, I switch off later to the Moxgen because it was an easy download able stand alone little program. I built all my tubing Moxons with Moxgen.
And correctly, I always seemed to build long to the frequency center I put into the program.
Thanks for all the hard work.

 

[Marconi]

No problem Homer.

I didn't remember, but I had a sense there was tension between us back then. I didn't want to go back an read all that might have been said on this topic. I was just talking out-loud, and I wondered why that thread just stopped.

 

[HomerBB]

I think you did bite my head off at one time, but I found some super glue and I can't even see the scar.
I hadn't remembered any tension so it must have been nothing.
The furniture has kept me off the forums quite a bit. Nothing more.
73

 

[Marconi]

Hello Marconi,

Old thread I know, but I am planning an 11 meter Moxon and I have a question about the two that you modeled for Homer. I believe that you used 27.4 MHz for the frequency, but is the Z axis dimension 27.4 feet in the model w/ mast? I have modeled mine using EZNEC demo but my EZNEC skills haven't progressed enough yet to add a mast. The elevation plot in your model is quite different from mine and I feel like I'm probably missing something. I used MoxGen for the dimensions.

Thanks and

73

I think you did bite my head off at one time, but I found some super glue and I can't even see the scar.
I hadn't remembered any tension so it must have been nothing.
The furniture has kept me off the forums quite a bit. Nothing more.
73

Sorry about any biting comments I might have made Homer. Maybe I forgot and there was no tension back then. I do seem remember posting my ideas for how different the numbers were between various moxon calculator.

In 2014, I posted a couple of examples for these differences that I saw among several Moxon calculators.

So here I am again, making the similar claims, but now I have 3 examples of mozon calculators at 27.205 Mhz using 0.50" inch tubing, and all are showing different results with the same input dimensions.

I think I also talked about my real world experience trying to change, modify, and tune a mozon made with wire and PVC, and having problems: just in case anybody cared or wanted to build one of these antennas using one of these "take your chances" moxon calculators. The models are very sensitive as to dimensions. One minute your close and the next...you're in the weeds.

Below are several examples of calculators, with one from tba2, another I think Homer posted, and one that Crawdad probably talked about, showing 27.4 MHz like he talked about in his post above. Sorry it can't be easily read...that is how it was posted on the Internet.

In the PDF file below are 2 models, one using the "Moxon Calculator" and another using the "Moxon Rectangle Calculator" that I did to demonstrate these differences.

1. calculators noted above.
2. Eznec models with the same frequency and wire diameter, but showing very different results

 

[HomerBB]

The first and third are closer to each other, except for the spacing between the elements. The second and third agree on the spacing.
I have to wonder whether the code writers for the calculators wrote them to match the results of their own Moxons they had built, or had tweaked to their satisfaction some models in EZnec and wrote code around their models.
Head scratcher.

 

[BJ radionut]

I'm not wanting to start a bunch of BS.
However, the models showing these gain factors in excess of 10-11dbi to me sounds a little "Over the Top"!
I have a 6 element wide space, which modeled is barely 10.5dbi (8.2 dbd)...
I guess I am a little suspect of the model when a 2 element "reduced" size beam models that type of gain.
When I have seen models of "full" size 2 element beams, that are tuned for max gain, and these run at best 6-7dbi. (4 to 5dbd)
The Moxon is a good little antenna, but certainly does not rival anything near a full size 2 element optimized for gain with .11-15 wavelength spacing. The .11 spacing producing the most gain. (slightly above 5 dbd).(source Bill Orr Radio Eng. Handbook)
The length differences I can understand to a point, but certainly not the gain figures.
My 2 cent's worth again.
All the Best
Gary

 

[HomerBB]

I noticed the dbi gain figures, too. Even the dbd is high. My focus was on the different dimensions each program suggested.

 

[711]

I’ve never used a 2 element but I did play with wire and tube moxons. Based on using my tube Moxon, I’d have to agree with it being closer to a loose 3 element then a 2. F-B wasn’t as tight as they advertise and you can talk off the back slightly. I built the wire Moxon out of necessity being I lived in military base housing and put it up on the ceiling of my garage fixed in one direction. I only used the Moxgen calculator from the website as that was the only calculator available back in the early 2000’s. I still use that calculator because I’m used to the results. For the tube Moxon , I used the 15m version and kept adjusting down till the analyzer tuned in. Took me 6 hours as what I thought would adjust the tune didn’t , I had to go against my thinking to get it tuned. I’ll take the Moxon any day, I do want to try a 3 element LFA against it.