I also realized that the way you call
gr_make_vector_source_s(in_bits,false,K );
is incorrect.
I think you have misunderstood what this block does.
You should use:
gr_make_vector_source_s(in_bits,false,1 );
or simply
gr_make_vector_source_s(in_bits,false);
and you really don’t need the vector2stream block.
Achilleas
In your code the “encoder” block is not connected to any other block…
It should be:
info bits -> encoder -> modulator -> channel -> metrics -> viterbi
Achilleas