What is the function of the SSB/CW-FM switch on a VHF power amplifier?
The correct answer is B: Set the amplifier for proper operation in the selected mode. The SSB/CW-FM switch on a VHF power amplifier sets the amplifier for proper operation in the selected mode. Different modes require different amplifier characteristics - SSB and CW are linear modes requiring linear amplification, while FM can use non-linear (class C) amplification which is more efficient. The switch adjusts the amplifier's bias, drive level, and operating class to optimize performance for each mode. For amateur radio operators, using the correct mode setting ensures proper amplifier operation, prevents distortion, and protects the amplifier. Setting it wrong can cause poor audio quality, distortion, or amplifier damage.
Exam Tip
SSB/CW-FM switch = sets amplifier for mode. Think 'S'witch 'S'ets amplifier for 'S'elected mode. It optimizes the amplifier, not the transceiver mode or frequency range.
Memory Aid
"SSB/CW-FM switch = Sets amplifier for mode. Think 'S'witch 'S'ets amplifier 'S'ettings for the mode. Optimizes amplifier operation, not transceiver mode."
Real-World Application
When operating SSB, you set the amplifier switch to SSB/CW position. This configures the amplifier for linear operation (class AB), ensuring your voice is amplified without distortion. When switching to FM, you set it to FM position, which may use more efficient class C operation since FM is less sensitive to non-linearity. Using the wrong setting can cause distortion on SSB or reduced efficiency on FM.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. The switch doesn't change the mode of the transmitted signal - that's determined by the transceiver. The amplifier amplifies whatever mode the transceiver sends.
Option C: Incorrect. The switch doesn't change frequency ranges - the amplifier operates across its designed frequency range regardless of mode setting.
Option D: Incorrect. The switch doesn't affect receiver noise - it's for the transmitter amplifier, not the receiver.
题目解析
The correct answer is B: Set the amplifier for proper operation in the selected mode. The SSB/CW-FM switch on a VHF power amplifier sets the amplifier for proper operation in the selected mode. Different modes require different amplifier characteristics - SSB and CW are linear modes requiring linear amplification, while FM can use non-linear (class C) amplification which is more efficient. The switch adjusts the amplifier's bias, drive level, and operating class to optimize performance for each mode. For amateur radio operators, using the correct mode setting ensures proper amplifier operation, prevents distortion, and protects the amplifier. Setting it wrong can cause poor audio quality, distortion, or amplifier damage.
考试技巧
SSB/CW-FM switch = sets amplifier for mode. Think 'S'witch 'S'ets amplifier for 'S'elected mode. It optimizes the amplifier, not the transceiver mode or frequency range.
记忆口诀
SSB/CW-FM switch = Sets amplifier for mode. Think 'S'witch 'S'ets amplifier 'S'ettings for the mode. Optimizes amplifier operation, not transceiver mode.
实际应用示例
When operating SSB, you set the amplifier switch to SSB/CW position. This configures the amplifier for linear operation (class AB), ensuring your voice is amplified without distortion. When switching to FM, you set it to FM position, which may use more efficient class C operation since FM is less sensitive to non-linearity. Using the wrong setting can cause distortion on SSB or reduced efficiency on FM.
错误选项分析
Option A: Incorrect. The switch doesn't change the mode of the transmitted signal - that's determined by the transceiver. The amplifier amplifies whatever mode the transceiver sends. Option C: Incorrect. The switch doesn't change frequency ranges - the amplifier operates across its designed frequency range regardless of mode setting. Option D: Incorrect. The switch doesn't affect receiver noise - it's for the transmitter amplifier, not the receiver.
知识点
Amplifier mode switching, SSB/CW/FM modes, Linear vs non-linear amplification, Power amplifier operation
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.