Question 3-67J3

Effective Radiated Power (ERP) represents the actual power radiated by an antenna in its favored direction, taking into account all system losses and antenna gain. To calculate ERP, we sum the gains and losses in decibels (dB) and then apply this net change to the transmitter output power. 1. **Calculate total system gain/loss in dB:** Antenna gain: +6 dB Feedline loss: -5 dB Duplexer and circulator loss: -4 dB Total net change = +6 dB - 5 dB - 4 dB = -3 dB 2. **Apply the net dB change to the transmitter power:** A -3 dB change means the power is approximately halved (specifically, multiplied by 10^(-3/10) or 0.501). ERP = Transmitter Power Output × 10^(Net dB / 10) ERP = 75 watts × 10^(-3 / 10) ERP = 75 watts × 10^(-0.3) ERP = 75 watts × 0.501187 ERP ≈ 37.589 watts Rounded to one decimal place, the ERP is approximately 37.6 watts. Option B, C, and D are incorrect as they do not reflect the correct calculation of net system gain and losses. For example, 150 watts (C) would be a +3 dB gain, not a -3 dB loss.