The Basic lessons · Station assembly, practice and safety · B-003-015

Digital Modes: From Sound to Signal

Learn how analog voice and images become digital data, and why narrow bandwidths let dozens of signals share the air. Discover the rules for setting audio levels and choosing frequencies to keep your digital transmissions clear and interference-free.

This lesson is part of SignalPrep Pro. The subsection's 11 exam questions are free to practise: practise B-003-015.

What this subsection asks

• Why can a modern digital radio system transmit voice and images, not just data?
• What is the fundamental difference between digital and analog data?
• What is the function of a digipeater?
• What does "network" mean in packet radio?
• Why can dozens of FT8 communications occur simultaneously in the space needed for one single-sideband transmission?
• Which of these modes can work at the lowest signal-to-noise ratio as measured in a 2500 Hz bandwidth?
• When selecting an RTTY transmitting frequency, what minimum frequency separation from a contact in progress should you allow (centre to centre) to minimize interference?
• When using a digital mode based on a computer sound card, how can you verify that the transmit audio level is NOT excessive?
• What feature of packet radio makes it especially useful for emergency communications?
• A digital protocol implements automatic repeat request (ARQ). What does it permit?
• With a digital communication mode based on a computer sound card, what is the result of feeding excessive audio into the transmitter?