Moxon for 11 meters

[sp5it]

1/4 GP at 5m is working great, I know, I tested it many times. Flat, horizontal antenna is different thing and it needs space below.
If you have some more pipes try m0plk SQ9JXB - SQ6MNO - Delta by M0PLK but one band only version

 

[Henry HPSD]

The RF choke you are using now isnt "designed" for 27 MHz.
Best would be in the order of 5 turns , 4.25 inch diameter.
Your present RF choke is probarbly "choking" between 10-15 MHz.

Your SWR issue now, are probarbly due to the house beeing so close.
However, you can change SWR.
You can not change the radiation pattern, which is far more important.
Why not leave the antenna as is, and fine tune it with a gamma-match for example ?

Kind regards,

H.

 

[Bow]

I actually started this adventure looking at Deltas.... but they are too tall for my allotted space...

That is why I was hoping to get the Moxon to work... horizontal and low profile...


If the Moxon doesn't pan out, I might try the phased 1/4 Wave Verticals... I pulled my Dipole out of the garage attic yesterday when I put the Moxon up, that is 2-102" whips right there...

 

[Bow]

The RF choke you are using now isnt "designed" for 27 MHz.
Best would be in the order of 5 turns , 4.25 inch diameter.
Your present RF choke is probarbly "choking" between 10-15 MHz.

H.

Oh! I'll have too fix that... Thanks Henry

 

[Bow]

Well, here is the pics...

I forgot to take a photo on the element spacers.. it is 105 on the roof right now... it is the same material as the drive isolation tubes (1/2" Sch 40 Grey PVC Conduit bored out to 5/8 for a tight fit over the 1/2 copper)

 

[Bow]

I built it speced for 27555 with MoxGen and built to to the exact measurments... it is pretty much correct for 27555, the lowest SWR, 1.8:1, is right in that area...

But here is how it looked for bandwidth.

I figured if the height above the roof was throwing it off, it would just change the resonate point, but I can't get 1:1 anywhere...

 

[vkrules]

Actually 28 mhz looks better, less reactive.Whats that black support under the driven element made of ? If it's metal that could be your problem. The original calculator doesn't compensate for metal boom or supports.I agree I don't think height is the problem here.

 

[sp5it]

Plate holding elements are too long. Maybe that pic will give you an idea how to mount it: https://twitter.com/sp5it/status/407593255120146432/photo/1
35mm pipe 12.56m long.
Mike

 

[vkrules]

Also whats going on at the feed point there seems to be an awful lot of hardware under the boom ?

 

[Bow]

Actually 28 mhz looks better, less reactive.Whats that black support under the driven element made of ? If it's metal that could be your problem. The original calculator doesn't compensate for metal boom or supports.I agree I don't think height is the problem here.

Aluminum Angle Boom (1"x1"x 1/16th" by 57" long)
Aluminum Angle Support (3/4"x3/4" x 1/16th" By 29" Long)

Plate holding elements are too long. Maybe that pic will give you an idea how to mount it: https://twitter.com/sp5it/status/407593255120146432/photo/1
35mm pipe 12.56m long.
Mike

Damn, that is a nice support! I like those clamping blocks

Also whats going on at the feed point there seems to be an awful lot of hardware under the boom ?

It is:
The Boom and Support
Phonolic Block mounted to the Boom and a PL-259, 2 12AWG solid Copper wires from the PL-259 to the Driven Element

This is my first attempt at building anything more directional than a Dipole, so I thank you for the help.

 

[vkrules]

Ok can you shorten the support and still hold the copper up? Don't give up yet the moxon will outperform phased 1/4 waves for DX.

 

[ghutch]

The bottom right photo seems to be the freqency the antenna is closest to resonant on...28.005. X=4 seems to be the best tune in your pictures.
Great post I've wanted to try a moxon this may push me over the edge

 

[ghutch]

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.

 

[Bow]

I'm thinking about what I can do with local supplies...

Remove the Aluminum Supports on the ends and replace them with...?

48" ash Rake Handles? LOL

 

[ghutch]

Fiberglas fence posts? Be sure they are all Fiberglas might find some glas rods for electric fences or tent poles, telescopic fishing poles are very strong at the large ends 800 each , hardwood dowels ???