Subjective Tests of a Companded, Frequency Modulated, Single Channel Per Carrier Communication System

Subjective tests were performed to evaluate components of an FM-SCPC communications system including a syllabic compandor, a VOX circuit, and a shallow emphasis network. The subjective improvements in the signal-to-noise ratio were determined for these components separately and in combination. Tests of the syllabic compandor were conducted at four talker levels and at two values of
C/kT
for the SCPC equipment. Further listening tests were conducted to evaluate the advantage produced by (a) the VOX alone, (b) the VOX operating with the compandor, and (c) the VOX, compandor and a shallow emphasis network. Group distributions of compandor advantages are presented for use in designing SCPC systems.