Radio,Television And Electronic Paper 3, WASSCE (SC), 2017

Question 1

  •  

    AIM: To test candidates knowledge of the components in a Radio receiver set.

    • You are provided with a Radio receiver.
    • State the specification of the Radio receiver in terms of:
      (i) model;

    (ii)input supply voltage;

    • frequency bands received;
    • output audio power.
    • Let the supervisor open the back cover of the Radio set.
    • List two tools used be the supervisor in opening the back cover.
    • Identify and record in Table 1, five:
    • active components;
    • passive components.

                                                         Table 1

    S/N

    Passive Components

    Active Components

    1

     

     

    2

     

     

    3

     

     

    4

     

     

    5

     

     

    • State the ratings in the loudspeaker in terms of:
    • resistance;
    • power rating.
    • State the components responsible for tuning the Radio receiver to desired stations.
    • State the components responsible for setting appropriate voltages in the circuit.
    • List the components responsible for audio output.
    • State two precautions taken in carrying out the activities listed.

Observation

 

(b) (i) Model

  • 5X-468
  • RX-608ACW
  • F-89
  • Any other acceptable model number.

      (ii) Input supply voltage

  • 220V – 240V a.c.
  • 12V d.c.
  • 9V d.c.
  • 6V d.c.
  • 3V d.c.

      (iii) Frequency bands received

  • FM  (88 – 108 MHz)
  • MW (540 – 1605 kHz)
  • SW (3 – 27 MHz)

      (iv) Output audio power – 3W – 80W (varies with size)      

(d) Tools for removing radio receiver back cover

  • Screw drivers
  • A pair of pliers/long nose pliers

(e)                                                        Table 1


S/N

Passive components

Active components

1

Resistor

Crystal diode

2

Capacitor

Transistor

3

Inductor

Integrated circuit

4

Switch

Zener diode

5

Fuse

Light Emitting Diode (LED)

6

Potentiometer

Operational amplifier

7

Antenna

Varicap diode

8

Air/variable/gang capacitor

Voltage regulator

9

RF transoformer

 

10

Power transformer

 

 (f) (i) Resistance - 4Ω - 8Ω                                                                                             
(ii) Power rating – 0.5W – 3.0W

(g) Components responsible for tuning radio receiver to desired station

  • Inductors/coils
  • Variable/gang capacitor
  • Antenna
  • Radio frequency transformer
  • Capacitor

 

(h) Components responsible for setting appropriate voltages

  • Resistor/potentiometer/variable resistor
  • Zener diode
  • Voltage regulator I.C.
  • Transformer
  • Electrolytic capacitor
  • Crystal diode
  • transistor      

       
(i) Components responsible for audio output

  • Transistors
  • Integrated circuits
  •  Resistors
  • Capacitors
  • Transformers     

                                                                 
(j) Precautions in carrying out the activities

  • I ensured the use of the right tools for the right jobs
  • I removed power source before opening the back of the receiver
  • I ensured that the high voltage capacitors were discharged.
  • I prepared the work area before starting work.
  • I wore necessary protective clothing.

                                                                
The candidates were expected to read off the specification of the Radio receiver from its back cover and quite a majority of them did just that. Some candidates listed a few passive components that cannot be found in a Radio receiver.