FT-1000D receiving "images"

[76155.1426@CompuServe.COM (Robert W. Eslaire)]

I recently noticed I am receiving an "image" of strong signals (S9+) 16.6 KHz
above and below (sometimes) the actual transmit frequency.  I have only noticed
this on 18MHz so far.  I tried to duplicate this effect on 20m but without
success.  

NB and pre-amp were off.  Changing the other controls seemed to have no affect
on the "image".

Anyone have any ideas?

Bob, W9UI.