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Questions and Answers
Which factor is critical for determining the quality of unguided transmission media?
Which factor is critical for determining the quality of unguided transmission media?
What does higher bandwidth in a transmission medium typically result in?
What does higher bandwidth in a transmission medium typically result in?
What type of guided transmission medium has the lowest typical attenuation at 1 kHz?
What type of guided transmission medium has the lowest typical attenuation at 1 kHz?
Which of the following best describes crosstalk in a transmission medium?
Which of the following best describes crosstalk in a transmission medium?
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How does electromagnetic interference (EMI) affect communication lines?
How does electromagnetic interference (EMI) affect communication lines?
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What is the typical delay for coaxial cable at 10 MHz?
What is the typical delay for coaxial cable at 10 MHz?
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In guided media, what is the primary concern regarding the number of receivers?
In guided media, what is the primary concern regarding the number of receivers?
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Which transmission medium has the highest typical attenuation in dB/km?
Which transmission medium has the highest typical attenuation in dB/km?
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What does a higher Attenuation-to-Crosstalk Ratio (ACR) indicate?
What does a higher Attenuation-to-Crosstalk Ratio (ACR) indicate?
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What is the formula used to calculate the ACR?
What is the formula used to calculate the ACR?
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Which of the following is considered a good ACR value?
Which of the following is considered a good ACR value?
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What is a primary disadvantage of using a two-wire open line?
What is a primary disadvantage of using a two-wire open line?
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What role do pair twists play in twisted pair cables?
What role do pair twists play in twisted pair cables?
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Which type of transmission line is most commonly used for power lines?
Which type of transmission line is most commonly used for power lines?
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What material is typically used to insulate twin lead cable?
What material is typically used to insulate twin lead cable?
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In a twisted pair cable, which factor does NOT influence its characteristics?
In a twisted pair cable, which factor does NOT influence its characteristics?
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What is the main characteristic of Shielded Twisted Pair (STP) cables compared to Unshielded Twisted Pair (UTP) cables?
What is the main characteristic of Shielded Twisted Pair (STP) cables compared to Unshielded Twisted Pair (UTP) cables?
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Which of the following applications is least likely to utilize coaxial cables?
Which of the following applications is least likely to utilize coaxial cables?
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In what situation is an amplifier typically required for analog transmission with twisted pair cables?
In what situation is an amplifier typically required for analog transmission with twisted pair cables?
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What is a primary disadvantage of Unshielded Twisted Pair (UTP) cables?
What is a primary disadvantage of Unshielded Twisted Pair (UTP) cables?
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Which category of unshielded twisted-pair cables is typically employed for high-speed data center applications?
Which category of unshielded twisted-pair cables is typically employed for high-speed data center applications?
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Study Notes
Guided vs. Unguided Transmission
- Guided transmission uses physical media (wires); unguided uses wireless.
- Medium quality significantly impacts guided transmission; antenna bandwidth is key for unguided.
- Data rate and distance are primary concerns for both.
Design Factors
- Higher bandwidth allows for higher data rates.
- Transmission impairments include attenuation and interference.
- The number of receivers impacts attenuation, especially in guided media; multi-point connections increase attenuation.
Transmission Media Characteristics
- Twisted Pair (with loading): 0-3.5 kHz frequency range, 0.2 dB/km attenuation at 1 kHz, 50 µs/km delay, 2 km repeater spacing.
- Twisted Pair (multi-pair cables): 0-1 MHz frequency range, 0.7 dB/km attenuation at 1 kHz, 5 µs/km delay, 2 km repeater spacing.
- Coaxial Cable: 0-500 MHz frequency range, 7 dB/km attenuation at 10 MHz, 4 µs/km delay, 1-9 km repeater spacing.
- Optical Fiber: 186-370 THz frequency range, 0.2-0.5 dB/km attenuation, 5 µs/km delay, 40 km repeater spacing.
- Attenuation: Signal strength loss during transmission.
Electromagnetic Interference (EMI) and Crosstalk
- EMI reduces signal-to-noise ratio (SNR), limiting distance and transmission rates.
- Crosstalk is undesired signal influence from adjacent lines.
- Near-End Crosstalk (NEXT): Signal coupling near cable ends; higher NEXT (dB) indicates better performance.
- Attenuation-to-Crosstalk Ratio (ACR): Balances signal loss and crosstalk; higher ACR (typically ≥20 dB) indicates better performance; ACR = Attenuation – Crosstalk (dB).
Two-Wire Open Line and Twin Lead Cable
- Two-wire open line: Two wires spaced apart; simple but with high radiation loss and noise pickup. Used for power lines, telephone, and telegraph lines.
- Twin lead cable: Two-conductor flat cable; used for RF signals; good insulator at radio frequencies.
Twisted Pair Cable
- Wire size, insulation, and twist tightness determine characteristics.
- Pair twists help cancel NEXT; maintaining twists near termination is crucial.
UTP and STP Cables
- Unshielded Twisted Pair (UTP): Inexpensive, easy to install, susceptible to EMI.
- Shielded Twisted Pair (STP): Metal shielding reduces interference; more expensive and harder to handle.
Twisted Pair Applications
- Widely used in telephone networks (subscriber loops, PBX connections), LANs (10/100 Mbps), and higher-category cables for data centers (Gbps).
Twisted Pair Transmission Characteristics
- Analog: Requires amplifiers every 5-6 km.
- Digital: Uses analog or digital signals; repeaters needed every 2-3 km.
- Limited transmission distance.
Coaxial Cable
- Versatile medium used in television distribution, long-distance telephone transmission (being replaced by fiber), and short-distance computer links.
Coaxial Cable Transmission Characteristics
- Analog: Amplifiers needed every few kilometers, more frequently at higher frequencies (up to 500 MHz).
- Digital: Repeaters needed every kilometer, more frequently at higher data rates.
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Description
Test your knowledge on the differences between guided and unguided transmission media. Explore the characteristics, design factors, and various transmission media including twisted pair, coaxial cable, and optical fiber. Understand how these elements impact data rate, distance, and overall transmission quality.
