Hi there, just went to the Wikipedia site and found out there are 4096 codes i believe… I just wanted to pass it along…I learn something new everyday…I also did a google search and that’s what told me that there were that many codes…List of transponder codes - Wikipedia
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Yep, that is because a Mode C transponder has 4 numbers from 0-7, which is 8 choices. With four digits, 8^4 = 4096.
That limited number is actually causing difficulties, and as a result, newer Mode S transponders now have unique 24-bit addresses that are assigned at manufacturing time and don’t change.*
* Exception: I believe they can also be changed if an aircraft or transponder were to change hands.
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If you’ve ever wondered how they assign the numbers (at least in the US), pages 7 and 8 of this document have some more info: https://www.faa.gov/documentLibrary/media/Order/2019-05-02_7110.66F_NBCAP_final.pdf
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That’s a cool list! I didn’t know that!
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