3 element 28MHz DK7ZB Yagi (28ohm) GW4RWR

Introduction
I wanted a monoband 28MHz HF antenna, since I rarely use the lower bands. There's just 0.8dB difference between a 3 element and a 4 element DK7ZB antenna, and since I've no need for the increased F/B ratio, I opted for the lighterweight, shorter antenna.

Aluminium Warehouse supplied the metal. Aerial-Parts supplied the clamps, bolts and end covers. The 1" square boom was easier to work with than the round boom used for the 70MHz antenna. The boom to mast clamp is made from a rectangle of 3mm plate, pressure clamped around the boom to avoid drilling through it, allowing its position to be moved along the boom for best balance. U-bolts through plate to the mast.

I suspect that I should have used more than one clamp for the parasitic elements. If this antenna was to be left up all year, I'd probably copy the driven element mounting arrangment, but with two rather than four clamps. A glue gun waterproofed the coax ends, and a plastic flower pot was cut down to size, inverted and seated snugly over the feedpoint.

Results?

DK7ZB calculated a midband gain of 5.5dBd. This was the first HF matching transformer I've made, it's length was so uncritical that I doubted it was working. But the antenna's reflected power bandwidth matches the design. No adjustment to any element was necessary.

This was built in April 2016, I should have built it two years ago whilst there was still some F2 propagation. Compared to the DX-32, I'm receiving much stronger signals from my only local beacon, GB3XMB. I wonder now whether most of the power in the DX-32 was just heating up the traps. Certainly its 3dB bandwidth was suspiciously wide.