Why this topic is important for ECET?
In ECET 2026, Data Communication & Computer Networks forms a vital part of the ECE syllabus. Understanding transmission media is essential because it decides how data signals travel in networks (wired or wireless). Questions often test basics like types, bandwidth, attenuation, formulas, and practical applications. Mastery here helps not only in ECET but also in real-life networking and job interviews.
📘 Concept Notes
1. What is Transmission Media?
Transmission media are the physical paths or channels through which data signals travel from sender to receiver.
It can be divided into:
- Guided Media (Wired) → Signals are guided through physical cables.
- Unguided Media (Wireless) → Signals transmitted through air, water, or vacuum.
2. Guided Media (Wired)
a) Twisted Pair Cable
- Two copper wires twisted together → reduces crosstalk.
- Types:
- UTP (Unshielded Twisted Pair) – cheap, used in LANs.
- STP (Shielded Twisted Pair) – reduced noise, more expensive.
- Example: Ethernet cables.
b) Coaxial Cable
- Central copper core, insulation, metallic shield, and outer jacket.
- High bandwidth, resistant to interference.
- Used in cable TV, broadband.
c) Optical Fiber Cable
- Uses light signals instead of electrical signals.
- Very high bandwidth (Gbps speed).
- Low attenuation, immune to EMI (Electromagnetic Interference).
- Used in long-distance communication, internet backbones.
3. Unguided Media (Wireless)
- Uses electromagnetic waves.
- Examples:
- Radio Waves (3 kHz – 1 GHz) → AM, FM, mobile networks.
- Microwaves (1 GHz – 300 GHz) → Satellite, Wi-Fi, radar.
- Infrared (IR) → Remote controls, short-range.
- Satellite Communication → Long-distance, global coverage.
4. Key Characteristics
- Bandwidth → Capacity of medium (optical fiber > coaxial > twisted pair).
- Attenuation → Signal loss over distance.
- Noise immunity → Fiber is best, twisted pair is weakest.
- Cost → Twisted pair cheapest, fiber costliest.
⚙️ Formulas
- Bandwidth of a channel:
Attenuation (in dB):
Propagation delay:
Data Rate (Nyquist Formula):
Wavelength relation:
🔟 10 MCQs
Q1. Which transmission medium provides the highest bandwidth?
a) Twisted Pair
b) Coaxial Cable
c) Optical Fiber
d) Radio Wave
Q2. Attenuation is measured in:
a) Ohms
b) Decibels (dB)
c) Hertz
d) Watts
Q3. A coaxial cable transmits at 10 Mbps with SNR = 1000. Bandwidth = 1 MHz. Find channel capacity using Shannon’s theorem.
Q4. Which of the following is immune to electromagnetic interference (EMI)?
a) Twisted Pair
b) Coaxial Cable
c) Optical Fiber
d) Radio
Q5. Propagation delay for 100 km optical fiber (velocity = 2 × 10⁸ m/s) is:
a) 0.25 ms
b) 0.5 ms
c) 1 ms
d) 2 ms
Q6. Which wireless band is widely used in Wi-Fi communication?
a) Infrared
b) 2.4 GHz and 5 GHz
c) 900 MHz
d) 60 GHz
Q7. In Nyquist formula, doubling bandwidth doubles:
a) Signal-to-noise ratio
b) Attenuation
c) Data rate
d) Delay
Q8. The wavelength of a 3 GHz microwave signal is:
a) 0.1 m
b) 0.3 m
c) 1 m
d) 3 m
Q9. Which medium is most commonly used in LANs?
a) Twisted Pair
b) Optical Fiber
c) Coaxial Cable
d) Satellite
Q10. Which of the following is an unguided medium?
a) UTP
b) Optical Fiber
c) Coaxial Cable
d) Radio Wave
✅ Answer Key
| Q No | Answer |
|---|---|
| Q1 | c |
| Q2 | b |
| Q3 | 9.97 Mbps |
| Q4 | c |
| Q5 | b |
| Q6 | b |
| Q7 | c |
| Q8 | 0.1 m |
| Q9 | a |
| Q10 | d |
🧠 Explanations
- Q1: Optical fiber supports Gbps speeds → highest bandwidth.
- Q2: Attenuation is expressed in decibels.
- Q3: Shannon capacity → C=1×106log2(1+1000)≈9.97MbpsC = 1×10^6 \log_2(1+1000) ≈ 9.97 MbpsC=1×106log2(1+1000)≈9.97Mbps.
- Q4: Optical fiber uses light, no EMI.
- Q5: t=d/v=100,000/2×108=0.5mst = d/v = 100,000 / 2×10^8 = 0.5 mst=d/v=100,000/2×108=0.5ms.
- Q6: Wi-Fi → 2.4 GHz & 5 GHz bands.
- Q7: Nyquist formula shows R∝BR ∝ BR∝B, so doubling B doubles R.
- Q8: λ=c/f=3×108/3×109=0.1mλ = c/f = 3×10^8 / 3×10^9 = 0.1 mλ=c/f=3×108/3×109=0.1m.
- Q9: LANs commonly use twisted pair (Ethernet).
- Q10: Radio waves travel unguided in air.
🎯 Motivation / Why Practice Matters
Transmission media questions in ECET are often direct and formula-based. Practicing ensures:
- Faster recall of Shannon & Nyquist formulas.
- Quick solving of attenuation, propagation delay problems.
- Avoiding silly mistakes in units (dB, ms, Mbps).
Regular practice gives you a competitive edge in ECET 2026, where time management is the key.
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