OnAirDecode Argos with an SDR
Argos: PTT uplink IDs and data at 401.65 MHz, or the 465.9875 MHz satellite downlink with its Doppler (receive only).
- In the mode list
- Platform data, 401 MHz
What Argos is
Argos satellite data collection, receive only. Uplink on 401.650 MHz (401.618 - 401.680): PTT-A2 bursts (160 ms carrier, then 400 bit/s Manchester phase modulation of +-1.1 rad) decoded to the 28 bit platform ID and the user data in hex, with each platform's burst frequencies as its Doppler and drift curve; PTT-A3, ZE and Argos-4 bursts are only counted and timed (their specifications are not….
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 Platform data, 401 MHz.
What OnAir shows
Argos satellite data collection, receive only. Uplink on 401.650 MHz (401.618 - 401.680): PTT-A2 bursts (160 ms carrier, then 400 bit/s Manchester phase modulation of +-1.1 rad) decoded to the 28 bit platform ID and the user data in hex, with each platform's burst frequencies as its Doppler and drift curve; PTT-A3, ZE and Argos-4 bursts are only counted and timed (their specifications are not public). Downlink on 465.9875 MHz from MetOp-B / -C: the carrier followed through the pass Doppler and compared with the predicted curve, 400 bit/s Manchester bits and HDLC frames in hex with their FCS (the frame contents are not public).
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 Argos
Can I decode Argos 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 Argos?
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 Argos 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.