  The calibration procedures for data collected for Argus and the 4mm Receiver
instruments on the GBT are presented. The measured beam size, aperture
efficiency, and main-beam efficiency are derived for the range of observing
frequencies (66--116 GHz) within the 3mm atmospheric window. The telescope
performs well even at the highest frequencies (>100 GHz). The amount of power
in the error pattern of the antenna beam is estimated. Approximately 95% of the
total antenna power is contained within 1 degree of the pointed direction. The
calibration derived using small sources follows theoretical expectations based
on the Ruze equation. In general, bright point source calibrators that are
monitored regularly by ALMA can be used to accurately derive the main-beam
efficiency of the telescope.
