When we lived in Atlanta, I had a half acre-sized backyard with big, mature trees that were great for hanging a half-wave 80m loop. We have been in the pacific northwest for a while now. Unfortunately, while we do have lots of trees on our lot, they are not in convenient locations or great for hanging antennas. Wire antennas without supports are out of the picture unless I intend to enlist neighbors around me. That doesn’t have many upsides.

I decided that the only real way for me to operate here at our house in the pacific northwest was to get a hex beam. And I like the bands above 40m and wanted some directionality. I can figure out something for 40m and 80m later. A giant tower is not an option in this neighborhood, so I needed something a little more moderate. I wanted to share some of the choices I make on this journey as I build out my station so that others may be able to learn or be inspired.

I plan to put a moderate-size hex beam on top of a rotator mounted to a 2″ diameter aluminum pole. And of course, a tilt-over base for maintenance or extreme weather — wind storms are a thing in the pacific northwest. I think it will be around 25′ or so in the air, which should be good enough to work well.

First, I need to dig down for the foundation. A concrete base will hold the DX Engineering Chromoly tube securely. This bottomless hole is 45″ deep, 42″ to the gravel base. Digging this with a posthole digger meant I had to enlarge the space to the sides. Only then could get the scissors of the post hole digger close and get something out of the bottom after about ~30″ down. The tube itself is 5′ 4″, and should be roughly 20″ above ground.

I suppose you could leave the Chromoly tube galvanized as it comes. That means you’ll end up with white oxide as it weathers, and it’ll just look dull gray at some point.

I was not too fond of the idea of leaving it as-is since it was going to be not completely hidden. SWMBO approval was needed as well. I wanted something that blended a bit more. So, low luster black paint it is. And it has to be durable paint to survive the elements. Galvanizing will react with the concrete to some amount, and maybe painting it will provide some additional protection there as well.

But before you can paint, you have to prep, prime if you want it to last.

Here is the tube as it comes from DX Engineering. 2″ diameter with a 1/4″ wall.
It is rigged up on an old ground rod between two chairs,
allowing me to rotate it as I work on it.

For paint or primer to adhere, you have to remove the white oxide and grease leftover from manufacturing. With an angle grinder, knotted wire wheel, protective gear, getting to bright zinc was pretty straightforward.

This is what it should look like when you’re done stripping the white/grey oxide off.

Use a microfiber cloth to clean off any dust or debris. Don’t use a painter’s tack cloth! They often have waxy substance on the cheesecloth and will make a mess out of the surface.

Next was degreasing and etching to help the primer adhere. I used 45% vinegar (acetic acid) for this. The acetic acid in this concentration is strong, and you need to handle it with protective gear and care. Double gloved nitrile or better, organic vapor half-face mask, and protective goggles required. I applied vinegar to a thick wad of paper towels and wiped down the tube to degrease and etch the metal.

Galvanizing after vinegar etching.

Neutralize the acid with plenty of water. If you just let it dry, the primer does weird things, curling and crumbling up. There still is acid on the metal. Rinse. Rinse. Rinse. Please don’t ask how I know. 😉

A heat gun is a great way to make sure it’s really dry once it looks dry.

Time for primer!

The primer adheres very well. Even though it may seem from the picture above as if it’s not covering, trust me, it is. Most of what you see that looks like metal is a reflection of the sky. The surface is white.

Three hours later, we can paint!

Wait. Wasn’t this supposed to be black? Yes, it will be. This paint goes on dark green, changes to dark blue, and then eventually dull black.

Woohoo! It did turn black.
I’m breathing again.
It will be less reflective when cured.

Now it’s time for this to cure. Tomorrow I will set the tube in concrete.

1 Comment

Of bungees and concrete – holdmybeer.io · July 9, 2020 at 7:41 pm

[…] It was time to pour the footing for the base of the mast, and embed the chromoly tube in the bottomless hole. […]

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