Frequency modulation (FM) encodes information in a radio signal by varying the frequency of the carrier wave. Unlike amplitude modulation (AM), which alters the signal’s amplitude, FM maintains a constant amplitude while adjusting the frequency to match the input audio signal. This method delivers better sound quality and strong resistance to interference.
The Invention of Frequency Modulation
In the 1930s, American electrical engineer Edwin Howard Armstrong invented frequency modulation. At the time, AM radio dominated the airwaves, but Armstrong aimed to reduce static and improve audio clarity.
He discovered that modulating the frequency instead of the amplitude created a signal less prone to noise from electrical equipment, weather, and other interference sources. His work led to the first FM radio broadcasts in the late 1930s, transforming the radio industry.
FM’s Role in Amateur Radio
Amateur radio operators widely use FM, particularly in the Very High Frequency (VHF) and Ultra High Frequency (UHF) bands. Many repeaters, which extend radio communication ranges, rely on FM for its clarity and effectiveness in handling voice communications. Handheld radios, or “handy-talkies,” use FM for local communications, offering a reliable and straightforward mode for operators.
FM in CB Radio
Recently, FM made its way into the world of Citizens Band (CB) radio. Traditionally, CB radio only supported AM and SSB modes, limiting audio quality and signal stability. However, regulatory changes by the Federal Communications Commission (FCC) in the US, have now authorized FM use on CB channels. Consequently, CB enthusiasts can enjoy clearer voice transmission, less interference, and improved communication experiences.
Although not all CB radios currently support FM, manufacturers have started releasing new models with this capability. The CB community is likely to see a shift toward FM with its enhanced sound quality and reduced background noise. FM will not increase the communication range compared to AM or SSB. Its outstanding noise resistance can lead to better performance in urban environments.
Is FM a Useful Mode in Ham Radio?
FM offers more than just clear voice communication in amateur radio. It also supports packet radio and data transmissions, enabling operators to send digital information over the airwaves. Its strong resistance to static and noise makes FM an ideal choice for emergency communications, where clear and consistent audio is crucial.
Advantages of Frequency Modulation
FM provides numerous benefits for radio communication. Because FM signals are less affected by amplitude-based noise, they deliver clearer audio even in environments with significant interference. The “capture effect” of FM ensures that only the strongest signal on a frequency is heard. This reduces clutter and confusion during communications.
Conclusion: A Versatile Tool in Radio Technology
Frequency modulation continues to be a valuable and versatile tool in both commercial and amateur radio. With its ability to produce clear audio, resist interference, and support various communication modes, FM remains essential to radio technology and will likely do so for years to come.