Made a Moxon

[davegrantsr]

Just so everyone understands, I do know what the inside joke is.
davegrantsr is one of the few who knows from whence my HomerBB name derives.

I answer to Homer with pride, however, Homer is the mascot of THD - The Home Depot. BB stands for Big Box stores. They are my long time employer. Looking closely at my avatar will introduce you to Homer, a large nosed, bib overall wearing somewhat rotund DIYer who personifies the happy personality of those who shop Home Depot.
And I resemble that remark

& to further explain the inside joke, in home depot-speak, a 'legend' creates an 'emotional connection', in this case, with his radio brethren .

& a moxon ain't no joke! IMO hardly worth the effort on 6 or 2m, though i've done them, 10-12-15m are where they excel. small size, noticeable gain & awesome rejection in such a small footprint. while i've done 2 for 20m, 26' x 13' or whatever is still just too big for my qth. i've built them on bamboo that grows.....where i dont want it, and whatever wire may be laying around-including old speaker wire, center conductor stripped from old coax, old spool of galvanized utility wire, wire left behind by the telephone pole lineman, etc. obviously the bamboo doesn't make a permanent antenna, but on the other hand i only paid for wire 1 time to build one!!!

gimme an h.........

 

[TheMooche]

& to further explain the inside joke, in home depot-speak, a 'legend' creates an 'emotional connection', in this case, with his radio brethren

Radio brethren!!!! **Jump_im**

That's classic

 

[Assaulter]

& to further explain the inside joke, in home depot-speak, a 'legend' creates an 'emotional connection', in this case, with his radio brethren .

& a moxon ain't no joke! IMO hardly worth the effort on 6 or 2m, though i've done them, 10-12-15m are where they excel. small size, noticeable gain & awesome rejection in such a small footprint. while i've done 2 for 20m, 26' x 13' or whatever is still just too big for my qth. i've built them on bamboo that grows.....where i dont want it, and whatever wire may be laying around-including old speaker wire, center conductor stripped from old coax, old spool of galvanized utility wire, wire left behind by the telephone pole lineman, etc. obviously the bamboo doesn't make a permanent antenna, but on the other hand i only paid for wire 1 time to build one!!!

gimme an h.........

I dont understand... if it only has a driven and reflector - no director - how does it have any gain? I was under the impression that with a 2 elem. it was either one or the other, gain or rejection (director OR reflector) and that's it?

 

[The DB]

I dont understand... if it only has a driven and reflector - no director - how does it have any gain? I was under the impression that with a 2 elem. it was either one or the other, gain or rejection (director OR reflector) and that's it?

A reflector is not limited to rejection, it also contributes to gain, just not as much as a director.


The DB

 

[HomerBB]

Gain is not the addition of power, but the containment and direction of the available power into a direction of preference.
The use of a reflector can be compared to a mirror and a light source.
By placing the mirror - the reflector - on one side of the light source , the light energy is reflected into the opposite direction adding gain, or intensity, of light in the direction toward which it was reflected. No more light is present than was there originally, but the available light was intensified in the direction of choice.
Adding directors adds to the gain, but a reflector is certainly a component of gain as well.
A reflector is not there simply to block, but to reflect.

 

[davegrantsr]

a moxon is a 2 element yagi with its tips folded towards each other. magically, a moxon can USUALLY outperform the 'normal' 2 element yagi.
a moxon only has about 3db forward GAIN, about a half of an S-unit. combined with more or less 15 db of rejection, or 2+ S-units, it is a MORE then noticeable improvement over a dipole/wire/basic antenna. if you can put up a monster quad or even 'just' a 3 element yagi, by all means do so. but if you have minimal capabilities for any antenna of 'size', a moxon is more then 'just an improvement'. i have mounted a 20m moxon on my chimney as a temporary test. while 26' x 13' is still way too big for my neighborhood, a 3 element or even 2 element full sized 20m yagi just ain't ever gonna happen. a moxon is doable, and if i didn't have antennas up for 2-6-10 & wires for 20 & 40, i could absolutely get away with it. again, a full size yagi? never.

 

[northern35s]

I dont understand... if it only has a driven and reflector - no director - how does it have any gain? I was under the impression that with a 2 elem. it was either one or the other, gain or rejection (director OR reflector) and that's it?

In addition to what others have said, a conventional 2 element yagi can be configured as either a driver/director, or driver/reflector, there are benefits to both, and it all depends on what you hope to achieve.
They both have directivity, which is the more correct way to describe the antenna, rather than just saying is has gain, the driver/director has a greater forward gain than the driver/reflector, but at the expense of good F/B rejection, so if your were looking to maximises it's forward gain then this configuration may suit you better, however in the UK, the bulk of the noise comes from the South and the East, if I was looking to work the US or Pacific, then I'd prefer a stronger F/B ratio.
A local chap who is a keen 11m DXer has decided to maximise his forward gain whilst retaining the ease of construction and lightweight benefit of a 2 element beam for his portable use, he has gone the driver/director route and says he doesn't suffer too much with the lower F/B ratio.

HTH

 

[Assaulter]

In addition to what others have said, a conventional 2 element yagi can be configured as either a driver/director, or driver/reflector, there are benefits to both, and it all depends on what you hope to achieve.

Thanks for the info, everyone.

I'm seriously considering trying out this MFJ Moxon they just released (it's a 10 meter antenna, technically, but since I do both 10 voice as well as the normal 40 on 11, i figure I could set min. SWR at around 27.9 and be okay..)

The problem is that I want to use it VERTICAL instead of horizontal. I know that I'd need to mount it on PVC or some non conductive mast to not skew the radiation pattern, but how on earth can that be done?

I mean, physically, the thing would have to go THROUGH the mast to be totally vertical on the bottom part of a moxons' elements. I take it that it's not going to kill it totally if it's mounted with a slight, slight tilt to avoid hitting the mast?

 

[Marconi]

Assaulter, I don't see an practical application for the Moxon in your case. It looks to me to be best setup as a horizontal antenna, and it does not appear to be that broadbanded.

 

[Assaulter]

Assaulter, I don't see an practical application for the Moxon in your case. It looks to me to be best setup as a horizontal antenna, and it does not appear to be that broadbanded.

From what I understood from the guys on Eham & QRZ, it's usable as a vertical over a pretty good chunk of bandwidth.... surely at least good enough to get 26.965 - 27.405 as well as 28.000-28.500 with a decent standing wave (Or usable at least)...

I know that for bands like 15 meters it's usually put above the ground (Ground mounted with some feet added) as such, and allegedly a vertical moxon is one of the best preforming directionals at a low height above ground (compared to a yagi, quagi, or quad, anyhow...)

For a 10/11 meter moxon, it's small enough to put on a mast in vertical formation...the problem is how to align it with the mast, since vertically the separator between the elements would have to go through the mast to make the antenna rest totally vertical. I guess if it was slightly tilted as to not hit the pole it'd be mostly vertical polarization with a tiny bit of horizontal?

 

[Marconi]

From what I understood from the guys on Eham & QRZ, it's usable as a vertical over a pretty good chunk of bandwidth.... surely at least good enough to get 26.965 - 27.405 as well as 28.000-28.500 with a decent standing wave (Or usable at least)...

I know that for bands like 15 meters it's usually put above the ground (Ground mounted with some feet added) as such, and allegedly a vertical moxon is one of the best preforming directionals at a low height above ground (compared to a yagi, quagi, or quad, anyhow...)

For a 10/11 meter moxon, it's small enough to put on a mast in vertical formation...the problem is how to align it with the mast, since vertically the separator between the elements would have to go through the mast to make the antenna rest totally vertical. I guess if it was slightly tilted as to not hit the pole it'd be mostly vertical polarization with a tiny bit of horizontal?

Well, all I have to go on is my Eznec models, and they show the antenna will work Ok with a conductive mast running up in the gap between the two elements, just like a yagi beam will do. You probably won't even have to slant the antenna of offset it like you suggest, as long as the gap insulators are supporting the antenna on the mast. Or you could offset the whole antenna a short ways from the mast and not have the mast in the middle.

The match I see with Eznec shows to get a bit worse when the Moxon is in the vertical position with the mast, but the bandwidth is severely reduced compared to the standard Moxon...which looks already to be a bit on the narrow side...even when horizontal.

Of course if the antenna is tuned pretty well, even adding a feed line to the antenna may tend to make the match and bandwidth show to be a little better that it really is at the feed point.

BTW, according to the models setting the Moxon just 48" above the Earth still allows the model to show a very good gain and angle at the horizon and that probably has a lot to do with the fact that the ends are bent back at 90* degrees to the rest of the radiator.

So, keep us posted and good luck.

 

[HomerBB]

Say, Marconi, could you drop your models into this thread. I like them. and did I read correctly 48 inches, or was that 48 feet?

Thanks

 

[Assaulter]

The match I see with Eznec shows to get a bit worse when the Moxon is in the vertical position with the mast, but the bandwidth is severely reduced compared to the standard Moxon...which looks already to be a bit on the narrow side...even when horizontal.

So, keep us posted and good luck.

What's eznec say about using a non conductive mast? (Im thinking thick walled pvc or my spiderbeam pole Ive got sitting in the closet - this antenna is only 7 lbs and some change...)

48 inches? That would go with what I've heard about these things. Pretty wicked antenna that can do that well at that low of a height. How's it seem to do at say - 20 or 25 feet?

Thanks!

 

[Henry HPSD]

Marconi,

Regading a moxon with a conductive mast :

In the past we have tested in real life as well as in Nec4.
The SWR can go up easy to a 2:1 reading and the front to back can suffer -20 dB etc.
And i didnt investigate "worse case" scenario hihi.
Perhaps there are "hot spots" but there certainly are "bad options".

Im having difficulties understanding: how one would consider this to be "oke" ?

Regarding the non-conductive mast part...
Well sadly it isnt the only part of interest.
Everybody seems to be talking about a "non-conductive" mast, but they tend to forget the feedline


Kind regards,

H.

 

[Marconi]

Marconi,

Regading a moxon with a conductive mast :

In the past we have tested in real life as well as in Nec4.
The SWR can go up easy to a 2:1 reading and the front to back can suffer -20 dB etc.
And i didnt investigate "worse case" scenario hihi.
Perhaps there are "hot spots" but there certainly are "bad options".

Im having difficulties understanding: how one would consider this to be "oke" ?

Regarding the non-conductive mast part...
Well sadly it isnt the only part of interest.
Everybody seems to be talking about a "non-conductive" mast, but they tend to forget the feedline


Kind regards,

H.

I think you may be right Henry, a non conductive mast may be the only way to go in this case.

After Homer requested the models, I went back to check the model with a mast and found that the two elements were not in the same plane as a result of my using the Rotate Feature in Eznec to make the horizontal model into a vertically polarized setup.

So, when I added the mast it looked like it was installed between the two elements of the Moxon on my computer like I planned, but when I looked down at the top of the antenna I could see the elements were staggered or offset from each other by several inches. This placed the mast I added in between the two elements with a space of about 24" between and that is why I was seeing minimal bad effects on adding the mast.

When I fixed the model the mast shows to be heavy with currents on the mast as one might expect, and it looked to produce a pattern similar to what I might expect with a very closely spaced 3 element Maxon.

I must have made a mistake in a data point when I rotated the antenna into the vertical plane. I gave up in disgust with my error...and deleted all the models. I figured I had created enough confusion already with this error.

BTW, I did set the working vertical model without a mast down to 4' feet above Earth and it did look to still produce a viable pattern, with some modest gain at a low angle. That said however, at this low height one would need to place the antenna well into the clear of all ground clutter however...in order to see the best results. And IMO, such an installation among a neighborhood of low profile houses might not be the best setting.

So Assaulter, this low height idea might not be so good unless your mounted on a hill maybe, overlooking the horizon all around.