Let the real hens teach you how to call.

If you do pre-season scouting, get out there early and just listen to them.
One neat little trick I learned this year while watching a gobbler with several hens:

Every time the gobbler sounded off, one of the hens would do this little soft yelping cadence....I tried imitating it this year when I had a gobbler out in front but just out of range. I did the "soft yelping cadence" (Think: "Now you just quiet down!")....softly-one soft yelp for every word. Immediately after he gobbles.

And yes! I got him!

Hope this helps!