1. A lossless transmission has a shunt capacitance of 20 pF/ft and a series inductance of 180 nH/ft. Its surge impedance is
A. 36 . C. 95 .
B. 80 . D. 300 .
2. What is the delay introduced by 1 foot of the cable described in question 1?
A. 1.9 ns C. 6.0 ns
B. 3.6 ns D. 9.0 ns
3. What is the velocity of propagation of the cable described in question 1?
A. 5.26 108 ft/sec C. 1.9 109 ft/sec
B. 5.26 108 m/sec D. 1.9 10-9 ft/sec
4. A slotted line is used to measure the voltage maximums and voltage minimums on a transmission line with a characteristic impedance of 50 . The voltage maximum is measured as 7.5 V and the minimum is 5 V. The line is terminated with a purely resistive load. What is the load impedance?
A. 5 C. 25
B. 12 D. 75
5. The transmission line input impedance is equal to its characteristic impedance when
A. it's lossless.
B. it has finite length.
C. it's nonresonant.
D. its capacitance is equal to its inductance.
6. A TDR is being used to analyze a transmission line problem. The oscilloscope display shows a positive-going voltage step with a DC level equal to twice the input voltage at 2 ms. What can be determined from this display?
A. There's a short circuit at a point 2ms Vp from the source.
B. There's a short circuit at a point 1ms Vp from the source.
C. There's an open circuit at a point 2ms Vp from the source.
D. There's an open circuit at a point 1ms Vp from the source.
7. A short-circuited line less than /4 in length is the same as a(n)
A. capacitor.
B. inductor.
C. quarter-wave matching transformer.
D. stub tuner.
8. Television sets generally have two screw terminals connected to an internal two-wire transmission line at their antenna input. If coax is to be connected to the TV, how should it be done?
A. Through a quarter-wave transformer
B. Through a balun transformer
C. Connect each conductor to one of the screws
D. With a double-stub tuner
9. A 300 transmission line is terminated with an antenna that presents a (450 - j 600 ) load impedance. What is the normalized load admittance?
A. 0.002 + j 0.0016 C. 1.5 - j 2
B. 0.24 + j 0.32 D. 1 + j 1.7
10. How far from the load should a short-circuit stub be placed to match the load in question 9?
A. 0.07 C. 0.052
B. 0.25 D. 0.130
11. How long should the stub in question 9 be?
A. 0.085 C. 0.334
B. 0.18 D. 0.601
12. What is the VSWR before matching at the load described in question 9?
A. 0.38 C. 1.7
B. 1.00 D. 4.62
13. What is the VSWR after matching at the input of the transmission line in question 9?
A. 1.7 C. 0.55
B. 1 D. 0.38
14. An open-circuited line is seldom used as a tuning component. Why?
A. Open circuits are hard to construct.
B. Open-circuit tuning uses more cable than short-circuit tuning.
C. Open circuits tend to radiate.
D. Open circuits create an unbalanced condition.
15. Increasing the separation of the conductors in a two-wire transmission line will
A. decrease Z0.
B. increase Z0.
C. increase e (dielectric constant).
D. decrease e (dielectric constant).
16. A short-circuited line greater than /4 long appears as a(n)
A. capacitor. C. open circuit.
B. inductor. D. resistance.
17. A shorted stub is used instead of an inductor in tuners because of
A. cost considerations. C. superior selectivity.
B. space considerations. D. broader bandwidth.
18. A load of 100 + j50 is to be matched to a 50 transmission line using a /4 matching section. How much transmission line is needed between the load and the /4 matching section?
A. 0.038 C. 0.28
B. 0.138 D. 0.78
19. What should the characteristic impedance of the matching section be?
A. 130 C. 81
B. 120 D. 50
20. In high-power applications, excessive losses can cause poor performance of the system because
A. the energy is reradiated.
B. energy is lost to magnetic coupling.
C. there's too much resistance between the conductors.
D. transmitter energy is converted to heat.
21. A twisted-pair transmission line is suffering from crosstalk interference. What can be done to improve the performance?
A. Twist the cable tighter.
B. Remove some twists from the cable.
C. Increase the dielectric constant of the cable.
D. Use larger conductors.
22. Dielectric losses occur when
A. the conductor separation is too great.
B. the conductor separation is too small.
C. currents flow from one conductor to the other through the dielectric.
D. the cable is unshielded.