Which of the following can reduce overload of a VHF transceiver by a nearby commercial FM station?
The correct answer is D: Installing a band-reject filter. A band-reject filter (also called a notch filter) can reduce overload of a VHF transceiver by a nearby commercial FM station. The filter is installed in the receive path and blocks the strong commercial FM signal (typically 88-108 MHz) while passing your amateur VHF signals (144-148 MHz). This prevents the strong commercial signal from overloading your receiver's front-end. For amateur radio operators, band-reject filters are essential when operating near commercial FM broadcast towers, which can cause severe receiver overload and make it impossible to receive weak amateur signals.
Exam Tip
Commercial FM overload = band-reject filter. Think 'B'and-'R'eject 'F'ilter = 'B'locks 'R'adio 'F'requency interference. It blocks the interfering frequency while passing desired signals. Preamplifiers make it worse.
Memory Aid
"Band-reject filter = blocks interfering frequency. Think 'B'and-'R'eject = 'B'locks 'R'adio interference. Filters out the unwanted frequency while passing desired signals."
Real-World Application
A commercial FM station on 100.5 MHz is overloading your 2-meter receiver, making it impossible to hear weak amateur signals. Installing a band-reject filter tuned to 88-108 MHz in your receive path blocks the commercial FM signal while passing your 144-148 MHz amateur signals. This allows your receiver to function normally despite the nearby strong commercial signal.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Installing an RF preamplifier would amplify the commercial FM signal along with your desired signals, making the overload worse, not better.
Option B: Incorrect. Double-shielded cable reduces RF pickup on cables but doesn't prevent a strong signal from overloading the receiver through the antenna.
Option C: Incorrect. Bypass capacitors on microphone cables prevent RF feedback in audio circuits but don't prevent receiver overload from strong signals.
题目解析
The correct answer is D: Installing a band-reject filter. A band-reject filter (also called a notch filter) can reduce overload of a VHF transceiver by a nearby commercial FM station. The filter is installed in the receive path and blocks the strong commercial FM signal (typically 88-108 MHz) while passing your amateur VHF signals (144-148 MHz). This prevents the strong commercial signal from overloading your receiver's front-end. For amateur radio operators, band-reject filters are essential when operating near commercial FM broadcast towers, which can cause severe receiver overload and make it impossible to receive weak amateur signals.
考试技巧
Commercial FM overload = band-reject filter. Think 'B'and-'R'eject 'F'ilter = 'B'locks 'R'adio 'F'requency interference. It blocks the interfering frequency while passing desired signals. Preamplifiers make it worse.
记忆口诀
Band-reject filter = blocks interfering frequency. Think 'B'and-'R'eject = 'B'locks 'R'adio interference. Filters out the unwanted frequency while passing desired signals.
实际应用示例
A commercial FM station on 100.5 MHz is overloading your 2-meter receiver, making it impossible to hear weak amateur signals. Installing a band-reject filter tuned to 88-108 MHz in your receive path blocks the commercial FM signal while passing your 144-148 MHz amateur signals. This allows your receiver to function normally despite the nearby strong commercial signal.
错误选项分析
Option A: Incorrect. Installing an RF preamplifier would amplify the commercial FM signal along with your desired signals, making the overload worse, not better. Option B: Incorrect. Double-shielded cable reduces RF pickup on cables but doesn't prevent a strong signal from overloading the receiver through the antenna. Option C: Incorrect. Bypass capacitors on microphone cables prevent RF feedback in audio circuits but don't prevent receiver overload from strong signals.
知识点
Band-reject filters, Receiver overload, Commercial FM interference, RFI mitigation
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.