GSM Network Section – SS2 Computer Hardware & GSM Repair Lesson Note (Second Term)

Class: SS2

Subject: Computer Hardware and GSM Repair

The network section of a phone is the group of parts that connects the phone to the mast (base station). It includes the antenna, which catches and sends radio waves, the RF IC, which translates radio waves into digital data, and the P.A. (Power Amplifier), which boosts the voice signal so it can reach the mast.

Behavioural objectives

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

• Describe the network section as the link between a phone and the mast.
• State the function of the antenna, the RF IC and the P.A.
• List the symptoms of a failing P.A.
• Carry out the SIM check, the manual search test and the internal cable check on a “No Signal” phone.
• Match common network fault messages to their likely causes.

What is the network section of a phone?

Imagine you are standing on one side of a river and your friend is on the other. To talk, you need a bridge or a very loud megaphone. In mobile communication, the Network Section is the “invisible bridge” that connects your phone to the “Mast” (Base Station).

When a phone shows “No Service” or “Searching,” it means the bridge is broken. The phone is either not “shouting” loud enough or it is “deaf” to the mast’s signal.

What are the main parts of the network section?

The antenna: the “ear and mouth”

The antenna is the part of the phone that catches the radio waves from the air and sends your voice back out.

• How it looks: In old phones, antennas were sticks that poked out. In modern smartphones, the antenna is a thin copper strip glued to the inside of the plastic back cover or a long, thin wire (coaxial cable) inside the phone.
• The “Human” Side: Think of the antenna like a radio’s aerial. If it is loose or dirty, the signal will be “shaky.”
• Common fault: If a phone only gets signal when you are standing right under the network mast but loses it inside a room, the Antenna Switch or the cable is likely loose.

The RF IC (Radio Frequency chip)

If the antenna is the ear, the RF IC is the part of the brain that understands what the ear is hearing. It is usually a square black chip located near the antenna points.

• What it does: It translates the “Radio Waves” from the air into “Digital Data” that the phone’s CPU can understand. It also does the reverse when you speak.
• The “Human” Side: It is like a translator. If the translator is sleeping or “confused,” you can have a perfect antenna, but the phone still will not know how to make a call.
• Identification: It is often shielded by a metal “can” (cover) to protect it from interference from other parts of the phone.

The P.A. (Power Amplifier): the “megaphone”

The P.A. IC is the muscle of the network section. Its only job is to take your voice and “boost” it so it is loud enough to reach a mast that might be 5 kilometres away.

Symptoms of failure:

1. The phone shows “No Service.”
2. The battery drains very fast when you try to make a call (because the P.A. is working too hard).
3. The phone suddenly turns off the moment you press “Call.”

Pro Tip: The P.A. is the most common part to fail after a phone is dropped or gets water in it.

How do you troubleshoot a “No Signal” phone?

When a student is faced with a “No Signal” phone, they should follow these steps.

Step A: The SIM check

Is the SIM card active? Is it inserted correctly? Sometimes the “SIM Pins” are bent, and the phone cannot even “talk” to the SIM card to start the network.

Step B: The “Manual Search” test

Go to Settings → Network → Manual Search.

• If it finds networks (MTN, Airtel, etc.) but will not join: The Antenna and RF IC are working, but the P.A. (Power Amplifier) is likely weak.
• If it finds NOTHING: The Antenna is disconnected or the RF IC is dead.

Step C: The internal cable

Check the thin “Antenna Wire” that runs along the side of the battery. If it is “unplugged” even a little bit, the signal will vanish.

Which fault message points to which cause?

Student practical activity

Take a working phone and wrap it tightly in several layers of aluminium foil. Try to call it. It will not ring. This is because the foil “blocks” the antenna. This shows you how important a clear “path” is for the antenna to work.

Evaluation

1. What is the network section of a phone?
2. State the job of the antenna, the RF IC and the P.A.
3. List three symptoms of a failing P.A.
4. A phone finds MTN and Airtel in a manual search but will not join either network. Which part is likely weak?
5. A phone only gets signal right under the mast and loses it inside a room. What is the likely fault?

Assignment

1. Explain why the battery of a phone with a faulty P.A. drains very fast when a call is made.
2. Using the table of network faults, state the likely cause and the fix for each of these messages: “Searching…” and “Emergency Calls Only”.