I personaly have never had any luck with locator calls. I haven't used them the past couple of seasons but when you never hear anything when using them it makes no sense for me to carry them any more.

I have more luck in the morning with soft yelps and as it get more light outside I add a little volume to it and have had alot of success getting them to gobble this way and I have many times after tring to get a shock gabble with an owl or crow call and hearing nothing then hit the slate with solf yelps and get birds to gobble within 100yrds of me.

I think it all depends on the area you hunt and what the birds are use to.