A communication system (20) includes a hub radio (22) that wirelessly communicates with any number of user radios (24). The hub radio (22) monitors signal quality measurements compiled from the communication signals (30') transmitted from the various user radios (24) and based upon baseband quadrature constellation point error to estimate out-of-band signal energy for the communication signals (30'). The hub radio (22) formulates commands based upon these measurements that instruct the user radios (24) how to adjust their power amplifier linearizers (66) so that their power amplifiers (74) become better linearized to minimize spectral regrowth and insure compliance with a spectral template.