Chipset?

[G4UMW]

You shuld know that the Aircraft reduce the output power on the Airport.

Wrong.

ICAO Annex 10, Volume 4, Chapter 3, section 3.1.1.7.11 details the power output requirements for transponders. For most commercial aircraft the output must be between 21dBW and 27dBW - that's roughly 126 Watts to 500 Watts. The only exception is equipment fitted to an aircraft that will not operate above 15,000 feet, in which case the minimum power output requirement is 18.5 dBW (70 Watts) - the upper power limit remains the same. A transponder fitted to a ground vehicle may use lower power but there is no such provision for aircraft equipment - output power remains constant, whether airborne or on the ground.