Transponder in octal

[Mike Lewis]

I used to know the answer to this question, but I seem to have forgotten it.

Does anyone know why a transponder uses octal instead of decimal?

 

[pscraig]

I believe your answer lies in the nature of a digital signal. A 4096-code transponder would likely reply to ATC with a 4-byte packet, consisting of 32 bits. The easiest way to encode this with analog knobs would be four knobs, each with eight possible positions-zero through seven.

 

[Mike Lewis]

Thanks for the response, PaulC.

I always thought it was odd.