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Old September 5th 08, 10:21 PM posted to rec.aviation.ifr
Mike[_22_]
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Posts: 466
Default Mode S transponder display to ATC?

"Jay Maynard" wrote in message
...
On 2008-09-05, Mike wrote:
"Jay Maynard" wrote in message
Not directly, but I got curious to see how it was assigned, and started
poking at the FAA registration database (which includes the assigned
code). The algorithm winds up assigning 50000001 to N1, 50000002 to N1A,
50000003 to N1AA, 50000004 to N1AB,... 50000032 to N1AZ, 50000033 to
N1B,
50000034 to N1BA,... 50001131 to N1ZZ, 50001132 to N10, 50001133 to
N10A,
and so on. I never got to the point of writing C code that would
generate
the code, but it would be fairly straightforward. The algorithm depends
on the rules for assigning N numbers, and works left to right, with the
letters in order from A to Z (skipping I and O), then 0-9, taking all of
the letter combinations in order before expanding the number field.

There's no need as it's already been done and put online.

http://www.airframes.org/


Well, it appears he's written the code, but it doesn't appear to be
available...I'd like to see the actual code, just to check if my thoughts
on
the programming required to go in the reverse direction are correct. I'd
also like to see if other countries assign their codes algorithmically.


The algorithm is part of the ICAO standard, so if other countries aren't
doing this, they are doing so outside the standard.

If you could find the written version of the standard in the ICAO
conventions, it would probably verify your suspicions, but ICAO standards
are a bit hard to find without paying for a copy as ICAO would like you to
do.