CW over CAT never worked on a Kenwood. The KY implementation was written against
Elecraft's, which accepts a string of any length, so "KY OH5CX;" went out and a
TS-590SG answered "?;". OpsLog read that as "this radio refuses CW over CAT" and
told the operator to fit a serial keyer — advice that was wrong, and expensive.
The TS-590 manual is explicit: P2 has a fixed length of 24, blanks are filled
with spaces, and those spaces are not keyed. So the fix costs nothing on air; it
is simply the shape the command has. Elecraft stays variable-length, where
padding would key the trailing spaces as word gaps.
The semicolon is also gone from the allowed CW characters. It TERMINATES a CAT
frame, the manual forbids it in P2, and one in a macro would have closed the
command early and left the rest of the message to be read as commands.
Found from a log and a manual page, not from a rig: nobody here owns a Kenwood.
What is proven is the frame shape; that a TS-590SG then keys it still needs the
operator to confirm.