The Defence Science and Technology Organisation (DSTO) and Institute for Telecommunications Research (ITR) at the University of South Australia have been investigating the possibility of employing the GPS antenna and associated RF circuitry on the Black Hawk Helicopter for L-band communications at voice rates. This is problematical because the helicopter's rotor can, intermittently obscure the signal from the satellite to the antenna. This paper will present the characterisation of this satellite to helicopter digital communications channel, propose some coding and modulation designs to overcome the idiosyncrasies identified, and describe their real-time implementation. The paper by describing the performance the systems over reconstructed channels. The paper will be supported by an audio tape showing the significant improvements achieved through this research.