In power line communications, multicarrier modulation is an efficient way to transmit information at a very high data rate. However, due to the presence of amplitude modulated broadcasting and amateur ham radio frequencies in the allocated frequency band (for example 1.8-30 Mhz for HomePlug AV), severe constraints have to be considered: the transmission mask includes notches and bandlimited noise has to be taken into account. This paper aims at evaluating the performance of the OFDM/OQAM modulation in such a context by studying its power spectral density and its robustness with respect to this particular noise.