9-18B4 C
 which of the following troubleshooting methods is not valid for finding the fault in a MF/HF transmitter operating in the F1B FEC mode?
A. Visual inspection of the transmitter (control settings, signs of physical damage or overheating, etc.)
B. Power supply testing with a DVM to ensure all prescribed operating voltages are within acceptable limits.
C. Modulation testing with a RF spectrum analyzer to measure frequency deviation in the transmit mode.
D. Input/Output checks with a 10:1 oscilloscope probe to identify any points of severe signal degradation.
