Yagi Beam

Overview

A Yagi is a beam antenna: one driven element with a reflector behind it and one or more directors in front, all mounted on a common boom. The extra elements do not radiate much themselves — they re-radiate the field from the driven element in a way that cancels energy to the rear and adds it to the front.

That concentration is the whole point. A three-element Yagi has roughly 8 dBi of gain and 15-20 dB of front-to-back ratio, which means both a stronger signal in the wanted direction and less interference from behind. The price is that it must be aimed, so a Yagi needs a rotator and a mast strong enough to carry the wind load.

Bands and modes

Band coverage

Modes

Safety note

Using it well

• Assemble the beam on the ground and check element spacing before it goes up.
• Set the SWR and front-to-back ratio at the height it will actually operate.
• Add a mast-mounted thrust bearing so the rotator carries torque, not weight.
• Log the beam heading with each contact so you can learn your own pattern.