Service Technician 3
A distribution amplifier requires a specific power input to function. How much Dc power is provided by the B+regulated DC voltage power supply?
+24 volts DC
What is the approximate forward voltage drop of a silicon diode
0.7 volts
What is the proper way to express a signal voltage of 10 mV in cable TV terms
20log (10mV/1mV)=10 dBmV
The output port RF signal level is ______dBmV at 50 MHz and the tap port signal level is __________ dBmV at 50 MHz for a two way feed through tap when (1) the input port signal level is 30.5 dBmV at 50 (2) the insertion loss is 3.3 dB at 50 MHz, and (3) the tap loss is 7.6 dB at 50 MHz
27.2 and 22.9
What is the downstream output port signal level for a directional coupler when (1)the input signal level is 35.0 dBmV, (2) the output port insertion loss value is 1.4 dB?
33.6 dBmV
How many electrons does silicon have in it's outer shell?
4
Calculate the capacitive reactance of a power inserters feed-through capacitor when (1) the frequency is 50 MHz and (2) the capacitance value is 1000 pF
5.30 Ohms
What would be the voltage drop across a cable 1,240 feet away from a 60 VAC power supply if the cable is .625 inch with a resistance of 1.1 ohm per 1000 feet, conduction 4 amperes?
5.5 VAC
What is the voltage into amplifier B the second amplifier in cascade, under the following conditions? Each amplifier draws 1.5 amps of current the output of the 60 VAC power supply is inserted 1.188 feet from the input of amplifier A on the output of amplifier A is 1320 feet of cable feeding amplifier B. The cable have the same resistance of 1.1 ohm per 1000 feet
53.9 VAC
What is the AC input voltage of a power inserter when (1)the cable between the power supply and the power inserter is 200 feet long (2) the cables loop resistance is 1.07 Ohms/1000 feet (3) the power supply output voltage is 60 VAC and (4) the total current requirement is 11.4 amps
54.92
How much intermodulation distortion degradation is created when two line extender amplifiers with similar distortion characteristics are in cascade?
6 dB
Which of the following directional coupler values will exhibit the highest output insertion loss?
7 dB
What is the tap port RF signal level at 550 MHz for a four way terminating tap when (1) the preceding taps output port signal is 25.0 dBmV at 550 (2) the cable length between the two taps is 110 feet (3) the cable loss rate specification is 1.82/100 feet at 550 and .54/100 at 50 MHz and the tap loss is 14.2 dB at 550 MHz
8.8 dBmV
Which tool do you use to measure the input current on the input wiring?
A Clamp-on Ammeter
In a conventional axial leaded diode (one with a cylindrical body and leads coming out either end) the cathode is usually denoted by
A band around the body of the diode
In a line extender, which component is used to correct positive tilt?
A cable simulator
What is one type of device used for output surge protection on a ferroresonant transformer?
A crowbar circuit
What does the output waveform of a ferroresonant transformer most closely resemble at maximum load?
A sine wave
Which tool do you use to accurately measure the output voltage of a ferroresonant power supply?
A true RMS (root mean square) DMM
Automatic level control (ALC) and thermal control are two methods used to maintain consistent signal levels in line extenders which type of application requires the use of one of these methods?
Aerial installation
Shorts in the coaxial cable and excessive amounts of current can damage the distribution amplifier. Several devices can be used to protect the distribution amplifier from these problems. Which device shorts to ground when a overvoltage situation occurs?
An FTEC (Fast Transfer Electronic Crowbar)
There are several passive components in a distribution amplifier. Each component changes the signal in a different way. Which component reduces the signal equally at all frequencies
An attenuator pad
Which type of distribution amplifier gain control maintains the amplifiers RF output at a set level if the input levels to the amplifier change (within design tolerances)?
An automatic gain control (AGC)
In a standby ferroresonant power supply, what device keeps the battery powered AC power from feeding back to the utility?
An isolation relay
When you service a line extender you measure AC and DC voltage levels. Where do you measure the AC ripple?
At the B+ test point
You are performing periodic maintenance on a standby ferroresonant power supply. Where should you measure the output current?
At the stinger wire.
On cable system design maps, standard symbols include a
Circle for a two-way tap, a square for a four-way tap, and a hexagon for an eight-way tap
As you work with distribution amplifiers on the cable system you must be aware that what you do can affect the various types of signal distortions. What type of distortion is defined as "an interfering beat whose frequency is +/- 75Mhz or 1.25 MHz from the video carrier frequency?
Composite second order (CSO)
A distribution amplifier is housed in a die-cast aluminum housing. What is another item that can be mounted to the housing cover that connects to the distribution amplifier?
DC power supply
In order to form a junction diode, you put p-type and n-type smeiconductor materials abutting each other. When you do, then some electrons cross the junction, as do some holes. The region occupied by the holes and semiconductors that have crossed the junction is referred to as the ______ region
Depletion region
What are the basic types of electronic circuit grounds we might encounter in a modern electronic circuit?
Earth ground, chassis ground and signal ground
Which of the following is better at making an extrinsic semiconductor a conductor?
Electrons and holes are equally important
Which of the following statements is true?
For each power inserter, the system design must ensure that (1) the current required by any one RF/AC port does not exceed that ports power-passing specification and (2) the current required by both RF/AC ports does not exceed the AC input port power-passing specification
An RF/AC bypass tap
Has the added feature of being able to maintain RF signal and AC voltage continuity during faceplate removal
Which of the following statements is true?
In general, the closer the tap is to the amplifier output port the higher the tap value
which of the following is the least important characteristic of an intrinsic semiconductor?
Intrinsic semiconductors are typically made of silicon material
The terminating tap
Is the last tap installed at the end of the feeder cable run
Which of the following describes a power inserter
It contains a high-pass filter network that passes RF signals between the two RF/AC ports and blocks 60-Hz 60 VAC between the same two ports.
Which characterizes a feed-through tap?
It has a directional coupler portion that efficiently routes most of the signal to the output port while removing a small amount of the signal and passing it to the splitter network
Line extenders can be powered from the cable system or from a 120 VAC source. Which of the following statements about line extender power sources is true?
Line extenders powered by the cable system can pass current to other devices
When you are installing or troubleshooting a distribution amplifier, what should you do to make sure that there is a flat frequency response coming from the amplifier?
Make sure the cover plates are tightened.
As the RF signal travels on the coaxial cable one portion of the signal may be attenuated more than the others. What term is used to describe a situation where cable attenuation is low causing signal levels to remain greater at the higher frequencies than at the lower frequencies?
Positive tilt
What are the three most common components of an atom, and where are thy located in the atom?
Protons and neutrons are located in the nucleus of the atom, and electrons are located in orbit around the nucleus.
Unity gain is achieved when the signal strength along a cable is maintained at a specific level by the amplifiers. If the gain generated by an amplifier is too high, what will the most likely result?
Signal distortion
Which of the following is created by an amplifier module?
Slope
Signal attenuation between two individual customer tap ports at a specific frequency, with all other ports terminated, is the definition of
Tap-to-tap isolation
Reverse test alignment is used to adjust which of the following signal types?
Test signals from the field to the headend.
current exists in a diode when which condition obtains?
The anode is more positive than the cathode.
Which statement characterizes a directional coupler?
The downstream signal level is greater at a 7 dB tap port than at a 12 dB tap port with the same input signal level
Many factors influence signal attention. what is the effect of temperature on cable signal attenuation?
The higher the temperature, the greater the cable signal attenuation
What does the configuration of the directional coupler faceplate and housing enable?
The housing can be installed in any orientation, regardless of the direction of signal flow
What is the valence band?
The outer layer, or shell, of electrons surrounding a nucleus
Which of the following distribution amplifier parts is controlled manually?
The response control
Tap loss is
The signal attenuation between the input port and each tap port at a specific frequency
What are two reasons why the output signal level from a directional coupler is less than the input signal level?
The signal power sent to the tap port is not available to go to the output port, and the loss in the transformers and other parts of the directional coupler
Three components of the tap housing (and not the tap faceplate) are
The threaded mounting tap, seizure screw mechanisms, and right angled input and output ports
In a ferroresonant transformer , what part regulates the load on the secondary winding?
The transformer Shunts.
Which type of signal level control uses passive circuitry to maintain a constant output signal level on a line extender?
Thermal control
What is the state of the RF signals in a line extender when they are fed into the pre-amplifier?
They are in a flat state
The are three filtering networks in a power inserter. What is the purpose of the high-pass filter?
To prevent the 60 VAC or 90 VAC from passing between the two RF/AC ports