AM, FM, SSB, and CW are different types of modulation used in radio communication. Each has its unique characteristics, advantages, and disadvantages, making them suitable for various applications in amateur radio.
Amplitude Modulation (AM) is the oldest and simplest modulation technique, where the amplitude (or strength) of a carrier wave is varied according to the modulating signal (usually an audio signal) while keeping the carrier wave’s frequency and phase constant. This results in a transmitted signal that consists of the carrier wave and two sidebands, which contain the modulating signal’s information.
In amateur radio, AM is primarily used on the HF bands and occasionally on the VHF and UHF bands for voice communication.
Frequency Modulation (FM) is a modulation technique in which the carrier wave’s frequency is varied according to the modulating signal, while the amplitude remains constant. FM has the advantage of being less susceptible to noise and interference compared to AM, making it the dominant mode for VHF and UHF communication.
In amateur radio, FM is widely used for local communication on VHF and UHF bands, especially for repeater operation and handheld radio communication.
Single Sideband (SSB) is a form of Amplitude Modulation (AM) where one of the sidebands and the carrier wave are removed, leaving only one sideband (either the upper or lower sideband) to carry the information. This makes SSB more efficient in terms of power usage and bandwidth compared to traditional AM.
In amateur radio, SSB is the most popular mode for voice communication on the HF bands and is also used on VHF and UHF bands for weak-signal work and long-distance communication.
Continuous Wave (CW) is not a modulation technique like AM, FM, or SSB, but rather a mode of operation where the carrier wave is turned on and off according to a predefined pattern, typically to transmit Morse code. Since CW transmits information by simply turning the carrier wave on and off, it is considered the most basic and efficient form of radio communication.
In amateur radio, CW remains popular among operators, particularly for long-distance communication on HF bands, weak-signal work, and as a foundation for learning and understanding radio communication principles.
Each of these modulation types serves a specific purpose in amateur radio, offering different advantages depending on the situation and desired communication range.
By understanding the differences between AM, FM, SSB, and CW, amateur radio operators can choose the most appropriate modulation type for their communication needs, whether they’re focused on local communication, long-distance contacts, or weak-signal work. Each modulation type has its unique set of advantages and disadvantages, so it’s essential for operators to be familiar with the various options and make informed decisions based on their specific requirements and goals.