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Author Topic: Need Ideas for Constructing an "Armstrong" AZ/EL Mount for a Single EME Antenna  (Read 241 times)

KC0W

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 I'm interested in a manually positioned AZ/EL mount for a single long boomed 2 meter EME Yagi. A camera tripod AZ/EL mount for an Arrow satellite antenna is not heavy duty enough. It's only a single antenna so a cross boom design is not needed. 

                                                                             Tom KH0/KC0W       
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KF4HR

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As for support and manual azimuth changes, take a look at the WiMo Mast Tripods on the DX Engineering website.  For manual elevation, consider modifying the antenna U-Bolt connection plate with curved slots (instead of single holes), and use Star Knobs to loosen and tighten the U-bolts for your manual elevation changes. 
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KC0W

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 Fantastic, thanks for your suggestion...............I'm open to other ideas as well if anyone else wants to chime in.

 I just took a look at the DX Engineering tripod. It's heavy duty enough. My only concern is machining the curved slot on the aluminum plate. I live on a remote island so a machine shop is not available. All aluminum parts will have to be imported from the mainland. No big deal but one really must measure twice and cut once. Items shipped from the mainland take typically 12- 20 days to arrive should a screw up occur.   :)   

                         
                                                                     Tom KH0/KC0W
« Last Edit: March 03, 2023, 05:13:09 PM by KC0W »
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N4UFO

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I know a ham here that did some portable EME a few years ago. He used a speaker stand (I have one of those, very sturdy) with a J mount attached to it (like for a sat dish) but admittedly that was a UHF yagi. The J mount might idea might still work for you as it's adjustable and offsets the boom. Have a look:

http://www.arrl.org/files/file/QST/This%20Month%20in%20QST/July2016/Schaefer.pdf

On another occasion, I believe he made a 'rope yagi' (elements suspended between two ropes), tied one end high in a tree and then tied off the lower end to stakes or some such and moved the lower end for aiming. Again, was UHF, but if upsized, might also work.

Fascinating stuff... if only I had the amps and gear to try it out. GL, Tom!  73, Kevin N4UFO
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KC0W

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 Thanks VERY much for the reply, Kevin................That's an interesting article. More food for thought.

 I don't think the mount will work for me but the article sure gives high hopes for anyone wanting to get started in EME. The channeled slot for elevation positioning & the star knobs as KF4HR described is the way to go. Routing out a smiling face slot is gonna be the Achilles heel of this project for me. I could do the same sort of thing with holes drilled & spaced maybe 1/4" apart in a smiling face pattern but then I would lose fluidity of full elevation positioning. Meaning I could only position the antennas elevation where there is a pre-drilled hole.

 I have seen several photos of portable EME setups in which the Yagi is attached to 2" - 3" PVC pipe arranged in a box formation. 90 degree elbows are on all corners. I can only surmise elevation positioning is accomplished by not using PVC glue and having the PVC tube free turning in between the two corner 90 degree elbows. Very, very hokey & a recipe for disaster.
 
 Any other ideas?

                   
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W1VT

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I used 3 foot Radio Shack TV tripods for sturdy mast supports.  I bolted angle iron to the flanges to create a self supporting version. 
I also had a metal plate and drove my car over the plate for a 7 band 432 to 10GHz antenna array.
I'd set a compass rose on the struts inside the tripod.  Maybe you could find something similar.
I drilled 1/4 holes in the steel TV mast with a cobalt drill bit for the rose pointer and a rotating table. Use lots of pressure to avoid work hardening the steel.
The rotating table sat on top and had a slot that acted as a key for a 1/4inch diameter steel rod.
If the equipment rotated with the antennas the feedline length there was no need for a rotator turn loop and feedline length could be minimized.

The 5ft version didn't seem to be as useful, but 3 feet seemed to be the right length. 
« Last Edit: March 04, 2023, 03:12:25 AM by W1VT »
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W9IQ

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If you can have basic welding done locally, I would think about using a pillow block bearing to support the elevation shaft with a band or disc brake to stop its rotation. The disk or band drum could be welded onto free end of the shaft. A piece of angle iron attached to the pillow block base could support the caliper or band mechanism.

Disc and band brake assemblies are widely used in the go-kart industry so they are easily and cheaply sourced.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

N4UFO

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Routing out a smiling face slot is gonna be the Achilles heel of this project for me.

Yeah... saw the base of the J mount has the smiley face arc. Didn't know if they used those on the islands for satellite dishes like in the states and you could scrounge one and adapt it. My house came with two when we bought it. The one with extra supports I added a mast on top of and use it to hold up a VHF/UHF Squalo and a 6m Omni loop. (See my QRZ page)

Good luck!!!   
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KC0W

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 Almost what I'm looking for. Missed the mark by just a little because it's maximum elevation is only 30 degrees.

           https://antennas-amplifiers.com/product/antenna-parts/hand-adjustable-elevation-antenna-bracket/
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KC0W

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 Success. So simple it's silly. 

 https://www.bigskyspaces.com/HingedMount.pdf
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N4UFO

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 Success. So simple it's silly. 

 https://www.bigskyspaces.com/HingedMount.pdf

There ya go! It's always the simple solution that gets overlooked 'til last...  :)
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WB6BYU

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    • Practical Antennas

Extend the back of the Yagi enough to clear ground
debris (wood or aluminum pole?).

Add a brace from the front of the Yagi to the ground
to support it at the desired peak elevation angle.

Orient the two ground ends North / South.
Anchor them so they won’t slip.

Now the antenna should pretty well cover one
pass of the moon from horizon to horizon as
the whole assembly is flopped from East to
West along the axis of the two anchor points.
So you don’t need separate az and el rotation.

And you probably could arrange to rotate the
Yagi about its axis to change the polarization
as well.

N4UFO

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Now the antenna should pretty well cover one
pass of the moon from horizon to horizon as
the whole assembly is flopped from East to
West along the axis of the two anchor points.
So you don’t need separate az and el rotation.

But unless you are right on the equator, the moon doesn't go directly overhead, east to west... does it? It doesn't here... makes an arc across the southern sky.
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WB6BYU

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    • Practical Antennas

Quote from: N4UFO

But unless you are right on the equator, the moon doesn't go directly overhead, east to west... does it? It doesn't here... makes an arc across the southern sky.




Correct.  The vertical angle of the Yagi is set
by the length of the front prop, making a
triangle with the (extended) Yagi length and
the distance between the ground anchors.

If the moon only reaches, say, 45 degrees on
a given pass, then you adjust the length of
the front prop for that, and the antenna won’t
point due East or West at the ends of travel,
but further to the South.

This method may not track the moon exactly,
but with a bit of compromise between the
angles for the center and the ends of the path,
lt may be close enough, depending on the
beamwidth of the antenna.

KC0W

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 Thanks for the suggestions. The elevation issue has been solved with the hinge mounting system as previously described.........The maximum elevation of the moon here is 81 degrees. I'm north of the equator by roughly 1,000 miles.

                                                                  Tom KH0/KC0W
                                                                      KH0W.com    
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