This paper proposes a new signaling technique which employs multilevel block codes in conjunction with phase/frequency modulation. The proposed scheme exhibits an increased minimum squared Euclidean distances (MSEDs) and outperforms other conventional schemes in terms of asymptotic coding gain and decoding complexity. The proposed scheme is also considered for non-constant amplitudes, which turned out to show even better performances at small modulation indices in some cases. Examples are given to demonstrate how to optimize the signal set for a given block code to maximize the coding gain.