Aldo IW2DZX has produced a very nice modification for the QRSS kit, to turn the output into plain original on/off keyed QRSS instead of FSK/CW. The absence of chirp is very impressive, it is difficult to remove. 

Here's the output (local copy) after Aldo's modification:

The modification requires removal of the LED varicap diode, and an additional transistor to control the bias on the 2N7000 amplifier. Please CLICK HERE to read Aldo's modification document.

Dave WB9OWN made this modification (click photo below) and writes:

View the embedded image gallery online at:
http://qrp-labs.com/qrsskit/qrsskitmod1.html#sigFreeIdfcec58c413
"Please note how I implemented IW2DZX's modification, I cut 2 traces,
drilled 2 holes for 2n3904 and jumpered the base connection across
the top of the board. Oh, the diode across the DC Vin is to protect me from doing something
stupid.  ;-)"