I use this, can't remember who do it. Kudos to him.
Switched Condition > Time more (10); Time less (15) > Set flag value (1,1); Set flag value (2,1)
Continuous action > Flag equals (1,1); Flag equals (2,1) OR Time since flag (1,60); Flag equals (2,1) > radio transmission (...); Flag set random value (1,2,30)