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Normal-Mode Helical (Rubber Duck)

Helical Antennas

A short, coiled flexible antenna that fits a quarter-wave into a stubby package.

Band: VHF/UHF
Gain: ~ -1 to +1 dBi
Polarization: Vertical

Photos

Real-world photo of a Normal-Mode Helical (Rubber Duck) in use — Real-world example. Source: Wikimedia Commons (Public domain; Wtshymanski at English Wikipedia).

Radiation / wave patterns

Idealized radiation pattern of the Normal-Mode Helical (Rubber Duck) — Idealized azimuth radiation pattern (illustrative, generated). Radial scale in dB.

How & why it works

The familiar 'rubber duck' winds a quarter-wave's worth of wire into a tight, short helix much smaller than a wavelength, operating in normal mode where it radiates broadside like a short vertical. Coiling the conductor adds inductance that resonates the physically short element, trading some efficiency and bandwidth for a rugged, pocketable size. It is the classic compromise antenna for handheld radios.

Real-world uses

Handheld transceivers, walkie-talkies, and portable consumer wireless devices.