FCC Exam Question: 3-67J5

What is the effective radiated power of a repeater with 100 watts transmitter power output, 5 dB feedline loss, 4 dB duplexer and circulator loss, and 10 dB antenna gain?

A. 126 watts.
B. 800 watts.
C. 12.5 watts.
D. 1260 watts.
Correct Answer: A

Explanation: Effective Radiated Power (ERP) quantifies the total power radiated by an antenna in its favored direction, taking into account all gains and losses between the transmitter and the antenna. To calculate ERP: 1. **Convert transmitter power to dBW:** 100 watts = 10 \* log(100) = 20 dBW. 2. **Sum all gains and losses in dB:** * Antenna gain: +10 dB * Feedline loss: -5 dB * Duplexer/circulator loss: -4 dB * Total system change: +10 dB - 5 dB - 4 dB = +1 dB. 3. **Add the total system change to the transmitter power in dBW:** 20 dBW + 1 dB = 21 dBW. 4. **Convert the final dBW value back to watts:** Watts = 10^(dBW/10) = 10^(21/10) = 10^(2.1) ≈ 125.89 watts. Rounding to the nearest whole number gives 126 watts. The other options are incorrect as they do not reflect the correct sum of gains and losses.

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Includes Elements 1, 3, 6, 7R, 8, and 9.