Made a Moxon

[Henry HPSD]

Hello Marconi,

Its certainly not about who is right or wrong, its more like what is rigth or wrong that is of use, thats why i like this forum.
Its has the tendancy of beeing polite.

I wrote down a lot of things, but delted them cause i appriciate this thread and you.

From here we can do two things:

1-we keep on going in this thread.
2-you contact me in private and continue from there…and be back with what we have “gained”.

Your call

Kind regards,

H.

 

[HomerBB]

I appreciate all the input here, and as for modeling, there is something to be gained. I don't know whether a thing is right or wrong in a model, but I do appreciate discussions that can bring light to the subject.

 

[Marconi]

Hello Marconi,

Its certainly not about who is right or wrong, its more like what is rigth or wrong that is of use, thats why i like this forum.
Its has the tendancy of beeing polite.

I wrote down a lot of things, but delted them cause i appriciate this thread and you.

From here we can do two things:

1-we keep on going in this thread.
2-you contact me in private and continue from there…and be back with what we have “gained”.

Your call

Kind regards,

H.

Henry I appreciate your consideration here. Thanks for standing by your ideas on this issue. I re-read your original post where you questioned my model with a mast and the claims I made, and I noted that your numbers were almost identical to what my model indicated at 27.275.

So, you are right on that count, and thus it would be more productive for us to do a vertical Moxon model that showed better design and results, rather than continue to talk about a questionable idea. You also commented in your post that even the use of a non-conductive support system would still have issues considering the feed line, and that is well noted as a potential problem.

I don't like trying to defend a less that worth product...even though I explained why my model was done with too few segments. So, let's continue with a new goal in mind and try to work together, OK?

I like your idea #1, and if we need to get together outside of the thread, then sobeit.

Regards,

Marconi

 

[rockytopcummins]

Thanks for sharing this.

 

[Marconi]

Homer, here is my best vertical Moxon model. I tweaked the model to the best match at the feed point, and it shows resonance at 27.335 and you used 27.4 on the Moxon calculator. I tried to improve the model using many iterations, but the calculator does a great job at any frequency based on what I see using Eznec.

I can't account for your low frequency finding using similar dimensions, but these models don't include environmental effects unless included to the model and it does not include a feed line.

I added hand written dimensions, but both models are set at 36' feet to the bottom, or about 42'+ feet to the feed point. As noted above I used your calculator dimensions that you posted earlier at 27.4 mhz.

I then added a mast to the model to consider an off-set installation. The model and the results shown...use a mast off-set of 108", and that is of course impractical for an installation, but shows the least affects on the antenna and the best results. It is also pretty close to the same model without a mast included at all.

I attached three antenna views to better show what I did, but the last view is a model with only 60" of off-set, and I did not include those results. The closer the mast is to the antenna the gain and the rejection decreases a little. In order to maintain approximately 30 db rejection, the model shows to need about 60" or more of separation.

I didn't add a view of my model using a shorter mast, say to the feed point instead up to the top of the antenna, but to do so ill-affects the pattern, and the rejection is notably reduced by more than 10 db, so the mast is in play with the Moxon performance and it appears that a shorter mast is less effective.

View attachment My Best Moxon .pdf

 

[HomerBB]

Thanks, Marconi. I'll look them over.
The antenna wires being suspended by the fiberglass poles are actually 3' above the top of the metal mast when considering the non-conducting supports under it.

 

[Marconi]

Thanks, Marconi. I'll look them over.
The antenna wires being suspended by the fiberglass poles are actually 3' above the top of the metal mast when considering the non-conducting supports under it.

I didn't make my model like your antenna, except for the dimensions you posted from the calculator. There is a little design difference, but personally I don't think that would make much difference.

The idea presented here is for the Vertical Moxon and to give some idea for an off-set mount using a mast, sorta like your 1/2 wave center fed dipole.

This model will work down to as little as 24" inches of off-set between the radiator and the mast. I did not model the off-set connector, but I think a metal support might work there in the middle of the antenna without too much ill-affect, just like it does when horizontal. I will have to a model that to be sure however. Since you wire is raised above the support, your antenna mounted vertical off of a mast in an off-set design would be 3' feet further away and that would be even better if it didn't sag.

 

[HomerBB]

Okay, I've got it.
I see photos of metal Moxons that have only a few inches - 3" t0 4" - of spacing between the plane of the antenna and that of the boom.

 

[HomerBB]

Put together a Metal Moxon in about 2 hours and put it up. It is working great.
I took the wire and FB pole Moxon down in order to duplicate it.

 

[2RT307]

Oh my goodness you got a rotor! :laugh: Looks great, Homer. I heard a fella in California talking to you yesterday. Unfortunately, no conditions into NW Arkansas from Fort Worth.

I really like all the stuff you make when the weather gets nice! lol

73,
Brett

 

[HomerBB]

I've had a rotor. It was just too small for the 4 element Yagi.

 

[Marconi]

Put together a Metal Moxon in about 2 hours and put it up. It is working great.
I took the wire and FB pole Moxon down in order to duplicate it.

The new Moxon looks nice Homer.

How does it compare to the wire model?

What does FB pole mean?

Can you tell any problems using the tappered 90* degree turns you used...that Henry warns in another thread somewhere coud be a problem with matching results?

 

[HomerBB]

This antenna is made from parts I had from around the place, so I will likely redo it when I can and streamline the boom to mast and boom to antenna parts. That boom was used on the 2 element Quad I made last Spring and as a result is a bit massive.
I wanted to get this one in the air and check it out against the wire model. So far, it appears to be a little more wide-banded, and the rejection is noticeably better. The side rejection is phenomenal, while the back easily reduces the signal at least a S-unit, maybe more, over the wire model. My conclusion so far is the metal model may be less exotic in appearance than the wire and fibergass fishing pole (fiberglass poles -FB pole) model, but has performance pluses. I have only had the time to get this one together and in the air so I've checked SWR and bandwidth through the feed line, about 85' of RG8, only. To my thinking, the SWR meter results are reliable to the extent of determining the antennas usefulness.

I will map out a bandwidth and SWR plot later, I hope.

When I get the analyzer fixed I will see what it says (The analyzer has a cold solder joint loose in it and I must open it and repair it).

As far as the tuning of the antenna due to the corners I can't say. I made it as close to the dimensions that MoxGen gave me, put it on the mast, and have 1.0:1 SWR at 27.405 and beyond up the band and down.

 

[Marconi]

This antenna is made from parts I had from around the place, so I will likely redo it when I can and streamline the boom to mast and boom to antenna parts. That boom was used on the 2 element Quad I made last Spring and as a result is a bit massive.
I wanted to get this one in the air and check it out against the wire model. So far, it appears to be a little more wide-banded, and the rejection is noticeably better. The side rejection is phenomenal, while the back easily reduces the signal at least a S-unit, maybe more, over the wire model. My conclusion so far is the metal model may be less exotic in appearance than the wire and fibergass fishing pole (fiberglass poles -FB pole) model, but has performance pluses. I have only had the time to get this one together and in the air so I've checked SWR and bandwidth through the feed line, about 85' of RG8, only. To my thinking, the SWR meter results are reliable to the extent of determining the antennas usefulness.

I will map out a bandwidth and SWR plot later, I hope.

When I get the analyzer fixed I will see what it says (The analyzer has a cold solder joint loose in it and I must open it and repair it).

As far as the tuning of the antenna due to the corners I can't say. I made it as close to the dimensions that MoxGen gave me, put it on the mast, and have 1.0:1 SWR at 27.405 and beyond up the band and down.

For what it's worth I say it again: my Moxon models, made using the Moxon Rectangle Generator (MRG) software Homer first posted, shows as close to a perfect match as any antenna models I've ever made. This antenna is amazing in this regard, and you and to a little less degree Sal Electronics confirm this to be true in real world testing and his modeling. The differences you see are inexplicable, so you will have to keep us posted on that.

Homer you say you can't say, but you did say, those larger tapered elbows made no difference. Don't you believe your own results?

If you didn't see this, here is what Henry said in this regard on this thread: http://www.worldwidedx.com/amateur-...sal-electronics-6-meter-moxon.html#post398328

This new metal model shows to be right on the mark, so have you given it any thought as to what might have happened to the wire model that showed it low in frequency when using MRG?

Concerning your comments on SWR results being good enough, I would agree, and that is for sure when we have proven and tested dimensions provided for us, an antenna that requires no matching device, and that can show a perfect match. This is why I asked for your thoughts on your problem with your previous wire Moxon results...simply because it just makes good sense and apparently it is provable in the real world and in modeling.

 

[HomerBB]

I will have to revisit the wire model when i have repaired the MFJ-259. On the feed line it has a great SWR where it is supposed to have it. It is the analyzer that raised the questions for me. I dropped it a couple times and now it shows some unreliability and I find it to be a possible cold solder joint.


As for the F/B differences between them I don't know, but the metal model is quite good, as good as any other beam I've had up.

I will read the thread you linked.