VHF Frequency Selection

VHF Frequency Band and Allocation

The VHF (Very High Frequency) band spans 30 MHz to 300 MHz, but aviation voice communications are strictly limited to 118–137 MHz. This allocation is reserved for the Aeronautical Mobile Service (AMS), ensuring minimal interference from other users of the VHF spectrum.

Channel Spacing and Frequency Selection

To maximize the number of available channels, European aviation now uses 8.33 kHz spacing between consecutive VHF frequencies (previously 25 kHz). This allows more aircraft to communicate simultaneously in congested airspace. Pilots select frequencies using cockpit radio panels, which display both the active (in use) and standby (preselected) frequencies. Changing frequency involves tuning the standby frequency and then swapping it to active, typically via a transfer button.

Factors Affecting VHF Communication

The effective range and quality of VHF transmissions depend on transmitter power, antenna height (both transmitting and receiving), and any terrain or obstacles between stations. VHF signals travel line-of-sight, so higher altitude generally improves range.

Practical Frequency Change Procedures

When ATC issues a frequency change, pilots must accurately select the new frequency, confirm it on the display, and read back the instruction before switching. Navigation aids are usually tuned automatically, but manual override is available if needed.