Other SOTA sites: SOTAwatch | SOTA Home | Database | Video | Photos | Shop | Mapping | FAQs | Facebook | Contact SOTA

2m Yagi for windy days... with option to be stacked

Hallo

Because of Corona, life is somewhat limited. Good thing the hardware stores are still open.

For my /P activities on 2m I have a 6 Elt.Yagi with 2m boom to DK7ZB. I have divided the boom in the middle. I found it very practical to have everything in one quiver. However, it turned out that a quiver with more than one meter length is not practical for hiking. Besides, it brings my telescopic mast to the limit.

The 4x Oblong I prefer has a small packing size and is light. It is really good - but only in calm weather.
The other day I was on the summit and wanted to be active with the transverter also on 2m. It was really windy and the Oblong made the biggest problems because of its surface.

I wanted to have a new antenna. I wanted the following features:
Small and easy to transport, not wind sensitive, wide bandwidth, no tools needed, 50 Ohm
(As I have always been a fan of antenna arrays, I wanted to be able to expand them to achieve more gain.)

The collection of DK7ZB let me find it:
A 50 Ohm 3 Elt. yagi with almost 5dBd, boom 50cm and thus half of the element length. Large bandwidth and therefore uncritical in construction. Can be operated individually or as a group.
The ideas for the details came during a walk through the hardware store. You can see them in the pictures. Now I only have to sew a quiver.

Elements are 6mm aluminium, screws with 4mm were pressed in with a vice, 4mm threaded sleeves were drilled through and fixed with 3mm screws in the boom. The length of the threaded sleeve was naturally taken into account in the length of the elements.

73 Armin

7 Likes

Congrats.
I made past year 4 elements yagi same like yours.

Works well vertical or horizontal polarized, lightweight and easy deploy and disasembly.

I made FM qsos about 400-500 kms distance.

2 Likes

Armin,

you may want to mount the yagis “upside down”, i.e. the balun box hanging below the boom instead of sitting on it. This gives more stability to the pole and thus higher wind speeds your array can take.

However, the clamps seem to be the weakest parts of the system. I wouldn’t trust that both antennas still point in the same direction after a light gust from the side. :wink:

Ahoi
Pom

Ahoy Pom

Thanks for the advice to mount the yagi upside down… that is quickly tried out.

Yesterday in the garden it worked well despite some wind. But on the summit it is something else.
But when it’s very windy, I only take one yagi anyway. The second yagi is an option. That was the intention.
But maybe I will add a third holder. It is made of light plastic and I still have something like that. Anyway, it needs some finishing touches. Shorter screws, stop nut, toothed washers…

I’ve just put in what I had lying around. :smile:

73 Armin

But when it’s very windy, I only take one yagi anyway.

I usually use 2x5 DK7ZB on the 144 MHz Tuesdays. When struggling with the wind, I rather remove the upper antenna that is 6.5 m up the pole. The remaining “lower” antenna is mounted at 4.5 m and due to the larger diameter of the pole, she stands like a rock up to wind speeds the operator doesn’t want to take anymore.

Another issue is fixing the antennas in a certain direction. From experience, with only two arms it is annoying to fix the pole with one hand when you have to operate a station, hold the mic or key, and log the QSOs with the other hand simultaneously. The solution on how to increase the friction between the pole and its fixation is specific to the location. What works for me most of the times is either applying some foam (e.g. my insulated sitmat) between the pole and the velcro that fixes the pole to a structure like a bench, rail or fence. Or I lower the mast by two elements and put a conical Hirschmann Büschel Plug in the gap.

Developing a weather independant SOTA VHF station is a challenge and takes time. :grinning:

Ahoi
Pom

Super, Harry! Looks really good!
Crimping is a good idea to connect the aluminum pipes to a screw going into the boom. I also tried this some times ago but I never got this connection very stable. I thought about using some glue additionally but I was frightened to loose the electrical connection then.

73, Martin