Output total power stability measured on the antenna, post- installation, after the second down-conversion in the four base-bands (USB, LSB for Pol0 and Pol1). Four base-bands have 2 GHz width (max bandwidth 8 GHz). Each base-band can be placed anywhere inside the receiver IF sideband and can overlap. The base-band signals are fed into the correlator. The blue and green lines show Allan variance (2-sample) for Pol0 and Pol1 correspondingly. The upper solid black line show the specification for regular ALMA antenna, the measured Allan variance value to be better than 4 × 10⁻⁷ between 0.05 and 100 seconds and better than 9 × 10⁻⁶ at 300 seconds. The lower solid black line is the specification for ALMA four single-dish antennas better than 1.6 × 10⁻⁷ between 0.05 and 1 seconds.