The DF-500 can receive which signals?

• A. 121.5 MHz, 243 MHz, 406 MHz, ARGOS, AIS-SART, and DSC-encoded beacon signals
• B. 121.5 MHz and 406 MHz only
• C. 243 MHz and 406 MHz only
• D. ARGOS and AIS-SART only

Answer: (A)

This question tests the DF-500’s ability to monitor a broad range of distress signaling formats, from legacy systems to modern satellite and digital methods. The DF-500 is designed to receive multiple types of distress signals so SAR teams can locate and assist quickly.

It can pick up classic homing beacons on 121.5 MHz and 243 MHz, which are traditional frequencies used for early-stage locating by nearby rescuers. It also receives 406 MHz distress signals, the current standard for satellite-based distress alerts tied to the COSPAS-SARSAT system; these transmissions include beacon IDs and can be used to pinpoint the distress event via satellite data. In addition, the DF-500 can receive ARGOS transmissions, which provide location and other data through the ARGOS satellite system. It can decode AIS-SART signals, which appear as AIS messages on the ship’s AIS channels and help nearby vessels and authorities identify the distressed vessel. Finally, it can receive DSC-encoded beacon signals, where distress alerts are sent digitally via the marine VHF DSC system.

Because it supports all of these signal types, the best answer is the one that lists every one of them. The other options omit one or more of these signal types, making them incomplete.