The error rate performance, obtained on a Rayleigh fading channel, is determined and illustrated graphically for concatenated codes in which the outer code is a dual-

convolutional code and the inner code is either a Hadamard block code or a block orthogonal code. Comparison of the performance of these two types of concatenated codes is made on the basis of the same bandwidth utilization. It is also illustrated that the concatenated dual-

code yields a significant improvement in performance relative to the performance achieved with the inner code alone.