Deep Dive: E9A06
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.
Why Other Answers 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.
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 Example
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.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E9A
Reference: FCC Part 97.313
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E9A topic.