Definition
The unit of frequency equal to one cycle per second. It measures how many times a repeating event — such as a radio wave oscillation — occurs each second. Symbol: Hz. Common multiples in aviation are kilohertz (kHz, thousands of cycles per second) and megahertz (MHz, millions of cycles per second).
Plain English
A way of counting how often something repeats every second. One hertz means one repeat per second; a million hertz means a million repeats per second.
Context Anchor
Pilots encounter hertz when reading about radio, navigation, and electronic signals, usually shown as kilohertz or megahertz for aviation frequencies.
Derivation
Named after Heinrich Hertz, the German physicist who first demonstrated radio waves in the late 1880s. The unit was adopted internationally in his honor, replacing the older term 'cycles per second.'
Why Pilots Care
All aircraft communication and navigation radios operate at specific frequencies expressed in Hertz or its multiples; selecting the wrong frequency means no contact with ATC or loss of navigation guidance.
Analogy
If a light flashed once every second, it would be flashing at 1 hertz. If it flashed ten times every second, it would be flashing at 10 hertz.
Intuition Check
Hertz is not a measure of strength or volume. A higher number of hertz does not mean a stronger signal — it means the wave repeats more times per second.
Example Sentence 1
Tower instructed the pilot to contact departure on 124.05 megahertz after takeoff.
Example Sentence 2
When programming the standby frequency, she entered the value in hertz to match the published approach chart.