T1 radio having coding gain adjustable for number of channels

A communication system for transmitting (T 1 ) digital communication signals between a transmit site and a receiver site includes an M:1 multiplexer, coupled to a rate 1/N convolutional encoder, which is operative to output an encoded output signal modulated in quaternary phase shift keyed (QPSK) space having a prescribed symbol rate. The receive site has a rate 1/N Viterbi decoder which is operative to decode the encoded output signal output by the rate 1/N convolutional encoder, and a 1:M demultiplexer having an input coupled to the Viterbi decoder and M plurality of outputs, and being operative to demultiplex the decoded signal from the Viterbi decoder into a plurality of M time division multiplexed digital communication signals. For any selected values for of M and N, the product of M and N is constant.