Abstract: A method for compensating for non-linearities in an end amplifier (F) having a given transfer function H.sub.R, H.sub..phi. for amplitude and phase respectively and included in a radio transmitter of quadrature type for linear, digital modulation, and in which table look-up units (ST, CT) store the digital sine and cosine values (I(t,.alpha.), Q(t,.alpha.)) of the quadrature components determined by a given signal vector .alpha.. According to the method of values of the transfer functions H.sub.R, H.sub..phi. for the quadrature modulated radio signals r(t,.alpha.) are calculated by addressing memory units (MH1, MH2) which store a number of values of H.sub.R and H.sub..phi.. The sine and cosine values of the addressed values of H.sub.R and H.sub..phi. are also formed. The thus calculated values are multiplied by the stored digital values in the table look-up units (ST, CT) and by the inverted value of H.sub.R. As a result, new modified values i(t,.alpha.), q(t,.alpha.