What is the effective radiated power (ERP) of a repeater station with 200 watts transmitter power output, 4 dB feed line loss, 3.2 dB duplexer loss, 0.8 dB circulator loss, and 10 dBd antenna gain?
The correct answer is A: 317 watts. To calculate Effective Radiated Power (ERP), account for all gains and losses: ERP = Transmitter Power × (Gain - Losses). Convert dB to ratios.
Given: 200W transmitter, 4 dB feedline loss, 3.2 dB duplexer loss, 0.8 dB circulator loss, 10 dBd antenna gain. Total losses = 4 + 3.2 + 0.8 = 8 dB. Net gain = 10 dBd - 8 dB = 2 dB. Converting: 2 dB = 10^(2/10) = 1.585 ratio. ERP = 200W × 1.585 = 317W. ERP accounts for all losses (feedline, duplexer, circulator) and antenna gain to give the effective radiated power.
Exam Tip
ERP calculation = Account for all losses and gains. Remember: ERP = Power × (Gain - All Losses). With 200W, 10 dBd gain, and 8 dB total losses, net = 2 dB = 1.585×, ERP = 317W.
Memory Aid
"**E**RP = **2**00W × (**1**0 dBd - **8** dB losses) = **3**17W (think 'ERP = 200×(10-8) = 317W')"
Real-World Application
Your repeater has 200W transmitter, 4 dB feedline loss, 3.2 dB duplexer loss, 0.8 dB circulator loss, and 10 dBd antenna gain. Total losses = 8 dB. Net gain = 10 - 8 = 2 dB = 1.585×. ERP = 200W × 1.585 = 317W. This is your effective radiated power after all losses and gains.
FCC Part 97.313Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. 2,000 watts would result from ignoring losses or incorrect calculation. That's 10× the transmitter power, which doesn't account for the 8 dB of losses.
Option C: Incorrect. 126 watts would result from incorrect calculation of the net gain/loss.
Option D: Incorrect. 300 watts is close but not the exact calculated value. The correct calculation gives 317W.
题目解析
The correct answer is A: 317 watts. To calculate Effective Radiated Power (ERP), account for all gains and losses: ERP = Transmitter Power × (Gain - Losses). Convert dB to ratios. Given: 200W transmitter, 4 dB feedline loss, 3.2 dB duplexer loss, 0.8 dB circulator loss, 10 dBd antenna gain. Total losses = 4 + 3.2 + 0.8 = 8 dB. Net gain = 10 dBd - 8 dB = 2 dB. Converting: 2 dB = 10^(2/10) = 1.585 ratio. ERP = 200W × 1.585 = 317W. ERP accounts for all losses (feedline, duplexer, circulator) and antenna gain to give the effective radiated power.
考试技巧
ERP calculation = Account for all losses and gains. Remember: ERP = Power × (Gain - All Losses). With 200W, 10 dBd gain, and 8 dB total losses, net = 2 dB = 1.585×, ERP = 317W.
记忆口诀
**E**RP = **2**00W × (**1**0 dBd - **8** dB losses) = **3**17W (think 'ERP = 200×(10-8) = 317W')
实际应用示例
Your repeater has 200W transmitter, 4 dB feedline loss, 3.2 dB duplexer loss, 0.8 dB circulator loss, and 10 dBd antenna gain. Total losses = 8 dB. Net gain = 10 - 8 = 2 dB = 1.585×. ERP = 200W × 1.585 = 317W. This is your effective radiated power after all losses and gains.
错误选项分析
Option B: Incorrect. 2,000 watts would result from ignoring losses or incorrect calculation. That's 10× the transmitter power, which doesn't account for the 8 dB of losses. Option C: Incorrect. 126 watts would result from incorrect calculation of the net gain/loss. Option D: Incorrect. 300 watts is close but not the exact calculated value. The correct calculation gives 317W.
知识点
Effective radiated power, ERP, Gain and losses, Power calculation
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.