Amateur ExtraE9A06
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?
A
Answer
Antennas and transmission lines
Type
A
317 watts
B
2,000 watts
C
126 watts
D
300 watts
Answer Notes
To find the Effective Radiated Power (ERP), you must first calculate the net system gain or loss in decibels (dB). Sum the losses: 4 dB (feed line) + 3.2 dB (duplexer) + 0.8 dB (circulator) = 8 dB of total loss. Subtract this loss from the antenna gain: 10 dBd (antenna gain) - 8 dB (loss) = a net gain of +2 dB.
Next, convert the net gain in dB to a power multiplier using the formula 10^(dB/10). For a 2 dB gain, the multiplier is 10^(2/10) or 10^0.2, which is approximately 1.585. Finally, multiply the transmitter power output by this factor: 200 watts * 1.585 = 317 watts. Note that ERP is calculated relative to a half-wave dipole (dBd), which matches the given antenna gain unit.
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What is the effective isotropic radiated power (EIRP) of a repeater station with 200 watts transmitter power output, 2 dB feed line loss, 2.8 dB duplexer loss, 1.2 dB circulator loss, and 7 dBi antenna gain?