Main Goal: To act as a “hybrid” system that extends System Ds by adding a ground-based (terrestrial) component. This was done specifically to provide robust and reliable reception for mobile listeners in urban areas where satellite signals are often blocked.

System Dh can be thought of as the next generation of System Ds, taking the original satellite system and enhancing it for listeners on the move. It combines the wide coverage of satellite with the reliability of ground-based transmitters in cities.

• Best of Both Worlds (Hybrid) The core feature of System Dh is its satellite/terrestrial hybrid nature. A receiver in a vehicle can listen to the signal directly from the satellite while driving in the countryside. When the vehicle enters a city where buildings block the satellite, the receiver can seamlessly switch to the same audio program being rebroadcast from a local ground-based transmitter, ensuring continuous, uninterrupted audio.
• Advanced Terrestrial Technology (MCM) The ground-based part of this system uses a powerful technique called Multi-Carrier Modulation (MCM). This technology is extremely effective at resisting the signal interference caused by reflected signals in built-up areas. It is a similar technology to that used in System A and is one of the best methods for ensuring clear reception in challenging urban environments.

Having seen how systems evolved to handle tricky reception, let’s turn to our final system, which was designed with a focus on broadcasting more than just sound.