The gravitic amplitude modulator or GAM, also known as a gravitic wave modulator or simply gravitic modulator, was a device created by the Galactic Empire to allow a starship to modulate gravity in its immediate area.
Danni Quee and Cilghal developed a modified modulator on Eclipse Station in 27 ABY, as part of Yammosk Action. A more complex and sophisticated version of the gravity well projector employed on Immobilizer 418 interdictors, it allowed the jamming of Yuuzhan Vong yammosks. The device would emit gravitic pulses capable of interfering with those generated by a yammosk, thus effectively jamming the creature's transmissions. The resulting confusion from losing this "hive mind" amongst Yuuzhan Vong pilots and/or warriors caused once tight formations and tactics to decompose into loose clusters fighting entirely independent from the remainder of their forces.
The first GAM was installed aboard the Errant Venture for use at the end of the Battle of Coruscant. The Galactic Alliance later installed one on the Imperial Remnant Star Destroyer Defiant. Gravitic modulators were used on the StealthX starfighter which was designed to defeat mass-detectors. This aided the craft in remaining undetected by enemy sensors. On a StealthX it replaced the third proton torpedo launcher.