ARRL Technician Practice Exam

Frequency Modulation (FM) is the most commonly used type of modulation for VHF (Very High Frequency) and UHF (Ultra High Frequency) voice repeaters due to several advantages it offers. FM provides better sound quality and greater resistance to noise and interference compared to Amplitude Modulation (AM) or Single Sideband (SSB) modulation. This makes it particularly suitable for voice communications, where clarity and intelligibility are essential.

In the context of repeaters, which are designed to extend the range of radio communications, FM is preferred because it allows for clear communication over longer distances and through various obstructions, like buildings or terrain. Additionally, FM transmitters operate at a higher power efficiency, which is important for maintaining reliable communication over the RF range used in VHF and UHF operations.

Other modulation methods like QAM (Quadrature Amplitude Modulation) are not typically used for voice communication in this context, as they are more complex and usually reserved for digital data transmission. Similarly, while AM can be used in some cases, it is far less common for voice repeaters due to its susceptibility to noise and lower quality of sound. SSB is more often employed in HF (High Frequency) communications instead of VHF and U