Understanding Radio Modulation

While radio transmitters have been a frequent topic in our discussions, it's essential to recognize that radios, much like individuals, come in various shapes, types, and functionalities.

There are numerous modulation types, each with distinct advantages and disadvantages. We explore these thoroughly in our Radio Hackers publication. Most individuals are familiar with AM and FM receivers found in cars, but there are many modulation methods, each suited for different scenarios. For example, FM (Frequency Modulation) is common in vehicles but suffers from the "Capture Effect," where the stronger signal completely overshadows the weaker one. In an aviation context, this can be problematic if two planes transmit simultaneously. Instead, AM (Amplitude Modulation) is preferred in aviation, allowing Air Traffic Controllers to detect overlapping transmissions more effectively.

In examining the accompanying image, we see that an AM signal comprises three parts: a carrier wave and two sidebands known as the Upper Sideband and the Lower Sideband. SSB transmitters suppress the carrier wave and one of the sidebands, resulting in reduced bandwidth, increased power output, and enhanced reliability. However, SSB does have its challenges, including susceptibility to noise from weather and interference, requiring skilled operators and quality antennas for optimal performance. Nonetheless, when conditions are right, SSB can facilitate long-distance communication with impressive reliability.

The Origins of Single Sideband Technology

The inception of SSB technology dates back to 1915, during World War I experiments. While initial applications were limited, commercial use surged in the mid-1920s, and by World War II, SSB transmitters were commonplace in both maritime and aviation contexts.

SSB technology played a crucial role in the Allied war effort, notably through SIGSALY, an advanced encryption system that utilized SSB transmissions to facilitate secure communication. Although SIGSALY was groundbreaking, its reliance on voice encryption quickly rendered it outdated due to advancements in cryptography.

The conclusion of World War II led to a boom in amateur radio operations, largely fueled by veterans who applied their military experience to their hobbies. By the 1950s, during the Cold War, SSB became the standard communication method for the Strategic Air Command's bomber fleet, benefiting from significant military investment and leading to more efficient use of the radio spectrum.

Civilian Applications of Single Sideband

Though many may think SSB is primarily a military tool, its relevance extends to civilian life, especially before the widespread adoption of mobile phones. SSB was once a popular mode for long-distance telecommunications, initially for voice communication, then evolving with digital advancements as computers and the internet emerged. Amateur radio operators capitalized on SSB to explore and innovate new communication methods.

Consider a remarkable instance when SSB technology proved indispensable.

On Christmas Eve 1974, Cyclone Tracy struck Darwin, Australia, with devastating winds of over 217 km/h. The storm caused widespread destruction, damaging military and commercial communication systems, leaving the town isolated and in need of urgent help.

Fortunately, an amateur radio operator named Bob Hooper (VK8RR) quickly set up a station, and rescuers salvaged a functional HF radio from a damaged aircraft. These makeshift stations, later joined by a maritime station, enabled vital communication with the outside world during a time of crisis.

The Lasting Influence of Single Sideband Technology

While modern innovations like mobile phones and GPS overshadow the SSB transmitter, its historical impact remains significant. Today, although satellite phones are more common, SSB still plays a crucial role in specific applications.

Airlines employ SSB for intercontinental flights, allowing aircraft to communicate safely across vast ocean expanses.

Maritime vessels continue to utilize HF transmitters, often as backup systems should satellite communications fail. In remote regions, law enforcement and military agencies rely on SSB for reliable communication when other options are limited. CODAN, a manufacturer of HF transmitters, operates globally, and modern technology has simplified the process of establishing and maintaining communication links.

While mobile phones and the internet are undeniably impressive, there's a unique fascination in using simple technology—a wire, a battery, and a transmitter—to send messages across vast distances.

"What the Tech?!" is our bi-monthly series exploring the technologies that have shaped our interconnected world.

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The first video, "Single Sideband (SSB): How does it do that? (036) - YouTube," explains the workings and significance of SSB technology.

The second video, "Understanding Single Sideband - YouTube," provides an in-depth look at SSB and its applications.