VHF Communication Procedures

VHF Band and Frequency Use

The VHF (Very High Frequency) band used in aviation voice communication spans 118.000 to 136.975 MHz. Frequencies are typically spaced at 25 kHz or, in congested areas, at 8.33 kHz intervals. This band is reserved for the Aeronautical Mobile Service (AMS) and supports short-range, line-of-sight communications between aircraft and ground stations.

Standard VHF Radio Procedures

• Always listen before transmitting to ensure the frequency is clear.
• Set receiver volume appropriately and avoid speaking until the microphone is properly positioned (not touching the lips).
• Use clear, standardized phraseology and speak at a moderate pace—no faster than 100 words per minute.
• When transmitting numbers, pause briefly before and after to improve clarity.
• Each transmission should be concise, limited to a single clearance, instruction, or information item.
• Activate the push-to-talk switch before speaking and hold it until the message is complete, then release it promptly.
• After transmitting, wait at least 10 seconds before repeating a message to allow for responses.

Radio Checks and Frequency Changes

To conduct a VHF radio check, state your identification and request a readability report. The reply should include the identification of the station called, the replying station, and the readability (e.g., "G-ABCD, Tower, readability 5").

When changing frequency, controllers will instruct the aircraft to contact a new frequency. The pilot acknowledges and reads back the frequency using the correct format, omitting trailing zeros when appropriate (e.g., "One two zero decimal three seven").

Factors Affecting VHF Communication

• VHF signals are line-of-sight and can be blocked by terrain, buildings, or the curvature of the earth.
• Atmospheric conditions, aircraft altitude, and antenna placement can reduce range and clarity.
• Interference from other transmissions or improper radio technique can degrade communication quality.