CRAC Class A (2025) — Questions 351–360
U0350. "Class of emission" means a set of characteristics of an emission designated by standard symbols, e.g., the main carrier modulation method, modulating signal, type of information sent, and other applicable signal characteristics. The emission class representing single-sideband (SSB) phone is:
发射类别（class of emission）是指用标准符号标示的某发射 的一组特性，例如主载波调制方式，调制信号，被发送信息的 类型以及其他适用的信号特性。表示单边带话的发射类别是：
Exam tips · 考试提示
单边带话 (SSB phone) is J3E: J (SSB, suppressed carrier), 3 (single channel with analog information), E (telephony/voice). A1A is CW, F2B/G2B are facsimile types.
U0351. "Class of emission" means a set of characteristics of an emission designated by standard symbols, e.g., the main carrier modulation method, modulating signal, type of information sent, and other applicable signal characteristics. The emission class representing an SSTV signal transmitted using SSB phone is:
发射类别（class of emission）是指用标准符号标示的某发射 的一组特性，例如主载波调制方式，调制信号，被发送信息的 类型以及其他适用的信号特性。表示用单边带话传输的SSTV信 号的发射类别是：
Exam tips · 考试提示
According to the source answer key, the designator for this SSTV case is F3F (frequency modulation, single channel, television). J3E is plain SSB phone, F3E is FM phone, and F2B is a facsimile type. (Note: in practice SSTV-over-SSB is often denoted J3F, but the official key for this item selects F3F.)
U0352. "Class of emission" means a set of characteristics of an emission designated by standard symbols, e.g., the main carrier modulation method, modulating signal, type of information sent, and other applicable signal characteristics. The emission class representing frequency-modulation (FM) phone is:
发射类别（class of emission）是指用标准符号标示的某发射 的一组特性，例如主载波调制方式，调制信号，被发送信息的 类型以及其他适用的信号特性。表示调频话的发射类别是：
Exam tips · 考试提示
调频话 (FM phone) is F3E: F (frequency modulation), 3 (single channel, analog), E (telephony). F3F is FM television (SSTV/ATV), J3E is SSB phone.
U0353. "Class of emission" means a set of characteristics of an emission designated by standard symbols, e.g., the main carrier modulation method, modulating signal, type of information sent, and other applicable signal characteristics. The emission class representing an SSTV signal transmitted using FM phone is:
发射类别是指用标准符号标示的某发射的一组特性，例如主载 波调制方式，调制信号，被发送信息的类型以及其他适用的信 号特性。表示用调频话传输的SSTV信号的发射类别是：
Exam tips · 考试提示
An SSTV signal carried by FM is F3F (frequency modulation, single channel, television/image). F3E would be FM phone (no image), J3E is SSB phone, F2B is facsimile. The image content makes the final symbol F.
U0354. "Class of emission" means a set of characteristics of an emission designated by standard symbols, e.g., the main carrier modulation method, modulating signal, type of information sent, and other applicable signal characteristics. The emission class representing FM ATV (amateur television) is:
发射类别是指用标准符号标示的某发射的一组特性，例如主载 波调制方式，调制信号，被发送信息的类型以及其他适用的信 号特性。表示调频ATV信号的发射类别是：
Exam tips · 考试提示
调频 ATV (analog amateur television by FM) is F3F (frequency modulation, single channel, television). F3E is FM voice, F2B is facsimile, J3E is SSB voice.
U0355. Out-of-band emission means:
带外发射是指：
Exam tips · 考试提示
带外发射 (out-of-band emission) is defined relative to the 必要 带宽 (necessary bandwidth): emissions just outside it caused by modulation, excluding spurious emission. The ITU/glossary term is "necessary bandwidth", so B (occupied), C (reference), D (fixed) are wrong.
U0356. In amateur radio communication the three most basic modulations are abbreviated AM, FM and PM. Their Chinese names are:
业余无线电通信中三种最基本调制的缩写是AM、FM和PM。 它们的中文名称是：
Exam tips · 考试提示
AM = 幅度调制 (amplitude modulation), FM = 频率调制 (frequency modulation), PM = 相位调制 (phase modulation). These are the three fundamental analog modulation types. B/C/D substitute pulse or code modulations that are not PM.
U0357. Which modulation is widely used for VHF or UHF local contacts?
以下哪种调制方式被广泛应用于VHF或UHF本地通联？
Exam tips · 考试提示
VHF/UHF local operation (repeaters, simplex) overwhelmingly uses FM (frequency modulation) for its noise immunity and simplicity. SSB is used on VHF/UHF mostly for weak-signal work, PSK is a digital HF mode, and AM is rarely used on these bands.
U0358. Which modulation is widely used for long-distance and weak- signal VHF or UHF voice contacts?
以下哪种调制方式被广泛应用于长距离和弱信号情况下的VHF 或UHF话音通联？
Exam tips · 考试提示
For weak-signal / long-distance VHF-UHF voice (e.g., troposcatter, EME, DX), SSB is preferred because of its narrower bandwidth and better weak-signal performance. FM needs stronger signals; AM/PM are not the standard.
U0359. Which modulation is widely used for HF voice contacts?
以下哪种调制方式被广泛应用于HF话音通联？
Exam tips · 考试提示
HF voice is dominated by SSB (single sideband) because of its narrow bandwidth and efficiency; FM is impractical on HF (it needs wide bandwidth and line-of-sight-like conditions), and AM is obsolete for phone.