The only thing wrong with this is that you don't know whether you've
stumbled on part of a QSO or a call... although it is a technique I have
used for years (I rarely call CQ EXCEPT on LF!).

I liked the "KA" idea. I also agree with Mike's suggestion of "Q" for
quicker and "S" for slower.

Dave G3YXM.

It would seem to me that just sending one's callsign followed by "K" would
be an invitation for anyone to go ahead. The "K" would differentiate this
from a beacon where no command is given.

John Andrews, W1TAG