public lands tough to hunt...hunting turkeys on public land's even tougher ...you might want to start your calling earlier than you have been. Start with some soft tree yelping...Rebel Hog had another post with authentic turkey sounds (nice post by the way Rebel)...if you cant find it try this...make the same yelp you would during daylight hours...but with your gloved hand over your mouth and calling into the palm of your hand..call sparingly..remember the birds are waking up too..one or two yelps everyfew minutes (move your gloved hand away from your mouth as you get further into this tree yelping series)...after maybe ten minutes give two or three regular yelps and a short cackle...then (Rebel has it on that post) a fly down cackle..start the cackle looking upwards into the treetops...but as you finish it your head should be looking down..the sound will appear as if it came from a roosted bird that flew down..once you've done that....wait..be patient, get out your box calls and slates, get comfy and ready to work a bird..start your ground calling with 'soft talk'..clucks, purrs, little whitt whitt's should be all you need..every so often you could throw out a yelp but what you want to do is let a tom turkey know the hens on the ground....and she aint going anywhere..if you've positioned yourself right..he'll know exactly where you are and will make his way to you..unless he flies down with a harem..if thats the case, all isnt lost, you may bring him in later.
I am surprised you havent heard dawn gobbling tho..weather might be a factor..not sure