As a cautionary tale to others, here is how I wasted an hour this 
afternoon.

I had just unbent my antenna after the recent high winds, and was 
tuning it up with some RF. At the end of my transmission, I sent my 
callsign at about 20WPM as a courtesy. It was then that I noticed the 
CW was distorted and rather clipped, especially the dots. I also had 
bad key clicks. After checking all sorts of things, I found that the 
distortion applied only to mid-range speeds, so that it did not 
affect below about 10WPM or above 30WPM. This was an important clue 
but I ignored it.

I then took numerous measurements, assuming that RF was getting into 
the keying circuitry or even the PSU, finally dismantling the Tx and 
looking for poor connections or flash-overs. After double-checking 
that I had not introduced any problems when working on the antenna, I 
stopped to have a think. Not a moment too soon.

It then dawned on me that I had switched on both of the noise 
blankers in my TS-850 to reduce the Loran noise by some 3dB. 
Switching these off solved the keying problem. Of course, I didn't 
have a keying problem at all - I had a receiver which had tried its 
hardest to suppress my CW dots, and had mostly succeeded!

Moral. Have a cup of tea and a think first, before stripping the 
station down.

Mike, G3XDV
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PS: Excellent signal from IK5ZPV this morning.