An Inmarsat-C terminal shows a "No Receive...

🔍 Key Concepts

• Inmarsat-C above deck equipment (ADE) design: how DC power is sent to the antenna/LNA via the coax center conductor • Difference between terminal DC supply fuse and antenna power fuse and where each one is located in the system • Function of a Low Noise Amplifier (LNA) versus mechanical parts like AZ/EL motors in relation to DC voltage on the feed line

💭 Think About

• If there is no DC voltage on the antenna center pin, which single failed component or protection device would most directly interrupt that DC feed? • Which option would affect only the receive signal path, and which would also affect or be unrelated to the DC voltage going up the coax? • Would a purely mechanical failure (like an AZ/EL motor) normally remove DC power from the antenna feed, or just affect pointing/tracking?

✅ Before You Answer

• Verify which fuse specifically protects the DC power feed to the antenna/LNA over the coax center conductor. • Check whether a defective LNA would usually cause loss of DC voltage on the center pin or instead draw too much current and blow a protection device. • Confirm that a blown terminal main DC line fuse would affect power to the entire terminal, not just the receive section.

An Inmarsat-C terminal shows a "No Receive Signal" alarm. There is no voltage on the antenna center pin. What is the most likely cause?

Defective AZ or EL motor in the above deck equipment.

Blown line fuse in the terminal's DC power supply.

Blown antenna power fuse in the above deck equipment.

Defective Low Noise Amplifier in the above deck equipment.

🔍 Key Concepts

💭 Think About

✅ Before You Answer