Potentially Dangerous Mobile Antenna Failure – Could Happen to You!

Maybe this should be called operator failure, and not antenna failure, but there is an important lesson in it… please read on!

Corona Ball

I am an amateur radio operator (“Ham”) and as such I have several antennae mounted on my truck, and as is often the case with antenna design, each one has a round ball at the top of the antenna, as you can see in the picture to the right.

It’s actually got a name, and a purpose. It’s called a “Corona Ball”, and no, it’s not there to save you from poking your eye out–the actual purpose is to prevent the accumulation of coronal energy at the end of the antenna, which can be harmful to your radio. I believe such coronal discharge is related to the phenomenon known as St. Elmo’s Fire, but this article isn’t about coronae and some-such… read on!

Recently I was staying at a hotel in Toronto, and at one point I decided to park in the parking garage. One of the antennas on my truck is nearly 2M (6 feet) long and mounted on the top edge of the fender, so the tip is easily 3M (10 feet) from the ground, if not more. Normally when driving in a parking garage, I fold my antenna over by drawing the antenna into the passenger side window and raising the window to just catch the corona ball tip.

But on this particular occasion I was not feeling well and decided I would just let the antenna drag along the garage ceiling as I carefully drove into the garage. Well, that was a mistake! As I was driving into the parking garage, the corona ball rode along a bundle of wires, and was captured, with amazing tenacity, by the overhead wire bundle. In fact, the bundle got hold of the antenna so firmly it literals ripped the antenna from my truck, and did so quite violently!

10M Antenna – in Better Times
Death of a 10M Antenna

In the pictures, you can see what my antenna looked like in better times, and what it looks like today, the silver part having remained screwed to my truck, with the black part staying with the extricated antenna.

This rapid evisceration of my beloved 10M HF antenna made quite the loud BANG… but as I was only moving at about 2-3kph, less than walking pace, and because I had not noticed this as the source of the bang, I’d assumed I had either hit something, or I had been hit by something. I got out of the truck to do a walk-around, and as I rounded the passenger side first noticed the antenna was missing, and then I looked behind the truck and there was my antenna, a few metres back, appearing to be standing in mid-air, hanging from the ceiling wire bundle!

I walked back and grabbed the antenna, intending to remove it by walking it backwards to free it from the wire bundle. While this was perfectly effective, in retrospect, it was a very stupid thing to do! I was standing on the ground, holding a metal rod in my hand, a metal rod that had been forcefully wedged into an overhead wire bundle. Think about that for a second. Imagine if that wire bundle had contained mains wiring, and the antenna had torn the mains sheathing!

Thankfully, the garage I was in conformed to Canada’s building code, and therefore no high current wiring would be included in that bundle, at least not without some form of armour, but it’s still quite a lesson to me, at least in retrospect. Even if the wiring had contained low voltage, it’s not something I would want injected into my radio!

So the moral of the story is, if you do have tall antenna on your vehicle, you cool nerd you, you may wish to consider a clip or some other retaining method, such as the corona-ball-in-the-window trick, as a way to ensure your safety, your radios safety, your vehicles safety, and the safety of the overhead wiring in parking garages!

Until another time, 73’s!

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