A Yagi puts a driven element between a reflector and one or more directors, concentrating radiation in one direction. You gain signal both ways — you transmit stronger and hear less noise from everywhere else.
What gain buys
A three-element Yagi gives roughly 6–7 dBd forward gain — about an S-unit — plus 15–25 dB of front-to-back rejection. That rejection is often more valuable than the gain, because it removes interference and noise from behind you.
What it costs
- A rotator, a mast or tower, and a structural engineering problem
- Wind loading, ice loading and a permit conversation with the neighbours
- Money: a small HF beam plus rotator plus tower is a four-figure project
On VHF/UHF it is cheap
A 2 m or 70 cm Yagi is small enough to build from tape measures and PVC for under $20. Handheld Yagis are how people work satellites and run direction-finding ("fox hunt") events.
Other directional antennas
- Moxon — compact two-element, excellent front-to-back, easy to build.
- Quad — loops rather than dipoles; slightly more gain per boom foot, more wind area.
- Hex beam — multiband, light, popular where a full-size Yagi will not fit.
- Log periodic — wide bandwidth, less gain, no retuning across bands.
Antenna restrictions
Deed restrictions and HOAs are the usual obstacle. Attic antennas, flagpole verticals, wires in trees and portable operating are the standard responses. Some states have laws requiring HOAs to reasonably accommodate amateur antennas; check yours.