usually, they're adjusted.. but then again sometimes they're not.. it's kinda a gamble, but this sort of thing is reversable
basically you gotta get a plastic screwdriver, or something that is Not metal to the screw in the hole in the top of the PCB. on the underside there should be a big white chunk of crap with wire wrapped around it, and you're adjusting the top of that.
stick in the screwdriver (remember, plastic!) and turn bit by bit, seeing if your range has increased/decreased. if it goes down, turn it the other way. if it goes up, keep goin til it starts goin down, then stick there.
it's not all that easy, as i discovered, but just so long as you're gentle and have a general idea what you're doing, you should get some increase in range. 40 feet isnt unheard of... but 30's still hella good... i'd be crazy happy if any of my new bits went for 30 feet.
*note: a toothpick shaved into a screwdriver shape can also do the trick, cuz plastic screwdrivers that small dont usually come along very often.
hope that helps!