Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
I would suggest the first thing to look at would be a proper antenna matching circuit. It will probably boost the output by 50% or so and reduce harmonic levels at the same time.
Goggle for "pi matching network" for more details.