T8 — Signals and Emissions
4 exam questions · 4 groups · 48 questions in pool
The modes themselves: FM and SSB and their bandwidths, working amateur satellites, the internet-linking and direction-finding activities, and the family of digital modes (CW, packet, PSK, APRS, DMR, FT8, mesh). No FCC citations.
T8A — FM and SSB Characteristics; Bandwidth; Emission Choice
12 questions
What this group tests: the two main voice modes, the bandwidth each mode occupies, and when you’d choose one over another.
Foundational concepts
Two voice modes dominate VHF/UHF. FM (or PM) is used for repeaters and packet — robust and clear but spectrum-hungry. SSB (single sideband), a form of amplitude modulation, is used for weak-signal/long-distance VHF/UHF work because it packs the signal into a narrower bandwidth. On 10 m HF and on VHF/UHF, the convention is upper sideband (USB).
Bandwidth is a recurring theme — memorize the ladder from narrowest to widest:
- CW (Morse) — narrowest, about 150 Hz
- SSB voice — about 3 kHz
- FM voice (repeater) — about 10–15 kHz
- AM fast-scan TV — about 6 MHz (huge — it carries a full video picture)
A trade-off question: a disadvantage of FM vs. SSB is that with FM (due to the “capture effect”) only one signal can be received at a time, whereas multiple SSB signals can coexist in the same space.
Key facts to retain
- FM/PM → repeaters, packet; SSB → weak-signal/DX, narrower bandwidth; use USB on 10 m & up.
- Bandwidths: CW ≈150 Hz < SSB ≈3 kHz < FM ≈10–15 kHz < fast-scan TV ≈6 MHz.
- FM disadvantage: only one signal received at a time (capture effect).
External reference anchors
- NCVEC syllabus: T8A — FM and SSB characteristics; bandwidth of modes; choice of emission
Per-question map
| Q | Asks for | Resolved by |
|---|---|---|
| T8A01 | Form of amplitude modulation | Single sideband |
| T8A02 | Modulation for VHF packet | FM or PM |
| T8A03 | Voice mode for VHF/UHF weak signal | SSB |
| T8A04 | Modulation for VHF/UHF repeaters | FM or PM |
| T8A05 | Narrowest bandwidth | CW |
| T8A06 | Sideband for 10 m/VHF/UHF | Upper sideband |
| T8A07 | SSB vs FM | SSB narrower bandwidth |
| T8A08 | SSB voice bandwidth | 3 kHz |
| T8A09 | FM repeater bandwidth | 10–15 kHz |
| T8A10 | AM fast-scan TV bandwidth | About 6 MHz |
| T8A11 | CW bandwidth | 150 Hz |
| T8A12 | FM disadvantage vs SSB | Only one signal at a time |
T8B — Amateur Satellite Operation
12 questions
What this group tests: the vocabulary and good practice of working amateur satellites — Doppler, modes, beacons, telemetry, tracking, and uplink power.
Foundational concepts
A satellite hears you on its uplink and transmits to you on its downlink; the two are usually on different bands, named by a mode letter pair. U/V mode means uplink on 70 cm, downlink on 2 m. Because the satellite is moving fast, Doppler shift — a change in observed frequency from relative motion — must be tracked. Spin fading is the signal rising and falling as the satellite and its antennas rotate. A LEO satellite is one in low Earth orbit. Amateur sats use many modulation types — “all of these.”
Tracking programs predict when and where a satellite will be; their input is the Keplerian elements (orbital parameters), and they provide azimuth/elevation, timing, and more — “all of these.” A beacon is a satellite transmission carrying status/health telemetry, and anyone may receive telemetry from a space station.
The big operating courtesy: don’t use excessive uplink power. Too much effective radiated power blocks other users (the satellite is a shared resource). The right amount is set by comparison: your downlink signal should be about as strong as the satellite’s beacon — if you’re louder than the beacon, turn down.
Key facts to retain
- Uplink/downlink; U/V = up on 70 cm, down on 2 m.
- Doppler = frequency shift from motion; spin fading = rotating satellite/antennas; LEO = low Earth orbit.
- Tracking input = Keplerian elements; beacon = status telemetry; anyone may receive telemetry.
- Don’t over-power the uplink (blocks others); match your downlink to the beacon level.
External reference anchors
- NCVEC syllabus: T8B — Amateur satellite operation: Doppler, orbits, protocols, telemetry, tracking, beacons, uplink/downlink, spin fading, LEO
Per-question map
| Q | Asks for | Resolved by |
|---|---|---|
| T8B01 | Beacon telemetry content | Satellite health & status |
| T8B02 | Excessive uplink ERP | Blocks other users |
| T8B03 | Tracking-program outputs | All these choices |
| T8B04 | Satellite transmission modes | All these choices |
| T8B05 | What a beacon is | Status-information transmission |
| T8B06 | Tracking-program input | Keplerian elements |
| T8B07 | Doppler shift | Frequency change from relative motion |
| T8B08 | U/V mode meaning | Up 70 cm, down 2 m |
| T8B09 | Cause of spin fading | Rotation of satellite/antennas |
| T8B10 | What a LEO is | Low Earth orbit satellite |
| T8B11 | Who may receive telemetry | Anyone |
| T8B12 | Setting correct uplink power | Match downlink to beacon strength |
T8C — Operating Activities: Direction Finding, Contests, Internet Linking, Grid Locators
11 questions
What this group tests: popular on-air activities and the internet-linking systems (IRLP, EchoLink, gateways, VoIP).
Foundational concepts
Radio direction finding (RDF) locates a transmitter — noise, jamming, or a “hidden transmitter hunt” (foxhunt) — and the key tool is a directional antenna. Contesting is contacting as many stations as possible in a set period; good contest etiquette is to send only the minimum info needed for ID and the exchange. A grid locator is a letter-number code for a geographic location (Maidenhead grid), commonly exchanged on VHF.
Internet linking connects radios over the net using VoIP (Voice over Internet Protocol — voice carried over the internet digitally). IRLP links repeaters/systems via VoIP, and you access IRLP nodes over the air with DTMF tones. EchoLink lets a station transmit through a repeater without using a radio to initiate it (from a computer/phone) — but you must first register your call sign and prove your license. A gateway is a station that connects other amateur stations to the internet.
Key facts to retain
- RDF finds transmitters; tool = directional antenna.
- Contesting = max contacts; send minimum exchange. Grid locator = geographic letter-number code.
- VoIP = voice over internet; IRLP links via VoIP, accessed by DTMF.
- EchoLink needs call-sign registration + license proof; a gateway bridges amateurs to the internet.
External reference anchors
- NCVEC syllabus: T8C — Operating activities: RDF, contests, internet linking, grid locators
Per-question map
| Q | Asks for | Resolved by |
|---|---|---|
| T8C01 | Locating noise/jamming | Radio direction finding |
| T8C02 | Useful for a hidden hunt | A directional antenna |
| T8C03 | Most contacts in a period | Contesting |
| T8C04 | Good contest procedure | Send minimum ID + exchange |
| T8C05 | What a grid locator is | Letter-number geographic code |
| T8C06 | Over-air IRLP access | DTMF signals |
| T8C07 | What VoIP is | Voice over the internet, digital |
| T8C08 | What IRLP is | Connect systems via VoIP |
| T8C09 | Transmit through repeater w/o radio | EchoLink |
| T8C10 | Before using EchoLink | Register call sign, prove license |
| T8C11 | Station connecting hams to internet | A gateway |
T8D — Non-Voice and Digital Communications
13 questions
What this group tests: the digital and image modes — CW, packet, PSK, APRS, DMR, NTSC, WSJT-X/FT8, mesh — and error-correction concepts.
Foundational concepts
A wide family of digital modes exists — “all of these” are digital. A few specifics worth knowing:
- CW is simply another name for a Morse code transmission.
- NTSC is analog fast-scan color TV.
- PSK stands for Phase Shift Keying (the digital keyboard mode).
- Packet radio transmissions carry several things (data, addressing, error checking) — “all of these,” and packet can carry many data types.
- APRS (Automatic Packet Reporting System) provides real-time tactical data tied to a map of station locations — GPS positions, weather, messages (“all of these”).
- DMR (Digital Mobile Radio) time-multiplexes two digital voice signals on one 12.5 kHz repeater channel, organized by talkgroups — a way for groups to share a channel at different times without hearing each other.
- WSJT-X is a software suite supporting several weak-signal activities — “all of these” — and FT8 is its flagship: a digital mode that works at very low signal-to-noise.
- A mesh network is an amateur data network built from commercial Wi-Fi gear with modified firmware.
On reliability, ARQ (Automatic Repeat reQuest) is error correction where the receiver detects errors and requests retransmission.
Key facts to retain
- CW = Morse; NTSC = analog fast-scan TV; PSK = Phase Shift Keying.
- APRS = real-time positions on a map; DMR = two voice streams on a 12.5 kHz channel via talkgroups.
- FT8 = low-SNR digital mode (WSJT-X suite); mesh = modified commercial Wi-Fi.
- ARQ = detect error, request resend.
External reference anchors
- NCVEC syllabus: T8D — Non-voice and digital communications: image/NTSC, CW, packet, PSK, APRS, error correction, DMR, WSJT modes, Broadband-Hamnet
Per-question map
| Q | Asks for | Resolved by |
|---|---|---|
| T8D01 | A digital mode | All these choices |
| T8D02 | DMR talkgroup | Groups share a channel at different times |
| T8D03 | Data APRS can send | All these choices |
| T8D04 | What “NTSC” indicates | Analog fast-scan color TV |
| T8D05 | APRS application | Real-time tactical data on a map |
| T8D06 | “PSK” meaning | Phase Shift Keying |
| T8D07 | Describes DMR | Two voice signals on 12.5 kHz channel |
| T8D08 | In packet transmissions | All these choices |
| T8D09 | What CW is | Another name for Morse code |
| T8D10 | WSJT-X activities | All these choices |
| T8D11 | ARQ system | Receiver detects error, requests resend |
| T8D12 | Amateur mesh network | Modified commercial Wi-Fi gear |
| T8D13 | What FT8 is | Low signal-to-noise digital mode |