Definition
A half-wave radio antenna whose physical length equals one half of the wavelength of the frequency being transmitted or received. It is ungrounded and operates independently of an electrical ground plane, with the radio energy distributed so that voltage is highest at the ends and current is highest at the center.
Plain English
A radio antenna cut to exactly half the length of the radio wave it is designed to handle, and which works on its own without needing to be connected to ground.
Context Anchor
Seen in aircraft radio and antenna discussions, especially when comparing antenna types used for communication or navigation equipment.
Derivation
Named after Heinrich Hertz, the German physicist who first demonstrated the existence of radio waves in the 1880s. The antenna design carries his name because his original experiments used this half-wavelength configuration.
Why Pilots Care
Most aircraft communication and navigation antennas are based on the Hertz design. Knowing that the length is tied to the operating frequency explains why VHF antennas are short and HF antennas are long, and why a damaged or incorrectly sized antenna degrades radio performance.
Intuition Check
Do not read Hertz here as just a frequency measurement. In Hertz antenna, it names a half-wave antenna type associated with Heinrich Hertz.
Example Sentence 1
The aircraft's VHF communication antenna is a Hertz antenna sized for the 118-137 MHz band.
Example Sentence 2
Before flight the pilot confirmed the Hertz antenna was securely mounted and free of corrosion.