Question

[5 Marks] uestion 1 A high frequency carrier is frequency modulated by a sinusoidal modulating frequency of 2 KHz, resulting in a frequency deviation of 7 Khz.Calculate the bandwidth of the modulated signal. a) [1 Mark] [1.Mark] 0.5 mark] 2.5 Marks] b) Explain how noise immunity is achieved in FM With aid of a neatly labelled illustration describe the Frequency Shift Keying c) Discuss the advantages and de merits of Frequency modulation d) [5 Marks] Question 2 n SSB transmitter operates at a frequency of 4.2 MHz using filter method. The voice frequency ange is 300 to 3400 Hz. a) In a block form draw this SSB transmitter b) Calculate the upper and lower sideband ranges. c) Calculate the approximate center frequency of a bandpass filter to select the lower sideband [1 Mark] [1.5 Mark] [1.5 Mark] [1 Mark] d) Define demodulation [5 Marks] Question 3 a) State the maximum power transfer theorem b) With aid of a circuit diagram describe the operation of a Hartley Oscillator e) To match a generator impedance of 6V to a 50-V load impedance, calculate the tuns ratio needed [1 Mark] [2 Marks) [1 Mark [1 Mark] With aid of a block diagram describe a radio transmitter d) -The End-

Answer 1

a) tom 21h Given tm= 2kH3 Af = 7KHZ We know that B- At- 743 B = 3.5 Since B B W = 2 (B+1) tm] BW= 2 (3.5+) 2k143 BW= 18 kH3 کل با I Noise 6) Noise immunity in FM FM is more immune to Noise & Noise is generally uniformly spread across the spectrum and varies randomly in amplitude IM systems are inherently immune to random by Noise, frequency & amplitude varies c) F«заnу wig by Here frequency of the Carrier is varied ording to the message signal FSK produlation is to a Voltage Converter frequency

Voltage Variations so vco is used to convert Variations in to to frequency data (vol tsk Esk f2 (ARE) I tve o eve ti= tot m(t) 2 to mark frequery I t space frequery tiz tetke on tiete- kg leton, ta , 2 Anamn fsk d) i) Advantages of Fm operate in very high frequency 11) Reduces adiacent channel interference i Noise may reduce by increasing deviation Dised demerits of fm. i) Bw is highes i used only at high frequently

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