OnAirDecode COSPAS-SARSAT 406 MHz with an SDR
COSPAS-SARSAT: 406 MHz distress beacon messages decoded, with the country and position on a map (receive only; test and self-test beacons are marked).
- In the mode list
- Distress beacons, 406 MHz
What COSPAS-SARSAT 406 MHz is
COSPAS-SARSAT 406 MHz distress beacons (EPIRB, ELT, PLB) on 406.025 - 406.076 MHz: 400 bit/s Manchester phase modulation, a burst of half a second about every 50 seconds. The 15 hex ID, the protocol, the country, the identification (MMSI, serial, aircraft address) and the position when the beacon sends one, both BCH checks, the 121.5 MHz homing flag, and a map. Receive only.
Frequencies and settings
OnAir takes any frequency you type; the numbers above are the mode's starting point and the range its table describes. In the app the shortcut label is Distress beacons, 406 MHz.
What OnAir shows
COSPAS-SARSAT 406 MHz distress beacons (EPIRB, ELT, PLB) on 406.025 - 406.076 MHz: 400 bit/s Manchester phase modulation, a burst of half a second about every 50 seconds. The 15 hex ID, the protocol, the country, the identification (MMSI, serial, aircraft address) and the position when the beacon sends one, both BCH checks, the 121.5 MHz homing flag, and a map. Receive only.
Limits and what it was checked with
Checked with generated signals and impairments; recordings of real signals welcome.
Which radio you need
Any radio that tunes this range works. An RTL-SDR covers roughly 24 MHz to 1.7 GHz, and every other radio in the radio guide reaches it too. Antenna height and a clear view of the transmitter matter most.
Receiving and the law
Questions about COSPAS-SARSAT 406 MHz
Can I decode COSPAS-SARSAT 406 MHz with an RTL-SDR?
Usually yes for narrowband signals, as an RTL-SDR tunes roughly 24 MHz to 1.7 GHz at up to about 2.4 Msps. Wide signals such as TV channels need a faster radio, and OnAir says next to the source what the selected radio can do.
Is it legal to receive COSPAS-SARSAT 406 MHz?
Receiving satellite downlinks is generally legal. Encrypted or spread content is not decoded, and voice codecs that are patented are not shipped with OnAir.
Can I try COSPAS-SARSAT 406 MHz in OnAir without a radio?
Yes. Most modes include a built-in synthetic test signal, so you can open the screen and try the controls before you own a radio.