New 4-ele 40m OWA Yagi

Stronger, Heavier, Costlier 🙂

Pre-history

This is the second version of the 4-ele OWA Yagi for 40m. The first one lasted 5 weeks and died when its boom broke during the summer storm of 2025.

2026.Mar.30 - circling around the nest 😉

Of course, I keep a very close eye on the wind forecast: installed an app with alerts … I don’t know what I can do about it, but it is more assuring to be informed … 🙂

2026.Mar.29 - the D-day - installation 🙂

There were several key steps and each was far less from guaranteed:

To install a new orbital bearing above the broken top one. Though not with a high probability but there could be something stupid on the top that could have prevented it from being installed at all. I minimized those probabilities by removing old winch and other elements from the tip of the tower on Saturday – the day before the installation
To switch the guys from the old bearing to the new one. That was a tough call because you are being attached to the tower, which is being held by the very same guys that you plan to switch while on the tower … – the switching moment is highly risky. To minimize the risks: we kept the crane holding the tower from the top – it would keep it in place in case I lose or drop the guy. A winch was used to pull the guy but then I had to press the guy with one of my leg, while balancing the remaining leg … – and everything on the 38-meter height …
Installing the antenna itself and trying not to break it or bend it … well, we eventually heavily bent a tip of D1 and I had to be raised by the crane to try to fix the tip… – it was already at the dusk. Despite all precautions, some drilling didn’t match, etc. So, several hours to somehow overcome everything
To install the only antenna that we managed to fix – the 10-meter 6-ele Yagi – back on the 30-meter height

I couldn’t risk the big day, so:

I called the same guys who helped me with the antenna assembly
My friends-in-radio – for the last-minute advice and checking my stupidity before it materializes in something dangerous
My wife – for overall support and human touch of the event
And the same crane/guy, who didn’t drop me two previous times with the hope he would do it perfectly this time as well. I love radio. However, 42 meters is a dangerous height requiring utmost carefulness

Saturday (2026.Mar.28) spent on manually putting down the antennas for repairing before raising the top crown. Only the 15-meter – the least damaged Yagi – remained on the tower. Though, later I noticed that it also lost a tip on the director 2.

I spent 5 hours on the tower. It is possible to put the antennas down with a winch and a couple of guys on the ground. But it takes a lot of time. Clearly, it is much easier with a crane (but costs money …).

2026.Mar.27

40-meter 4-ele OWA Yagi dimensions

Final SWR with antenna 5 meters above the ground. It is expected to shift up substantially when lifted to the final height of 40 meters.

The 40-meter OWA Yagi design is based on the scaled-up 15-meter OWA Yagi:

https://g0ksc.co.uk/2013-yagis/hf-yagis/4el-21mhz-owa.html

Everything is done and the antenna is waiting for lift off
What is not ready will be discovered right after the crane leaves the scene and nothing can be changed anymore 🙂
Added a lot of supporting Kevlar guys – the second layer of vertical support for elements, and two-side horizontal support
Painting the steel parts to minimize rusting. The antennas don’t tend to live too long for the rust to be a true problem but still
Applying the compound to prevent nuts from unscrewing due to constant vibration. And there will be vibration because it is always there
Adding wires through the elements to prevent them from being loose and lost. Several antennas on the 42-meter tower simply lost their elements after the vibration and the wind. So, like a grenade safety pin, there are now pins for each element and each tube
As the final straw – a bearing was placed near the end of the elements to absorb the vibration. No calculations. Just a wild guess and a risky move
It was very windy, yesterday, when we were finishing – with gusts up to 15 m/s – not suitable to high antenna operations at all. On Sunday, the gusts are up to 7-8 m/s … – not as calm as I would like …
The elements were longer in advance … and still, we have to increase the total length by 50 cm to tune the frequency lower. I expect, the frequency will move higher, when the antenna is lifted to the proper height. It is a always a risk… Maybe, we better lift to the air, measure the SWR again on 10-15 meters height and, if still OK, proceed with lifting … or, when it is on the 42 meter height, it will be too late to change anything …

Big risks and uncertainties for Sunday:

I am not sure it will be this Sunday, because it is Friday now and the boys who help me with the antenna work haven’t confirmed their availability yet
The wind … without wind, everything is much nicer and comfortable …
We will need to replace or, actually, add a new orbital bearing above the top one, which is broken and stuck and to swap the layer four guys to the new bearing from the old one … and it must be done, while I am on the mast … I very hope that everything goes smooth with that because it is a potential show-stopper for everything
Before the new bearing is installed the top antenna – the wind beat-up 20-meter 4-ele Yagi must be grounded. While I will be replacing the bearing, it must be fixed by my helpers
Other bent Yagis must be grounded and fixed, and tested, and then placed back
Meanwhile, the 40-meter Yagi must be displaced by the crane from the point where it was assembled and tested to the place from where it will be lifted to the tip of the tower, which about 70 meters away. Not a straightforward task. We thought about carrying to by hand by several people, but the antenna is too heavy and it is too easy to damage it while trying to carry because of its size

2026.Mar.22

A lot of work and changes over the last month but no time to update. So, in short:

Some of the nearest next steps:

To find the way to hold the elements and connect them with supporting guys

A few boom supporting guys are missing – to be made – and one element supporting guy has been lost as well
16 element-fixing guys with Kevlar lines are to be made. A lot of small work ahead

I am looking forward to see the first SWR measurements in a few days 🙂

2026.Feb.21

There are few changes as compared to the first version:

Boom is now larger and thicker: 80x80x4 mm – 3×6000 mm. Connected together with 1.5m 90x90x4 mm sections. The central part has two tubes one over another: 80x80x4 + 90x90x4 mm – it is super-heavy and I am not sure that that is right. However, I don’t it to break and when I experience the local gusts in reality, the feeling is that nothing is enough and when I imaging a 18-meter boom on the 40-meter height, nothing can withstand those winds. But let’s hope for the best and pray all radio supporting gods :-). The tubes for the new boom were purchased and brought from Moscow. The previous boom was clearly inadequate – 50x50x2mm and purchased on the local marker (bazaar) in Almaty. The tubes were clearly inferior quality – there weren’t a square tube, it least not a welded ones … – they were 4 sided “folded paper” and one side didn’t really have and strong connection with another one – no welding, nothing. So, it unfolded under the pressure of the wind in on of the corners like nothing was holding the sides of the tube together … Overall, the boom was too thin, too low diameter, too low quality overall – I didn’t expect that such tubes even can exist. Of course, I new that it is too thin and too low size, but that was the largest I could purchase locally and I didn’t want to wait long
Elements have higher diameters and thicker. Starting diameter was 32x2mm and purchased locally. The new diameter: 50×4 mm, then 40×4 mm, and on then 32×2 mm. The new thick tubes also purchased in Ural – not locally
New taper profile. I used to have longer elements. Now, it is planned to be:

The base for the design is this:

https://g0ksc.co.uk/2013-yagis/hf-yagis/4el-21mhz-owa.html – I built a couple of this 15-m antennas – they are shorty and sturdy and tune very well – OWA rules overall. These dimensions I had to increase by 10 cm of each side – see the table (original and final) – which is a lot
For the 40-meter version, I scale the design and fine-tune based on the SWR measurements and overall understanding of what affects what when the change the taper profile. See the table below. It is not final design, because I haven’t tested the 40-meter yagi yet. The position of elements I won’t change. However, the sizes will likely grow and substantially. If it was 10+10 cm increase for 15 m, it is likely to be 2-3 times more than that for 40 meters. The tuning will be done by the 8-mm diameter tip tubes

My old dog-friend died last summer. According to the local guy – the dog ate frozen chicken and died in 2-3 days. I was on a business trip and was shocked to learn the news. RIP.

The new friend is not as close to my heart as the old one, but he is a friend and very much wants to be a friend 🙂

The weather was +20C two days ago, +10C yesterday, and there was 20cm of thick and heavy snow a weak ago and there will be only -4C to +0C and raining next week.