What is the effective radiated power of a repeater with 75 watts transmitter power output, 4 dB feedline loss, 3 dB duplexer and circulator loss, and 10 dB antenna gain?
• How to convert dB (decibels) to a power ratio • The relationship between gains, losses, and effective radiated power (ERP) • How to apply dB values: subtract losses, add gains when working in dB
• First, combine all the dB values (losses and gains) into a single net dB value. Should it be positive or negative? Why? • Once you have the net dB value, how do you convert that into a linear power multiplier and apply it to the 75 W transmitter power? • Which of the answer choices best matches the power you get after applying the net gain/loss factor?
• Be sure you are using 10^(dB/10) (not 20) when converting dB to a power ratio • Double-check that you subtract the feedline and duplexer/circulator losses and add the antenna gain before converting back to watts • After calculating, confirm that the result is reasonable: should the ERP be higher or lower than the original 75 W, given the combination of gains and losses?
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