Springtime + Aluminum (12-m OWA construction)

3/27/2022 – With a box of shiny tubing from DXE, and an OWA design from my friend, I tackled an antenna construction project today.

Shiny tubing for tower bling!

Since selling my Lightning Bolt 2-element 5-band cubical quad a few years ago, I have not had an antenna for 12 meters. My DXCC count is low on that band, so I figured that with the uptick in propagation, now is as good a time as any to tackle this project.

Some time ago I asked around for an OWA design to use a 24-foot boom (salvaged from an old TH6?). Once I had the design in hand, I plugged it into EZNEC 6.0, and agreed with the designer’s conclusions. Download my EZNEC file for this antenna. I made a parts list and placed an order from DXE for the tubing (surely there are others suppliers around, but I can’t find them using Google search) and another from McMaster-Carr for the hardware needed.

With some aluminum flat bar cut to length, a drill press made quick work punching holes in the boom-to-element plates (I used a DXE model as a template).

A pile of shavings!
Stack of six boom-to-element plates

The Sawzall was employed to cut the tubing to the needed lengths, followed by a thorough deburring of all tubing ends. Measured and marked the “exposed” lengths of tubing, inserted to the marks, and drilled three 1/8″ holes for pop rivets. Pulled the tubing out, deburred the drilled holes, then coated the insertable tip with a copper-impregnated anti-seize compound. Aligned the holes and riveted the tubing together. The halves of the driven element are separated by 2-inches, supported by a 0.75″ fiberglass rod inserted into both halves.

With the elements assembled, I moved outdoors to assemble the boom and install the boom-to-element plates. After that, installing the elements was a piece of cake.

This perspective doesn’t present the antenna well

Still sitting on sawhorses, the initial SWR and R,X sweeps are nearly identical to the EZNEC model.

Initial sweep still sitting on sawhorses
EZNEC 6.0 model’s SWR curve

I’ll update this post when the antenna is in service. I think it is going to be a flamethrower!

EZNEC 6.0 modeled pattern

4/15/2022 – Good Friday, and good Friday! I was off work. Woke up at 0400 and was wide-awake. Decided today was a good day to install the antenna. So, working alone with tractor and pallet forks, along with an 8-foot ladder, I was able to remove the KT-34 and install the 12-meter yagi. Initial tests are promising – worked YV4 and VP2V right away, 100 watts CW.

4/15/22 – 12-meter yagi now flying at 50 feet