Which of the following is a form of amplitude modulation?
The correct answer is C: Single sideband. Single sideband (SSB) is a form of amplitude modulation (AM). SSB is derived from AM by suppressing the carrier and one sideband, leaving only one sideband (upper or lower) with the audio information. This is more efficient than full AM because it uses less bandwidth and power. For amateur radio operators, SSB is the primary voice mode on HF bands and is also used on VHF/UHF for weak-signal work. Understanding that SSB is a type of AM helps explain its characteristics and why it requires more complex receivers than FM.
Exam Tip
SSB = form of AM. Think 'S'ingle 'S'ideband = 'S'uppressed carrier 'A'M. SSB is AM with carrier and one sideband removed. Spread spectrum, packet radio, and PSK are different modulation types.
Memory Aid
"SSB = Single Sideband = form of AM. Think 'S'ingle 'S'ideband = 'S'uppressed carrier 'A'M. AM with carrier and one sideband removed for efficiency."
Real-World Application
On 20 meters, most voice communications use SSB, which is a form of AM. Your transceiver generates an AM signal, then suppresses the carrier and one sideband, transmitting only the upper sideband. This is more efficient than full AM - it uses half the bandwidth and all the power goes into the information-carrying sideband, not the carrier.
Key Concepts
Why Other Options Are Wrong
Option A (Spread spectrum): Incorrect. Spread spectrum spreads the signal across a wide frequency range using techniques like frequency hopping or direct sequence. It's not a form of amplitude modulation.
Option B (Packet radio): Incorrect. Packet radio is a digital communications mode using data packets, not amplitude modulation. It's a digital mode, not an analog AM mode.
Option D (Phase shift keying): Incorrect. PSK is a digital modulation technique that shifts the phase of the carrier, not amplitude. It's phase modulation, not amplitude modulation.
题目解析
The correct answer is C: Single sideband. Single sideband (SSB) is a form of amplitude modulation (AM). SSB is derived from AM by suppressing the carrier and one sideband, leaving only one sideband (upper or lower) with the audio information. This is more efficient than full AM because it uses less bandwidth and power. For amateur radio operators, SSB is the primary voice mode on HF bands and is also used on VHF/UHF for weak-signal work. Understanding that SSB is a type of AM helps explain its characteristics and why it requires more complex receivers than FM.
考试技巧
SSB = form of AM. Think 'S'ingle 'S'ideband = 'S'uppressed carrier 'A'M. SSB is AM with carrier and one sideband removed. Spread spectrum, packet radio, and PSK are different modulation types.
记忆口诀
SSB = Single Sideband = form of AM. Think 'S'ingle 'S'ideband = 'S'uppressed carrier 'A'M. AM with carrier and one sideband removed for efficiency.
实际应用示例
On 20 meters, most voice communications use SSB, which is a form of AM. Your transceiver generates an AM signal, then suppresses the carrier and one sideband, transmitting only the upper sideband. This is more efficient than full AM - it uses half the bandwidth and all the power goes into the information-carrying sideband, not the carrier.
错误选项分析
Option A (Spread spectrum): Incorrect. Spread spectrum spreads the signal across a wide frequency range using techniques like frequency hopping or direct sequence. It's not a form of amplitude modulation. Option B (Packet radio): Incorrect. Packet radio is a digital communications mode using data packets, not amplitude modulation. It's a digital mode, not an analog AM mode. Option D (Phase shift keying): Incorrect. PSK is a digital modulation technique that shifts the phase of the carrier, not amplitude. It's phase modulation, not amplitude modulation.
知识点
Single sideband, Amplitude modulation, SSB, Modulation types
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.