Question 31C1

Inmarsat-C terminals typically supply DC voltage through the antenna's center conductor to power the Low Noise Amplifier (LNA) located in the above-deck equipment (ADE). The LNA is critical for amplifying the weak satellite signals before they reach the terminal. If there is no voltage on the antenna center pin, it means the LNA is not receiving power. Without power, the LNA cannot function, preventing the amplification of satellite signals. This directly leads to a "No Receive Signal" alarm. A blown antenna power fuse in the ADE is the most direct and common cause for the cessation of DC power supply to the LNA via the center conductor. Options A (AZ/EL motor) is incorrect because Inmarsat-C uses omnidirectional antennas and does not typically have steerable motors. Option B (blown fuse in terminal’s DC power supply) would likely result in the terminal itself not powering on, not just a "No Receive Signal" alarm. Option D (defective LNA) would cause a "No Receive Signal" alarm, but the *absence of voltage* specifically points to a power supply issue *to* the LNA, making a blown fuse a more probable initial cause than the LNA simply failing while still drawing power.