Formulas are derived for the power spectral density function of a sinusoidal carrier, frequency modulated by a random baseband pulse train in which the signaling interval equals

. The signal pulses of duration

overlap. In the analysis presented different shapes of the signal pulses are approximated by staircase functions. Variations of the instantaneous frequency of the binary FM signal are accompanied by suitable staircase variations of the amplitude. It is shown that an FM signal considered in This paper has a psdf that is narrower than the psdf of the same FM signal with a constant amplitude. Some examples are given to illustrate the results.