Definition
A VHF communication radio channel arrangement in which the available frequency band is divided into slots 8.33 kilohertz wide, allowing roughly three times as many usable channels as the older 25 kHz spacing. Aircraft operating in airspace where 8.33 kHz spacing is required must have a radio capable of tuning and transmitting on these narrower channels.
Plain English
It's a way of slicing up the radio band into smaller slots so more channels fit into the same range. Some areas — mainly in Europe — require radios that can use these smaller slots.
Context Anchor
Seen in radio equipment discussions, especially when checking whether an aircraft communication radio can tune the required channels for a particular area or country.
Derivation
kHz stands for kilohertz, a measure of radio frequency. The 8.33 figure is simply 25 divided by 3 — the original 25 kHz channel was split into three narrower channels to ease frequency congestion.
Why Pilots Care
It relieves congestion on busy voice channels by creating many additional discrete frequencies pilots can select.
Intuition Check
8.33 kHz channel spacing does not mean the radio is stronger or has longer range. It means the available radio channels are placed closer together.
Example Sentence 1
Before the trip to France, he confirmed the aircraft's COM radio supported 8.33 kHz channel spacing.
Example Sentence 2
Before departure the pilot verified the VHF radio supported 8.33 kHz steps for the planned route across Europe.