Mode S Transponder Hex & Bitmask Decoder
Analyze 24-bit ICAO aircraft Mode S addresses broadcast by ADS-B transponders over 1090 MHz. Translate hexadecimal addresses to 24-bit binary bitmasks and identify the sovereign civil aviation authority of registry.
Key Facts
- Decodes 24-bit ICAO aircraft transponder hex addresses into binary bitmasks and registration blocks.
- Identifies state of registry according to official ICAO Doc 9684 allocation tables.
- Simulates Mode A/C secondary surveillance radar (SSR) squawk code octal matrix (0000 to 7777).
- Links transponder telemetry directly to live airframe registration profiles and ADS-B tracks.
1. Enter Hex Transponder Address
24-Bit Binary Bitmask
2. Decoded Telemetry Profile
Registry Analysis
Major ICAO 24-Bit National Allocation Blocks
Sample address ranges assigned by ICAO Doc 9684 / Annex 10 to sovereign nations.
| Country / Authority | Hex Range (Start to End) | Binary Prefix | Address Capacity | Primary Tail Prefix |
|---|---|---|---|---|
| United States (FAA) | A00000 to AFFFFF | 1010 xxxx | 1,048,576 | N- |
| United Kingdom (CAA) | 400000 to 43FFFF | 0100 00xx | 262,144 | G- |
| France (DGAC) | 380000 to 3BFFFF | 0011 10xx | 262,144 | F- |
| Germany (LBA) | 3C0000 to 3FFFFF | 0011 11xx | 262,144 | D- |
| China (CAAC) | 780000 to 7BFFFF | 0111 10xx | 262,144 | B- |
| Japan (JCAB) | 840000 to 87FFFF | 1000 01xx | 262,144 | JA |
| Canada (TCCA) | C00000 to C3FFFF | 1100 00xx | 262,144 | C-F, C-G |
| Australia (CASA) | 7C0000 to 7FFFFF | 0111 11xx | 262,144 | VH- |
| United Arab Emirates (GCAA) | 896000 to 896FFF | 1000 1001 0110 | 4,096 | A6- |
| Qatar (QCAA) | 06A000 to 06A3FF | 0000 0110 1010 | 1,024 | A7- |
Frequently Asked Questions
What is a 24-bit ICAO Mode S aircraft address?
An ICAO 24-bit address is a unique worldwide transponder identifier assigned to each aircraft airframe upon civil registration. Broadcast over 1090 MHz ADS-B out, it enables automated secondary surveillance radar tracking.
How are ICAO hex addresses allocated across nations?
ICAO allocates discrete address blocks to sovereign states based on fleet size. For example, the United States is allocated A00000 to AFFFFF, the United Kingdom holds 400000 to 43FFFF, and France holds 380000 to 3BFFFF.
Can a Mode S hex address change during an aircraft life?
Yes. If an airframe is exported or transferred to an airline registered in another country, its civil registration changes and its Mode S transponder is reprogrammed with a new address from the recipient state block.
What is the relationship between Mode S hex and 4-digit squawk codes?
A 24-bit Mode S hex is permanent to the airframe registration, while a 4-digit Mode A/C squawk code (such as 7700 for emergency or 1200 for VFR) is assigned dynamically by air traffic control for a single flight.