Lesson 2: Digital Modulation

Common Digital Modes in Ham Radio

Each digital mode uses one or more modulation techniques to send data. Here are some of the most popular:

RTTY (Radio Teletype)

• Oldest digital mode, dating back to the 1930s

• Uses FSK (Frequency Shift Keying) — shifts between two frequencies to represent 1s and 0s

• Think of it like Morse code with automatic typing

Pros: Simple and nostalgic

Cons: Inefficient and prone to noise compared to modern modes

PSK31 (Phase Shift Keying, 31 baud)

• Uses BPSK or QPSK (Phase Shift Keying)

• Very narrow bandwidth (~31 Hz!)

• Optimized for live keyboard-to-keyboard chats

Pros: Very efficient, works well in weak conditions

Con: Less resilient to noise than newer protocols

FT8 (Franke-Taylor 8-FSK)

• Extremely popular weak-signal digital mode

• Uses 8-level FSK, forward error correction, and synchronized timing

• Messages are short and structured (callsign, grid, signal report)

• Takes 15 seconds to send ~13 characters

Pros: Works even when you can’t hear the signal, great for low power and poor conditions

Cons: Not conversational; highly automated

DMR (Digital Mobile Radio)

• A voice-and-data protocol used on VHF/UHF repeaters

• Uses TDMA (Time Division Multiple Access) — splits a channel into alternating time slots

• You get two conversations on one frequency!

Pros: Clear audio, built-in contact lists, and digital IDs, uses repeaters and internet to link global users

Cons: Requires programming radios and understanding "code plugs"

System Fusion (Yaesu) & D-STAR (Icom)

• Proprietary digital voice/data modes

• Use digital voice encoding (like vocoders) with extra data support

• Allow GPS tracking, short messages, callsign routing, etc.

Pros: Feature-rich for digital voice, often cross-linked with internet gateways

Con: Less interoperable across brands