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. What is the intermediate frequency (IF) of your superheterodyne receiver? 2. W

ID: 2082677 • Letter: #

Question

. What is the intermediate frequency (IF) of your superheterodyne receiver?

2. What is the bandwidth of an AM signal?

3. What is the envelope of an AM signal?

4. A standard AM broadcast station is allowed to transmit modulating frequencies up to 5

    kHz. If the AM station is transmitting on a frequency of 980 kHz, compute the

    maximum and minimum upper and lower sidebands and the total bandwidth occupied

    by the AM station.

5. An AM transmitter has a carrier power of 30 W. The percentage of modulation is

     85 %. Calculate the following:

the total power.

the power in one sideband.

Explanation / Answer

5)

a) Total power

Pt=30(1+(.85^2)/2)=40.8375W

b) Power in one side band

Plsb+Pusb=Pt-Pc=40.8375-30= 10.8375W

Pssb=10.8375/2 = 5.4188W

2) Bandwidth of AM Signal = 60MHz

4) Maximum Frequency fUSB = 980 + 6 = 986 kHz

Minimum Frequency fLSB = 980 - 6 = 974 kHz

Bandwidth BW = fUSB - fLSB = 986 - 974 = 12 kHz

(or) = 2(6 kHz) = 12 kHz

1) IF is a fixed RF frequency . The receiver after the IF section has to deal with only one carrier frequency of IF. That is the beauty of it. All the different received station carrier frequencies are down converted to this single IF carrier which the receiver is happy to easily demodulate and present to the output.