[Elecraft] K3 QSK - not so good?

[Graham Kimbell G3TCT]

OK, I'll put my head in the lion's mouth. I'm using qsk on cw and I find 
that if the rf gain is turned up to hear some background noise, there's 
a transient or click when the rig switches to rx (but not when it 
switches from rx to tx).  To hear this really badly, try opening the cw 
b/w up to 2kHz and sending a stream of dots. The effect is there even at 
400Hz, and it's rather off-putting. What am I doing wrong?

Graham