Plane Wave Generators (PWG) have proven to be an effective solution for testing antennas and active devices in compact anechoic environments. Precise control over excitation coefficients is critical for achieving uniform amplitude and phase in the Quiet Zone (QZ), as excitation errors can adversely impact measurement accuracy. This paper investigates different calibration techniques to minimize excitation discrepancies in a 19-element PWG subarray operating at UHF/VHF frequencies. The array was characterized using the Pulsar by AGC spherical near-field automotive range, employing different post-processing techniques to determine the realized excitation when all elements are excited simultaneously. An excellent correlation was observed between conducted measurements of individual components, such as phase shifters, and full radiated array measurements analyzed using a field expansion method. This approach requires a single measurement of the fully excited subarray and the measurements (or accurate modelling) of the individual sub-arrays, streamlining the calibration process while maintaining high accuracy.