Question 18B6

F1B FEC (Forward Error Correction) is a digital mode that uses Frequency Shift Keying (FSK). For FSK modes, the transmitter's output power should be relatively constant during transmission, as the information is conveyed by shifting frequency, not by varying amplitude. * **D) The RF power meter indicates an output that fluctuates between 0 and 150 watts during transmission.** This indicates improper operation. Such large fluctuations suggest a significant problem, like an intermittent connection, severe distortion, or a faulty transmitter, which would severely degrade the digital signal and likely violate emission standards for a constant-envelope mode. * **A) The RF power meter indicates constant output at a level between 125 watts and 150 watts during transmission.** This is proper. A steady output is expected for F1B, and operating slightly below maximum power is normal. * **B) The SWR meter indicates 125 watts forward RF power and 5 watts reflected RF power during transmission.** This is proper. This calculates to an SWR of approximately 1.5:1, which is an excellent match between the transmitter and antenna, indicating efficient power transfer. * **C) The RF “S” meter fluctuates depending on the strength of the received signal during NBDP reception.** This is proper. The S-meter measures *received* signal strength, and it *should* fluctuate as propagation conditions and the transmitting station's signal strength change. This describes normal receiver behavior, not improper transmitter operation.