In article ,
George Davailus wrote:

Hello,

I'm George Davailus from Masten Space Systems. I need a Mode C
Transponder for a 100,000 foot rocket flight. All transponders I have
found only go to 62,000 ft or lower. Does anyone know of a device that
would meet our requirement, or know of a way to modify an existing
transponder? Please respond to this thread or email me at
.

George

What you are referring to is the encoder, which has, at its hert, a
barometric pressure sensor. Since the pressure differential between
62Kft and 100 Kft is so small, its accuracy diminishes as altitude
increases. I am not sure that anyone makes such an instrument.

You might try, however, to adapt a GPS altitude reader to transmit
altitude, since GPS measures altitude the same way it resolves position
-- by differential signals, and is good to whatever calibration the GPS
unit is good for.