GSM Signal – JSS2 Computer Hardware & GSM Repair Lesson Note (Second Term)

A GSM signal is the radio wave that carries your voice or message between your phone and the nearest cell tower. GSM stands for Global System for Mobile Communications.

Behavioural objectives

By the end of the lesson, students should be able to:

1. Define a signal and radio waves.
2. Explain the job of the antenna in a phone.
3. Describe the five steps a call takes from one phone to another.
4. State four things that weaken or block a phone signal.
5. Explain what the signal bars show.

What is a signal?

A signal is a piece of information, such as your voice or a text message, that has been turned into an electrical wave.

• Outgoing signal: your phone turns your voice into a radio wave and sends it into the air.
• Incoming signal: your phone catches a wave from the air and turns it back into a voice you can hear.

What are radio waves?

Radio waves are invisible waves that carry information through the air without wires.

• Invisible: we cannot see them with our eyes, but they move all around us.
• Carriers: they act like vehicles that carry your voice from one place to another.
• Needs an antenna: a phone needs an antenna to send and catch them.

What are signal bars?

Signal bars are the marks on the phone screen that show how strong the radio waves are where you are.

• Many bars: the signal is strong and calls are clear.
• Few bars: the signal is weak and calls may break or fail.
• No bars: the phone cannot catch any signal, for example in a basement or deep forest.
• Number of bars: most phones show up to 4 or 5 bars.

What is the role of the antenna?

The antenna is the part of the phone that sends and receives radio waves, like an “ear” and a “mouth”.

What are the types of phone antenna?

There are two types of phone antenna: external and internal.

• External antenna: a long stick poking out of the top, as on very old “brick” phones.
• Internal antenna: a small piece of metal hidden inside the casing, usually near the top or bottom, as in modern phones.

Why does the way you hold a phone matter?

• Hand position: your hand may cover the internal antenna and weaken the signal.
• Result: the bars may drop when you grip the phone in a certain way.

How does a signal travel from one phone to another?

A call passes through a base station (cell tower) and a switching centre before it reaches your friend’s phone.

• Base station: the “middleman” tower that catches and sends radio waves for phones nearby.
• Switching centre: a large computer centre that works out where the person you are calling is.

What are the steps of a call?

1. Your phone: you say “Hello” and your antenna sends out a radio wave.
2. The cell tower: the nearest tower catches your wave.
3. The switching centre: the tower passes the signal to the centre, which finds your friend.
4. The destination tower: the signal is sent to a tower near your friend.
5. Friend’s phone: that tower sends the wave to your friend’s antenna and the phone rings.

What things block or weaken a phone signal?

Metal, thick concrete, bad weather and long distance from the tower are the main things that block or weaken a signal.

• Metal: the biggest enemy of signals, because it reflects the waves away, as in a lift or a zinc building.
• Thick concrete: large, thick walls soak up the signal.
• Bad weather: very heavy rain or thunderstorms can scatter the waves and make a call crackly.
• Distance: far from the nearest tower, the waves become too weak for the antenna to catch.

How can you get a better signal?

• Move outside: go to an open place away from thick walls and metal.
• Go near a window: waves pass through glass more easily than through walls.
• Move your hand: hold the phone so that you do not cover the antenna area.
• Move closer to a tower: a shorter distance gives stronger waves.

What are the quick facts about GSM signal?

The table below gives each part of the signal system and its job.

Evaluation

1. Does a modern smartphone have an antenna? If yes, where is it?
2. Why does your phone signal get weak when you go into a deep room or a lift?
3. What is the name of the tall towers in our neighbourhoods that help our phones work?
4. True or False: Radio waves are visible to the human eye.

Assignment

Draw the path of a call from your phone to a friend’s phone in five labelled boxes. Then list three things that can block a phone signal.

Teacher’s note

• Outdoor activity: take students outside to spot a telecommunications tower (MTN, Glo, Airtel and others) in the distance.
• Key idea to explain: their phones are constantly “talking” to that tower.