Question 47G5

When installing multiple Inmarsat-C antennas, a minimum separation distance is crucial to prevent mutual interference. This 8-meter guideline is a standard recommendation from Inmarsat to ensure reliable operation, especially for GMDSS (Global Maritime Distress and Safety System) functions where service reliability is paramount. The primary reasons for this separation are: 1. **Desensitization:** The transmit signal from one Inmarsat-C antenna can be strong enough to desensitize or overload the receiver of a nearby Inmarsat-C antenna, preventing it from hearing the much weaker satellite signals. 2. **Intermodulation:** Strong signals from closely spaced transmitters can mix in non-linear components (even in the antennas themselves or nearby metallic structures) to create new, unwanted frequencies (intermodulation products) that can fall into the receive band of another system, causing interference. 3. **RF Coupling:** Adequate physical separation minimizes direct RF coupling between antennas, ensuring that each system can operate optimally without degrading the performance of its neighbors. Maintaining at least 8 meters of separation mitigates these effects, ensuring that each terminal can reliably acquire and maintain a satellite link.