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Yagi that thinks it's a wind vane

A short tale, with a question at the end…

I’m really new to SOTA operating and have been on a steep learning curve, mainly figuring things out for myself on repeated climbs of (very) local hills.

I constructed a “100 gramme 2m yagi” from a spare bit of fibreglass mast section and some aluminium welding rods, having had little success on summits with the tape measure version, due to it folding in the slightest breeze.

Yesterday was a breezy day, so off I went up Pressendye (GM/ES-047) to try it out, intending to lash it to the summit trig point. It was so windy on top that I instead retreated to the substantial stone shelter and guyed the mast there. All good so far.

I made three contacts using my ft-3d HT. One off the front, one off the side and one off the back of the beam. I couldn’t make any more because every time I moved it round, the wind blew it back in line with the wind direction, like a weather vane.

So, I’m looking for suggestions! The beam needs to turn when I want it to and not at other times. It’s currently mounted on the fibreglass pole using pvc conduit fixings.
And yes, the guys are rigged too high. Schoolboy error.

Looking over to Morven GM/ES-018, my “even more local” SOTA summit.

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I can’t see it clearly in the picture: Can the mast rotate in the bracing?

You should have a ring that holds the ropes and in which the mast can turn with the yagi.
Just tie the end of the boom to a stone and hold it in that direction you want.

73 Armin

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The spacing looks odd, may be just the photo.

The antenna needs to be fixed to the mast so it cannot move relative to the mast. The whole mast is then turned and the antenna moves with the mast. The mast can turn because you have some form of slip ring where the guys attach to the mast.

Having the feed dangle by the reflector will spoil the pattern possible negating significant amounts of the Yagi benefit. Feed routing is always an issue with vertically polarised Yagis though.

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Thanks Both. I’ll look into a ring. I was just rotating the upper white section, which is a push fit into the lower pipe fitting.

As for the element spacing and aerial design, I got it here:

I was receiving great signal reports from operators up to 45 miles away, so my initial thoughts are that it’s a big improvement over the diamond extendable whip that I was using.

Armin is correct.
take an extra guy and tie it to the rear of the boom, with the other end attached to a peg or rock. Use the extra guy to keep the aerial pointing where you want it. A bit of a faf as you need to keep moving the peg / rock, but it does work OK.

Stuart
G1ZAR

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This may work well with VHF Yagi. I tried this method with my HF Delta Loop and it was not OK, too much moving around operating position. IMO, better solution would be to put some kind of friction between fixed mast and antenna part (white section) as long as it is not too high. In my case I use a suitable pipe clamp (with butterfly nut) - release the clamp - turn antenna - fix the clamp. Simple!

73,
Mirko S52CU

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I like that idea! Thanks Mirko. :+1:

You can also reduce the tendency to act as a weather vane by balancing the wind resistance about the pivot point. From your photo, it looks as though the boom extends further to the right of the mount than to the left, so I guess it will want to point into the wind.
If you can’t easily change the mounting point of the boom (because it tapers, and that’s where it wedges into the “T” piece, for example) then maybe you could add a small vane of some kind to the short end of the boom.
If you do that, then whatever you use to hold it in position will have much less work to do.

73
Adrian

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