[Lowfer] From another list:

[JD]

>>>it seems to be a pretty old technique.

It is, and it has long ties to 22 meters, too.  Several years ago I prepared 
an article for The LOWDOWN that was based on an RCA Review article from the 
early Sixties.  They had made some very slow CW transmissions in the 
vicinity of 13.56 MHz with a pocket-size rig running Part 15 power levels, 
and received them halfway or more across the continent.  At the time, there 
were no PCs or software like Argo, of course.  They used closely spaced 
crystal filters and integrated the detected signals in hardware rather than 
FFT bins.  I seem to recall they tried a number of speeds, and what we now 
call QRSS3 was considered the slowest rate practical for that band because 
of QSB.

Ah, the good old days.  However, I definitely like Alberto's solution 
better!

John