An antenna system, comprising: a modal antenna comprising a driven element and a parasitic element, the modal antenna operable in a selected mode of a plurality of modes, each mode of the plurality of modes associated with a different radiation pattern or polarization; a tuning circuit configured to control an electrical characteristic associated with the parasitic element to operate the modal antenna in each of the plurality of modes; a radio frequency circuit; a transmission line coupling the radio frequency circuit to the modal antenna; wherein the radio frequency circuit is configured to modulate a control signal onto an RF signal to generate a transmit signal for communication over the transmission line to the tuning circuit, the control signal comprising a first frame and a second frame, the first frame and the second frame each having a plurality of bits associated with the selected mode of the modal antenna, wherein the radio frequency circuit is configured to encode the plurality of bits associated with the selected mode in accordance with a coding scheme, the coding scheme specifying a unique code for each mode of the plurality of modes, wherein the unique code for each mode of the plurality of modes differs by at least two bits relative to the unique code for each other mode of the plurality of modes, wherein the first frame has a first frame size and the second frame has a second frame size, the second frame size being different from the first frame size; and wherein the tuning circuit is configured to: demodulate the control signal from the transmit signal such that the tuning circuit can adjust a mode of the modal antenna based at least in part on the control signal; alternately process the first frame of the control signal and the second frame of the control signal to obtain a first code associated with the first frame and a second code associated with the second frame; and detect an error associated with the control signal when the first code or the second code do not match one of the unique codes specified by the coding scheme. a modal antenna comprising a driven element and a parasitic element, the modal antenna operable in a selected mode of a plurality of modes, each mode of the plurality of modes associated with a different radiation pattern or polarization; a tuning circuit configured to control an electrical characteristic associated with the parasitic element to operate the modal antenna in each of the plurality of modes; a radio frequency circuit; a transmission line coupling the radio frequency circuit to the modal antenna; wherein the radio frequency circuit is configured to modulate a control signal onto an RF signal to generate a transmit signal for communication over the transmission line to the tuning circuit, the control signal comprising a first frame and a second frame, the first frame and the second frame each having a plurality of bits associated with the selected mode of the modal antenna, wherein the radio frequency circuit is configured to encode the plurality of bits associated with the selected mode in accordance with a coding scheme, the coding scheme specifying a unique code for each mode of the plurality of modes, wherein the unique code for each mode of the plurality of modes differs by at least two bits relative to the unique code for each other mode of the plurality of modes, wherein the first frame has a first frame size and the second frame has a second frame size, the second frame size being different from the first frame size; and wherein the tuning circuit is configured to: demodulate the control signal from the transmit signal such that the tuning circuit can adjust a mode of the modal antenna based at least in part on the control signal; alternately process the first frame of the control signal and the second frame of the control signal to obtain a first code associated with the first frame and a second code associated with the second frame; and detect an error associated with the control signal when the first code or the second code do not match one of the unique codes specified by the coding scheme. demodulate the control signal from the transmit signal such that the tuning circuit can adjust a mode of the modal antenna based at least in part on the control signal; alternately process the first frame of the control signal and the second frame of the control signal to obtain a first code associated with the first frame and a second code associated with the second frame; and detect an error associated with the control signal when the first code or the second code do not match one of the unique codes specified by the coding scheme.