Emergency Antenna Repair

I needed to realign the yagi with respect to the rotary dipole. I established that it was not the 40m dipole that moved during a stormy night last November. It was the yagi’s boom that shifted away from its bearing. My plan was to tackle this once and for all because by now I know what the problem is.

Way back, in 2005 when I was still a construction n00b and my father was still in charge of all things metallic, he made special plates for the boom-to-mast clamps. By now it’s clear that these plates are made of too thin sheet. The plates deform and compress when the bolts are tightened. So the distance between nut and bolt head shortens, which in turn decreases the clamping force to the mast. This was one of the jobs on my list for this summer. But even with a tilt over tower it isn’t always easy to reach certain parts. So I was thinking of an easy way to access these remote parts. I was looking for a scaffold. But where to store that away the other 364 days a year?

Earlier this week I was moving stuff in the garden. When walking under the yagi I saw a part on the lawn. I immediately recognized it and knew where it came from: the parts I used to keep the current choke balun from touching the yagi’s phasing lines on the feed point. I strapped this part to the yagi with zip ties. In April 2007. And now it seemed the zip ties broke. Both. At once. I looked up and saw I was right. A second part had also come loose too but it was still bungling up there. The balun was still in place but was now attached only to the PL-socket on the driven element. So all the stress of the weight was on the PL socket. Not good.

For over six months I got upset by seeing the dipole and the yagi not perfectly aligned. But that’s nothing but a visual nuisance. This was far more serious. The feed point connection could snap under the weight of the balun and coax. So last Wednesday I tilted the tower over and reinstalled the spacers. Now with six cable ties instead of four. And a beefier type. I find it hard to believe that four zip ties snapped at once due to being ‘worn out’ or so. But I see no other possibility. They clearly look broken, snapped in half. But four at a time? In a short interval? Could it be exposure to the elements for over nine years? Anyway this was a quick and easy fix.

With the tower down anyway, my plan was to realign both antennas and change the plates while I was at it. For that I needed to loosen and remove the bolts and replace the plates on the clamps. But I can’t access these bolts because my ladder is too short.

Wait a minute. I hear you thinking: “You still need a ladder with a tilt over tower? And your ladder is too short? What’s the use to tilt it over then?” Exactly. Two problems. First of all, I can’t get the tower lower than the longest yagi element or the lower boom half. When something hits the ground, the tilting has to come to an end or I will bend or break something. But to me, the major problem is a helluva design flaw. The manufacturer, a notorious brand of crank up towers in the BeNeLux, decided to put the winch to crank up the tower, on the side of the triangular tower that faces ground when tilting it over. So you can’t completely lower the tower or the winch would get squashed between a few hundred kilograms of tower aluminum and the ground. OT1A has exactly the same tower, and his winch is mounted on another side of the tower, so the side facing the ground being clear. He can put his tower completely horizontal on the lawn when there is no antenna on it.

A dozen years ago I was so glad the tower finally arrived after a long delay past the due date that I didn’t notice it at first. Slim chance that I would have sent it back though, risking another few months of delay. So this is a major screw up by the engineer and welder who put this thing together. Oh well.

So with the antenna parts still out of reach with my modest ladder, I decided to quit trying to fix the boom to mast clamps. I actually tried reaching the bolts but I had to stretch my arm and the wrench slipped and I bumped into a protruding part. That hurt. This is exactly the situation that causes injuries or worse. A scaffold would be nice. The working platform only needs to be two meters high. A few years ago I used one of a friend and it was really handy but the owner doesn’t have it anymore.

In the end I was able to align the yagi to the dipole. Just by pushing the boom opposite to the displacement and rotating it over the mast. Another proof that the clamps are loose. That means that the next strong gust or modest storm will dislocate that thing again. It’s still clamped enough that it won’t completely come down, but this needs a decent permanent fix.

After the repair I took the antenna analyzer to see if all was still fine but this one died suddenly. It already had a few problems. Like not operating from batteries anymore. But now the display is black and it doesn’t respond to the keyboard anymore. It has served me well since 2002 or so. It wasn’t an El Cheapo either! You can now buy better, smaller and lighter analyzers for half the price. Which is what I have done right away.

No pictures. I never carry my phone when working and I’m so preoccupied with the job at hand that I forget to take pictures with the big camera. I’m just over a thousand words so the text will be close enough to a picture.