sorry for my late reaction.

Thanks for all the help. In my memmory the burgers where to smokey for just
a charcoal fired grill. I just bought a new concrete grill. I'll try
grilling my burgers on a wood grill (when the weather improves). smoking the
burgers before grilling sounds like a great idea. I will give that a try
next time.
will get back with the results.

Adriaan