[NTG-context] newbie tabulate question

This is probably an easy one, but I couldn't figure it out: I want to set up a tabulation with a whitespace of 0.5 lines between rows. But no matter where I put my \blank, the tabulation always appears as packed. Thanks for your help! (Is there any more elaborate docu on tabulate than the three pages in the manual and the few lines in core-tbl.tex?) Thomas