| Type | Modulation technique |
| Subject | Frequency Modulation (FM) |
| Used by | Ships • planes |
| Benefits | Improves safety • increases efficiency |
| Developed | Early 20th century |
| Application | Long-range radio navigation |
| Main features | Stable • long-range communications |
| Common practices | Triangulation |
Frequency Modulation (FM) is an advanced modulation technique used to encode information on a carrier wave by varying its frequency. In this alternate timeline, while FM did not become popular for audio communication and broadcasting, it had significant roles and impacts on other fields - primarily in the context of long-range radio navigation.
Dr. John Carson first proposed the concept of FM in the early 1920s, and the method was later refined and developed by engineers and musicians alike. Like our timeline, FM was initially seen as a stable and high-quality method of transmitting musical and spoken content, replacing amplitude modulation (AM) due to superior fidelity and stability.
However, in this reality, FM's benefits in audio transmission did not drive its widespread adoption. The unique properties of FM, such as its resistance to atmospheric interference and more complex encoding, were recognized as opportunities for other applications. Alternative use cases of FM, including radio navigation and meteorology, led to further research and development in the technology.
The most impactful area of FM utilization in this alternate history became long-range radio navigation. Radio beacons (beacon stations), located in strategic positions, emitted FM signals encoding their position and related information. This allowed ships, planes, and other vehicles to accurately determine their location by triangulating signals from multiple sources.
In this alternate timeline, the design of FM radio navigation systems focused on maintaining high stability and long-range signal propagation. FM signals proved far less susceptible to atmospheric disturbances, unlike the AM-based navigation systems previously used in real life. The increased stability enabled highly precise long-range communication between beacon stations and receiving vehicles, improving safety and the overall accuracy of navigation.
The adoption of FM technology in long-range radio navigation was transformative for air and maritime transportation. The precise location data made it possible for pilots and sailors to make more accurate decisions while traveling, eliminating the need for dead reckoning and improving safety. Maintaining a consistent line of communication with ground stations enabled real-time updates on positioning, weather forecasts, and other critical information.
The integration of FM technology in long-range radio navigation dramatically altered the development of shipping and aviation. With greatly enhanced communication capabilities and more accurate positioning, both industries saw exponential growth and progress. Air traffic increased significantly, while shipping routes expanded, opening new regions for exploration and commerce. These advancements, in turn, sparked innovations in related technologies and industries, leading to new discoveries and applications.
In the end, the decision to direct the development of Frequency Modulation (FM) toward a more specialized role in navigation, and away from audio-based transmissions, significantly altered the course of history, reshaping the landscape of global communication and transportation.
