Also known as: dipole antenna, dipole

A dipole antenna is a simple resonant antenna made of two conductors fed at the centre, classically a half wavelength long.¹ It is the reference against which other antennas’ gain is often compared.

A half-wave dipole is two quarter-wave rods fed in the middle, most sensitive broadside to its length.

How it works

A half-wave dipole radiates most strongly broadside (perpendicular to its axis) and least off the ends, giving an omnidirectional doughnut pattern around a vertical dipole. Its polarization follows its orientation.

Relevance to SDR

A dipole (or its grounded cousin, the quarter-wave whip) cut for the target band is a cheap, effective receive antenna for scanning.

Sources

1. Dipole antenna — Wikipedia, for the construction and radiation pattern of the half-wave dipole. ↩

See also

• Antenna
• Antenna gain
• Polarization
• Wavelength

Learn it step by step

• Antennas 101