T8: Signals and Emissions – Ham Radio Technician License Study Guide

T8 covers how amateur radio signals are shaped, transmitted, and used across a variety of modes and operating activities. Four exam questions come from this subelement, one from each group.

T8A covers the basic characteristics of FM and SSB modulation and compares bandwidth across modes: CW uses the least spectrum, SSB is narrow and efficient, FM is wider and standard for repeaters, and TV transmission is widest of all. T8B covers amateur satellite operations — Doppler shift, LEO orbits, satellite beacons, tracking software, uplink power management, and operating protocols. T8C covers on-air operating activities including radio direction finding, contesting, grid locators, and systems that link amateur radio to the internet such as VoIP, IRLP, and EchoLink. T8D covers non-voice and digital communication modes: CW, packet radio, APRS, PSK, DMR, WSJT-X, FT8, ARQ, and amateur mesh networks.

T8A: FM, SSB, and Bandwidth

T8A establishes the vocabulary and numbers behind modulation modes. FM (frequency modulation) is the standard mode for VHF and UHF voice repeaters and packet radio. SSB (single sideband) is a form of amplitude modulation — narrower than FM — and is preferred for long-distance weak-signal work on VHF and UHF. Upper sideband is the convention for 10-meter HF, VHF, and UHF SSB contacts. CW (Morse code) has the narrowest bandwidth of all common modes, requiring only about 150 Hz. SSB voice occupies approximately 3 kHz, FM voice on a VHF repeater occupies 10–15 kHz, and analog fast-scan TV (ATV) requires about 6 MHz. A key disadvantage of FM is that it can only receive one signal at a time — stronger signals capture the receiver, blocking weaker ones.

T8B: Amateur Satellite Operation

T8B covers the vocabulary and operating practices for amateur satellites. A satellite beacon is a transmission from the satellite that contains health and status information. Satellite tracking programs use Keplerian elements as input and provide real-time position maps, pass timing, and Doppler shift predictions. Doppler shift is the observed change in signal frequency caused by the relative motion between the satellite and the Earth station — signals rise in pitch as the satellite approaches and drop as it recedes. LEO stands for low earth orbit. Spin fading is caused by the rotation of the satellite and its antennas. Operating mode designations like U/V indicate uplink and downlink bands: U/V means the uplink is in the 70-centimeter band and the downlink is in the 2-meter band. Using excessive ERP on the uplink blocks access by other users. Uplink power is correct when your downlink signal strength matches the satellite beacon. Anyone may receive telemetry from a space station — no license or registration is required to listen.

T8C: Operating Activities

T8C covers several popular amateur radio activities. Contesting involves contacting as many stations as possible during a specified period; good contest procedure is to send only the minimum information needed for identification and the contest exchange. Radio direction finding is the method used to locate sources of noise interference or jamming; a directional antenna is the key tool for a hidden transmitter hunt. A grid locator is a letter-number designator assigned to a geographic location, commonly used in VHF contests and satellite work. VoIP (Voice Over Internet Protocol) delivers voice communications over the internet using digital techniques. IRLP (Internet Radio Linking Project) connects amateur radio systems such as repeaters via the internet using VoIP; it is accessed over the air using DTMF signals. EchoLink allows transmitting through a repeater without a radio, over the internet; users must register their call sign and provide proof of license. An amateur station that connects other amateur stations to the internet is called a gateway.

T8D: Digital and Non-Voice Communications

T8D introduces the variety of digital and non-voice modes available to Technician licensees. CW is simply another name for Morse code transmission. Packet radio transmissions include a checksum for error detection, a header with the destination call sign, and automatic repeat request (ARQ) — all three. PSK stands for Phase Shift Keying. APRS (Automatic Packet Reporting System) transmits GPS position data, text messages, and weather data, and its primary application is providing real-time tactical digital communications displayed on a map. NTSC is an analog fast-scan color TV signal. DMR (Digital Mobile Radio) time-multiplexes two digital voice signals on a single 12.5 kHz repeater channel; a DMR talkgroup lets groups of users share a channel at different times without hearing other users. ARQ (Automatic Repeat reQuest) is an error correction system in which the receiving station detects errors and requests retransmission. FT8 is a digital mode capable of low signal-to-noise ratio operation. WSJT-X supports Earth-Moon-Earth, weak signal propagation beacons, and meteor scatter. An amateur radio mesh network uses commercial Wi-Fi equipment with modified firmware to create a data network.

Study These Topics