The conventional FM discriminator is subject to wideband distortion (WBD) which increases with increasing modulation frequency for wide frequency deviations. The output filtering for such discriminators cannot, in general, be optimized (i.e., in the Wiener sense). The SCEM-PLL (Sine-Cosine

-Matrix Phase-Lock-Loop) is not subject to WBD; also, optimum output filtering can be used. Experimental studies (of noise effects and of WBD) in the SCEM-PLL are presented to support these claims.