In the real-time processing, only receiver gain and atmospheric transmission have been calibrated. Remaining terms affecting the effective antenna gain (in K/Jy), such has pointing errors, focus errors, and decorrelation due to atmospheric phase noise and oscillator phase jitter must also be compensated for. Amplitude calibration involves interpolating the time variations of the antenna gains measured with the phase calibrator, assuming its flux is known.
This is done by plotting the SCALED amplitude for calibrators as function of time, then fitting a curve through it. Discontinuities (breaks) can be introduced at appropriate times if needed.