What is the effective radiated power (ERP) of a repeater station with 150 watts transmitter power output, 2 dB feed line loss, 2.2 dB duplexer loss, and 7 dBd antenna gain?
The correct answer is D: 286 watts. To calculate Effective Radiated Power (ERP), you account for all gains and losses: ERP = Transmitter Power × (Gain - Losses). Convert dB to ratios: gain = 10^(dB/10), loss subtracts from gain.
Given: 150W transmitter, 2 dB feedline loss, 2.2 dB duplexer loss, 7 dBd antenna gain. Net gain = 7 dBd - 2 dB - 2.2 dB = 2.8 dB. Converting: 2.8 dB = 10^(2.8/10) = 1.905 ratio. ERP = 150W × 1.905 = 286W. ERP accounts for transmitter power, feedline losses, duplexer losses, and antenna gain to give the effective power radiated by the antenna.
Exam Tip
ERP = Power × (Gain - Losses). Remember: ERP accounts for transmitter power, feedline loss, duplexer loss, and antenna gain. Net gain = antenna gain - feedline loss - duplexer loss. Convert dB to ratio: 10^(dB/10).
Memory Aid
"**E**RP = **P**ower × (**G**ain - **L**osses) (think 'ERP = P×(G-L)', 150W, net +2.8dB = 286W)"
Real-World Application
Your repeater has 150W transmitter output. After 2 dB feedline loss and 2.2 dB duplexer loss, you have 7 dBd antenna gain. Net gain = 7 - 2 - 2.2 = 2.8 dB = 1.905×. ERP = 150W × 1.905 = 286W. This is the effective power your antenna radiates, accounting for all losses and gains.
FCC Part 97.313Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. 469 watts would result from not properly accounting for losses or using incorrect dB conversions.
Option B: Incorrect. 78.7 watts would result from subtracting gains instead of properly calculating net gain minus losses.
Option C: Incorrect. 420 watts would result from incorrect calculation of the net gain/loss combination.
题目解析
The correct answer is D: 286 watts. To calculate Effective Radiated Power (ERP), you account for all gains and losses: ERP = Transmitter Power × (Gain - Losses). Convert dB to ratios: gain = 10^(dB/10), loss subtracts from gain. Given: 150W transmitter, 2 dB feedline loss, 2.2 dB duplexer loss, 7 dBd antenna gain. Net gain = 7 dBd - 2 dB - 2.2 dB = 2.8 dB. Converting: 2.8 dB = 10^(2.8/10) = 1.905 ratio. ERP = 150W × 1.905 = 286W. ERP accounts for transmitter power, feedline losses, duplexer losses, and antenna gain to give the effective power radiated by the antenna.
考试技巧
ERP = Power × (Gain - Losses). Remember: ERP accounts for transmitter power, feedline loss, duplexer loss, and antenna gain. Net gain = antenna gain - feedline loss - duplexer loss. Convert dB to ratio: 10^(dB/10).
记忆口诀
**E**RP = **P**ower × (**G**ain - **L**osses) (think 'ERP = P×(G-L)', 150W, net +2.8dB = 286W)
实际应用示例
Your repeater has 150W transmitter output. After 2 dB feedline loss and 2.2 dB duplexer loss, you have 7 dBd antenna gain. Net gain = 7 - 2 - 2.2 = 2.8 dB = 1.905×. ERP = 150W × 1.905 = 286W. This is the effective power your antenna radiates, accounting for all losses and gains.
错误选项分析
Option A: Incorrect. 469 watts would result from not properly accounting for losses or using incorrect dB conversions. Option B: Incorrect. 78.7 watts would result from subtracting gains instead of properly calculating net gain minus losses. Option C: Incorrect. 420 watts would result from incorrect calculation of the net gain/loss combination.
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.