Definition
The unit of frequency equal to one cycle per second. In aviation, hertz measures the frequency of radio waves, electrical signals, and other oscillating phenomena. Common multiples are kilohertz (kHz, thousands of cycles per second) and megahertz (MHz, millions of cycles per second).
Plain English
A way of measuring how many times something repeats in one second. One hertz means one repeat per second. Higher numbers mean faster repeats.
Context Anchor
Pilots may see Hz in avionics, radio, audio, electrical, and maintenance information when a signal or tone rate is being described.
Derivation
Named after Heinrich Hertz, the 19th-century German physicist who first proved that radio waves exist. The unit honours his work, which is why frequency is now measured in 'hertz' rather than 'cycles per second' as it once was.
Why Pilots Care
Radio frequencies are specified in Hz or its multiples, so correct understanding prevents tuning errors on comm and nav radios.
Analogy
If a light flashes once every second, that is 1 Hz. If it flashes ten times every second, that is 10 Hz.
Intuition Check
Hz does not mean how strong or loud something is. It means how often it repeats each second.
Example Sentence 1
The tower frequency is 124.5 MHz, which means the radio signal oscillates 124.5 million times per second.
Example Sentence 2
The localizer operates at 110.3 MHz or 110,300,000 Hz.