SURVIVAL SOLUTIONS — READ PUBLIC TRANSPONDER SIGNALS
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Identify and legally receive aircraft ADS-B and vessel AIS broadcasts using a receive-only SDR, then interpret basic message fields and data limitations.

Transponders and automatic identification systems broadcast structured information. The best beginner project is reception and decoding of publicly broadcast ADS-B and AIS—not probing, interrogating or retransmitting.

SAFETY: Receive only. Never spoof, jam, inject, or interrogate transponders. ADS-B/AIS data can be delayed, incomplete or false; do not use it to navigate vessels, aircraft or rescue operations.

1. Distinguish aviation and marine broadcasts
Aircraft Mode S/ADS-B Extended Squitter is typically received at 1090 MHz. In the United States, UAT ADS-B also uses 978 MHz. Ships generally use AIS 1 at 161.975 MHz and AIS 2 at 162.025 MHz. Mode S interrogation at 1030 MHz is a separate system, not the normal ADS-B downlink.

2. Select receive-only equipment
Use an RTL-SDR or equivalent receive-capable dongle and a suitable 1090 MHz antenna for ADS-B, or a marine-VHF antenna for AIS; use a computer with sufficient power. An antenna must suit its frequency; expect range to vary with terrain, height and line of sight.

3. Connect and confirm a signal
Install SDR drivers and an established ADS-B decoder (for example readsb or dump1090) or AIS decoder (for example AIS-catcher) from their official project repositories. Choose the correct center frequency, gain and sample rate according to the receiver and decoder documentation. Do not transmit.

4. Interpret typical decoded fields
ADS-B may carry an aircraft identifier, position, altitude, ground speed and heading. AIS may carry an MMSI identifier, navigation status, position, course and speed. A record is meaningful only if its timestamp and validity flags are known.

5. Validate and account for missing data
Use a decoder that checks framing and CRC where applicable. Missing position, random-looking identifiers, stale timestamps and local reception gaps are common. Not every aircraft/vessel is required to broadcast usable position; no single SDR gives complete coverage.

6. Handle received data responsibly
Compare with trusted public reference feeds where permitted, and avoid publishing private or sensitive movements. Respect local radio monitoring and data-sharing laws. For emergencies rely on official rescue services rather than an SDR screen.

REFERENCES
- FAA ADS-B installation guide: https://www.faa.gov/air_traffic/technology/equipadsb/installation
- ITU-R M.1371-6 AIS specification: https://www.itu.int/epublications/fr/publication/recommendation-itu-r-m-1371-6-02-2026-technical-characteristics-for-vhf-automatic-identification-system-using-time-division-multiple-access-in-the-maritime-mobile-se/en