None that I've ever used! LOL
I like setting up on a cross wind when using the ecaller. If the wind is blowing from 9 o'clock, I'll set the caller about 11 o'clock about 30-40 yards, depending on wind speed, and try to place a coyote that wants downwind of the ecaller to right in front of me and my clients. I always elevate the ecaller, as KAF said, for better sound carrying and remote response.
Tony