Abstract: To determine the phase and amplitude response of a superheterodyne instrument, a fixed frequency signal is applied to the instrument's signal input port. The superheterodyne local oscillator is then swept to translate the fixed frequency input signal into a sweeping sinusoid that traverses the I.F. passband. Data is acquired as the signal sweeps the passband and is analyzed to determine the phase and amplitude characteristics of the instrument. These characteristics are logged in a memory and are used to remove artifacts of instrument-induced frequency response errors from subsequent measurements.