Rebuilding Aluminium Antennas

I’ve rebuilt a lot of HyGain and Mosely antennas over the years and recently built a copy of a Force 12 Tribander from assorted scrounged corroded tubing. Aluminium corrodes over time and it’s a problem. There are a few things that you can do to take the work out of corroded tubing.

1) Most hardware stores and some engineering supply companies have a 3M product which fits into an electric drill chuck. The abrasive wheel part is a course raspy hard synthetic wheel designed to remove paint. It comes with it’s own arbour shaft and the abrasive wheel is about 120mm diameter and about 30mm thick. It takes all the work out of restoring the outside of any badly corroded alloy tube. One wheel will last long enough to restore the shine to most 3 or 4 el.

2) The second problem is cleaning the inside end of tubing. You just can’t get at it easily and you need to so that good quality contact is made with the next tube that slips inside. I solved the problem by going into a gun shop and buying 2 brass wire brush rifle pull throughs normally used to clean barrels. They are about 90mm in length with brass bristles and have a 1/4″ shaft. The small one will clean the inside of 3/8″ up to about 5/8″ tubing. The larger one for a 12 gauge shotgun does the larger tubes. To use them, I soldered on a 6″ long, 1/4 dia shaft extension onto the pullthrough shaft and put the shaft in a cordless drill running at slow speed. it works a treat and the tubing insides are sparkling clean!

3) For the past 20 years i have used a electricians conduction compound made by Utillux It’s P/N is H-2397 Jointing Compound. It preserves and conducts between the metal tubes. Brilliant.

4) I don’t rely on clamps any more. Although I use them and tighten them, I also use 1/8 Pop rivets in the same way that Force-12 do to secure the elements in their antennas.

5) Have a look at http://www.zl2al.com/3219/building-a-multiband-yagi/ on my website and you will see some ideas for clamps. The standard muffler clamps drove me crazy for years. I don’t use them now. I don’t have to endlessly pull the antennas down re-tighten the clamps any more and the elements stay where they should be for years.

73, Lee ZL2AL