Subelement C: Satellite Systems— Topic :
Question 31C2
Element 9 (GMDSS Maintainer)An Inmarsat-C terminal will not “LOG IN”. A test antenna cable with a new ADE attached in view of the satellite allows the terminal to “LOG IN”. What steps would you take?
Explanation
The critical information is that the terminal *does* log in successfully when connected to a *new* Above Deck Equipment (ADE) with a test cable. This demonstrates two things:
1. The Inmarsat satellite signal is available.
2. The terminal unit itself (below deck) is functional.
Since the original ADE did not allow the terminal to log in, but a new ADE does, the problem is isolated to the original ADE or the original feedline. However, the direct evidence of a *working* new ADE strongly points to the original ADE being faulty. Replacing the faulty component, the ADE (D), is the logical next step.
Options A and B are incorrect. Inmarsat-C terminals typically use omnidirectional or electronically steered antennas and do not have mechanical AZ/EL motors. Trying a different satellite (B) will not resolve a hardware fault in the ADE. Option C, while checking the feedline can be part of troubleshooting, a DVM is not ideal for assessing the RF performance (loss, impedance, noise) of a satellite feedline; specialized RF test equipment would be needed. More importantly, the test already confirmed the ADE is the likely culprit.
Related Questions
30C6 What error message may be displayed if a connection to the Inmarsat Mobile Packet Data Service (MPDS) network fails?31C1 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?31C3 An Inmarsat-C terminal will not “LOG IN” and shows an “Antenna not connected” alarm. What action would you take?31C4 The antenna goes past the AZ EL of the satellite but does not initialize but you can manually point the antenna at the satellite and acquire signal. What is the most likely problem?31C5 The antenna creeps up and down after initialization. What action would you take?