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Technician Course, Module 6: Modes, Digital, and Space
Covers NCVEC 2026-2030 Technician Pool, Subelement T8 (Signals and Emissions). Four questions on your exam come from this material.
Ray sets a kitchen timer on the bench. "In forty minutes a satellite the size of a shoebox comes over the horizon, and we are going to work somebody through it with a handheld and this antenna I made from a tape measure. Before it rises, you need to understand what a mode actually is."
6.1FM, SSB, and the Price of Bandwidth
Modulation, from Module 5, is combining your voice with an RF carrier. The different ways of doing it are called modes, and each one trades fidelity, bandwidth, and convenience differently.
FM (frequency modulation) varies the carrier's frequency with your voice. It is the mode of repeaters and mobile radio because it is punchy, noise-resistant, and effortless to tune. FM or PM is what VHF and UHF voice repeaters use, and it is also the modulation used for VHF packet radio. Its costs: an FM voice signal is wide, occupying between 10 and 15 kHz, and FM receivers capture only one signal at a time. When two FM stations transmit at once, the stronger one wins and the weaker vanishes, which is FM's disadvantage compared with SSB.
SSB (single sideband) is a form of amplitude modulation with the carrier and one sideband stripped away, leaving all the transmitter's energy in a single 3 kHz slice of voice. That narrow bandwidth is SSB's advantage over FM, and it is why SSB is the voice mode for long-distance weak-signal work on VHF and UHF. The convention: upper sideband (USB) is used on 10-meter HF, VHF, and UHF SSB. The price of SSB is that it is harder to tune, which is why your radio has an RIT knob.
CW (Morse code) is the bandwidth champion at roughly 150 Hz, the narrowest signal of the common modes. At the other extreme, analog fast-scan TV swallows about 6 MHz, an entire band's worth.
Ray's ladder, narrowest to widest: CW (150 Hz), SSB (3 kHz), FM (10 to 15 kHz), fast-scan TV (6 MHz). Bandwidth is spectrum rent. Pay only for what the message needs.
Knowledge Check 6.1
Tap an answer. In your own words first, then check yourself.
1. Which mode is standard on VHF and UHF voice repeaters?
2. Rank these by bandwidth, narrowest first:
3. Which sideband is the convention above 10 meters?
T8A the easy way: all 12 questions, with the right answer
Every pool question in this group. Read the answer, let the tip make it stick.
T8A01 Which of the following is a form of amplitude modulation?
Answer Single sideband
Tip SSB is amplitude modulation with the carrier and one sideband stripped away, so it is still a form of AM.
T8A02 What type of modulation is commonly used for VHF packet radio transmissions?
Answer FM or PM
Tip VHF packet rides on the same FM or PM gear you already use for voice, just feeding data instead of a mic.
T8A03 Which type of voice mode is often used for long-distance (weak signal) contacts on the VHF and UHF bands?
Answer SSB
Tip For weak-signal VHF and UHF DX, hams reach for SSB because it puts all the power into a thin, efficient signal.
T8A04 Which type of modulation is commonly used for VHF and UHF voice repeaters?
Answer FM or PM
Tip Voice repeaters on VHF and UHF run FM or PM, the clean and quiet mode everyday handhelds use.
T8A05 Which of the following signal types has the narrowest bandwidth?
Answer CW
Tip CW is just an on-off tone, so it squeezes into the narrowest bandwidth of them all.
T8A06 Which sideband is normally used for 10-meter HF, VHF, and UHF single-sideband communications?
Answer Upper sideband
Tip Think USB for the high bands. Ten meters, VHF, and UHF SSB all use upper sideband.
T8A07 What is one characteristic of single sideband (SSB) compared to FM?
Answer SSB signals have narrower bandwidth
Tip SSB packs a voice into about 3 kHz, far less room than wideband FM, so its bandwidth is narrower.
T8A08 What is the approximate bandwidth of a typical single sideband (SSB) voice signal?
Answer 3 kHz
Tip An SSB voice signal fits in roughly 3 kHz, just enough to carry speech.
T8A09 What is the approximate bandwidth of an FM voice signal on VHF repeaters?
Answer Between 10 and 15 kHz
Tip FM voice on a repeater spreads out to about 10 to 15 kHz, much wider than SSB.
T8A10 What is the approximate bandwidth of AM fast-scan TV transmissions?
Answer About 6 MHz
Tip Fast-scan AM television is a bandwidth hog, taking about 6 MHz to carry a full moving picture.
T8A11 What is the approximate bandwidth required to transmit a CW signal?
Answer 150 Hz
Tip CW needs only around 150 Hz because a simple keyed tone carries very little information.
T8A12 Which of the following is a disadvantage of FM compared with single sideband?
Answer Only one signal can be received at a time
Tip FM uses a capture effect, so the strongest station wins and you hear only one signal at a time.
6.2Working the Birds
The timer is down to twenty minutes, so Ray briefs you like a mission.
Amateur satellites are repeaters in the sky. Most are LEO satellites: Low Earth Orbit, circling the planet with a period of around 100 minutes, which means each pass over your head lasts only ten or fifteen. A satellite tracking program tells you when: it shows maps of the satellite's real-time position, the time, azimuth, and elevation of each pass from start to peak to end, and even the apparent frequency including Doppler shift. All of that. What you feed the program is the satellite's Keplerian elements, the numbers describing its orbit.
Doppler shift is the observed change in signal frequency caused by the relative motion between the satellite and your station: frequency reads high as the bird approaches, slides low as it recedes, and you tune along with it.
The frequency plan is named by band pairs. A satellite in U/V mode has its uplink in the 70-centimeter band and its downlink in the 2-meter band. Satellites carry FM, SSB, and CW/data transponders, so the answer to "what modes do amateur satellites use" is all of them. Every satellite also transmits a beacon, a transmission containing status information, and the telemetry it carries describes the health and status of the satellite. Anyone is permitted to receive that telemetry, licensed or not.
Etiquette matters more on a satellite than anywhere else, because the transponder's power is shared among every station using it. Excessive uplink power blocks access by other users. The self-check: your own signal on the downlink should be about as strong as the beacon. Louder than the beacon means you are hogging the bird.
Two last details. Spin fading is the slow flutter caused by the rotation of the satellite and its antennas. And who may be the control operator of a station transmitting through a satellite? Any amateur allowed to transmit on the uplink frequency. Your Technician license is a satellite license.
Knowledge Check 6.2
Tap an answer. In your own words first, then check yourself.
1. Your downlink signal is much louder than the satellite's beacon. What should you do?
2. What does U/V mode mean?
3. Who may operate through an amateur satellite?
T8B the easy way: all 12 questions, with the right answer
Every pool question in this group. Read the answer, let the tip make it stick.
T8B01 What telemetry information is typically transmitted by satellite beacons?
Answer Health and status of the satellite
Tip A satellite beacon is a status report, telling you the health and condition of the spacecraft.
T8B02 What is the impact of using excessive effective radiated power on a satellite uplink?
Answer Blocking access by other users
Tip Running too much ERP on the uplink hogs the satellite and blocks other users from getting through.
T8B03 Which of the following are provided by satellite tracking programs?
Answer All these choices are correct
Tip Tracking software does it all, predicting passes, pointing, and Doppler, so the answer covers every choice.
T8B04 What mode of transmission is commonly used by amateur radio satellites?
Answer All these choices are correct
Tip Amateur satellites carry many modes, so the correct pick is that all the choices apply.
T8B05 What is a satellite beacon?
Answer A transmission from a satellite that contains status information
Tip A beacon is simply a satellite transmission carrying its status information.
T8B06 Which of the following are inputs to a satellite tracking program?
Answer The Keplerian elements
Tip Keplerian elements are the orbit numbers you feed a tracking program so it knows where the bird is.
T8B07 What is Doppler shift in reference to satellite communications?
Answer An observed change in signal frequency caused by relative motion between the satellite and Earth station
Tip Doppler shift is the frequency change you hear as the satellite races toward you and then away.
T8B08 What does it mean if a satellite is operating in U/V mode?
Answer The satellite uplink is in the 70-centimeter band and the downlink is in the 2-meter band
Tip U over V means uplink on 70 cm and downlink on 2 meters. Say uplink first, downlink second.
T8B09 What causes spin fading of satellite signals?
Answer Rotation of the satellite and its antennas
Tip Spin fading comes from the satellite tumbling, so its antennas keep swinging toward and away from you.
T8B10 What does the term LEO mean in reference to communication satellites?
Answer Low Earth Orbit, which has a period of around 100 minutes
Tip LEO is Low Earth Orbit, circling close and fast with a period near 100 minutes.
T8B11 Who is permitted to receive telemetry from an amateur radio satellite?
Answer Anyone
Tip Satellite telemetry is open to anyone, licensed or not, so the answer is simply anyone.
T8B12 Which of the following is a way to determine whether your satellite uplink power into a linear transponder satellite is neither too low nor too high?
Answer Your signal strength on the downlink should be about the same as the beacon
Tip Match the beacon. If your downlink is about as strong as the satellite beacon, your uplink power is right.
6.3Games Hams Play
The satellite pass succeeds: two contacts in nine minutes with a tape-measure antenna. Ray grins and asks what grid you are in. Time to learn the hobby's recreation department.
A grid locator is a letter-number designator assigned to a geographic location. The planet is diced into grid squares, and exchanging them is standard currency in VHF work and contests.
Contesting is the activity of contacting as many stations as possible during a specified period. Good contest practice is efficiency: send only the minimum information needed for identification and the required exchange. Nobody in a contest wants your weather report.
Radio direction finding is the method used to locate sources of noise interference or jamming, and its sporting form is the hidden transmitter hunt, or foxhunt. The essential tool is a directional antenna, which is exactly why Ray's tape-measure beam exists: cheap, bendable, and perfect for chasing signals through the woods.
Then there is the internet, which hams absorbed rather than resisted:
- VoIP (Voice Over Internet Protocol) is delivering voice communications over the internet using digital techniques.
- The IRLP (Internet Radio Linking Project) connects amateur systems like repeaters via the internet, and you access an IRLP node over the air using DTMF tones, the touch-tones from Module 9's radios.
- EchoLink lets an amateur transmit through a distant repeater without using a radio to initiate the connection, from a computer or phone app. Before using it you must register your call sign and provide proof of license.
- A station that connects other amateur stations to the internet is called a gateway.
Knowledge Check 6.3
Tap an answer. In your own words first, then check yourself.
1. A jamming signal keeps appearing on the local repeater's input. What technique locates it?
2. What is exchanged in "FM05" or "EM74" during a VHF contest?
3. What must you do before using EchoLink?
T8C the easy way: all 11 questions, with the right answer
Every pool question in this group. Read the answer, let the tip make it stick.
T8C01 Which of the following methods is used to locate sources of noise interference or jamming?
Answer Radio direction finding
Tip To hunt down noise, interference, or a jammer, you use radio direction finding to trace where it comes from.
T8C02 Which of these items would be useful for a hidden transmitter hunt?
Answer A directional antenna
Tip A directional antenna is the key hidden-transmitter hunting tool because it shows you which way the signal is.
T8C03 What operating activity involves contacting as many stations as possible during a specified period?
Answer Contesting
Tip Contesting is the game of working as many stations as you can within a set time window.
T8C04 Which of the following is good practice when contacting another station in a contest?
Answer Sending only the minimum information needed for proper identification and the contest exchange
Tip In a contest, keep it lean. Send just your call and the required exchange, nothing extra.
T8C05 What is a grid locator?
Answer A letter-number designator assigned to a geographic location
Tip A grid locator is the letter-and-number code, like a Maidenhead square, that marks your spot on the map.
T8C06 How is over the air access to Internet Radio Linking Project (IRLP) nodes accomplished?
Answer By using Dual-Tone Multi-Frequency (DTMF) signals
Tip You reach IRLP nodes over the air by pressing DTMF tones, the same touch tones a phone uses.
T8C07 What is Voice Over Internet Protocol (VoIP)?
Answer A method of delivering voice communications over the internet using digital techniques
Tip VoIP carries voice over the internet using digital techniques instead of a dedicated phone line.
T8C08 What is the Internet Radio Linking Project (IRLP)?
Answer A technique to connect amateur radio systems, such as repeaters, via the internet
Tip IRLP ties radio systems like repeaters together through the internet so far-apart stations can link up.
T8C09 Which of the following protocols enables an amateur station to transmit through a repeater without using a radio to initiate the transmission?
Answer EchoLink
Tip EchoLink lets you key up a repeater from a computer or app, no radio needed to start the transmission.
T8C10 What is required before using the EchoLink system?
Answer Register your call sign and provide proof of license
Tip Before you use EchoLink you must register your call sign and prove you hold a license.
T8C11 What is an amateur radio station that connects other amateur stations to the internet?
Answer A gateway
Tip A gateway is the station that bridges other amateur stations onto the internet.
6.4The Digital Revolution
Last section of the module, and it is the one that has changed fastest. Ray opens a laptop, plugs it into the radio, and the waterfall display fills with stripes of signal.
"Every stripe is a conversation," he says. "Most of them are too weak for your ears."
FT8 is the star: a digital mode capable of low signal-to-noise operation, decoding signals literally below the noise your ear could use. It lives in the WSJT-X software suite, which also supports Earth-Moon-Earth, meteor scatter, and weak-signal propagation beacons. All of those, from the same free program.
The older workhorses each contribute a concept the exam tests:
- CW is simply another name for Morse code transmission, the original digital mode.
- PSK stands for Phase Shift Keying, modulating by shifting the carrier's phase.
- Packet radio sends data in bundles that include a header with the destination call sign, a checksum permitting error detection, and automatic repeat request in case of error. All of these.
- That last idea has its own name: ARQ is the error correction method in which the receiving station detects errors and requests a retransmission.
- APRS (Automatic Packet Reporting System) provides real-time tactical digital communications along with a map showing station locations, and it can carry GPS position data, text messages, and weather data. All of these.
Digital voice gets one technical definition: DMR is a technique that time-multiplexes two digital voice signals on a single 12.5 kHz repeater channel, two conversations sharing one frequency by taking turns thousands of times a second. You will program and use DMR in Modules 8 and 9; here, just own what it is.
Two image and network definitions close it out. NTSC is the analog fast-scan color TV signal standard. And an amateur radio mesh network is a data network using commercial Wi-Fi equipment with modified firmware, hams reflashing off-the-shelf routers into license-band data networks.
Knowledge Check 6.4
Tap an answer. In your own words first, then check yourself.
1. What makes FT8 remarkable?
2. In ARQ error correction, what happens when the receiving station detects an error?
3. What is an amateur mesh network built from?
T8D the easy way: all 12 questions, with the right answer
Every pool question in this group. Read the answer, let the tip make it stick.
T8D01 Which of the following is a digital communications mode?
Answer All these choices are correct
Tip The question lists several true digital modes, so the right answer is that all of them count.
T8D02 What is FT8?
Answer A digital mode capable of low signal-to-noise operation
Tip FT8 is a digital mode built to dig signals out of the noise, working even at very low signal to noise.
T8D03 What kind of data can be transmitted by APRS?
Answer All these choices are correct
Tip APRS can carry position, weather, messages, and more, so every listed data type is correct.
T8D04 What is meant by the term "NTSC?"
Answer An analog fast-scan color TV signal
Tip NTSC is the old analog fast-scan color TV standard, the format of classic broadcast television.
T8D05 Which of the following is an application of APRS?
Answer Providing real-time tactical digital communications in conjunction with a map showing the locations of stations
Tip APRS shines at real-time tactical nets, plotting station locations live on a map.
T8D06 What does the abbreviation "PSK" mean?
Answer Phase Shift Keying
Tip PSK stands for Phase Shift Keying, sending data by shifting the signal phase.
T8D07 Which of the following describes DMR?
Answer A technique for time-multiplexing two digital voice signals on a single 12.5 kHz repeater channel
Tip DMR time-slices two digital voice calls onto one 12.5 kHz repeater channel using time division.
T8D08 Which of the following is included in packet radio transmissions?
Answer All these choices are correct
Tip A packet transmission wraps up several parts, so all the listed items are included.
T8D09 What is CW?
Answer Another name for a Morse code transmission
Tip CW is just another name for Morse code sent on the air.
T8D10 Which of the following operating activities is supported by digital mode software in the WSJT-X software suite?
Answer All these choices are correct
Tip WSJT-X hosts several weak-signal modes and activities, so the answer is all of these choices.
T8D11 What is the role of ARQ in a transmission system?
Answer An error correction method in which the receiving station detects errors and sends a request for retransmission
Tip ARQ is error correction by asking again. The receiver spots an error and requests a resend.
T8D12 Which of the following best describes an amateur radio mesh network?
Answer An amateur-radio data network using commercial Wi-Fi equipment with modified firmware
Tip A ham mesh network repurposes commercial Wi-Fi gear running modified firmware to pass data.
Review: every Exam Anchor from this module
T8A SSB is a form of amplitude modulation. FM or PM: VHF/UHF repeaters and VHF packet. SSB: long-distance weak-signal VHF/UHF voice, and narrower bandwidth than FM. USB on 10-meter HF, VHF, and UHF. Bandwidths: CW about 150 Hz (narrowest), SSB about 3 kHz, FM voice 10 to 15 kHz, fast-scan TV about 6 MHz. FM disadvantage: only one signal received at a time. SSB disadvantage: harder to tune.
T8B LEO: Low Earth Orbit, period around 100 minutes. Tracking programs provide maps, pass times/azimuth/elevation, and Doppler-corrected frequencies (all of these), and take Keplerian elements as input. Doppler shift: frequency change from relative motion. U/V mode: 70 cm uplink, 2 m downlink. Satellites use SSB, FM, and CW/data (all). Beacon: transmission containing satellite status; telemetry reports health and status; anyone may receive it. Excessive uplink power blocks other users; correct uplink power makes your downlink about equal to the beacon. Spin fading: rotation of the satellite and its antennas. Control operator: any amateur allowed to transmit on the uplink frequency.
T8C Grid locator: letter-number designator for a geographic location. Contesting: contact as many stations as possible in a set period; send only the minimum needed for ID and exchange. Radio direction finding locates noise or jamming sources; a directional antenna is the tool for hidden transmitter hunts. VoIP: voice over the internet by digital techniques. IRLP: connects repeaters via the internet, accessed with DTMF. EchoLink: transmit through a repeater without initiating by radio; requires call sign registration with proof of license. Gateway: station connecting amateurs to the internet.
T8D FT8: digital mode capable of low signal-to-noise operation. WSJT-X supports EME, meteor scatter, and propagation beacons (all). CW: Morse code. PSK: Phase Shift Keying. Packet includes destination header, checksum for error detection, and ARQ (all). ARQ: receiver detects errors and requests retransmission. APRS: tactical real-time communications with mapped positions; carries GPS position, text, and weather (all). DMR: two voice signals time-multiplexed on one 12.5 kHz channel. NTSC: analog fast-scan color TV. Mesh network: commercial Wi-Fi gear with modified firmware. Digital modes include packet, IEEE 802.11, and FT8 (all).
Before you move on
You can now choose a mode by its bandwidth and purpose, brief a satellite pass like Ray briefed you, speak the language of grids, contests, and foxhunts, and explain the digital modes that dominate the modern bands. The tape-measure antenna that worked the satellite is also the foxhunt weapon, which tells you something about this hobby: the same physics keeps showing up wearing different hats.
Module 7 is about the most important piece of gear you own, the one that is not electronic at all: the antenna.
© 2026 Anthony Pelfanio, K4DIA. All rights reserved.