In this paper, a novel on-line error detection technique for wireless RF transmitters is proposed. Spectral features of the real time streaming data are monitored at the baseband input of the system to trigger the on-line tests whenever specific conditions on these spectral features are met. Embedded spectral sensors at specific RF nodes that generate DC output values are used to monitor the spectral response signature of the system to the real time data. The spectral features at the baseband input and the corresponding spectral signature at the RF node are jointly processed by the DSP in the system to determine the ?health? of the transmitter. The major contribution of this work is in the development of an error detection scheme that determines the health of the complex RF systems based on random streaming data as opposed to prior test methods that rely on the use of a controlled test stimulus and therefore must be run off-line.