VHF Communication Systems and Procedures
VHF airband (118.000-136.975 MHz) uses amplitude modulation with 8.33 kHz or 25 kHz channel spacing. Candidates must know frequency assignment by ICAO region, emergency frequencies (121.5 MHz civil, 243.0 MHz military), and the standard phraseology and readback requirements. Understand simplex operation, line-of-sight coverage, and the factors affecting communication range: aerial height, terrain, transmitter power and receiver sensitivity. Know the difference between primary and standby radios, and the purpose of the audio selector panel.
Procedures tested include distress (MAYDAY), urgency (PAN PAN), and the correct readback of clearances, runway and altimeter settings. Know that a clearance must be read back in full when it contains route, altitude or frequency instructions. Understand the use of the phonetic alphabet and standard words (ROGER, WILCO, AFFIRM, NEGATIVE, STANDBY).
Traps: confusing MAYDAY with PAN PAN; forgetting that 121.5 is monitored by emergency services and not for routine use; assuming VHF works over the horizon. Another trap is misreading 8.33 kHz channel designations (e.g. 118.005 becomes 118.010 in 8.33 spacing).
Rule of thumb: if a clearance contains a number you must act on (heading, level, frequency, squawk), read it back. If in doubt, ask for clarification rather than guess.