Where is an RF preamplifier installed?
The correct answer is A: Between the antenna and receiver. An RF preamplifier is installed between the antenna and receiver to amplify weak received signals before they enter the receiver. This position is critical because the preamplifier amplifies the signal (and noise) early in the receive chain, improving the signal-to-noise ratio before the receiver's internal noise is added. For amateur radio operators, RF preamplifiers are essential for weak-signal work, improving receiver sensitivity, and reducing the impact of feed line losses. The preamplifier must be located close to the antenna (often at the antenna) to be most effective, as amplifying after feed line losses doesn't help as much. Understanding preamplifier placement is important for optimizing receive performance.
Exam Tip
RF preamplifier = between antenna and receiver. Think 'P'reamplifier = 'P'ositioned early (before receiver). It amplifies weak RF signals before they enter the receiver, improving sensitivity.
Memory Aid
"RF preamplifier = between antenna and receiver. Think 'P'reamplifier = 'P'ositioned 'P'rior to receiver. Amplifies RF signals early in the receive chain."
Real-World Application
For weak-signal VHF work, you install an RF preamplifier at your antenna or in the feed line near the antenna. This amplifies the weak signals from space before they travel through the feed line and enter your receiver. The preamplifier improves your ability to hear weak signals that might otherwise be lost in receiver noise. Without it, feed line losses and receiver noise might make weak signals undetectable.
Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. Preamplifiers are for receiving, not transmitting. Installing at the transmitter output would amplify transmit signals, which is not the purpose of a preamplifier.
Option C: Incorrect. Between transmitter and antenna tuner is in the transmit path. Preamplifiers are receive-only devices and must be in the receive path.
Option D: Incorrect. At the receiver audio output is after all RF processing. Preamplifiers must amplify RF signals before they're processed, not audio after processing.
题目解析
The correct answer is A: Between the antenna and receiver. An RF preamplifier is installed between the antenna and receiver to amplify weak received signals before they enter the receiver. This position is critical because the preamplifier amplifies the signal (and noise) early in the receive chain, improving the signal-to-noise ratio before the receiver's internal noise is added. For amateur radio operators, RF preamplifiers are essential for weak-signal work, improving receiver sensitivity, and reducing the impact of feed line losses. The preamplifier must be located close to the antenna (often at the antenna) to be most effective, as amplifying after feed line losses doesn't help as much. Understanding preamplifier placement is important for optimizing receive performance.
考试技巧
RF preamplifier = between antenna and receiver. Think 'P'reamplifier = 'P'ositioned early (before receiver). It amplifies weak RF signals before they enter the receiver, improving sensitivity.
记忆口诀
RF preamplifier = between antenna and receiver. Think 'P'reamplifier = 'P'ositioned 'P'rior to receiver. Amplifies RF signals early in the receive chain.
实际应用示例
For weak-signal VHF work, you install an RF preamplifier at your antenna or in the feed line near the antenna. This amplifies the weak signals from space before they travel through the feed line and enter your receiver. The preamplifier improves your ability to hear weak signals that might otherwise be lost in receiver noise. Without it, feed line losses and receiver noise might make weak signals undetectable.
错误选项分析
Option B: Incorrect. Preamplifiers are for receiving, not transmitting. Installing at the transmitter output would amplify transmit signals, which is not the purpose of a preamplifier. Option C: Incorrect. Between transmitter and antenna tuner is in the transmit path. Preamplifiers are receive-only devices and must be in the receive path. Option D: Incorrect. At the receiver audio output is after all RF processing. Preamplifiers must amplify RF signals before they're processed, not audio after processing.
知识点
RF preamplifiers, Receiver front-end, Signal amplification, Weak signal reception
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.