What is one reason to use an impedance matching transformer at a transmitter output?
The correct answer is B: To present the desired impedance to the transmitter and feed line. A reason to use an impedance matching transformer at a transmitter output is to present the desired impedance to the transmitter and feed line. Transformers match impedances, allowing maximum power transfer. For amateur radio operators, this is essential for efficient operation. Understanding this helps when designing matching networks.
Exam Tip
Impedance matching transformer purpose = present desired impedance to transmitter and feed line. Think 'I'mpedance 'M'atching = 'I'mproves 'M'atching. Transformers match impedances, allowing maximum power transfer. Not minimize power, not reduce ripple, not minimize radiation resistance - just impedance matching.
Memory Aid
"Impedance matching transformer purpose = present desired impedance to transmitter and feed line. Think 'I'mpedance 'M'atching = 'I'mproves 'M'atching. Transformers match impedances, allowing maximum power transfer. Essential for efficient operation."
Real-World Application
Your transmitter wants 50 ohms, but your antenna presents 200 ohms. You use an impedance matching transformer (e.g., 4:1 transformer) to match 200 ohms to 50 ohms. This presents the desired impedance to both the transmitter and feed line, maximizing power transfer. This is why impedance matching transformers are used.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Transformers don't minimize transmitter power output - they match impedance to maximize power transfer, not minimize it. Power minimization isn't the purpose.
Option C: Incorrect. Transformers don't reduce power supply ripple - that's done by power supply filters, not transformers. Ripple reduction isn't the purpose.
Option D: Incorrect. Transformers don't minimize radiation resistance - radiation resistance is an antenna property, not something transformers minimize. Radiation resistance isn't the purpose.
题目解析
The correct answer is B: To present the desired impedance to the transmitter and feed line. A reason to use an impedance matching transformer at a transmitter output is to present the desired impedance to the transmitter and feed line. Transformers match impedances, allowing maximum power transfer. For amateur radio operators, this is essential for efficient operation. Understanding this helps when designing matching networks.
考试技巧
Impedance matching transformer purpose = present desired impedance to transmitter and feed line. Think 'I'mpedance 'M'atching = 'I'mproves 'M'atching. Transformers match impedances, allowing maximum power transfer. Not minimize power, not reduce ripple, not minimize radiation resistance - just impedance matching.
记忆口诀
Impedance matching transformer purpose = present desired impedance to transmitter and feed line. Think 'I'mpedance 'M'atching = 'I'mproves 'M'atching. Transformers match impedances, allowing maximum power transfer. Essential for efficient operation.
实际应用示例
Your transmitter wants 50 ohms, but your antenna presents 200 ohms. You use an impedance matching transformer (e.g., 4:1 transformer) to match 200 ohms to 50 ohms. This presents the desired impedance to both the transmitter and feed line, maximizing power transfer. This is why impedance matching transformers are used.
错误选项分析
Option A: Incorrect. Transformers don't minimize transmitter power output - they match impedance to maximize power transfer, not minimize it. Power minimization isn't the purpose. Option C: Incorrect. Transformers don't reduce power supply ripple - that's done by power supply filters, not transformers. Ripple reduction isn't the purpose. Option D: Incorrect. Transformers don't minimize radiation resistance - radiation resistance is an antenna property, not something transformers minimize. Radiation resistance isn't the purpose.
知识点
Impedance matching transformer, Transmitter output, Desired impedance, Feed line matching
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.