What type of modulation is most commonly used for VHF packet radio transmissions?

The most commonly used modulation for VHF packet radio transmissions is Frequency Modulation (FM). This is primarily due to FM's robustness and efficiency in handling the characteristics of VHF signals, which are generally subjected to noise and interference.

FM allows for a clearer transmission over the relatively short distances typically associated with VHF operations. It is particularly effective at providing good audio quality and signal clarity, which is important in data communications like packet radio where accurate transmission of digital data is crucial.

In contrast, other modulation types such as Single Sideband (SSB) and Amplitude Modulation (AM) are not as prevalent in packet radio applications. SSB is typically used for voice communications, while AM generally has a lower efficiency and less resistance to noise in this context. Spread Spectrum is a more complex technology that offers certain benefits in terms of interference resistance but is not the prevalent form of modulation for standard VHF packet radio operations.