Term
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Definition
.
UNIT 1 EXAM
A group of components that work together to complete a job or task is/are known as a:
A. System
B. Subsystem
C. Unit
D. None of these |
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Term
|
Definition
.
UNIT 1 EXAM
What type of diagram is useful fro determining how a system works?
A. System
B. Block
C. Schematic
D. None of these |
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Term
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Definition
.
UNIT 1 EXAM
A device that converts one form of energy into another (such as converting sound into an electrical signal) is known as a/an:
A. Inductor
B. Capacitor
C. Transducer
D. None of these |
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Term
| A. It is an electrical duplicate of the information |
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Definition
.
UNIT 1 EXAM
Which of these is the most important property of the intelligence signal?
A. It is an electrical duplicate of the information
B. It is a pure sine wave
C. It contains no DC level; its average value is zero
D. None of these |
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Term
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Definition
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UNIT 1 EXAM
What type of energy makes up radio waves?
A. Electric
B. Magnetic
C. Electromagnetic
D. None of these |
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Term
D. None of these
(wavelength) |
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Definition
.
UNIT 1 EXAM
The distance that a radio wave travels in one AC cycle is called the:
A. Peak
B. Trough
C. Minima
D. None of these |
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Term
|
Definition
.
UNIT 1 EXAM
As the frequency of a radio wave increases, its wavelength:
A. Increases
B. Decreases
C. Remains unchanged
D. None of these |
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Term
D. 2.0648 m
(wavelength = V/f --> 300,000,000 / 145,290,000 Hz = 2.0648 m) |
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Definition
.
UNIT 1 EXAM
The WOERH Amateur Radio repeater transmits on a frequency of 145.290 MHz. What is the wavelength of the transmitted signal?
A. 4.009 m
B. 8.6753 m
C. 1.0382 m
D. 2.0648 m |
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Term
A. 1 MHz
(f = V/wavelength --> 300,000,000 / 300 m = 1 MHz) |
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Definition
.
UNIT 1 EXAM
A certain radio signal has a wavelength of 300 meters. What is its frequency?
A. 1 MHz
B. 10 MHz
C. 100 MHz
D. 300 MHz |
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Term
| B. Antenna lengths become shorter (and reasonable) |
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Definition
.
UNIT 1 EXAM
Why are radio frequencies used to carry information (as opposed to directly sending information signals to a transmitting antenna)?
A. No oscillators are needed if this approach is used
B. Antenna lengths become shorter (and reasonable)
C. To avoid the need for modulation and demodulation
D. All of the above are correct reasons for carrier transmission |
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Term
A. 470 MHz
6.28" * 4 = 25.12" wavelength --> 25.12" / 39.37" = 0.638 m = wavelength
f = V/wavelength --> 300,000,000 / .638 m = 470 MHz |
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Definition
.
UNIT 1 EXAM
A quarter-wavelength (1/4 wl) whip antenna on a police car measures 6.28". What approximate frequency is the antenna made for? Note: 1" = 2.54 cm (1 meter = 39.37").
A. 470 MHz
B. 1880 MHz
C. 175 MHz
D. None of these |
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Term
B. 10.7 m
wavelength = V/f --> 300,000,000 / 14,000,000 Hz = 21.4 m
1/2 wavelength --> 21.4 m / 2 = 10.7 m |
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Definition
.
UNIT 1 EXAM
How long, in meters, will a half-wavelength dipole be if it is resonant within the 14 MHz Amateur Radio band?
A. 21.4 m
B. 10.7 m
C. 5.4 m
D. None of these |
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Term
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Definition
.
UNIT 1 EXAM
The process whereby a low-frequency information signal is made to "ride" on top of a high-frequency carrier signal is called:
A. Detection
B. Oscillation
C. Modulation
D. None of these |
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Term
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Definition
.
UNIT 1 EXAM
Which of these are possible ways that a carrier signal can be modulated?
A. amplitude
B. Frequency
C. Phase
D. All of these |
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Term
| A. Places the information onto the radio-frequency carrier |
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Definition
.
UNIT 1 EXAM
What is the purpose of the modulator stage in a transmitter?
A. Places the information onto the radio-frequency carrier
B. Produces the radio frequency carrier frequency from the DC power supply energy
C. Recovers the information signal
D. None of these |
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Term
| B. To select the correct carrier signal from those presented by the antenna |
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Definition
.
UNIT 1 EXAM
Why is a bandpass filter needed in a radio receiver?
A. To recover the information from the incoming carrier signal
B. To select the correct carrier signal from those presented by the antenna
C. To prevent the receiver from distorting the recovered information signal
D. None of these |
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Term
| C. The orignal information signal at the transmitter |
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Definition
.
UNIT 1 EXAM
The output signal from the detector in a radio receiver should look exactly like:
A. The signal from the carrier oscillator in the transmitter
B. A pure sine wave
C. The orignal information signal at the transmitter
D. None of the above |
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Term
| A. The information signal is recovered from the incoming carrier signal |
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Definition
.
UNIT 1 EXAM
What happens int he detector circuit of a radio receiver?
A. The information signal is recovered from the incoming carrier signal
B. The carrier signal is created
C. One of many incoming carrier signals is selected (and the undesired ones are discarded)
D. None of the above |
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Term
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Definition
.
UNIT 1 EXAM
An AM broadcaster is transmitting on a frequency of 0.710 MHz, and its satellite downlink is at 500 MHz. The AM signal is _____ signal, and the satellite downlink is a _____ signal. (Choose the appropriate band descriptors.)
A. HF, VHF
B. LF, MF
C. SHF, EHF
D. MF, UHF |
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Term
C. 100 m
wavelength = V/f --> 300,000,000 / 30,000,000 Hz = 10 m |
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Definition
.
UNIT 1 EXAM
The maximum wavelength for an HF radio signal is:
A. 1 m
B. 10 m
C. 100 m
D. None of these |
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Term
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Definition
.
UNIT 2 EXAM
An oscilloscope measures signals in what domain?
A. Time
B. Frequency
C. Complex Frequency
D. None of these |
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Term
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Definition
.
UNIT 2 EXAM
The horizontal axis of an oscilloscope is calibrated in what units?
A. Frequency
B. Time
C. Resistance
D. None of these |
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Term
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Definition
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Term
|
Definition
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Term
|
Definition
.
UNIT 2 EXAM
To view signals in the frequency domain, what instrument is used?
A. Oscilloscope
B. Digital Multimeter
C. Spectrum Analyzer
D. None of these |
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Term
|
Definition
.
UNIT 2 EXAM
The horizontal axis of a spectrum analyzer is calibrated in what units?
A. Frequency
B. Time
C. Resistance
D. None of these |
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Term
| A. A 50 kHz pure sine wave |
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Definition
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Term
|
Definition
|
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Term
|
Definition
|
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Term
|
Definition
|
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Term
|
Definition
|
|
Term
|
Definition
|
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Term
|
Definition
.
UNIT 2 EXAM
Which of these is an external noise source?
A. Johnson
B. Thermal
C. Shot
D. None of these |
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Term
|
Definition
.
UNIT 2 EXAM
The noise energy emitted by the sun and other stars is known as:
A. Cosmic
B. Thermal
C. Atmospheric
D. None of these |
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Term
|
Definition
.
UNIT 2 EXAM
Which of these noise energies results from the random vibrations of atoms in a solid material?
A. Cosmic
B. Thermal
C. Atmospheric
D. None of these |
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Term
Vn = sqrt(4(1.38 x 10^-23)*50kHz*100k ohms)
B. 9 microvolts |
|
Definition
.
UNIT 2 EXAM
What noise voltage will be generated acorss a 100K ohm resistor at a temperature of 20 degrees C if the circuit bandwidth is 50 kHz?
A. 5 microvolts
B. 9 microvolts
C. 25 microvolts
D. None of these |
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Term
SNR (dB) = 20 log(Vs/Vn)
SNR (dB) = 20 log(1V/10V)
SNR (dB) = 20 log(0.1V)
SNR (dB) = -20 dB
D. None of these |
|
Definition
.
UNIT 2 EXAM
At the input of an amplifier, there is a noise voltage of 10V and a signal voltage of 1V. What is the resulting signal to noise ratio in dB?
A. 20 dB
B. 10 dB
C. 40 dB
D. None of these |
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Term
|
Definition
.
UNIT 2 EXAM
At the antenna terminals of a radio receiver, there is a signal voltage of 100 mV and a noise voltage of 1 mV. What is the SNR power ratio of the signal?
A. 1000:1
B. 10000:1
C. 100000:1
D. None of these |
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Term
SNR (dB) = 10 log(2/1)
SNR (dB) = 3 dB
C. 3 dB |
|
Definition
.
UNIT 2 EXAM
A certain signal has a power SNR of 2:1. What is the decibel signal-to-noise ratio?
A. 10 dB
B. 20 dB
C. 3 dB
D. None of these |
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Term
NF = Input - Output
NF = 55 dB - 53 dB
NF = 2dB
D. None of these
D. none of these |
|
Definition
.
UNIT 2 EXAM
The input signal of a certain amplifier has a S/N ratio of 55 dB, and the output signal of the same amplifier has a S/N ratio of 53 dB. What is the noise figure of the amplifier?
A. 10 dB
B. 20 dB
C. 30 dB
D. none of these |
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Term
|
Definition
.
UNIT 3 EXAM
In amplitude modulation (AM), what characteristic of the carrier signal is changed to convey the information?
A. Amplitude
B. Frequency
C. Phase
D. None of these |
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Term
|
Definition
|
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Term
|
Definition
.
UNIT 3 EXAM
For an amplifier (or other circuit) to generate an AM signal, what operating characteristic of the amplifier must be varied in step with the information signal?
A. The power supply voltage
B. The input impedance (resistance)
C. The voltage gain
D. None of these |
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Term
| A. The envelope is a replica of the information signal |
|
Definition
.
UNIT 3 EXAM
What is the significance of the envelope of a AM signal?
A. The envelope is a replica of the information signal
B. The envelope is what carries the information through space
C. The envelope represents the carrier signal
D. None of these |
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Term
|
Definition
.
UNIT 3 EXAM
The maximum allowed value for AM modulation index is:
A. 0.25
B. 0.50
C. 1.00
D. None of these |
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Term
|
Definition
.
UNIT 3 EXAM
What is the percentage of modulation of an AM transmitter that is operating with a modulation index of 0.75?
A. 75%
B. 50%
C. 25%
D. None of these |
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Term
|
Definition
|
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Term
| B. Splatter and interference with other stations |
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Definition
.
UNIT 3 EXAM
What is a possible consequence of overmodulating an AM transmitter?
A. The bandwidth of the station will decrease
B. Splatter and interference with other stations
C. Reduction of power to the antenna
D. None of these |
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Term
| B. A 10 kHz pure sine wave |
|
Definition
|
|
Term
|
Definition
.
UNIT 3 EXAM
Which frequency-domain portion of an AM signal carries the information?
A. The carrier frequency component
B. The DC component
C. The sidebands
D. None of these |
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Term
|
Definition
|
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Term
|
Definition
|
|
Term
|
Definition
|
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Term
fusb = fc + fm
fusb = 710 kHz + 5 kHz = 715 kHz
flsb = fc - fm
flsb = 710 kHz - 5kHz = 705 kHz
BW = fusb - flsb
BW = 715 kHz - 705 kHz
BW = 10 kHz
B. 10 kHz |
|
Definition
.
UNIT 3 EXAM
If an AM transmitter is being modulated with a 5 kHz sine wave, what will the resulting bandwidth be, assuming that its carrier frequency is 710 kHz?
A. 5 kHz
B. 10 kHz
C. 20 kHz
D. None of these |
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|
Term
BW = 835.2 kHz - 824.8 kHz
BW = 10.4 kHz
D. 10.4 kHz |
|
Definition
.
UNIT 3 EXAM
An AM transmitter is producing an upper sideband at 835.2 kHz, and a lower sideband at 824.8 kHz. What is the bandwidth of the resulting signal?
A. 5.2 kHz
B. 835.2 kHz
C. 824.8 kHz
D. 10.4 kHz |
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Term
m = Vm/Vc
.2 = Vm/1000v
Vm = (.2)*1000v
Vm = 200v
B. 200 volts |
|
Definition
.
UNIT 3 EXAM
An AM transmitter is operating on a carrier frequency of 1580 kHz, with 1000 volts of carrier (Vc = 1000 V). What intelligence voltage (Vm) will be needed to get 20% modulation?
A. 100 volts
B. 200 volts
C. 400 volts
D. 300 volts |
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|
Term
Pt = Plsb + Pc + Pusb
Plsb = 12.5 W
Pusb = 12.5 W
Pc = 50V^2/50 ohms = 50 W
50W + (50 * 1/2) = 75 W
A. 75 W |
|
Definition
.
UNIT 3 EXAM
If an AM transmitter has a carrier voltage (Vc) of 50 V and is operating at 100% modulation, what is the total power? The load resistance is 50 ohms.
A. 75 W
B. 100 W
C. 1600 W
D. Insufficient information |
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|
Term
Pc = 400 W
400 W + (400 * 1/2) = 600 W
A. 600 W |
|
Definition
.
UNIT 3 EXAM
An amateur station is using AM on a carrier frequency of 1750 kHz. The station consists of a medium powered exciter (transmitter), a Yaesu FT890, followed by a Alpha model 77 linear power amplifier. The unmodulated carrier power is adjusted to be 400 watts. What will the total power be when 100% modulation is achieved?
A. 600 W
B. 800 W
C. 1000 W
D. 1500 W |
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Term
|
Definition
|
|
Term
|
Definition
|
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Term
| B. Near the beginning of the transmitter |
|
Definition
.
UNIT 4 EXAM
Where does a low-level AM transmitter perform the process of modulation?
A. At the last or final amplifier stage
B. Near the beginning of the transmitter
C. At the power supply
D. None of these |
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Term
| A. At the last or final amplifier stage |
|
Definition
.
UNIT 4 EXAM
Where does a high-level AM transmitter perform the process of modulation?
A. At the last or final amplifier stage
B. Near the beginning of the transmitter
C. At the power supply
D. None of these |
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Term
|
Definition
.
UNIT 4 EXAM
What stage in a transmitter isolates the RF carrier oscillator from the stages that follow it, in order to minimize unwanted frequency changes?
A. Driver amplifier
B. Final amplifier
C. Buffer amplifier
D. None of these |
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|
Term
| B. To minimize frequency drift |
|
Definition
.
UNIT 4 EXAM
Why is the power supply to the oscillator stage in a transmitter usually regulated?
A. To minimize harmonic distortion products at the oscillator
B. To minimize frequency drift
C. To produce maximum power output from the oscillator
D. None of these |
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Term
|
Definition
.
UNIT 4 EXAM
Which of these AM transmitter stages requires two separate signal inputs?
A. Oscillator
B. Buffer
C. Driver
D. None of these |
|
|
Term
Pout / Pin
100 W / (20V * 10)
100/200
.50
B. 50% |
|
Definition
.
UNIT 4 EXAM
A certain AM transmitter requires 20 V at 10 A, and produces 100 W of RF output. What is its efficiency?
A. 25%
B. 50%
C. 75%
D. 100% |
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Term
|
Definition
.
UNIT 4 EXAM
A circuit that converts DC power supply energy into an AC output signal is called a/an:
A. Oscillator
B. Buffer
C. Driver
D. Final |
|
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Term
| A. Be able to continue running if it is already oscillating, but won't start on its own |
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
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Term
| A. Less sensitive to the inter-electrode capacitances of the active device |
|
Definition
.
UNIT 4 EXAM
What is the advantage of the Clapp oscillator over the other configurations (for example, Colpitts)?
A. Less sensitive to the inter-electrode capacitances of the active device
B. Uses less power from the DC power supply
C. Voltage regulation requirements aren't as great
D. None of these |
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Term
|
Definition
.
UNIT 4 EXAM
If a certain LC resonant tank circuit has a Q of 100 and an operating frequency of 100 kHz, what will its bandwidth be?
A. 10 kHz
B. 100 kHs
C. 50 kHz
D. None of these |
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Term
|
Definition
|
|
Term
|
Definition
.
UNIT 4 EXAM
When a quartz crystal is series resonant, it ideally appears to the rest of the circuit is a/an:
A. Open
B. Medium resistance
C. Short
D. None of these |
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|
Term
|
Definition
.
UNIT 4 EXAM
When a quartz crystal is parallel resonant, it ideally appears to the rest of the circuit is a/an:
A. Open
B. Medium resistance
C. Short
D. None of these |
|
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Term
| B. To minimize stray inductance and capacitance |
|
Definition
.
UNIT 4 EXAM
Why must component leads be kept very short in RF circuits?
A. To maximize circuit gain
B. To minimize stray inductance and capacitance
C. To obtain the best possible circuit efficiency
D. None of these |
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Term
|
Definition
.
UNIT 4 EXAM
In order to prevent undesired signal coupling between two or more circuits, what is often used?
A. Metal shields
B. Plastic dust covers
C. Wire loops
D. None of these |
|
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Term
| C. To short any undesired RF signal to ground |
|
Definition
.
UNIT 4 EXAM
What is the function of an RF bypass capacitor?
A. To improve the regulation of the DC power supply
B. To couple RF signal between one stage and the next
C. To short any undesired RF signal to ground
D. None of these |
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Term
| B. The efficiency of the stage would be too low |
|
Definition
.
UNIT 4 EXAM
Why would it be unlikely to have a 200 Watt RF power amplifier operate in class A?
A. The distortion of the signal would be excessive
B. The efficiency of the stage would be too low
C. Too many harmonics would be generated by the stage
D. None of these |
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Term
| A. The relative strength of two signals is being compared |
|
Definition
.
UNIT 4 EXAM
When a measurement is given in dB units, what is the meaning?
A. The relative strength of two signals is being compared
B. The absolute value of a signal is being given
C. The power level of a signal is being given
D. None of these. |
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Term
|
Definition
.
UNIT 4 EXAM
What is the reference level for dBm units?
A. 1 mW
B. 1 W
C. 1 microWatt
D. None of these |
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Term
|
Definition
.
UNIT 5 EXAM
The purpose of the antenna in a radio receiver is:
A. Signal selection
B. Signal acquisition
C. Information recovery
D. None of these |
|
|
Term
|
Definition
.
UNIT 5 EXAM
What type of filter is used in a radio receiver for selecting the appropriate incoming carrier signal?
A. Bandpass
B. Low-pass
C. High-pass
D. None of these |
|
|
Term
| C. The barrier potential of germanium is smaller |
|
Definition
.
UNIT 5 EXAM
Why is germanium preferred over silicon as the active material in an AM detector diode?
A. Lower distortion will be produced by this material
B. Stronger signals can be handled by the germanium detector
C. The barrier potential of germanium is smaller
D. None of these |
|
|
Term
|
Definition
.
UNIT 5 EXAM
In order for a device to modulate or demodulate an AM signal, what property is required?
A. Nonlinearity
B. High level of gain
C. Positive feedback
D. None of these |
|
|
Term
|
Definition
|
|
Term
| C. High frequency information, 90% or more modulation |
|
Definition
.
UNIT 5 EXAM
Under what condition is an AM detector most likely to produce diagonal clipping distortion?
A. Low frequency information, 50% or less modulation
B. Low frequency information, 75% or less modulation
C. High frequency information, 90% or more modulation
D. None of these |
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Term
| A. The incoming carrier frequency |
|
Definition
.
UNIT 5 EXAM
In a TRF receiver, the bandpass filter used for signal selection is tuned to what frequency?
A. The incoming carrier frequency
B. The IF frequency
C. The LO frequency
D. None of these |
|
|
Term
|
Definition
.
UNIT 5 EXAM
A loopstick antenna has a core made of _____ and is sensitive to the _____ field of the incoming radio wave. (Choose the best pair of responses.)
A. Steel, Electric
B. Vinyl, Magnetic
C. Ferrite, Magnetic
D. Aluminum, Electric |
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|
Term
|
Definition
.
UNIT 5 EXAM
The ability of a radio receiver to select or choose a desired signal (while rejecting all others) is referred to as its:
A. Selectivity
B. Sensitivity
C. Noise Figure
D. None of these |
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|
Term
|
Definition
.
UNIT 5 EXAM
The selectivity of a radio receiver is largely controlled by what property of its circuitry?
A. Power gain
B. Nonlinearity
C. Bandwidth
D. None of these |
|
|
Term
BW = F/Q
700 kHz/ 100 = 7kHz
D. None of these |
|
Definition
.
UNIT 5 EXAM
The tuned circuit in the front end of a TRF radio receiver is resonant at 700 kHz, and the Q of the circuit is 100. What will the resulting bandwidth of the receiver be?
A. 70 kHz
B. 700 kHz
C. 7 MHz
D. None of these |
|
|
Term
| B. The Q of the tuned circuits changes with frequency |
|
Definition
.
UNIT 5 EXAM
Why does the bandwidth of a TRF receiver vary greatly as its operating frequency is changed?
A. The gain of the RF amplifier stages varies with frequency
B. The Q of the tuned circuits changes with frequency
C. The power supply regulation is inadequate
D. None of these |
|
|
Term
|
Definition
.
UNIT 5 EXAM
What type of radio receiver converts all incoming signals to a constant frequency before amplification and filtering?
A. TRF
B. Superheterodyne
C. Homodyne
D. None of these |
|
|
Term
| A. Most of the amplification and RF bandpass filtering takes place at a fixed frequency |
|
Definition
.
UNIT 5 EXAM
Why does a superhet receiver have a constant bandwidth?
A. Most of the amplification and RF bandpass filtering takes place at a fixed frequency
B. The preselector circuit has a variable Q, which forces bandwidth to be constant
C. A superhet receiver employs AGC (automatic gain control)
D. None of these |
|
|
Term
| C. To convert the incoming carrier to the IF frequency |
|
Definition
.
UNIT 5 EXAM
What is the purpose of the frequency converter section of a superhet receiver?
A. To provide a constant signal gain
B. To correct for frequency drift in the receivers tuned circuits
C. To convert the incoming carrier to the IF frequency
D. None of these |
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Term
| A. 500 kHz, 700 kHz, 1200 kHz, 200 kHz |
|
Definition
.
UNIT 5 EXAM
A mixer has two input frequencies being applied, 500 kHz and 700 kHz. What frequencies will be in the output of the mixer?
A. 500 kHz, 700 kHz, 1200 kHz, 200 kHz
B. 500 kHz, 900 kHz, 1400 kHz, 100 kHz
C. 1000 kHz, 1400 kHz, 200 kHz, 1200 kHz
D. None of these |
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|
Term
920 kHz + 455 kHz = 1375 kHz
B. 1375 kHz |
|
Definition
.
UNIT 5 EXAM
If a certain superhet receiver has an IF of 455 kHz and is to be tuned to 920 kHz using high-side injection, what will the resulting local oscillator frequency be?
A. 465 kHz
B. 1375 kHz
C. 455 kHz
D. None of these |
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Term
|
Definition
.
UNIT 5 EXAM
What is the image frequency for 760 kHz assuming high-side injection and an IF of 455 kHz?
A. 465 kHz
B. 1375 kHz
C. 455 kHz
D. None of these |
|
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Term
|
Definition
.
UNIT 5 EXAM
Which section of a superhet receiver is responsible for eliminating the image frequency?
A. Preselector
B. Mixer
C. Local oscillator
D. None of these |
|
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Term
|
Definition
.
UNIT 5 EXAM
What stage in an AM receiver produces the AGC voltage?
A. Preselector
B. Mixer
C. Detector
D. None of these |
|
|
Term
| A. The various tuned circuits are adjusted for correct frequency of operation |
|
Definition
.
UNIT 5 EXAM
What takes place during the alignment of a radio receiver?
A. The various tuned circuits are adjusted for correct frequency of operation
B. The RF amplifiers are adjusted for maximum gain
C. The power supply voltages are adjusted for maximum output
D. None of these |
|
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Term
| B. To prevent the AGC system from activating |
|
Definition
.
UNIT 5 EXAM
Why is it important to use the weakest possible RF signal for aligning a receiver?
A. To prevent the local oscillator from being pulled off frequency
B. To prevent the AGC system from activating
C. To minimize distortion
D. None of these |
|
|
Term
|
Definition
.
UNIT 5 EXAM
What portion of an alignment procedure ensures that the preselector and local oscillator sections keep a difference of Fif?
A. IF alignment
B. Antenna alignment
C. Tracking alignment
D. None of these |
|
|
Term
| B. Visual and other inspection |
|
Definition
.
UNIT 5 EXAM
What is the first step that should be performed when troubleshooting a system?
A. Check power supplies
B. Visual and other inspection
C. Check inputs and outputs
D. None of these |
|
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Term
|
Definition
.
UNIT 5 EXAM
What is the most likely fault in a unit that appears totally dead (inoperative)?
A. RF amplifier
B. IF amplifier
C. Power supply
D. None of these |
|
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Term
| A. The frequency stability of such oscillators is poor |
|
Definition
.
UNIT 7 EXAM
Why isn't an LC-controlled oscillator usually an option for generating a variable range of frequencies?
A. The frequency stability of such oscillators is poor
B. It is difficult to get more than one frequency from such an oscillator
C. Such oscillators usually produce excessive harmonic energy
D. None of these |
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Term
|
Definition
.
UNIT 7 EXAM
What is typically used to provide the REF frequency for a phase locked loop frequency synthesizer?
A. An LC controlled oscillator
B. A crystal oscillator
C. An RC controlled oscillator
D. None of these |
|
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Term
| C. The voltage controlled oscillator is producing the same frequency as the reference oscillator |
|
Definition
.
UNIT 7 EXAM
When we say that a PLL is "locked," what do we mean?
A. The voltage controlled oscillator is free running
B. The voltage controlled oscillator has stopped
C. The voltage controlled oscillator is producing the same frequency as the reference oscillator
D. None of these |
|
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Term
|
Definition
.
UNIT 7 EXAM
Which portion of a PLL converts voltage changes into frequency changes?
A. VCO
B. Phase detector
C. Loop Filter
D. None of these |
|
|
Term
|
Definition
.
UNIT 7 EXAM
Which portion of a PLL can be thought of as a decision maker -- constantly comparing the reference and VCO frequencies?
A. VCO
B. Phase detector
C. Loop filter
D. None of these |
|
|
Term
|
Definition
.
UNIT 7 EXAM
Which portion of a PLL is responsible for smoothing the pulsating DC voltage from the phase detector?
A. VCO
B. Divider
C. Loop Filter
D. None of these |
|
|
Term
|
Definition
.
UNIT 7 EXAM
When no input signal is applied to a PLL, the circuit will be in what state?
A. Free run
B. Capture
C. Lock
D. None of these |
|
|
Term
| B. Check that both phase detector inputs are exactly the same frequency |
|
Definition
.
UNIT 7 EXAM
How can a technician determine that a PLL is in lock?
A. Check the phase detector output for a 50% duty cycle
B. Check that both phase detector inputs are exactly the same frequency
C. Check that the VCO is producing an output signal
D. None of these |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
.
UNIT 7 EXAM
What type of data is a microcontroller likely to send to a PLL on initial reset?
A. Command
B. Initialization
C. Reset
D. None of these |
|
|
Term
| A. Change the frequency setting on the front panel (knob or pushbutton) |
|
Definition
.
UNIT 7 EXAM
What could a technician do to a unit in order to force its CPU to send command data to the PLL?
A. Change the frequency setting on the front panel (knob or pushbutton)
B. Press the RESET switch (or short the RESET contacts) for the CPU
C. Turn the unit off, then back on.
D. None of these |
|
|
Term
|
Definition
.
UNIT 7 EXAM
A DDS synthesizer has only one analog component. What is it?
A. Phase detector
B. High-pass filter
C. Voltage controlled oscillator
D. None of these |
|
|
Term
fout = fclk * (N/M) = 17 MH
B. 17.006249 MHz |
|
Definition
.
UNIT 7 EXAM
What frequency will be produced by a DDS ship if it is known that fclk = 40 MHz, M = 23^2 (the number of counts for one cycle), and N (the phase accumulator count increment value) = 1,826,032,055?
A. 21.100000 MHz
B. 17.006249 MHz
C. 14.318180 MHz
D. None of these |
|
|
Term
4.915200 MHz = 30 MHz*(N/2^32)
(4.915200 MHz*2^32)/30 MHz = N = 703 million
C. 703,687,442 |
|
Definition
.
UNIT 7 EXAM
What value of N is needed to produce an output frequency of 4.915200 MHz if a DDS chip has a 30 MHz clock and M = 2^32 (the number of counts for one cycle)?
A. 492,158,123
B. 123,654,789
C. 703,687,442
D. None of these |
|
|
Term
| A. Incorrect frequency output |
|
Definition
.
UNIT 7 EXAM
What is the primary symptom of a malfunctioning frequency synthesizer circuit?
A. Incorrect frequency output
B. Excessive harmonic strength
C. Distorted sine wave output
D. None of these |
|
|
Term
| B. Power supply, VCO input voltage, VCO output signal |
|
Definition
.
UNIT 7 EXAM
IF a PLL frequency synthesizer is producing no RF output signal at all, what items should be checked first and in what order?
A. Phase detector output, Loop filter output
B. Power supply, VCO input voltage, VCO output signal
C. VCO output signal, Phase detector "B" input
D. Phase detector "A" input, Reference oscillator |
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Term
|
Definition
.
UNIT 8 EXAM
Frequency modulation is best achieved at what stage in a transmitter?
A. Oscillator
B. Buffer
C. Driver
D. Final |
|
|
Term
|
Definition
.
UNIT 8 EXAM
The frequency produced by an FM transmitter when no information signal is being fed into the transmitter is called the:
a) Deviation
b) Center Frequency
c) Average
d) None of these |
|
|
Term
fmin = 95 kHz
fmax = 105 kHz
fc = 200 / 2 = 100 kHz
dev = fmax - fc = 105 kHz - 100 kHz = 5kHz
b) 5 kHz |
|
Definition
.
UNIT 8 EXAM
A certain FM transmitter has a minimum frequency of 95 kHz and a maximum frequency of 105 kHz. It is swinging between these two frequency extremes 1,000 times a second. What is the resulting deviation?
a) 10 kHz
b) 5 kHz
c) 20 kHz
d) None of these |
|
|
Term
fmax - fmin = 10 kHz
c) 1 kHz |
|
Definition
.
UNIT 8 EXAM
A certain FM transmitter has a minimum frequency of 95 kHz and a maximum frequency of 105 kHz. It is swinging between these two frequency extremes 1,000 times a second. What is th resulting deviation rate?
a) 10 kHz
b) 5 Khz
c) 1 kHz
d) None of these |
|
|
Term
Vi = 1 Vp
dev = 2.5 kHz
2.5 kHz * 2 = 5 kHz
d) None of the above |
|
Definition
.
UNIT 8 EXAM
An FM transmitter has a carrier frequency of 145.290 MHz and a deviation of 2.5 kHz. The information voltage is 1 Vp, and the information frequency is 880 Hz. What will happen to the deviation if the information voltage is changed to 2 Vp?
a) Deviation will stay the same (2.5 kHz)
b) Deviation will decrease to 1.25 kHz
c) Deviation will increase to 4 kHz
d) None of the above |
|
|
Term
|
Definition
.
UNIT 8 EXAM
What is the percentage of modulation of a 99.1 MHz FM broadcast signal whose deviation is 25 kHz?
A. 33%
B. 50%
C. 75%
D. None of these |
|
|
Term
|
Definition
.
UNIT 8 EXAM
An FM transmitter has a carrier frequency of 145.290 MHz and a deviation of 2.5 kHz. The information voltage is Vp, and the information frequency is 1.25 kHz. What will the resulting FM modulation index be?
A) 1.5
B) 2.0
C) 3.0
D) None of these |
|
|
Term
|
Definition
.
UNIT 8 EXAM
An FM transmitter is being modulated with 5 kHz intelligence and is producing 10 kHz of deviation. What will its bandwidth be according to Carson's rule?
A) 20 kHz
B) 25 kHz
C) 30 kHz
D) None of these |
|
|
Term
|
Definition
.
UNIT 8 EXAM
In theory, how many side frequencies are generated by the process of frequency modulation?
A) 2
B) 4
C) 8
D) None of these |
|
|
Term
|
Definition
.
UNIT 8 EXAM
An FM signal that produces only one significant pair of side frequencies is referred to as a/an:
A) Narrowband signal
B) Wideband signal
C) AM signal (with low)
D) None of these |
|
|
Term
|
Definition
.
UNIT 8 EXAM
The ratio of power for an FM broadcast signal from 0% to 100% modulation is:
A) 2.0 : 1
B) 1.0 : 1
C) 3.0 : 1
D) None of these |
|
|
Term
| B) converts a voltage into a reactance |
|
Definition
.
UNIT 8 EXAM
What is the function of a reactance modulator?
A) Converts a frequency into a voltage (FM detection)
B) Converts a Voltage into a reactance
C) Converts capacitive reactance into inductive reactance
D) None of these |
|
|
Term
|
Definition
.
UNIT 8 EXAM
A varactor diode is normally operated _____ biased, and as the magnitude of this bias voltage is increased, the total capacitance of the diode can be expected to _____. Choose the best response.
A. Forward, decrease
B. Forward, increase
C. Reverse, decrease
D. Reverse, increase |
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|
Term
| A. Insufficient deviation is produced |
|
Definition
.
UNIT 8 EXAM
What problem is introduced by attempting to directly control the frequency of an FM transmitter with a quartz crystal?
A. Insufficient deviation is produced
B. The crystal frequency becomes unstable
C. The crystal tends to stop oscillating at high temperatures
D. None of these |
|
|
Term
|
Definition
|
|
Term
| B. Compares the down-converted signal to a center frequency of 2.0 MHz |
|
Definition
.
UNIT 8 EXAM
What is the purpose of the frequency discriminator in a Crosby FM transmitter?
A. Provides the necessary carrier frequency changes (modulation)
B. Compares the down-converted signal to a center frequency of 2.0 MHz
C. Doubles the frequency of the reference oscillator
D. None of these |
|
|
Term
|
Definition
.
UNIT 8 EXAM
The input being applied to the frequency multiplier above is a 1 MHz FM signal with a deviation of 5 kHz. If the output tank is tuned to 3 MHz, what will the resulting output carrier and deviation frequencies be?
A. 3 MHz, 5 kHz
B. 1 MHz, 3 kHz
C. 3 MHz, 15 kHz
D. None of these |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
.
UNIT 8 EXAM
In the FM transmitter, fosc = 10.000 MHz, R = 1000, and N = 28,475. What will the output frequency at test point E be?
A. 2.8475 MHz
B. 4.9152 MHz
C. 8.8285 MHz
D. None of these |
|
|
Term
| C. High information frequencies are boosted in deviation at the transmitter |
|
Definition
.
UNIT 8 EXAM
What takes place during the process of preemphasis?
A. Low information frequencies are boosted at the transmitter
B. Mid-range information frequencies are reduced in amplitude at the transmitter
C. High information frequencies are boosted in deviation at the transmitter
D. None of these |
|
|
Term
| A. To reduce bothersome high-frequency noise |
|
Definition
.
UNIT 8 EXAM
What is the purpose of using preemphasis and deemphasis in FM transmitters and receivers?
A. To reduce bothersome high-frequency noise
B. To reduce distortion in the received audio information signal
C. To improve stereo separation
D. None of these |
|
|
Term
|
Definition
.
UNIT 8 EXAM
What type of filter is used for deemphasis in an FM receiver?
A. High pass
B. Low pass
C. Band pass
D. Band stop |
|
|
Term
|
Definition
.
UNIT 8 EXAM
In order to transmit FM stereo, what type of multiplexing is used?
A. TDM
B. FDM
C. CDM
D. None of theses |
|
|
Term
|
Definition
.
UNIT 8 EXAM
When a radio station is broadcasting an FM stereo program, what information will appear at the audio output of the FM receiver's detector to let the receiver know that the program is in stereo?
A. A 5 volt DC level
B. A 1 kHz square wave
C. A 10 kHz triangle wave
D. None of these |
|
|
Term
| A. Frequency to voltage converter |
|
Definition
.
UNIT 9 EXAM
An FM detector can be thought of a/an:
A. Frequency to voltage converter
B. Frequency converter
C. Voltage to frequency converter
D. None of these |
|
|
Term
|
Definition
.
UNIT 9 EXAM
Which stage in an FM receiver is responsible for removing most of the noise (in the form of amplitude changes) from an incoming signal?
A. Local oscillator
B. Limiter
C. AFC circuit
D. None of these |
|
|
Term
|
Definition
.
UNIT 9 EXAM
What system is necessary in an FM receiver to correct for local oscillator drift?
A. AGC
B. AFC
C. ALC
D. None of these |
|
|
Term
|
Definition
.
UNIT 9 EXAM
Assuming an IF frequency of 10.7 MHz and high-side injection, what local oscillator frequency would be required for an FM superheterodyne receiver to tune a station at 99.7 MHz?
A. 89.0 MHz
B. 104.3 MHz
C. 110.4 MHz
D. None of these |
|
|
Term
|
Definition
.
UNIT 9 EXAM
Which FM detector works by converting the signal to AM, then detecting it?
A. Slope
B. Foster-Seeley
C. Ratio
D. None of these |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| B. A frequency synthesizer circuit |
|
Definition
.
UNIT 9 EXAM
What replaces the local oscillator in a synthesized FM receiver?
A. An AFC circuit
B. A frequency synthesizer circuit
C. A RF buffer amplifier circuit
D. None of these |
|
|
Term
|
Definition
.
UNIT 9 EXAM
What controls the frequency of a modern synthesized FM receiver?
A. A mechanical variable capacitor
B. A variable resistor
C. Computer software
D. None of these |
|
|
Term
|
Definition
.
UNIT 9 EXAM
What device is usually used to tune the preselector bandpass filter in a synthesized FM receiver?
A. A varactor diode
B. A mechanical variable capacitor
C. A JFET
D. None of these |
|
|
Term
| B. From the VCO control voltage of the local oscillator synthesizer |
|
Definition
.
UNIT 9 EXAM
Where is the tuning voltage for the preselector bandpass filter in a synthesized FM receiver typically obtained?
A. From the AFC DC voltage produced by the detector circuit
B. From the VCO control voltage of the local oscillator synthesizer
C. From a variable resistor on the rear panel of the receiver
D. None of these |
|
|
Term
| B. By frequency-doubling the 19 kHz pilot |
|
Definition
.
UNIT 9 EXAM
How is the 38 kHz subcarrier recovered by an FM stereo decoder?
A. By frequency-dividing the local oscillator frequency by 1,024
B. By frequency-doubling the 19 kHz pilot
C. By locking a 38 kHz quartz crystal onto the 67 kHz subcarrier
D. None of these |
|
|
Term
| C. The L-R difference signal |
|
Definition
.
UNIT 9 EXAM
What information is contained in the frequency range 23 kHz - 53 kHz at the output of an FM detector, assuming that an FM stereo station is being received?
A. The L+R monaural signal
B. The FM stereo pilot signal
C. The L-R difference signal
D. None of these |
|
|
Term
|
Definition
.
UNIT 9 EXAM
An FM receiver detects a stereo transmission by looking for what frequency at the output of the FM detector stage?
A. 23 kHz
B. 67 kHz
C. 19 kHz
D. None of these |
|
|
Term
| A. An FM detector circuit |
|
Definition
.
UNIT 9 EXAM
What type of circuit must be connected to the output of the FM detector in order to recover the SCA programming?
A. An FM detector circuit
B. An AGC circuit
C. A clamper circuit
D. None of these |
|
|
Term
| 1st limiter clips top and bottom of signal to create common amplitude. 2nd rids the signal of any AM noise. |
|
Definition
.
UNIT 9 EXAM
What is the function of the limiter in an FM receiver? |
|
|
Term
1. Overcome local oscillation noise
2. Keep signal from bleeding back out to the antenna |
|
Definition
.
UNIT 9 EXAM
Give two reasons for the use of an RF amplifier in FM receivers. |
|
|
Term
| A. Poor high frequency response |
|
Definition
.
UNIT 11 EXAM
The primary disadvantage of twisted-pair transmission line is:
A. Poor high frequency response
B. High cost
C. Excessive resistance
D. None of these |
|
|
Term
|
Definition
.
UNIT 11 EXAM
Above 1000 MHz or so, what type of transmission line is the most efficient?
A. Coaxial
B. Waveguide
C. Twisted pair
D. None of these |
|
|
Term
|
Definition
.
UNIT 11 EXAM
Which of these transmission lines is considered to be balanced?
A. Coaxial
B. Ladder line
C. Waveguide
D. None of these |
|
|
Term
| C. A series inductance and a shunt capacitance |
|
Definition
.
UNIT 11 EXAM
An infinitely small section of lossless transmission line can be considered to be made of what components?
A. A series capacitance and a shunt resistance
B. A series resistance and a shunt inductance
C. A series inductance and a shunt capacitance
D. None of these |
|
|
Term
|
Definition
.
UNIT 11 EXAM
In order to prevent reflection of signal energy from the load, the load impedance for a 50 ohm transmission line should be:
A. 25 ohm
B. 40 ohm
C. 75 ohm
D. None of these |
|
|
Term
|
Definition
.
UNIT 11 EXAM
A certain transmission line has a maximum voltage of 100 volts, and a minimum voltage of 50 volts. What is the SWR on this line?
A. 1.5:1
B. 2:1
C. 4:1
D. None of these |
|
|
Term
|
Definition
.
UNIT 11 EXAM
A 50 ohm transmission line is terminated in a 40 ohm load. What percentage of the incident wave voltage from the transmitter will be reflected at the load?
A. 25.2%
B. 11.0%
C. 50.0%
D. None of these |
|
|
Term
|
Definition
.
UNIT 11 EXAM
What SWR will result if a 75 ohm transmission line is terminated in 100 ohm?
A. 1.25:1
B. 1.33:1
C. 2.00:1
D. None of these |
|
|
Term
|
Definition
.
UNIT 11 EXAM
What piece of test equipment can be used to measure standing waves on a transmission line?
A. Spectrum analyzer
B. DMM
C. Directional wattmeter
D. none of these |
|
|
Term
|
Definition
.
UNIT 11 EXAM
How many electrical degrees are represented by a half-circle of movement on a Smith chart?
A. 180
B. 90
C. 360
D. None of these |
|
|
Term
1. Ohmic loss
2. Radiation loss |
|
Definition
.
UNIT 11 EXAM
List the ways a transmission line can lose signal. Which can cause interference with other systems? |
|
|
Term
Both Leads
Different impedances |
|
Definition
.
UNIT 11 EXAM
Explain the difference between balanced and unbalanced transmission lines and give an example of each one. |
|
|
Term
| Because of the capacitance that exists between the wires. |
|
Definition
.
UNIT 11 EXAM
Why isn't twisted pair line useful at radio frequencies? |
|
|
Term
| At really high frequencies, the signal is forced to move along the outside (circumference) of the line. |
|
Definition
.
UNIT 11 EXAM
What is skin effect? |
|
|
Term
| When load resistance and line impedance are not equal, the incident wave is not fully absorbed by the load but instead reflected. To eliminate reflections one must simply match load resistance to line impedance. |
|
Definition
.
UNIT 11 EXAM
What causes reflections on transmission lines? How can reflections be eliminated? |
|
|
Term
wavelength = V/f = (3*10^8 m/sec) / 200 MHz
A. 1.5 meters |
|
Definition
.
UNIT 12 EXAM
What is the wavelength of a 200 MHz signal in free space?
A. 1.5 meters
B. 3.0 meters
C. 0.6 meters |
|
|
Term
| B. The orientation of the electric (E) field |
|
Definition
.
UNIT 12 EXAM
The polarization of a radio wave is characterized by:
A. The orientation of the magnetic (H) field
B. The orientation of the electric (E) field
C. The direction of flow of the RF energy field
D. None of these |
|
|
Term
|
Definition
.
UNIT 12 EXAM
What type of RF energy source radiates equally well in all directions?
A. Homogeneous
B. Isotropic
C. Dipole
D. None of these |
|
|
Term
| B. Characteristic impedance |
|
Definition
.
UNIT 12 EXAM
The ratio of electric to magnetic field density in a medium is known as its:
A. Resistivity
B. Characteristic impedance
C. Conductivity
D. None of these |
|
|
Term
| C. From two 1/4 wavelength conductors placed in a straight line, and fed at the center |
|
Definition
.
UNIT 12 EXAM
How is a Hertz dipole constructed?
A. From a 1/8 wavelength section of conductor, perpendicular to the ground
B. From a full wavelength loop of conductor
C. From two 1/4 wavelength conductors placed in a straight line, and fed at the center
D. None of these |
|
|
Term
|
Definition
.
UNIT 12 EXAM
A certain antenna is stated to be 90% efficient and has a claimed radiation resistance of 100 ohms. What is the approximate total input resistance of the antenna?
A. 111.1 ohms
B. 90.9 ohms
C. 150 ohms
D. None of these |
|
|
Term
| C. Shorter antenna length |
|
Definition
.
UNIT 12 EXAM
What is the primary advantage of a Marconi antenna over a Hertz?
A. Higher radiation resistance
B. More narrow beamwidth
C. Shorter antenna length
D. None of these |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| B. The forward gain increases |
|
Definition
.
UNIT 12 EXAM
What is the general effect seen when the beamwidth of an antenna is reduced?
A. The SWR at the feedpoint increases
B. The forward gain increases
C. The radiation resistance decreases
D. None of these |
|
|
Term
|
Definition
.
UNIT 12 EXAM
Which of the following specifications is the best way of comparing the directionality of an antenna system?
A. Antenna bandwidth
B. Front to back ratio
C. SWR
D. None of these |
|
|
Term
|
Definition
.
UNIT 12 EXAM
Which of these antennas is typically used when a wide bandwidth is required on VHF and UHF?
A. Yagi-Uda
B. Hertz
C. Log-Periodic
D. None of these |
|
|
Term
|
Definition
.
UNIT 12 EXAM
At frequencies above 1 GHz, which of these antennas would most likely be used?
A. Hertz
B. Log-Periodic
C. Dish
D. None of these |
|
|
Term
|
Definition
|
|
Term
|
Definition
.
UNIT 12 EXAM
What type of antenna is used by AM broadcasters when a directional pattern is desired?
A. Collinear array
B. Phased array
C. Marconi
D. None of these |
|
|
Term
| Electric and Magnetic maintaining a 90 degree angle between each other |
|
Definition
.
UNIT 12 EXAM
What are the two fields that make up a radio wave? What angle is maintained between them? |
|
|
Term
| Isotropic point radiation pattern is used as a reference (comparison) to help better understand antenna radiation patterns. (Water balloon comparison) |
|
Definition
.
UNIT 12 EXAM
What theoretical antenna radiates equally in all directions? Why is it needed? |
|
|
Term
| The natural electric and magnetic field density in open air around the antenna. |
|
Definition
.
UNIT 12 EXAM
What is meant by the characteristic impedance of free space? |
|
|
Term
| The shape of the path of the signal that is emitted from the antenna. |
|
Definition
.
UNIT 12 EXAM
What is the radiation pattern of an antenna? |
|
|
Term
1. GHz frequency antennas --> stay clear of signal
2. Capacitor discharges --> properly discharge before work
3. Falling off towers --> use harness
4. ESD --> In RF, use precautions
5. Plan your climb |
|
Definition
.
UNIT 12 EXAM
List at least four safety precautions for working with antennas, RF sources, and towers. |
|
|
