John Savard wrote:
On Saturday, March 25, 2017 at 11:53:32 AM UTC-6, Michael Black wrote:

But why should five-bit code be saved?

That's true - if one is concerned with saving bandwidth, which will still be
a concern in some applications, no matter how technology advances - one could
always use compression algorithms like those used for ZIP files, or, if
simplicity is an issue, a static Huffman code.

5-level codes are typically used with FSK or AFSK modulation so there
is a lot of efficiency to be gained by implementing a more efficient
modulation method. When doing that, you can do some compression as well.

Wait. This has already been done! It is called PSK31.