Predator Call

I have hunted three mornings in the vast open plains of northeastern New Mexico this winter when there was little to no wind.  It seems that everytime I sat down with the electronic game call, the wind was so light that I could not discern where it was blowing.  While one would think that these calm mornings would be perfect, I have not had any success.  After it warms up a little and the wind has a defined direction, the coyotes would begin to respond to my calls. I am not sure if the coyotes are hearing my approach in the truck and staying away or if they are just uncomfortable responding to a distress sound when they cannot use their nose to assist their hunt.  I have not had this problem in the tight cover of South Texas and loved those calm days.