Sample Problems

Solved Problems About Characteristic Impedance 1. A coaxial cable with inner diameter of 5mm and an outer diameter of 9mm. Determine the characteristic impedance if the dielectric is polyethylene having Ɛ r = 2.3.

2. A transmission line has 2.5 pF of capacitance per foot and 100 nH of inductance per foot. Calculate its characteristic impedance.

3. A transmission line has 1.5 pF of capacitance per foot and 150 nH of inductance per foot. Calculate its characteristic impedance.

4. Determine the characteristic impedance of a transmission line which has a capacitance of 30pF/m and an inductance of 75nH/m

5. Two wires with air as a dielectric are one inch apart. The diameter of the wire is .04 inch. Calculate, approximately, its characteristic impedance.

Solved Problems About Attenuation per unit Length in Transmission Line 1. An open-wire line has an attenuation of 2.4 dB per 100 ft. The attenuation for 275 ft is

2. An open-wire line has an attenuation of 4 dB per km. The attenuation for 275km is

3. A certain transmission line has a loss of 12dB/miles. Find the attenuation for a length of 25 miles.

4. RG – 45 cable has an attenuation of 0.15 dB/m. Find the total loss in dB for 500m of RG -45 cable.

5. An attenuation of 1 Neper is equal to _____ dB

Solved Problems for Velocity Factor 1. TDR equipment receives the signal 250ns after the test signal had been transmitted. If the discontinuity of the line is found 55 meter from the test point, what is the velocity factor of the line?

2. If a coaxial cable uses plastic insulation with a dielectric constant r = 2.6 , what is the velocity factor for the cable?

3. If a cable has a velocity factor of 0.8, how long would it take a signal to travel 3000 kilometers along the cable?

4. If a cable has a velocity factor of 0.8, what length of cable is required for a 90° phase shift at 100 MHz?

5. Calculate the wavelength of a EM wave travelling in a certain transmission line if it has a velocity factor of 0.95 at frequency of 90MHz.

Solved Problems About Reflection Coefficient and SWR 1. A cable has a VSWR of 10. If the minimum voltage along the cable is 20 volts, what is the maximum voltage along the cable?

2. A lossless line has a characteristic impedance of 50 ohms, but is terminated with a 75-ohm resistive load. What SWR do you expect to measure?

3. If a cable has an SWR of 1.5, what will be the absolute value of its voltage coefficient of reflection?

4. A generator matched to a line with a voltage coefficient of reflection equal to 0.2 transmits 100 watts into the line. How much power is actually absorbed by the load?

5. The minimum voltage along a transmission line is 260V, while the maximum voltage is 390V. The SWR is

Solved Problems About Electrical Length 1. A 500 m transmission line has a relative permittivity of 2.5. A 200 MHz RF signal is transmitted using that transmission line. Compute the electrical length of the transmission line.

2. A 550 KHz RF signal is transmitted using RG-45 cable. The distance from the transmitted to the receiver is 200m. Calculate the electrical length of the transmission line if it has a velocity factor of 0.7.

3. A 110 m transmission line has a relative permittivity of 2.0. A 1200 MHz RF signal is transmitted using that transmission line. Compute the electrical length of the transmission line.

4. A 550 KHz AF signal is transmitted using RG-45 cable. The distance from the transmitted to the receiver is 200m. Calculate the electrical length of the transmission line. Assume that the AF signal is travelling at speed of light.

5. A 10 km transmission line has a relative permittivity of 1.5. A 10 MHz RF signal is transmitted using that transmission line. Compute the electrical length of the transmission line.

Closed Loop Systems 1.

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