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Consider a superheterodyne FM receiver designed to receive the frequency band of 1 to 30 MHz with an IF frequency 8 MHz. What is the range of frequencies generated by the local oscillator for this receiver? An incoming signal with a carrier frequency of 10 MHz is received at the 10 MHz setting. At this setting of the receiver, we also get interference from a signal with some other carrier frequency if the receiver RF-stage bandpass filter has poor selectivity. What is the carrier frequency of the interfering signal?

User Marlowe
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Final answer:

A superheterodyne FM receiver designed to receive the frequency band of 1 to 30 MHz with an IF frequency of 8 MHz will generate a local oscillator frequency range of -7 MHz to 38 MHz. If the receiver is set to receive a signal with a carrier frequency of 10 MHz the interfering signal could be any frequency within the range of -7 MHz to 38 MHz other than 10 MHz itself.

Step-by-step explanation:

A superheterodyne FM receiver is designed to receive the frequency band of 1 to 30 MHz with an IF frequency of 8 MHz. the local oscillator in the receiver is used to generate the intermediate frequency (IF) signal. to calculate the range of frequencies generated by the local oscillator we need to consider the upper and lower frequencies of the desired range. the upper frequency generated by the local oscillator is obtained by adding the IF frequency to the upper frequency of the desired band. so, the upper frequency is 30 MHz + 8 MHz = 38 MHz. the lower frequency generated by the local oscillator is obtained by subtracting the IF frequency from the lower frequency of the desired band. So, the lower frequency is 1 MHz - 8 MHz = -7 MHz. (Negative frequency indicates that the local oscillator signal is inverted.)

therefore, the range of frequencies generated by the local oscillator for this receiver is -7 MHz to 38 MHz. to determine the carrier frequency of the interfering signal, we need to assume that the interfering signal is within the range of frequencies generated by the local oscillator. Since the receiver is set to receive a signal with a carrier frequency of 10 MHz, the interfering signal could be any frequency within the range of -7 MHz to 38 MHz, other than 10 MHz itself.

Keywords: superheterodyne FM receiver, frequency band, IF frequency, local oscillator, carrier frequency, interfering signal

User Nandi
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