Technician License Study Module

Modulation and Activities (T8)

Overview

Modulation is the process of adding information (voice, data, Morse code) to a radio carrier wave so it can be transmitted and received. Different modes have different characteristics, bandwidth requirements, and uses. Technician operators primarily use FM on VHF/UHF, but also encounter CW, SSB, and digital modes. This module covers the most common modes, satellite operation, and popular amateur activities.

This lesson covers:

• Common voice and data modulation types
• FM vs SSB vs CW bandwidth and characteristics
• Satellite operation basics
• Popular digital modes (Packet, FT8, APRS)
• Amateur activities: repeaters, nets, public service, contesting, DXing

Common Modulation Types

FM (Frequency Modulation)

• Primary voice mode on 2 m and 70 cm bands
• Wide bandwidth (~10–15 kHz)
• Good audio quality, resistant to static and amplitude noise
• Requires more spectrum than SSB or CW
• Used for repeaters, simplex, and most local communication

SSB (Single Sideband)

• Voice mode used mainly on HF (General/Extra), but Technicians have limited 10 m SSB privileges
• Very efficient — uses about 2–3 kHz bandwidth
• Transmits only one sideband + suppressed carrier → more power in the voice
• Requires precise tuning and good receiver stability
• Long-distance (DX) capability with modest power

CW (Continuous Wave / Morse Code)

• Uses very narrow bandwidth (~100–500 Hz)
• Extremely efficient — best range for given power
• Used for weak-signal work, contests, emergency comms
• No voice — requires learning Morse code (not required for Technician license)

Bandwidth Comparison

• CW: ~100–500 Hz (narrowest)
• SSB: ~2–3 kHz
• FM voice: ~10–15 kHz
• Digital modes: Packet ~1–2 kHz, FT8 ~50 Hz

Higher bandwidth modes (FM) give better audio quality but use more spectrum and are more affected by propagation limits.

Satellite Operation

Amateur radio satellites (OSCARs) allow long-distance VHF/UHF contacts via space.

Key concepts:

• Uplink: Frequency you transmit on (to satellite)
• Downlink: Frequency satellite transmits on (to you)
• Many satellites use Mode J (2 m uplink / 70 cm downlink) or Mode U (70 cm uplink / 2 m downlink)
• Doppler shift: Adjust frequency as satellite moves toward/away
• FM satellites: Use full-duplex (transmit and receive simultaneously) or split operation
• SSB/CW linear transponder satellites: Allow multiple simultaneous contacts

Track passes with software (Orbitron, Heavens-Above, AMSAT tools). Always listen before transmitting.

Digital Modes

Packet Radio

• Early digital mode using AX.25 protocol
• 1200 baud on 2 m, 9600 baud on higher bands
• Used for APRS, BBS, Winlink email over radio

FT8

• Weak-signal digital mode (WSJT-X software)
• Very narrow bandwidth (~50 Hz)
• Worldwide contacts possible with low power
• Technicians can use FT8 on 10 m HF segment

APRS (Automatic Packet Reporting System)

• Position reporting, messaging, weather stations
• Common on 144.390 MHz (North America)
• Used for tracking, emergency messaging, telemetry

Popular Amateur Activities

• Repeater nets: Weekly check-ins, announcements, training
• Public service / emergency comms: ARES, RACES, Skywarn
• Contesting: Competitive contacts on specific bands/modes
• DXing: Contacting distant stations (mostly HF, but possible on 6 m/2 m with propagation)
• Satellite operating: Fun and educational
• Building projects: Kits, QRP, homebrew

Modulation and Activities Review Questions

These questions are representative of those found in the Technician license exam question pool.

1. Which emission mode is most commonly used for VHF/UHF voice repeaters?
• A. SSB
• B. FM
• C. CW
• D. AM
2. What is the approximate bandwidth of a single-sideband voice signal?
• A. 1 kHz
• B. 3 kHz
• C. 6 kHz
• D. 15 kHz
3. What does the term “uplink” mean in satellite operation?
• A. Receiving frequency from the satellite
• B. Transmitting frequency to the satellite
• C. Satellite beacon signal
• D. Satellite telemetry downlink
4. Which digital mode is known for very narrow bandwidth and weak-signal performance?
• A. Packet
• B. RTTY
• C. FT8
• D. APRS
5. What frequency is most commonly used for APRS in North America?
• A. 144.390 MHz
• B. 146.520 MHz
• C. 223.500 MHz
• D. 446.000 MHz

Answer Key

1. B
2. B
3. B
4. C
5. A

Recommended Resources

• KB6NU No-Nonsense Technician-Class Study Guide (Chapter 8): Download PDF
• AMSAT Satellite Basics and Getting Started: AMSAT Intro to Satellites
• ARRL Operating Resources: ARRL Operating

Experiment with FM repeaters first, then try digital modes and satellites as you gain experience — they open up exciting new ways to enjoy ham radio.