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InterviewSolution
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Write a note on choice of local oscillator frequency. |
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Answer» If the frequency of local oscillator is higher than the required signal frequency, then maximum to minimum capacitance ratio required by the variable capacitor is 4.4:1 But the tuning capacitors available commercially have a capacitance ratio of 10:1. If the oscillator frequency is kept lower than the signal frequency, the maximum to minimum capacitance ratio required is 158:1. It is not practicable to make a tunable capacitance with this type of range. Hence the local oscillator frequency is made higher than the signal frequency in all AM receivers. |
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