ELTs operate on which combination of frequencies?

ELTs operate on which combination of frequencies?

• A. 121.50 MHz & 406 MHz
• B. 121.50 mHz & 406 mHz (picked up by military)
• C. 406 MHz only
• D. 121.5 kHz & 406 kHz

Answer: (B)

ELTs are designed to be detected both by satellites and by rescuers on the ground, using a two-frequency approach. The 406 MHz signal is the primary satellite-detected beacon; it transmits a digital message with a registered ID and, often, location data, allowing rapid alerting and coordination through the COSPAS-SARSAT system. The 121.5 MHz signal serves as a veiled, near-field homing beacon that helps rescuers in the vicinity locate the beacon more precisely once they’re nearby. Using both frequencies gives broad, reliable detection and efficient direction finding. The other options mix up units or omit a frequency. Millihertz or kilohertz values are not used for ELT transmissions, and relying on only one frequency would eliminate either the satellite-guided alerting or the ground-based homing capability. So ELTs operate on 121.5 MHz and 406 MHz.

ELTs are designed to be detected both by satellites and by rescuers on the ground, using a two-frequency approach. The 406 MHz signal is the primary satellite-detected beacon; it transmits a digital message with a registered ID and, often, location data, allowing rapid alerting and coordination through the COSPAS-SARSAT system. The 121.5 MHz signal serves as a veiled, near-field homing beacon that helps rescuers in the vicinity locate the beacon more precisely once they’re nearby. Using both frequencies gives broad, reliable detection and efficient direction finding.

The other options mix up units or omit a frequency. Millihertz or kilohertz values are not used for ELT transmissions, and relying on only one frequency would eliminate either the satellite-guided alerting or the ground-based homing capability.

So ELTs operate on 121.5 MHz and 406 MHz.