Hi Fred
I pick up Tornados and other Mil virtually every day and I have no problem with them populating even with a low message count. I do get the odd flights that do not populate even when I can see them by line of sight but I am told that receiving the signal can depend on the carrier strength sent by the aircraft and weather conditions. Also, the aerial position and its integrity are other factors. How true this is I am not sure, I always hated electonics!
Regards
Keith