Aviation Radio and Navigation Aids Flashcards

What modulation is used for VHF aeronautical voice communications in the 118-137 MHz band?

Answer: Amplitude modulation (AM)

Aviation VHF voice uses double-sideband AM, allowing a stronger signal to be heard over a weaker one.

What is the international aeronautical emergency frequency monitored by ELTs and aircraft?

Answer: 121.5 MHz

121.5 MHz is the VHF aeronautical emergency frequency and the ELT homing signal frequency.

Modern ELTs transmit a digitally encoded distress message for satellite detection on which frequency?

Answer: 406 MHz

406 MHz ELTs send coded messages to Cospas-Sarsat satellites, with 121.5 MHz used for homing.

Which transponder code indicates an aircraft is experiencing a general emergency?

Answer: 7700

Squawk 7700 signals an emergency; 7600 is radio failure and 7500 is unlawful interference.

What type of emission is typically used for long-range HF aeronautical communications over oceans?

Answer: Single sideband suppressed carrier (J3E)

HF aeronautical mobile service uses upper sideband SSB voice for efficient long-range communications.

What is the purpose of SELCAL on HF and VHF aeronautical radios?

Answer: To alert a specific aircraft crew with a unique tone code so they need not monitor continuously

SELCAL transmits a four-tone code that triggers a chime or light only on the addressed aircraft.

A radar altimeter typically operates in which frequency band?

Answer: 4.2 to 4.4 GHz

Radio altimeters use the 4.2-4.4 GHz band to measure height above terrain.