Every time when I visit the station I always check the antennas for SWR to avoid the surprises. I did the same way couple of days ago.
OK, 40m did it again. Unfortunately I have way too narrow place for proper guying distance from the wall @north direction which is the usual wind direction at the QTH. I added the 4th guying direction during autumn as I had 3 only I thought this will solve this risk. Obviously it did not but now I will go hard on this to fix this for ever.
Had a walk to see which tube elements needed to be swapped for the vertical but the 4th director on the 6el 10m Yagi became suspicious too.
It seemed a bit short compared to the others and the symmetry does not turn out either. As these element joints have been reinforced with pop rivets at spring it is not possible to be pushed back inside of the bigger element. So started to watch the ground and took very short to find the missing part.
Seeing this the element vibration crossed my mind however this time the vibration happened on the 10m Yagi. The “sinus” is visible on the element’s end.
Checking the tips it is confirmed that the continuous vibration made the material fatigue ended up here. It is well visible on the darker and lighter arc third of the tube.
This survived a bit more then 3 years. I’m kinda sure I accelerated the process with the pop rivets as now all the forces concentrated on the tip of the elements. Actually I could not cut the tube more symmetrical than this… The SWR bandwidth did not changed too much (from 1.1:1.0 to 1.4:1.0) but guess I have a 5el Yagi now. Need to rent a cherry-picker to replace the element tips. Have to check the other elements as well.