A calibration method for reducing modulation errors in a telecommunication transmitter apparatus includes providing a plurality of pairs of test signals; the test signals of each pair are substantially in quadrature to each other, and the pairs of test signals are at least in part different with all the pairs of test signals that have a substantially equal energy. A plurality of modulated signals are generated, with each modulated signal that is generated by modulating a corresponding pair of test signals. A plurality of transformed signals are calculated, each one corresponding to the square of a corresponding modulated signal in the frequency domain. A plurality of partial error indicators are calculated, each one as a function of the modulus of a corresponding transformed signal. The partial error indicators are indicative of the modulation errors associated with the modulated signals. A compensation for counterbalancing the modulation errors is calculated according to a combination of the partial error indicators and an indication of the compensation is stored for the application of the compensation to each further pair of operative signals during operation of the telecommunication transmitter apparatus.