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The Back Story
Last century I was fortunate enough to have a tower adorned with all manner of directional antennae. There were trees everywhere and there was no need for additional poles or masts to suspend a wire antenna from.
When we moved house, I had no such luxury. I sold th emast and the few trees that were around were either not in my yard or not more than 3m (10 feet) high. I did have a number of poles scattered around the yard but they were all 6m (20 feet) or less and it made my home look like a porcupine. So when I re-entered the world of Amateur Radio in 2019, I though I'd try my hand at a vertical antenna.
After all, one pole at 10m (33 feet) was far better than four or five at 6m (20 feet), right?
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Element Speaders. |
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Base Assembly. |
Building & Proving.
While researching vertical antenna I stumbled across M0MCX Callum YouTube channel: DX Commander. He was using telescopic fibreglass poles to hold up wires for a multi-band ¼ wave vertical. Like a fan dipole on its end. I gave some serious thought to buying one of his fine (I'm sure) antennae. But the exchange rate between the UK pound and Aussie banana soon put paid to that.
So with Callums' inspiration and my metal working background, I decided to make a version of my own from what I had on hand.
As it happened I had two lengths of aluminium tubing, some aluminium plate plus some aluminium angle and a couple of rolls of wire lying around that survived the "The Great Sell Off of 2011".
Most of the parts were already there.
I just had to buy some Teflon cutting boards from Kmart for the element supports/ spreaders and stainless steel bolts & worm drive clamps to fasten it all together.
To tune the antenna I found you must start with the lowest band (40m in my case) and tun it first. Then progressively add the additional elements tuning each one as they are added.
Doing it any other way makes the whole process much longer and tedious.
Another thing I found during testing is to run as many ground radials as you can around the base. I have thirty two ground radials at 5m (16-1/2 feet) each spread around the radiating element.
Don't get hung up on the Ground Radials must be ¼ wave to be an effective ground plane caper. It is somewhat true...if you're a broadcast station.
Just put down as man as you can (thirty two is optimum) and make them as long as you can, they don't even have to be the same length.
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Base Assembly With Ground Wires In Place. |
Some Observations
I've been using this antenna for nearly 12 months and I must say it works remarkably well.
This antenna is never going to compete with a directional antenna such as a Yagi or Quad.
Directional antenna will always open the band earlier and close the band later than a vertical. But the vertical will hold it own at other times.
The only problem with my build, is the antenna is flimsy due to the element size I had on hand. As a result the antenna requires guying to hold it up.
Over time the radiating element has begun to resemble the S bend of a toilet. This is due to high winds and putting it up and down many times during testing and refinement stage.
If I were to build this antenna again, I would change a few things to make it more robust to with stand the elements
Watch this space.
Cheers
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10m High In Total. |
