CDC 3D153 v1 Flashcards
(269 cards)
1
Q
Name the AM signal that does not fluctuate in amplitude by the modulating signal.
A
The carrier.
2
Q
What are the two primary purposes for modulating a signal?
A
- Ease of radiation.
2. Channel allocation.
3
Q
What must we do first to radiate a signal over long distances?
A
The signal must first be converted to analog format using modulating techniques.
4
Q
What frequencies do the amplitude modulated waveform contain?
A
The carrier frequency, carrier plus the modulating frequency (USB), and carrier minus the modulating frequency (LSB).
5
Q
What part of the modulated carrier wave contains the information carrying component?
A
The sidebands.
6
Q
In AM, what is the relation between the bandwidth required to transmit the signal and the frequency of the modulating signal?
A
Two times the modulating signal frequency.
7
Q
Define “percent of modulation.”
A
It refers to the amount of effect or change that the intelligence has on the carrier.
8
Q
Find the % mod if a 4V pk-pk RF signal is modulated by a 2.5 V pk-pk audio signal.
A
The percent of modulation is 62.5 percent. %mod= A/R * 100
9
Q
If a signal has an E max of 50m Vrms and an E min of 5m Vrms, what is the % mod?
A
81.8% …….
10
Q
What are the two results of overmodulation?
A
- Severe distortion.
2. Increase bandwith of an AM signal.
11
Q
What determines the amount of divination of a FM carrier?
A
The amplitude of the modulating signal.
12
Q
How does the rate of deviation relate to the frequency of the modulating signal?
A
They are directly porportional.
13
Q
To prevent interference with other FM stations, who establishes limits on the maximum amount of deviation in FM?
A
The FCC establishes the maximum amount of deviation.
14
Q
What is a significant sideband?
A
A sideband that contains at least 1% of the total transmitted power.
15
Q
How do you determine the modulation index in FM?
A
By dividing the amount of frequency deviation by the frequence of the modulating signal.
16
Q
Where do FM sidebands get their power?
A
From the unmodulated carrier.
17
Q
What is the relationship between modulation index and sideband power?
A
A higher modulation index means more power in the sidebands. It is even possible to have all the power in the sidebands and none in the carrier. At this point, any futher increase in modulation would start taking power from the sidebands and placing it back in the carrier resulting in a redistribution of power.
18
Q
In PM, what effect does the change in carrier frequency have?
A
None. The frequency change in PM is incidental.
19
Q
Describe the effect the positive and negative alterations of a modulating signal have on the phase of the carrier in PM.
A
During the positive alteration of a modulating signal, the phase of the carrier lags behind the unmodulated carrier. During the negative alteration it leads the unmodulated carrier.
20
Q
When is the carrier at its rest frequency in PM?
A
During the constant amplitude part of the modulating frequency.
21
Q
What part of the modulating signal controls the amount of phase shift in PM?
A
Amplitude.
22
Q
What part of the modulating signal controls the rate of phase shift?
A
Frequency.
23
Q
What is the advantage for using QPSK over BPSK?
A
QPSK has faster data rates, doubling the data carrying capability over BPSK.
24
Q
How can higher levels of PSK be achieved?
A
By using smaller phase shifts to allow for more phase shifts and increase capability as each shift represents more bit combinations.
25
Define the term "digitization."
The process of converting analog signals into digital signals.
26
Name the four steps of PCM.
1. Band limiting.
2. Sampling.
3. Quantizing.
4. Encoding.
27
State the main purpose of the band-limiting filter.
It ensures the input to the sampler never exceeds a maxinum frequency.
28
Define sampling.
Converting a continuous time signal into a discrete time signal.
29
What part of the pulse train is varied using PAM, PWM, and PPM?
```
PAM = amplitude.
PWM = with or duration.
PPM = position.
```
30
What is the Nyquist sampling rate?
Taking samples at twice the highest frequency in the bandlimited signal.
31
Which step of PCM assigns discrete amplitude values to the sampled amplitude valuse?
Quantization.
32
Name the two methods of quantization.
1. Uniform quantizing.
| 2. Non-uniform quantizing.
33
Which method assigns amplitude values based on equal amplitude range?
Uniform quantizing.
34
With ATM, what is the length of each transmission unit?
One character in length.
35
What part of an ATM transmission tells the receving device that a character is coming and that the character has been sent?
The start and stop bits.
36
How does the receiving device determine whether it has received a correct character?
By summing the 1 bit. If the characters arrives with an even number of 1 bit, the device assumes that it has received the correct character.
37
What is an advantage of synchronous transmission over asynchronous transmission?
To reduce the overhead cost of data transmission.
38
How does synchronous transmission differ from asynchronous transmission?
Synchronous transmission blocks many characters together for transmission.
39
What does VRC check each incoming character for?
Odd or even parity.
40
In LRC, what transmitted character does the receiver use to determine if a transmission was error-free?
Block Check Character (BCC).
41
When using the checksum method error detection, what binary number is used to divide the sum of all the characters in order to derive the checksum?
255.
42
How does the CRC method of error detection determine the dividend when computing the BBC?
CRC treats the binary ones and zeros in the frame address, control, and information fields as one long binary number.
43
How effective is CRC at detecting errors in most applications?
99% in most applications.
44
How does ARQ work?
The receiver automatically sends a retransmittial request to the sender if it finds an error in a received frame.
45
Using FEC, at which end of the transmission link are errors corrected?
The receiving end.
46
Using FEC, what is the transmitter's function in error correction?
To transmit multiple copies of the same message to the distant end.
47
Using FEC, what is the reciever's function in error correction?
Compare all copies of the transmitted message, then reconstruct thee message using the good portions of the message copies received.
48
What are the three basic components that make up a fiber optics link?
1. An optical transmitter.
2. A transmission medium.
3. A detector or optical receiver.
49
Name three components that make up the optical transmitter?
1. A driver.
2. An optical source.
3. A Fiber Optics (FO) pigtail.
50
Waht are the three main types of light sources for optic waveguides?
1. LED.
2. Semiconductor laser diode LD.
3. Non-Semiconductor laser diode (LD).
51
Give the three main requirements of a light source.
1. Operating speed or rise time must be fast enough to meet the application's bandwidth (BW) requirements.
2. Must provide enough optical power through the fiber to operate the detector.
3. It must produce a wavelength that takes advantage of the fiber's long-loss propagation characteristics.
52
What are the advantages of LED's over lazers?
Small size, ruggedness, capability of single and direct modulation, reduce expense, and spectral match with both fiber waveguides and silicone photodetectors.
53
What are the two basic designs of LED's?
1. The edgeemitter.
| 2. The surface emitter.
54
How are lasers different from LED's?
LED's differ from lasers in that their light output in incoherent and the laser's is coherent.
55
How are lasers' output power measured?
Milliwat.
56
What are lasers sensitive to?
Temperature.
57
What factors limit a detector's performance?
Dispersion or attenuation.
58
What two factors control the light signal that is received by the detector?
1. Noise floor (noise equivalent power).
| 2. The Signal to Noise Ratio (SNR).
59
What terms refer to the relationship between the signal and noise?
Signal to Noise Ratio (SNR) and Bit Error Rate (BER).
60
Upon what does a detector's responsitivity depend?
Wavelength of the light.
61
What are the two main types of photodetectors?
1. Positive Intrinsic Negative (PIN) diode.
| 2. The Avalanche Photodiode (APD).
62
For what type of application are Avalanche Photodiodes (APD) ideally suited?
High-speed, long-distance applications.
63
What are the purposes of repeaters in a fiber optics communication link?
To extend the distance and to preserve signal integrity.
64
How do regenerators work?
Regenerators receive incoming low-level, dispersed (distorted) digital pulses. After conversion to the electrical domain, the pulses are regenerated (the leading and falling edges are sharpened and the pulses are amplified). Finally the regenerated pulses are retransmitted optically.
65
Which repeter device does not require converting to and from the electrical domain for amplification.
Optical amplifier.
66
Describe the diffrences between a fiber optic patch cord, pigtail, and breakout cable.
A fiber optic patch cord is a short section of single fiber cable with a connector on each end. Each end is connected to a patch panel to connect circuits together. Pigtails are similar to patch cords but they only have a connector on one end, the other end is spliced into the fiber optic cable. Breakout cables are similar to pigtails but they are spliced into multifiber cables.
67
Which fiber optic connector has a conical shape?
Biconic connector.
68
Which fiber optic connector uses push-pull arrangement for mating?
SC connector.
69
Which fiber optic connector is used in high-vibration enviroments?
FC connector.
70
Which fiber optic connector is most widely used for LAN and premise wiring?
ST connector.
71
Which fiber optic connector uses threaded coupling nut without a keying device?
SMA connector.
72
Which fiber optic connector uses a quick-release keyed bayonet coupling?
ST connector.
73
Which fiber optic connector was the first to be used on single mode fiber optic cable?
Biconic connector.
74
What are "tunable" fiber optic connectors?
The keying slot in the connector can be rotated to find the optimal alignment.
75
Why are SC fiber connectors better for use in high-density applications than other types of connectors?
The other types of connectors require room to twist them for alignment. SC connectors use a push-pull arrangement and do not need this extra room.
76
What activity must occur to produce an EMP?
Nuclear explosion.
77
Which two elements produce the EMP effects?
1. Gama rays.
| 2. Secondary neutron radiation.
78
What are the electromagnetic pulse forms produced by the derived environment?
1. HEMP
2. SGEMP
3. SREMP
79
Why is high-altitude EMP environment protection important for critical, time urgent mission
systems?
It can affect many systems simultaneously.
80
Why is system-generated EMP a problem for satellites and reentry vehicles?
They are directly exposed to the nuclear radiation thrown from high-altitude bursts.
81
What are the two distinct regions of importance for SREMP?
1. Source.
| 2. Radiated.
82
What effects on communications are there after a nuclear detonation?
Scintillation and blackout.
83
What capabilities can be employed by Milstar to mitigate communications loss within a
contaminated area?
Crosslink.
84
Describe the difference between long-line and local effect of EMP on facilities?
Long-line effects are the currents and voltage induced on long power lines, communication cable links, or even other conductors, such as pipelines. Some EMP effects may be induced far away and guided facility shield, building structure, wiring, equipment cabinets, and so forth.
85
How can a facility be survivable against EMP?
To create an EMP survivability facility, it should be shielded as much as possible. Furthermore, all openings to the facility need to be filtered and protected. The facility also needs to be isolated from any external electric EM propagation in the earth.
86
What happens in an EMP induced event?
Can cause magnetic or electric field to be induced in an electrical circuit that can cause an error in the response of the circuit.
87
Why is bonding important in EMP protection?
To ensure a mechanically strong, low impedance interconnection between metal objects.
88
Where should all metallic penetrations entering the protected area be located?
At a common location.
89
To reduce coupling into susceptible circuits, what element is installed on both signal and power
lines?
Filters.
90
What is EMI?
It is any electromagnetic disturbance that interrupts, obstructs, or otherwise degrades or limits the effective performance of electronics/electrical equipment.
91
How do you differentiate an unintentional interference from jamming signal?
Unintentional interferance normally travels only a short distance; a search of the immediate area may reveal the source of this type of interference. Moving the receiving antenna for a short distance may reveal the source of this type of interference. Moving the receiving antenna for a short distance may cause
92
What type of EMI occurs when an unwanted carrier frequency follows the normal signal path
through the effected receiver?
Co-channel.
93
How can you eliminate broadband transmitter noise?
By using a band pass filter.
94
What type of equipment often generates many spurious emissions?
Receiver responding to off frequency signals.
95
What type of equipment often generates many spurious emissions?
Rapid tuning transmitter.
96
What intermodulation frequency components can cause EMI in the receiver/transmitter?
Sum and difference.
97
What type of intermodulation can have a very large bandwidth and cause more severe
interference problems than intermodulation products created in either transmitters or receivers?
Rusty bolt.
98
What type of EMI occurs when high level radiated signals penetrate and induce a radio frequency voltage in the internal circuits of a system or equipment?
Brute force.
99
What AM receivers are particularly susceptible to power line noise?
HF and VHF.
100
Relays may cause interference inside receivers because of broadband radiated noise originating
from what?
The opening and closing of the contacts.
101
How would you normally eliminate electromagnetic interference caused by sodium and mercury
vapor lights?
Installing a new bulb.
102
What is the purpose of the AFSIR program?
Document and resolve spectrum interference problems.
103
Under the AFSIR program, what organizational level must begin an investigation to identify the
source of EMI?
Lowest unit level.
104
Why must you ensure maintenance personnel responsible for the affected equipment check it
before submitting an EMI report?
To ensure the equipment is not causing the problem.
105
How do you confirm an EMI problem?
Check with other users of the same frequency and determine whether they receive the EMI.
106
If your EMI sounds like noise, what are the possible sources of these interferences?
The source may be power lines, welding equipment, and so forth.
107
Who is responsible for recording specific information concerning EMI?
The operator.
108
What types of EMIs are exempt from AFSIR reporting?
USAF units under the operational control of a combatant command, transient EMI from natural sources, suspected or confirmed cause of interference from space weather, interference is only experienced aboard ISR aircraft aloft and is localized when mission equipment or payload equipment is turned on/off or used, and If EMI is only affecting frequencies assigned on a noninterference basis for training purposes.
109
How should an AFSIR report be submitted?
All reports are submitted through their chain of command, through MAJCOM, and to the AFFMA.
110
What document contains guidelines for classifying EMI reports?
CJCSI 3320.02B, JSIR.
111
What service provided by the 85 EIS analyzes and recommends corrective actions for reported
EMI problems?
QFIRC.
112
What is the objective of the JSIR program?
Report and assist with the resolution of EW and recurring EMI.
113
Who maintains a central database of EMI cases, resolutions, and lessons-learned for all DOD
EMI?
JSC.
114
Which control do you use to select the meter’s different measurement functions?
The rotary switch.
115
List the four types of information presented in the multimeter’s display section.
1. Digital display.
2. Visual annunciators.
3. Analog bar graph.
4. Range indicator.
116
Which information in the display section shows the absolute value of the input?
Analog bar graph.
117
Describe the function of the range push button.
Lets you manually select the measurement range.
118
What is the purpose of the touch-hold push button?
Locks the measurement into the display for viewing and automatically updates the display when you take a new measurement.
119
List the multimeter’s four input jacks.
1. Amperes.
2. Milliamps/microamps.
3. Volts/ohms/diode.
4. Common.
120
When does the 8025A perform a power-up self test?
When you move the rotary switch to any position from the OFF position.
121
What two ranges of DC voltages can you measure using the 8025A multimeter?
1. −1,000 to +1,000 volts DC.
| 2. −320 to +320 millivolts DC.
122
What is the maximum amount of continuous AC current that you can measure with the
multimeter?
10 amps.
123
When using the Fluke 8025A, how do you know you’re in the resistance measurement function?
The Ω annunciator is showing in the display.
124
How do you determine if you’re testing a “good” diode with the 8025A?
Placing the leads across a “good” diode produces “OL” in the display while reversing the leads produces a continuous audible tone.
125
What type of display does the oscilloscope present?
Amplitude vs. time.
126
On which axis of an oscilloscope is voltage, time, and depth information presented?
Voltage = vertical axis, time = horizontal axis, and depth = intensity.
127
What is the purpose of the delay line at the input of the vertical amplifier?
It allows the sweep generator circuitry time to start a sweep before the signal reaches the cathode ray tube vertical deflection plates. This enables you to view the leading edge of the signal waveform.
128
What position of the input coupling switch is used to view digital-type or square wave signals?
DC coupling.
129
What is the basic purpose of the oscilloscope probe?
To provide isolation for scope inputs and prevent circuit loading.
130
List four types of probes?
1. The high resistance.
2. Passive divider and x1 probes.
3. Active (field effect transistor).
4. Current probes.
131
What is the typical input impedance of most oscilloscopes?
One megaohm shunted by 20 pF of capacitance.
132
When making an amplitude measurement and the source impedance is unknown, greatest
accuracy is achieved when the probe’s Z is what?
Highest (maximum).
133
What is the biggest difference between digital storage oscilloscopes and analog scopes?
Digital storage oscilloscopes digitize the input signal for storage or display.
134
What is the function of charged coupled devices in the digital storage oscilloscope’s signal
sampling process?
Charged coupled devices accept fast-changing data and send it to the analog-to-digital-converter at a slower rate for more accurate data collection.
135
Define the following waveform storage terms: Waveform points.
Sampled data points stored in the digital storage oscilloscopes memory.
136
Define the following waveform storage terms: Waveform record.
Stored waveform points that make up the waveform record.
137
Define the following waveform storage terms: Record length.
Number of waveform points used to make the waveform record.
138
What advantage does retrieving data from memory have on the cathode ray tube?
It allows the cathode ray tube to receive data at a slower rate as opposed to keeping up with some of the high frequency signals fired directly on a cathode ray tube in an analog scope.
139
List two digital storage oscilloscope sampling techniques.
1. Real-time.
| 2. Repetitive-sampling.
140
Define interpolation.
This is a process that estimates what the signal will look like between samples and “fills in the blanks” between data points.
141
What are the two types of interpolation?
1. Linear.
| 2. Sine.
142
What is the difference between sequential and random sampling?
Sequential sampling takes a sample at a predetermined time after the trigger in a progressive order until there are enough data points to reconstruct several periods of the signal. Random sampling takes samples at an undetermined point on a signal and stores them.
143
What is a common cause of aliasing?
Undersampling due to having the time base turned down too low, thus reducing the sample rate for a frequency that is too high for a given setting.
144
Describe the three types of acquisition modes.
1. In sample mode, the digital storage oscilloscope creates a record point by saving the first sample in a collection of sample points.
2 In peak detect mode, the digital storage oscilloscope saves the highest and lowest points in a collection of samples.
3. In averaging mode, the digital storage oscilloscope shows a record that is a collection of several acquisitions of a repeated signal that is averaged over time.
145
What is the function of the acquisition controls?
To set the digital storage oscilloscope’s sampling rate, determine what type of processing will occur and how many record points can be shown.
146
What is the range of record points that the Tektronix 2230 digital storage oscilloscope can
acquire?
1,000 (1K) to 4,000 (4K) points.
147
Which control sets up acquisition either before a trigger or at the beginning of a waveform?
PRETRIG/POST TRIG switch.
148
What happens to the NORM and P-P AUTO trigger modes while in ROLL mode?
These triggers are disabled allowing the digital storage oscilloscope to continuously acquire and display incoming signals.
149
In the NORM trigger mode, how are the pretrigger waveform and post trigger scan updated?
By the trigger and post trigger scan from the trigger position to the right.
150
In the SAVE mode, what happens to the acquisition and display update in progress?
It stops.
151
What types of measurements in the STORE mode are made with CURSORS controls?
Delta volts, delta time, one over delta time, and delay time measurements.
152
Which switch establishes the function of the CURSORS position control?
POSITION/CURS/SELECT WAVEFORM switch.
153
Explain how a 4K record length is shown on the display.
A 4-bar graph on the screen indicates which portion of the record you are viewing. A 4K record length displays 1K samples at a time. You have to look at four different screens to see the entire record length.
154
In the SELECT WAVEFORM mode using the SELECT C1/C2 (cursor-select) switch, what happens when the C1/C2 switch is pressed?
It moves the cursor set between displayed waveforms.
155
What is the purpose of the MEMORY and menu controls?
They control the MENU operation while the MENU is displayed, and they control the storage and display of the SAVE reference waveforms when the MENU is not displayed.
156
What is the purpose of the BERTS?
To provide a bit error detection system that can determine the received data quality.
157
What type of test can the BERTS perform?
Bit error analysis, timing analysis, or delay measurements. Also the BERTS is a source of PCM data used to test a communications data link or a bit synchronizer output. Many BERT can generate command test patterns, telemetry PCM formats, and bit coding patterns at telemetry data rates.
158
What is the purpose of the internal clock generator?
To provide an internal clock reference—usually selectable from the front panel.
159
What is the purpose of the voltage controlled oscillator, and how is it calibrated?
As the basic clock generator, it provides all clock phases. It is periodically frequency calibrated by a crystal-controlled oscillator in the AUTO-CAL section.
160
What is the purpose of the countdown section of the internal clock generator?
To divide the voltage controlled oscillator clock and provide a frequency equal to the bit rate selected.
161
What is the purpose of the digital-to-analog converter and the decode range splitter, and for what purpose does this section use the binary coded decimal information?
To use the binary coded decimal information to control the voltage controlled oscillator center frequency, and to control the range the countdown circuits will decode. They use the binary coded decimal information
to control the voltage controlled oscillator center frequency, and to control the range the countdown circuits will decode.
162
What is the purpose of the pattern simulator?
To accept either the external or internal clock and generate either a pseudo-random noise pattern or a 48-bit pattern you program from the front panel.
163
Which pattern simulator section controls the clock selector and selects either the external clock or
the internal clock for processing?
Data/clock selects encoder.
164
What is the purpose of the pseudo random noise generator?
To receive the internal clock from the clock selector and generate a 2,047 bit long pseudo-random pattern.
165
What is the purpose of the pseudo random noise blanking generator, and what are the blanking
periods?
To provide a blanking period at the start of the 2,047 bit pseudo random noise frame (under the control of the blanking selector switch). The blanking period can be 0, 32, 64, 96, or 128 bits long.
166
What is the purpose of the 48-bit register and 8-bit word display?
To accept six 8-bit words, one word at a time, from the data entry switches and stores them in a 48-bit register.
167
What controls the data/clock select encoder, and what does it generate?
The pattern select and clock select switches; it generates a data select code and a clock select code.
168
Which pattern simulator section selects either pseudo random noise data, external data, or 48-bit
data—depending on which data select code is received?
Data/sync selector.
169
What is the purpose of the code converter?
To convert the NRZ-L data into the desired coding, such as NRZ-M.
170
What is the purpose of the clock drivers and the data drivers, and where are their outputs sent?
The clock drivers convert the selected clock signal to a system compatible level and a buffered TTL level, and the data drivers convert the encoded data signal to a system compatible level and a buffered TTL level. The outputs are input to the pattern synchronizer and error counter data/clock receivers block.
171
What is the output from the output amplifier?
After mixing the three input signals linearly, it provides a front panel adjustable offset and output level for a low impedance load.
172
What is the purpose of the pattern synchronizer and error counter?
To receive the selected pattern, automatically synchronizes on the pattern, and determine the bit error rate induced after transmission through the system.
173
What are the inputs to the data/clock receivers?
Either system-compatible data or buffered TTL data from the clock drivers and the data.
174
Which pattern synchronizer and error counter sections combine the system compatible and TTL
signals together so only one signal will be present at one time?
Data/clock receivers.
175
To what sections are the outputs from the data/clock receivers sent?
To the 48-bit synchronizer/comparator, the pseudo random noise synchronizer/comparator, the external data synchronizer/comparator, and the error rate counter and display sections.
176
What is the purpose of the 48-bit synchronizer/comparator?
To accept the received clock and data, and synchronize on the pattern when it’s equal to the 48-bit parallel input.
177
What is the purpose of the pseudo random noise pattern synchronizer/comparator?
To accept the received clock and data, from the data/clock receivers, and will synchronize with the pattern when it’s equal to its own 2,047 bit pseudo random noise pattern.
178
What is the purpose of the external data pattern synchronizer/comparator?
To accept the external data, delay it under the front panel control, and compare it with the received data from the data/clock receivers.
179
Where does the error/IN SYNC selector send the correct error and IN SYNC signals?
To the error rate counter and display.
180
When will the pattern synchronizer and error counter error/IN SYNC section provide an output to
the front panel display, and what will interrupt this output?
At the end of the count cycle or when you push the reset switch. A reset pulse will interrupt this output.
181
What is the primary means of measuring the quality of transmitted digital information?
To compare the number of bits in error to the total number of bits transmitted. The ratio of the number of bits in error to total number of bits transmitted.
182
What is the basic quality measurement for a transmission channel?
The bit error rate.
183
What is the difference between random distribution of errors and an error rate with a clustered
distribution?
In a random distribution, each bit is equally likely to be in error. In a clustered distribution, the errors occur in clusters.
184
What are the steps in the basic bit error rate testing procedure?
1. A known bit pattern, usually pseudo random, is generated at the sending end of the data channel or equipment under test, and is transmitted through the channel.
2. At the receiving end, an identical pattern is generated and synchronized with the incoming signal.
3. The received signal is compared to the locally generated pattern in the receiving equipment.
4. If any bit in the received signal is not the same as the generated bit, it is assumed the received bit is in error.
5. An error signal is generated and used to operate a counter.
185
Although BERTSs use the same basic technique to count errors, how do you interpret the results
and display information?
In many different ways. So, you must use and understand the technical manual for the particular test equipment.
186
What are some significant bit error rate test equipment parameters?
1. Bit rate and timing.
2. Test patterns.
3. Synchronization.
4. Interface and data coding.
5. Readouts and special features.
187
How can the BERTS, with internal timing for a low or intermediate bit rate range, be used to operate at higher bit rates?
With external timing.
188
What data circuit speed would normally use the shorter generated bit error rate test pattern lengths, and what is the data circuit bit rate?
Low to intermediate; 1,200 to 9,600 bps.
189
What data circuit speed would normally use the longer pattern lengths, and what is the data
circuit bit rate?
Higher speed circuits; 50 kbps to 64 kbps.
190
What data circuit speed would normally use a 1,048,575 bit pattern length, and what is the data circuit bit rate?
Very high speed T–1 circuits; 1.544 Mbps.
191
What bit rate would you use to test a 9,600 bps data circuit?
A bit rate of 9,600 bps, or the closet bit rate available, to test the maximum output of the equipment.
192
What bit rate would be used to perform a bit error rate test on a 64 kbps data circuit?
64 kbps.
193
What subsection in the receiving section of the BERTS must be synchronized with the received
pattern from either the bit synchronizer or the distant end?
The pattern generator.
194
What is one of the major problems encountered in making bit error rate tests?
The detection of an “out-of-sync” condition by the test set receiver.
195
What should you know about synchronization in order to interpret the bit error rate test data
correctly?
You need to know how test equipment responds to the out-of-sync condition.
196
What type of connectors do test sets, designed to operate with data modems, usually use?
25-pin connectors, usually the EIA RS–232 type.
197
What must you check to determine impedance and voltage levels before connecting the BERTS to the point of test?
The technical manuals.
198
What information must be available to you from the BERTS readout or special features?
Information to count the number of errors that occur in a specified number of transmitted bits.
199
Why do we test ground?
To verify the ground-resistance specification that the ground rod or grid must meet.
200
What test equipment is used to identify poor ground?
Earth ground tester.
201
How many points of contacts are used in the Fall of Potential testing method?
3.
202
What is each point of contact called in the Fall of Potential testing method?
The test ground, voltage probe, and current probe.
203
What distance represents the closest value to the theoretical true resistance measurement?
61.8% of the total distance.
204
How is the earth stake placed in the soil?
In a direct line away from the earth electrode.
205
Which law is used to calculate the resistance of the earth electrode automatically with the earth
ground tester?
Ohm’s Law.
206
Where are the probes placed in order to achieve the highest degree of accuracy?
Placed outside the sphere of influence of the ground electrode under test and the auxiliary earth.
207
What is the recommended ground resistance value by the NFPA and IEEE?
5 ohms or less.
208
What are the primary capabilities provided by a protocol analyzer?
Digital network diagnostics and software development.
209
Explain the difference between a protocol analyzer NIC and other NICs.
The NIC in a protocol analyzer is configured to process all frames.
210
What function of the protocol analyzer excludes specific types of frames?
Capture filters.
211
List four types of specific occurrences that can be displayed by counters.
Any four of the following:
1. Packets transmitted.
2. CRC errors.
3. Undersize packets.
4. Oversize packets.
5. ARP requests.
6. Collisions.
7. Bit errors.
212
What menu is best used to report errors that occur at the physical layer such as bad FCS, short
frames, and jabbers?
MAC node statistics.
213
What kind of information does the connection statistics menu provide?
Connection statistics provide information concerning the bandwidth utilization and the number of connections that are related to specific nodes.
214
Identify the three types of active tests that are conducted with a protocol analyzer.
1. PING.
| 2. Trace route.
215
What is the frequency range of the HP 8640B RF signal generator?
500 kHz to 512 MHz (450 kHz to 550 MHz with over-range).
216
What extends the HP 8640B range from 20 Hz to ultra high frequencies?
A variable audio oscillator can extend the output range of the generator down to 20 Hz and a doubler can extend it to 11,000 MHz. This, together with a calibrated output and modulation, permits complete radio frequency and intermediate frequency performance tests on virtually any type of high frequency, very high
frequency, or ultra high frequency receiver.
217
What is the function of the oscillator section?
To produce a signal that can be set accurately in frequency at any point within the range of the generator.
218
What is the function of the modulator?
To produce an audio modulating signal to superimpose on the radio frequency signal produced in the
oscillator.
219
What types of modulated signals are possible with the radio frequency generator?
Either sine waves, square waves, or pulses of varying duration.
220
What does the output circuit of the radio frequency signal generator usually contain, and what are
their functions?
A calibrated attenuator and an output level meter. The attenuator lets you select the amount of output required. The output level meter provides an indication and permits control of the generator output voltage.
221
List some applications of the radio frequency generator.
1. Verify transmission within designated frequency ranges by comparing transmitter outputs with known radio frequencies.
2. Align a receiver by injecting the system with range-standard modulated radio frequency.
3. Check transmission lines and antenna systems for proper operation.
222
The decibel is part of what larger unit of measure?
Bel.
223
A power ratio of 10,000:1 can be represented by how many bels?
Four.
224
What’s the most commonly used industry standard power reference level?
The 1-milliwatt standard.
225
What is the refrence for dBm?
As decibels referenced to a 1-milliwatt standard or dBm.
226
Rewrite these sentences so they use the term dB correctly.
(a) This TWT has 25 dB of output power.
(b) The final amp is pumping out a 30 dB package.
(a) This TWT has a power gain of 25 dB.
| (b) The final amp is pumping out a package that’s 30 dB more than its input.
227
What will every 3 dB increase in gain do to the power level?
Roughly double it.
228
How many dB of gain does an amplifier have if there are 10 watts in and 80 watts out?
There’s a gain of 9dB.
229
You have installed an in-line 3 dB attenuator between a power source and the power sensor of a
power meter. How will this affect the power level displayed by the power meter?
It will cut it in half.
230
What two power characteristics are reflected by the term dBm?
1. Gain level.
| 2. Power level.
231
How do the terms dB and dBm differ?
Because dBm is always referenced to a 1-milliwatt standard, it can be used to reflect a power level, in
addition to gain or loss. The term dB can’t reflect a power level; instead, it can only reflect gain or loss because it’s purely a ratio.
232
How much more power is available at 6 dBm than at 3 dBm?
Twice as much.
233
What power levels are indicated by these measurements?
(a) 3 dBm.
(b) 9 dBm.
(c) 12 dBm.
(d) 36 dBm.
(a) 2 mW.
(b) 8 mW.
(c) 16 mW.
(d) 4,096 mW (approx 4.1 watts).
234
List at least three of the units that can be displayed by the HP 436A power meter.
1. Watts.
2. Milliwatts.
3. Microwatts.
4. Nanowatts.
5. dBm.
6. Relative dB.
235
Briefly explain how to use the relative power measurement mode for frequency response testing.
After the input is connected, press dB(REF) to lock in this frequency level as the reference, then tune the transmitter to other frequencies and observe any changes up or down in the power level.
236
What is the 4391M RF Power Analyst designed to measure?
The 4391M RF Power Analyst is an RF Directional Thruline Wattmeter designed to measure power flow, load match, and AM in 50 ohm coaxial transmission lines.
237
What are the two switches on the front panel of the instrument used for?
Two switches on the front panel of the instrument are set by the user to correspond to the power range of the forward element.
238
If only the forward element is used, what is filled in the other socket?
If only one element is used, the other socket should be filled with a dust plug or a higher power element.
239
Why are the elements clamped into place by the hold-down catches on the face of the line
section?
These catches must be used to avoid error due to the element not contacting the bottom or seating plane of
the socket.
240
When powered up, which mode is the 4391M wattmeter always goes into?
When powered up, the 4391M wattmeter always goes into the forward CW power mode.
241
When reading forward power, what will be displayed if the applied power exceeds 120 percent of the range?
If the applied power exceeds 120 percent of the range, two right facing arrow heads will be displayed.
242
Where is the reflected CW reading taken?
Readings are taken from the element in the socket marked “reflected.”
243
Between what power ranges will a SWR be displayed?
SWR will be displayed if the average forward power is between 10 percent and 120 percent of the full scale and the average reflected power is less than 120 percent of the reflected element range.
244
What is the difference between the readings CW and PEP?
Readings are displayed directly as peak power in PEP. To formulate CW power, the wattmeter measures peak and minimum square root of power and combines them.
245
How is over-modulation displayed on the wattmeter?
Over-modulation will be indicated as 99.9 percent.
246
What must be added to the dBm reading when the range is in kilowatts?
30 must be added to all dBm readings when the range is in kilowatts.
247
When measuring return loss, what does a reading of 21.6 indicates?
The measurement of return loss reading of 21.6 indicates that reflected power is 21.6 dB down from forward power.
248
In order to recall the maximum reading, what key do you press?
To recall the maximum reading, hold the MAX or MIN key down.
249
How do you clear the minimum and maximum register?
To clear the minimum and maximum register, the mode key must be pressed again or a new selected.
250
Which mode is useful for making adjustments to optimize any of the parameters which the wattmeter measures?
Peaking aid.
251
What is a major difference between the oscilloscope and the spectrum analyzer?
The oscilloscope displays frequency information in the time domain, whereas the spectrum analyzer displays frequency information in the frequency domain.
252
Describe how the spectrum analyzer displays information in the frequency domain.
By complex signals (i.e., signals composed of more than one frequency) that are separated into their frequency components, and the power level of each frequency is displayed.
253
What functions does the spectrum analyzer perform?
1. Locate and identify signals over a wide frequency spectrum.
2. Magnify parts of the spectrum for detailed analysis with stable, calibrated sweeps and resolution.
3. Minimize display clutter for spurious responses within itself.
4. Furnish wide dynamic range and flat frequency response.
254
What advantage do the spectrum analyzer’s sensitivity and wide dynamic range provide?
A way to measure low-level modulation.
255
List some uses of the spectrum analyzer.
1. Measure AM, FM, and pulsed radio frequency.
2. Measure long- and short-term frequency stability.
3. Measure parameters such as subcarrier oscillator outputs, channels of complex signals.
4. Measure frequency drift during system warm-up.
256
What is the frequency range of an electronic frequency counter?
Low audio frequencies up to 550 MHz. Some methods are available to extend the frequency range of
counters to more than 20 GHz.
257
What provides the time reference for the precise timing and where does this function take place?
A quartz-crystal oscillator inside the counter.
258
What is a CSM?
The CSM is a microprocessor controlled, digitally synthesized test set which combines the operations of many different test instruments into a single, compact unit.
259
How are meters on the major operations screens displayed?
On the major operations screens, these meters display as bar graph display and digital data or just as digital data, depending on the oscilloscope/spectrum analyzer display size.
260
What part of the CSM edits the operation screens to reflect changes in parameters imposed by the operator?
Microprocessor.
261
How can the meter operation screens be accessed?
The meter operation screens can be accessed through the mode operation screen that is being supported by that specific meter operation or through the meter menu.
262
When a specific mode of operation is selected, what operational parameters appear on the screen?
Once a specific mode of operation is selected, the parameters shown reflect the parameters last entered in that operation.
263
Which screens can operator entry and edit of data is performed?
Operator entry and edit of data is performed on the operation screen or on the setup menu.
264
Once the parameter is accessed, how is data selected?
Once the parameter is accessed, data can be selected with DATA SCROLL spinner or DATA SCROLL keys or by using the alphanumeric DATA ENTRY keypad.
265
What is a multi-task soft function keys?
Multi-task “soft” function keys perform set up, edit and entry. Each operation screen defines soft function keys to fit the specific needs for that operation.
266
How many system configurations can the user store?
Allows the user to store and recall up to nine system configurations.
267
How many frequencies are allowed to be stored into a list for use when performing tasks that
require the same instrument setup to be utilized on many different frequencies?
100.
268
Name several function or operation of the communication service monitor?
RF generator, AF generator, oscilloscope, deviation (peak) meter, SINAD meter, frequency error meter, modulation meter, bit error rate meter, deviation (RMS) meter, cable fault detector, receiver, spectrum
analyzer, digital multimeter, distortion meter, AF meter, RF power meter, signal strength meter, phase
meter, and tracking generator.
269
Which receiver access input point would you use for higher-powered signals?
T/R connector.
