Agree 100% re tenterfield whistle pal, have been using it for years and have not found anything better to get then in from distance, and again you can change the pitch when they come in close, also use the U-Caller and find it very good, but if I only had one to pick it from would be the terterfield whistle. Once you master it you will never look back. Simple to make.
At least someone knows what they're talking about lol. Cheers lurcher atb