Moxon for 11 meters

[sp5it]

I just looked at the blocks in the yagi picture.....check out any industrial hydraulic hose biz in your area. The block clamps are available at most hydraulic shops.....used as pipe supports etc. come in many sizes...cheaper that radio suppliers.

You are right. From local manufacturer:

Clamp to boom is from car parts shop - exhaust pipe clamp.
Mike

 

[Bow]

Damn Mike.. That rocks...

I can't find a local hydraulic shop around here...

 

[M0GVZ]

Agree with everyone else that there is too much metal too near the elements especially under the feed wires. It'll be having the effect of capacitive coupling and skewing the figures. As I found out when I accidentally used plastic covered metal tubes as supports it makes tuning it properly impossible. You would actually do better using wood.

 

[HomerBB]

My work often lacks elegance, but it usually works out well. I have a metal boom, too, but my supports are less complex.

assembly breakdown:

http://www.worldwidedx.com/cb-antennas/160237-materials-moxon-2.html#post446110

antenna:

 

[HomerBB]

This bears reading for anyone working on a Homebrew Moxon.

N1RIK'S 6 METER MOXON

Of particular notice is this bandwidth experience which is fairly typical of my experience with the Moxon:

SWR:

48.5 MHz - 2.0
49.0 MHz - 1.5
49.5 MHz - 1.2
50.0 MHz - 1.1
50.5 MHz - 1.1
51.0 MHz - 1.2
51.5 MHz - 1.3
52.0 MHz - 1.4
52.5 MHz - 1.5
53.0 MHz - 1.6
53.5 MHz - 1.7
54.0 MHz - 1.8
54.5 MHz - 2.0

My 2:1 SWR Bandwidth is greater than 6 MHz and 1.5:1 bandwidth is greater than 3.5 MHz. This is antenna is very wide banded and covers the whole 6 meter band. Also it has a 2:1 bandwidth of 11 MHz from 158 - 169 MHz, and 162 - 164 MHz is flat 1:1.

If your dimensions are close to what Mox-Gen called for then I see your issue resolvable when you redo the mounting plates from the loop to the boom with a non-conducting material as others have said. I see little reason to change the boom itself as I have no problem with a metal boom unless it proves to be too close to the loop at it's ends.
Good luck.

 

[Bow]

Well, it looks like the Moxon isn't good for the allotted location I have to work with. With out being able to get it low enough to consider "resonate".

I'm not sure if the height above the roof was causing it or the proximity of the house was, but even after a quick attempt to test a theory (I replaced the Aluminum end Supports with Bamboo for a test, the antenna was not any happier. So I think I am calling it an unsuccessful adventure... but it was a learning experience...

..oh.. and the beauty police busted me.... she is a rough one to deal with....

I am starting to believe I am doomed to a life of Dipoles and Verts... Speaking of that...

I have enough copper to just this thing into a J-Pole or....

www.antennex.com/preview/Sep09/the_x-pole.pdf

 

[vkrules]

Shame it sounds like your mind is made up. I still think it's something in your build rather than your rooftop.Yes it's less than optimal and obstacles in the near field can effect swr ,but you should be able to get it to work. Have you tried changing the feed harness that y lead going around the metal boom could be problematic .

 

[ghutch]

Look at skypper antennas 4 fishing poles 4 irrigation tees a few schedule 40 PVC fittings and wire = 3 element beam......might pass the boss? Small and very light.
I sure was wanting to see the moxon kickin {Cry_river}

 

[Bow]

Shame it sounds like your mind is made up. I still think it's something in your build rather than your rooftop.Yes it's less than optimal and obstacles in the near field can effect swr ,but you should be able to get it to work. Have you tried changing the feed harness that y lead going around the metal boom could be problematic .

Well, It is still in one piece...

I took the boom off and end supports and had it supported off the roof.. If I mount it low enough where it doesn't show from the ground, I can keep it up...

But I'm thinking the proximity to the roof and the house will distort the pattern to reduce and "gains' I should get off the Moxon

Look at skypper antennas 4 fishing poles 4 irrigation tees a few schedule 40 PVC fittings and wire = 3 element beam......might pass the boss? Small and very light.
I sure was wanting to see the moxon kickin {Cry_river}

I looked at the Skypper first, but it isn't much smaller than a moxon, and I think I'll have the same issue with the near field objects...

ahhh... if I was a single man.... :w00t:

 

[Marconi]

Well, it looks like the Moxon isn't good for the allotted location I have to work with. With out being able to get it low enough to consider "resonate".

I'm not sure if the height above the roof was causing it or the proximity of the house was, but even after a quick attempt to test a theory (I replaced the Aluminum end Supports with Bamboo for a test, the antenna was not any happier. So I think I am calling it an unsuccessful adventure... but it was a learning experience...

..oh.. and the beauty police busted me.... she is a rough one to deal with....

I am starting to believe I am doomed to a life of Dipoles and Verts... Speaking of that...

I have enough copper to just this thing into a J-Pole or....

www.antennex.com/preview/Sep09/the_x-pole.pdf

Bow, you still don't know for sure if the construction ideas you used for your 1/4 wave GP or your Moxon is the problem, or if the problem is being too close to the roof in both cases. Get your antenna off the roof and out in the clear as best you can and check the match.

Do you really think a homemade J-Pole is your answer?

Did you read in W4JOQ's article that he is comparing the results between a J-Pole and an X-Pole. I read this a long time ago. I haven't re-read it all, but I think this idea is in dispute as to which idea is the best, and I don't think a J-Pole is as easy to get right as it appears. I also don't think the J-Pole is as bad as detractors suggest either, but for 11 meters it ends up being pretty tall, and it may need the bottom raised up well in the clear too. W4JOQ suggested at least 12' feet above ground, and if your roof is the problem, that might mean your 5' foot clearance above you flat top roof...is not enough clearance.

Sounds to me like you're jumping from the frying pan into the fire without really understanding the problem issues you might have on that roof, and for sure with only 5' feet of clearance allowed.

A good rule of thumb for antennas and making local contacts...is getting them high and into the clear. If your antenna is below the peaks of your roof and those around you...then expect to see some noticeable attenuation in signals.

 

[Marconi]

Well, It is still in one piece...

I took the boom off and end supports and had it supported off the roof.. If I mount it low enough where it doesn't show from the ground, I can keep it up...

But I'm thinking the proximity to the roof and the house will distort the pattern to reduce and "gains' I should get off the Moxon



I looked at the Skypper first, but it isn't much smaller than a moxon, and I think I'll have the same issue with the near field objects...

ahhh... if I was a single man.... :w00t:

What does this mean, "...had it supported off the roof.."? Did you test the Moxon in your back yard or some place else that was higher and better in the clear all around the antenna?

Bow, you can only guess as to pattern and gain without high tech gear, but if the antenna construction and location are good...you can actually test the match and maybe get a good tune.

IMO, your antenna shows a bad match, and the bandwidth is not so good either. Both measurements suggest the antenna is not right.

I feel the Moxon can show nearly perfect matching results, and a <2.00:1 bandwidth near 2-3 mhz at the feed point for 11 meters. Your Moxon does not appear to me to be resonant where you suggested, at 27.555 mhz. Plus the value of R=27 ohms shows to be way low and tending down lower at or near resonance, which looks to be above 28.000 mhz.

Have you ever had an antenna that really worked well all around...on that roof?

 

[M0GVZ]

They're certainly capable of low SWR across the entirety of the 10m amateur band which is 1.9MHz.

R should be damned near 50 Ohms with a 1:1 SWR easily possible over a few hundred kHz and if you can't get that there's something going on. As I posted earlier, when I made mine unknowingly using plastic coated metallic rods it was impossible to tune with similar results. On my current design other than the wire, the only metal on it is the small X bracket used to bold the fibreglass rods to.

 

[Marconi]

Here is a

Mosley designed dipole element on a multi-band multi-element beam that uses non-conductive insulators on a conductive rectangular support right below the driven element. I see this as similar to what Bow did with his first design. So, I question whether Bow's Moxon will, for sure, have serious issues with his metal support setup.

Plus Bow told us that he replaced his metal angle iron support with something non-conductive...and it made little to no difference.

My Eznec model also indicates such construction is not problematic.

This said however, I think I would prefer the wire design like Homer's first wire Moxon model that was raised up a little above the mount, and thus would remove doubts about such cause and effects.

Here is another image:

Bow, this image is a good example of a short coaxial pig tail that would be far less reactive on your Moxon if you get back at it.

 

[Bow]

Bow, you still don't know for sure if the construction ideas you used for your 1/4 wave GP or your Moxon is the problem, or if the problem is being too close to the roof in both cases. Get your antenna off the roof and out in the clear as best you can and check the match.

Actually, my 1/4 wave works very well, considering it is a 1/4 wave GP at 5' off the roof, about 18' AGL. it has been talking well. The night I put up the Moxon, I mounted the 1/4 Wave up on a vent pipe on the high roof, which is probably 30' AGL..., and about 1' off the roof... The Ground Radials are really laid out in an "odd' fashion, but the SWRs are 1.2 across 26.9 - 28.4...

The 1/4Wave has got me from Australia/New Zealand/Fiji to Europe and everywhere in between in the past 2 months with 100W on SSB... now locally, it isn't very hot, but niether is the scene around here, for the most part, isn't worth keying up for...

Do you really think a homemade J-Pole is your answer?

Hell Marconi, I don't know, but I've had a twisted desire to put 30' of copper in the air... :tongue:

Did you read in W4JOQ's article that he is comparing the results between a J-Pole and an X-Pole. I read this a long time ago. I haven't re-read it all, but I think this idea is in dispute as to which idea is the best, and I don't think a J-Pole is as easy to get right as it appears. I also don't think the J-Pole is as bad as detractors suggest either, but for 11 meters it ends up being pretty tall, and it may need the bottom raised up well in the clear too. W4JOQ suggested at least 12' feet above ground, and if your roof is the problem, that might mean your 5' foot clearance above you flat top roof...is not enough clearance.

The first antenna I build was a 2Meter J-pole when I got my ticket.. I still have it 2 cross-country moves later. It was mounted 1' off a roof (about 15' AGL) on a vent pipe and worked like a champ... I could hit repaters 60 miles away... (that was in Houston BTW, I use to chat with the crew on 38 in the morning during the commute ) from Huffmiester/290 to the NASA repeater in Clear Lake

Now don't get me wrong, I understand that I am at a different house now and the construction is totally different, these houses are Stucco/Tile Roof/Composite Roof out here compared to the Fiber Siding/composite roof style in Houston...

Sounds to me like you're jumping from the frying pan into the fire without really understanding the problem issues you might have on that roof, and for sure with only 5' feet of clearance allowed.

Ha! That wouldn't be the first time! :drool:

A good rule of thumb for antennas and making local contacts...is getting them high and into the clear. If your antenna is below the peaks of your roof and those around you...then expect to see some noticeable attenuation in signals.

Yup, I see them... makes me miss the setup I had in Houston... Maco V-5000 on a 35' Pushup, and a fan dipole for 80/40/20/10 Meters... smokin'...

What does this mean, "...had it supported off the roof.."? Did you test the Moxon in your back yard or some place else that was higher and better in the clear all around the antenna?

Actually, the roof I have to play with is flat, but there is a pitched tile roof that raises up from it... I put the reflector on the tile and propped the Driven yup 3' off teh flat roof with 3' of PVC lashed to it... not the best way, but a quick check after the boom assembly was removed...

Bow, you can only guess as to pattern and gain without high tech gear, but if the antenna construction and location are good...you can actually test the match and maybe get a good tune.

Agreed

IMO, your antenna shows a bad match, and the bandwidth is not so good either. Both measurements suggest the antenna is not right.

I would agree about that, but my only concern is that I can't find a "resonate' point anywhere from 26 to 50 Mhz...

I feel the Moxon can show nearly perfect matching results, and a <2.00:1 bandwidth near 2-3 mhz at the feed point for 11 meters. Your Moxon does not appear to me to be resonant where you suggested, at 27.555 mhz. Plus the value of R=27 ohms shows to be way low and tending down lower at or near resonance, which looks to be above 28.000 mhz.

I firmly believe the Moxon is a smoking antenna, but the location I am dealing with is my enemy at the moment...

[/quote]Have you ever had an antenna that really worked well all around...on that roof?[/QUOTE]

My 1/4W GP mounted on the roof worked very well, considering the antenna

They're certainly capable of low SWR across the entirety of the 10m amateur band which is 1.9MHz.

R should be damned near 50 Ohms with a 1:1 SWR easily possible over a few hundred kHz and if you can't get that there's something going on. As I posted earlier, when I made mine unknowingly using plastic coated metallic rods it was impossible to tune with similar results. On my current design other than the wire, the only metal on it is the small X bracket used to bold the fibreglass rods to.

M0GVZ,

I did a good amount of research on the Moxon and I agree, it should be a flat antenna with plenty of Bandwidth...

Like I mentions, I think my biggest problem is the location and not being able to get it up free and clear in the air (due to the second story of the house being about 6' from the side)

 

[northern35s]

Try the Moxon as a vertical, you have nothing to lose and something to gain, it won't benefit from the far field like a horizontal version would, but should offer a directional improvement over the ground plane