This article presents the evaluation of out-of-band spectral pollution caused by the nonlinearities of the PA at the RF front-end for FBMC/OQAM signals, as well as the improvement of those spectral performances thanks to an envelope dynamic reduction method based on precoding. We also study the in-band spectral pollution by creating notches in the spectrum, in the perspective of fragmented spectrum access. The impact on in- and out-of-band performances is compared to well-known OFDM signals, and evaluated through simulations of ACPR and NPR. Measurements on an RF platform with a commercial amplifier are presented to confirm the simulation results.