This is the Chapter 15: Cable Television end chapter exercise in Basic Television – Grob TV as one of the Electronics Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Exam Questions in Electronics Engineering field, Electronics Books, Journals and other Electronics References.
Start Grob TV End Chapter Exercise 15
Answers are Underlined
- a. The superband channel number just above VHF broadcast channel 13 is 23.
- b. VHF broadcast channel does a TV receiver with a cable converter stay tuned at 2, 3 or 4.
- a. The outer conductor of coaxial cable serves as a shield.
- b. Generally RG-59U cable is used for the drop line. T
- c. Thinner cable has greater losses. T
- a. The value of Resistance that was used to terminate RG-59U coaxial cable for impedance matching is 75 ohms.
- b. A line with more C per unit length has a lower Zo.
- c. Open ends of transmission line correspond to a parallel resonant circuit.
- d. The value of the VSWR when a cable is terminated in its Zo is 1.0.
- a. Cable losses increases at higher frequencies. T
- b. Coaxial cables have I2R losses.
- c. A 6-dB loss reduces the signal level by one-half.
- a. The head end of a cable system is the starting point of cable signals. T
- b. A trunk cable is the main line for cable signals. T
- c. The insertion loss is lower than the tap loss for line taps.
- d. A balun is used to match the 75-W coaxial cable to the 300-W receiver input.
- a. The reference level for the dBmV unit is 1 mV.
- b. The signal level of 2 mV in dBmV units is 6 dBmV.
- c. The signal level of 0.5 mV in dBmV units is –6 dBmV.
- a. Sync and blanking bars from another channel can be caused by overload distortion. T
- b. Losses increase with higher temperature.
- c. A slope-control circuit increases the amplifier gain for higher-frequency channels. T
- a. In two-way cable systems, the same cable for downstream and upstream signals.
- b. The upstream signal is in the band of 5 to 30 MHz.
- c. The poling signal is in the band of 107 to 119 MHz.
- a. The cable converter uses two local oscillators. T
- b. The video IF carrier in a cable converter is generally 612.75 MHz.
- c. The local oscillator for the up converter operates in the UHF range. T
- d. Each cable channel is selected by setting the frequency of the VCO for the up converter. T
- a. Wave traps to attenuate premium channels are usually located in the feed line to each subscriber.
- b. A scrambled channel usually has a picture that is out of sync, as evidenced by rolling and diagonal bars.
- c. A scrambles channel needs decoding pulses to restore the sync. T
- a. Supertrunks have the cable channels that are heterodyned down to lower frequencies.
- b. The frequency of 13 GHz is in the microwave band. T
- c. FM can be used for microwave links for television. T
- a. Fiber-optics cable has very low losses. T
- b. A light-modulated signal is limited to narrow bandwidth in the modulation. F
- c. Refraction means the bending of light waves. T
- d. Fiber-optic cable makes use of internal reflections of light. T
- e. Typical index of refractions: glass – 1.8, diamond – 2.4, water – 1.3
1. Which of the ff is a midband cable TV channel is A or 14.
2. Coaxial cable for distribution systems has an impedance of 150 ohms.
3. The cable converter output for the TV receiver is usually on channel 3.
4. A tap for the subscriber drop line has a high tap loss.
5. The most popular plug for the RG-59U coaxial cable is the F connector.
6. Which of the ff is true? Weak signal causes snow in the picture.
7. The upstream signal in two-way cable systems has the frequency of 5 to 30 MHz.
8. A typical value for the IF signal, in megahertz, for up-down cable converter is 612.75.
9. Frequency synthesis is used for the VCO in the up-converter.
10. For in-band descramblers, the decoding pulses are sent on the sound carrier.
11. A trunk cable run has a loss of –20 dBmV. To make up for this loss, the voltage gain of the next amplifier should be at least 10.