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.