RE: How Close Is To Close ?
Estimating the distance between the gobble and you is very difficult. It can be more complicated if the bird is facing away from you when he gobbles whether he is still on the limb or on the ground. Foliage will further muffle the sound as will a light wind. All of these things should be taken into careful consideration when you are trying to close in on a turkey.
It's better to err on the side of setting up too far away than too close. You need to get close enough to call him effectively, but not so close that you spook the bird.
So when you are out there this spring, remember that the biggest mistake you can make is to be discovered by the bird. They have excellent hearing and even better eyesight. It's all very simple. It's OK to be heard but it's not OK to be seen.
I believe that 150' to 165' (45yds/50yds) isa safe zone.