An AM transmitter has an output of 20KW when modulated to a depth of100%. Calculate the output power when(a) the carrier is unmodulated(b) When after modulation to a depth of 50% one sideband issuppressed and the carrier component is reduced by 24dB
Question
An AM transmitter has an output of 20KW when modulated to a depth of100%. Calculate the output power when(a) the carrier is unmodulated(b) When after modulation to a depth of 50% one sideband issuppressed and the carrier component is reduced by 24dB
Solution
Sure, let's break down the problem step by step.
(a) When the carrier is unmodulated: In an AM transmitter, the carrier power is a part of the total power. The total power Pt in an AM system is given by the formula Pt = Pc(1 + (m^2)/2), where Pc is the carrier power and m is the modulation index. When the system is 100% modulated, m = 1.
So, we can rearrange the formula to find Pc: Pc = Pt / (1 + (m^2)/2).
Substituting the given values, Pc = 20000 / (1 + (1^2)/2) = 20000 / 1.5 = 13333.33 W or approximately 13.33 KW.
(b) When after modulation to a depth of 50% one sideband is suppressed and the carrier component is reduced by 24dB: When the modulation depth is 50%, m = 0.5. The total power Pt is then given by Pt = Pc(1 + (m^2)/2) = 13333.33(1 + (0.5^2)/2) = 13333.33 * 1.125 = 15000 W or 15 KW.
When one sideband is suppressed, the power is halved, so the power is now 15000 / 2 = 7500 W or 7.5 KW.
When the carrier component is reduced by 24dB, we convert the dB value to a ratio using the formula ratio = 10^(dB/10). So, the ratio = 10^(-24/10) = 0.0631.
The power is then reduced by this ratio, so the final power is 7500 * 0.0631 = 473.25 W.
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