Question
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?
Answer Options
- A) 317 watts
- B) 2,000 watts
- C) 126 watts
- D) 300 watts
Correct Answer: A
Explanation
Effective Radiated Power (ERP) is the net power radiated by the antenna relative to a dipole. To calculate ERP, first sum all gains and losses in the system (all values must be in dB or dBd), and then convert the net dB gain/loss back into a power ratio to multiply by the transmitter output power in Watts.
First, calculate the total gain/loss in dB: G_{Total} = Antenna Gain - Feed line Loss - Duplexer Loss - Circulator Loss = 10 dB - 4 dB - 3.2 dB - 0.8 dB = +2 dB. The ERP is 200 W \times 10^{(2/10)} \approx 200 W \times 1.585 \approx 317 W. Therefore, the ERP is approximately 317 watts.
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