What is the effective isotropic radiated power (EIRP) of a repeater station with 200 watts transmitter power output, 2 dB feed line loss, 2.8 dB duplexer loss, 1.2 dB circulator loss, and 7 dBi antenna gain?
The correct answer is B: 252 watts. To calculate Effective Isotropic Radiated Power (EIRP), account for all gains and losses: EIRP = Transmitter Power × (Gain - Losses). Convert dB to ratios. Note: EIRP uses dBi (gain relative to isotropic), while ERP uses dBd (gain relative to dipole).
Given: 200W transmitter, 2 dB feedline loss, 2.8 dB duplexer loss, 1.2 dB circulator loss, 7 dBi antenna gain. Total losses = 2 + 2.8 + 1.2 = 6 dB. Net gain = 7 dBi - 6 dB = 1 dB. Converting: 1 dB = 10^(1/10) = 1.259 ratio. EIRP = 200W × 1.259 = 252W. EIRP is similar to ERP but uses dBi (isotropic reference) instead of dBd (dipole reference).
Exam Tip
EIRP calculation = Account for all losses and gains in dBi. Remember: EIRP = Power × (Gain in dBi - All Losses). With 200W, 7 dBi gain, and 6 dB losses, net = 1 dB = 1.259×, EIRP = 252W.
Memory Aid
"**E**IRP = **2**00W × (**7** dBi - **6** dB) = **2**52W (think 'EIRP = 200×(7-6) = 252W')"
Real-World Application
Your station has 200W transmitter, 2 dB feedline loss, 2.8 dB duplexer loss, 1.2 dB circulator loss, and 7 dBi antenna gain. Total losses = 6 dB. Net gain = 7 - 6 = 1 dB = 1.259×. EIRP = 200W × 1.259 = 252W. EIRP uses dBi (isotropic reference), while ERP uses dBd (dipole reference).
FCC Part 97.313Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. 159 watts would result from incorrect calculation of the net gain/loss combination.
Option C: Incorrect. 632 watts would result from not properly accounting for losses or using incorrect dB conversions.
Option D: Incorrect. 63.2 watts would result from subtracting gains instead of properly calculating net gain minus losses.
题目解析
The correct answer is B: 252 watts. To calculate Effective Isotropic Radiated Power (EIRP), account for all gains and losses: EIRP = Transmitter Power × (Gain - Losses). Convert dB to ratios. Note: EIRP uses dBi (gain relative to isotropic), while ERP uses dBd (gain relative to dipole). Given: 200W transmitter, 2 dB feedline loss, 2.8 dB duplexer loss, 1.2 dB circulator loss, 7 dBi antenna gain. Total losses = 2 + 2.8 + 1.2 = 6 dB. Net gain = 7 dBi - 6 dB = 1 dB. Converting: 1 dB = 10^(1/10) = 1.259 ratio. EIRP = 200W × 1.259 = 252W. EIRP is similar to ERP but uses dBi (isotropic reference) instead of dBd (dipole reference).
考试技巧
EIRP calculation = Account for all losses and gains in dBi. Remember: EIRP = Power × (Gain in dBi - All Losses). With 200W, 7 dBi gain, and 6 dB losses, net = 1 dB = 1.259×, EIRP = 252W.
记忆口诀
**E**IRP = **2**00W × (**7** dBi - **6** dB) = **2**52W (think 'EIRP = 200×(7-6) = 252W')
实际应用示例
Your station has 200W transmitter, 2 dB feedline loss, 2.8 dB duplexer loss, 1.2 dB circulator loss, and 7 dBi antenna gain. Total losses = 6 dB. Net gain = 7 - 6 = 1 dB = 1.259×. EIRP = 200W × 1.259 = 252W. EIRP uses dBi (isotropic reference), while ERP uses dBd (dipole reference).
错误选项分析
Option A: Incorrect. 159 watts would result from incorrect calculation of the net gain/loss combination. Option C: Incorrect. 632 watts would result from not properly accounting for losses or using incorrect dB conversions. Option D: Incorrect. 63.2 watts would result from subtracting gains instead of properly calculating net gain minus losses.
知识点
Effective isotropic radiated power, EIRP, dBi, Gain and losses
Verified Content
Question from official FCC Extra Class question pool. Explanation reviewed by licensed amateur radio operators.