1. A field configurable radio frequency communications system comprising: a radio frequency unit having a transmitter section for receiving carrier based modulated digital signals for transmission, and having a receiver section for receiving carrier based modulated signals and outputting carrier based modulated digital signals; a configurable carrier based digital signal processing circuit, responsive to digital commands, for configuration in accordance to any of a plural communications signaling schemes to receive digital input signals for modulation as carrier based signals modulated digital signals to be supplied to the transmitter section, and for configuration in accordance to any of a plural communications signaling schemes to receive carrier based modulated digital signals from the receiver section for demodulation as digital signals; an input circuit adapted for receiving digital commands for selecting the transmitter and receiver modes of operation and for selecting the communications signaling scheme, and a control system, including at least one digital processor that is responsive to digital commands received by the input circuit, for processing digital commands to configure the digital signal processing circuit to modulate input digital signals as carrier based modulated digital signals in the transmitter mode of operation in accordance with the selected communications signaling scheme, and to demodulate carrier based modulated digital signals as digital signals in the receiver mode of operation in accordance with the selected communications signaling scheme.