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Subel. A
616 questions
Subelement A
General
Section A
SITOR-ARQ is a common mode of data communications in the maritime service. It is a system based on transmission bursts and acknowledgements. What is the baud, and interval between the burst transmissions:
  • Correct Answer
    100 baud, 240 ms interval
  • 50 baud, 1000 �s interval
  • 200 baud, 10 ms interval
  • None of the above
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Weather information is commonly sent by radio in map form by one-way facsimile transmission. Two common parameters which must be set by the receiving station are:
  • Lines-per-inch (LPI), and primary scan direction (PSD)
  • Frequency shift (FS), and phase response pattern (PRP)
  • Black-mode signal (BMS), and frequency jitter tolerance (FJT)
  • Correct Answer
    Index of cooperation (IOC), and revolutions per minute (RPM)
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2182 kHz is the international radiotelephone distress frequency. It is also used for a calling channel. The authorized mode of emission is H3E (single-sideband full carrier). A3E (double-sideband full carrier) is only authorized for equipment:
  • Correct Answer
    Solely intended for distress and safety communications
  • Built and sold after the GMDSS implementation date
  • Built and sold before the GMDSS implementation date
  • Solely intended for ship-to-shore public correspondence
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Ship's power is generated as 3-phase and is ungrounded. On a delta-wound transformer with 120 VAC line-to-line secondary, what is the voltmeter reading from line to ground:
  • Approx 67 volts for a normal balanced system with no faults
  • 0 VAC for a system with that phase faulted to ground
  • 120 VAC when another phase is faulted to ground
  • Correct Answer
    Any of the above
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When passing through areas of static charge, high voltages can accumulate on antennas which are insulated from ground. What protects a connected receiver from damage?
  • Lightning arresters and suppressors
  • Protection diodes on receiver input
  • Capacitive coupling and static dissipative circuits
  • Correct Answer
    Any combination of the above
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Vertical shipboard antennas for use in the MF band (410-525 kHz) are often fitted with top-hat loading sections. What is the purpose of these structures?
  • Provides aerodynamic compensation for stress during high winds
  • Correct Answer
    Permits a physically short antenna to appear electrically longer
  • Improves the near-field radiated pattern at the expense of the far-field pattern
  • Prevents salt build-up on antennas from shunting RF energy to ground
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Modern reserve transmitters are solid-state designs and transmit using only A2 modulation. When measuring transmitter center frequency, what precaution must be taken:
  • Antenna must be grounded to suppress spurious side-lobes
  • Correct Answer
    Modulation must be reduced to zero to eliminate sidebands
  • Voltage to the PA must be kept at half-value
  • Antenna current must be reduced to about 2.5 uA
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Voltage may be expressed by what other expression?
  • Difference of potential
  • IF drop
  • Electromotive force
  • Correct Answer
    All of the above
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Amperage may also be known by:
  • Electron flow
  • Electron drift
  • Electric current flow
  • Correct Answer
    All of the above
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Factors which determine the amplitude of the voltage induced in a conductor which is cutting magnetic lines of force:
  • Flux density
  • Velocity that the conductor cuts the magnetic lines of force
  • The angle at which the conductor cuts through the magnetic lines of force
  • Correct Answer
    All of the above
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An electrical potential may be generated by:
  • Varying a magnetic field through a circuit
  • Chemical action
  • Photo-electric action
  • Correct Answer
    All of the above
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Ohm's law is stated as:
  • E = IR
  • I = E / R
  • R = E / I
  • Correct Answer
    All of the above
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The unit of electrical power is:
  • Watt
  • Joule per second
  • Correct Answer
    Both A & B
  • None of the above
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The unit of conductance is:
  • Ohm
  • Correct Answer
    Mho
  • Henry
  • Ampere
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The unit of inductance is:
  • Correct Answer
    Henry
  • Joule
  • Coulomb
  • Ohm
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The ratio of current through a conductor to the voltage which produces it is:
  • Inductance
  • Correct Answer
    Conductance
  • Resistance
  • None of the above
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The product of the number of turns and the current in amperes used to describe relative magnitude is:
  • Correct Answer
    Ampere turns
  • Joules per second
  • Push-pull convergence
  • Dissipation collection
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The property of a conductor or coil which causes a voltage to be developed across its terminals when the number of magnetic lines of force in the circuit or coil is changed is:
  • Capacitance
  • Correct Answer
    Inductance
  • Conductance
  • None of the above
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The charge of electricity which passes a given point in one second when a current of one ampere is flowing is:
  • Correct Answer
    Coulomb
  • Joule
  • Watt
  • None of the above
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C = capacity in farads. Q = the measure of the quantity of charge of electricity in Coulombs. E = the applied voltage. So Q = CE:
  • Correct Answer
    Determines the quantity of charge in a capacitor
  • Determines the Q of a circuit
  • Both A & B
  • None of the above
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Resistance is:
  • The quantity which determines power loss or dissipation
  • The factor of proportionality between voltage and current
  • Measured in ohms
  • Correct Answer
    All of the above
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The unit of AC impedance in a circuit is:
  • Correct Answer
    Ohm
  • Mho
  • Joule
  • None of the above
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The unit of capacitance is:
  • Farad
  • Microfarad
  • Coulomb
  • Correct Answer
    A & B
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Decibel is:
  • The unit used to express the ratio between two sound power levels
  • The unit used to express the ratio between two electrical power levels
  • Correct Answer
    Both A & B
  • None of the above
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What factors determine the charge stored in a capacitor?
  • Capacitance of the capacitor
  • The applied voltage
  • Correct Answer
    Both A & B
  • None of the above
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Ohm's law for AC circuits when I = amperes, E = volts, Z = impedance in volts is:
  • I = E/Z
  • E = IZ
  • Z= Z/I
  • Correct Answer
    All of the above
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The formula for determining the power in a DC circuit when the voltage and resistance are known is:
  • Correct Answer
    P = ( E squared) R
  • P = EI
  • P = ( I squared) R
  • PF = W/IE
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The formula for finding power in a DC circuit when current and resistance are known:
  • P = IE
  • Correct Answer
    P = ( I Squared) R
  • PF = W/IE
  • None of the above
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The formula for finding power in a DC circuit when current and voltage are known:
  • Correct Answer
    P = EI
  • P = ( I squared ) R
  • PF = W/IE
  • None of the above
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The prefix " kilo " means:
  • Correct Answer
    To multiply by 1000 whatever quantity follows
  • To divide by 1000 whatever quantity follows
  • To add 1000 to whatever quantity follows
  • None of the above
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The prefix " micro " means:
  • Correct Answer
    Divide by 1,000,000 whatever quantity follows
  • Multiply by 1,000,000 whatever quantity follows
  • Add 1,000,000 to whatever quantity follows
  • Divide by 1,000 whatever quantity follows
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The factor by which the product of volts and amperes must be multiplied to obtain true power is:
  • Correct Answer
    Power factor
  • Apparent power
  • Phase angle
  • None of the above
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The prefix " meg " means:
  • Correct Answer
    Multiply by 1,000,000 whatever quantity follows
  • Multiply by 100,000 whatever quantity follows
  • Multiply by 1,000 whatever quantity follows
  • Divide by 1,000,000 whatever quantity follows
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Factors which influence the resistance of a conductor:
  • Cross-sectional area
  • Length
  • Temperature
  • Correct Answer
    All of the above
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Halving the cross-sectional area of a conductor will:
  • Correct Answer
    Double the resistance
  • Half the resistance
  • Not affect the resistance
  • None of the above
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Name four conducting materials in order of their conductivity.
  • Gold, silver, copper, platinum
  • Correct Answer
    Silver, gold, zinc, platinum
  • Silver, copper, zinc, aluminum
  • Aluminum, zinc, copper, platinum
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Good insulators at radio frequencies are:
  • Pyrex, mica
  • Isolantite, steatite, polyethylene
  • Rubber, porcelain
  • Correct Answer
    A & B
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A resistance across which a constant voltage is applied is doubled. What power dissipation will result?
  • Correct Answer
    One half
  • One fourth
  • Doubled
  • None of the above
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The needle of a magnetic compass when placed within a coil carrying an electric current:
  • Will tend to become parallel with the axis of the coil
  • Will point to the north pole end of the coil
  • Will point to the south pole end of the coil
  • Correct Answer
    A & B
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Electrical resistance is measured with:
  • Correct Answer
    An ohmmeter
  • A wattmeter
  • An Ammeter
  • A voltmeter
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The sum of all voltage drops around a simple DC circuit, including the source, is:
  • Correct Answer
    Zero
  • Insignificant
  • Infinite
  • None of the above
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If a resistance to which a constant voltage is applied is halved, what power dissipation will result?
  • Correct Answer
    Doubled
  • Halved
  • Tripled
  • Same
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The diameter of a conductor six inches long is doubled, what will be the effect on the resistance?
  • One-fourth the original value
  • One-half the original value
  • The resistance varies inversely with the cross-sectional area of the conductor
  • Correct Answer
    A & C
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A minute subdivision of matter having the smallest known unit of negative electrical charge is:
  • Correct Answer
    Electron
  • Ion
  • Gilbert
  • Joule
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Conductors differ from nonconductors, i.e.:
  • There are a large number of free electrons in a good conductor
  • There is a small number of free electrons in a non-conductor
  • There is an equal amount of free electrons in a good conductor and in a non-conductor
  • Correct Answer
    A & B
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Direction of flow of DC electricity in a conductor can be determined by:
  • A magnetic compass and the left hand rule
  • A magnetic compass and the right hand rule
  • Connecting an ammeter with marked polarities in series with the circuit
  • Correct Answer
    A & C
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The difference between electrical power and electrical energy is:
  • Electrical power is the rate of doing work by electricity
  • Electrical energy is the ability to accomplish work by electricity
  • Correct Answer
    A & B
  • None of the above
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A positive temperature coefficient means:
  • Resistance increases as the temperature increases
  • Resistance decreases as the temperature decreases
  • Correct Answer
    Both A & B
  • None of the above
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A liquid which is capable of conducting electricity, but undergoes decomposition while doing so is:
  • Correct Answer
    An electrolyte
  • A ferromagnetic material under the influence of a magnetizing force
  • Equal to the ohmic resistance of the circuit
  • None of the above
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The effective value of an RF current and the heating value of the current are:
  • Correct Answer
    The same
  • Effective value divided by two equals the heating value
  • Effective value multiplied by two equals the heating value
  • None of the above
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One horsepower is:
  • 746 Watts
  • Roughly 3/4 kilowatt
  • Corresponds to lifting 550 pounds at the rate of one foot per second
  • Correct Answer
    All of the above
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What factors determine the heat generated in a conductor?
  • It is directly proportional to the resistance
  • It is directly proportional to the square of the current
  • Correct Answer
    Both A & B
  • None of the above
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What is the ratio of peak to average value of a sine wave?
  • 1.57 to 1
  • 1 to 0.636
  • 1 to 1
  • Correct Answer
    A & B
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When the current sine wave in a circuit reaches its peak value before the voltage wave:
  • Correct Answer
    It is said to have a leading power factor
  • It is said to have a lagging power factor
  • It is said to be in phase
  • None of the above
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An "harmonic" is:
  • Correct Answer
    A whole multiple of an original frequency
  • The heating value of an RF current
  • The internal impedance of a power source
  • A multiple of the power factor
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Assuming a power source to have a fixed value of internal impedance, maximum power will be transferred to the load when:
  • Correct Answer
    The load impedance equals the internal impedance of the source
  • The load impedance is higher than the source impedance
  • The load impedance is lower than the source impedance
  • None of the above
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When two sine waves of the same frequency do not reach their maximum or minimum values simultaneously:
  • A phase difference exists
  • A phase difference does not exist
  • The sign waves are out of phase
  • Correct Answer
    A & C
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Which method may be used to obtain more than one value of voltage from a fixed DC source?
  • Use a resistance type voltage divider
  • Connect voltage regulator tubes of suitable values and tap off the desired output voltage
  • Correct Answer
    Both A & B
  • None of the above
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The conductance (G) of a circuit if 6 A flows when 12 VDC is applied is:
  • Correct Answer
    0.5 mho
  • 1.0 mho
  • 0.25 mho
  • None of the above
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Two 10 W, 500 ohm resistors in parallel will dissipate how many watts?
  • Correct Answer
    20 watts
  • 10 watts
  • 30 watts
  • 40 watts
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A 20 ohm resistor with a current of 0.25 A passing through it will dissipate how many watts?
  • 10 watts
  • 20 watts
  • 0.025 watts
  • Correct Answer
    1.25 watts
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If the voltage to a circuit is doubled and the resistance is increased to three times the original value, what will be the final current?
  • 1/3 the original current
  • Correct Answer
    2/3 the original current
  • 3 times the original current
  • None of the above
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If a vacuum tube with a filament rating of 0.25 A and 5 V is operated from a 6 volt battery, what value of resistor is necessary?
  • Correct Answer
    4 ohms
  • 5 ohms
  • 10 ohms
  • 2 ohms
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The minimum power dissipation rating of a resistor of 20,000 ohms across a potential of 500 V should be:
  • Correct Answer
    25 watts
  • 12.5 watts
  • 15 watts
  • None of the above
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The total power dissipation capability of two 10 watt, 500 ohm resistors connected in series is:
  • Correct Answer
    20 watts
  • 10 watts
  • 5 watts
  • None of the above
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What is the total power dissipation capability of two 10 watt 500 ohm resistors connected in parallel?
  • Correct Answer
    20 watts
  • 40 watts
  • 5 watts
  • None of the above
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What is the maximum current carrying capacity of a resistor of 5000 ohms, 200 watts?
  • Correct Answer
    0.2 A
  • 1 A
  • 1.2 A
  • None of the above
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What is the total resistance of a parallel circuit consisting of a 10 ohm branch and a 25 ohm branch?
  • @ ohms
  • 10.3 ohms
  • 7.0 ohms
  • Correct Answer
    7.14 ohms
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The current through two resistors in series is 3 A. Resistance #1 is 50 ohms, resistance #2 drops 50 V across its terminals. What is the total voltage?
  • Correct Answer
    200 V
  • 220 V
  • 110 V
  • 180 V
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An 18 ohm and a 15 ohm resistor are connected in parallel; a 36 ohm resistor is connected in series with this combination; a 22 ohm resistor is connected in parallel with this total combination. The total current is 5 A. What current is flowing in the 15 ohm resistor?
  • Correct Answer
    0.908 A
  • 1.000 A
  • 1.908 A
  • 0.809 A
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A circuit passes 3 A. The internal resistance of the source is 2 ohms. The total resistance is 50 ohms. What is the terminal voltage of the source?
  • Correct Answer
    150 V
  • 100 V
  • 110 V
  • 240 V
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A relay coil has 500 ohms resistance, and operates on 125 mA. What value of resistance should be connected in series with it to operate from 110 VDC?
  • Correct Answer
    380 ohms
  • 400 ohms
  • 200 ohms
  • None of the above
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Given: Input power to a receiver is 75 watts. How much power does the receiver consume in 24 hours of continuous operation?
  • 1800 watthours
  • 1.80 kilowatthours
  • Correct Answer
    A & B
  • None of the above
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The total reactance when two capacitances of equal value are connected in series is:
  • The product of the two individual reactances in ohms
  • Correct Answer
    The sum of the two individual reactances in ohms
  • The difference of the two individual reactances in ohms
  • None of the above
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A capacitor's charge is stored:
  • Upon the inner surface of the capacitor plates
  • As an electrostatic field which exists in the space between the plates
  • Correct Answer
    A & B
  • None of the above
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The voltage drop across an individual capacitor of a group of capacitors connected in series across an AC source is:
  • Inversely proportional to the ratio of the capacitance of the capacitor being considered
  • Inversely proportional to the total capacitance of the combination
  • Directly proportional to the applied voltage across the series combination
  • Correct Answer
    All of the above
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What is the total capacitance of the capacitors of 3, 5, and 7 microfarad connected in series?
  • 14.79 microfarad
  • Correct Answer
    1.479 microfarad
  • 15 microfarad
  • None of the above
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If capacitors of 3, 5, and 7 microfarad are connected in parallel, what is the total capacitance?
  • Correct Answer
    9 microfarad
  • 15 microfarad
  • 10 microfarad
  • 3 microfarad
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How many capacitors of 400 volts and 2 microfarad each would be necessary to obtain a combination rated at 1600 volts and 1.5 microfarad?
  • 10
  • Correct Answer
    12
  • 14
  • 16
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If a turn in an inductor is shorted:
  • There will be an decrease of induction
  • There will be a decrease of Q
  • There will be overheating with possible burnout
  • Correct Answer
    All of the above
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The relationship between the number of turns and the inductance of a coil may be expressed by:
  • Correct Answer
    The inductance varies approximately as the square of the number of turns
  • The inductance varies approximately as the square root of the number of turns
  • Both A & B
  • None of the above
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The formula for determining the resonant frequency of a circuit when the inductance and capacitance are known is:
  • f = 1/(2 pi times the square root of LC)
  • f = 0.159/(the square root of LC)
  • Correct Answer
    Both A & B
  • None of the above
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The formula for determining the wavelength when the frequency is known is:
  • Wavelength = 300,000/ f kHz
  • Wavelength = 300,000,000/ f Hz
  • Wavelength = 300/ f MHz
  • Correct Answer
    All of the above
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The wavelength of the period of one complete cycle of a radio wave of 0.000,001 second is:
  • Correct Answer
    300 M
  • 3000 M
  • 30 M
  • 70 cm
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The efficiency of a radio device is:
  • The ratio of the power input to the power output
  • Correct Answer
    The ratio of the useful power output to the power input
  • The ratio of the minimum power output to the maximum power output
  • None of the above
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What is the total impedance of a parallel capacitor and inductor with equal values of reactance?
  • Infinite total reactance
  • Zero total reactance
  • Parallel impedance is resistive and infinite
  • Correct Answer
    B & C
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The total inductance of two coils in parallel without any mutual coupling is:
  • Correct Answer
    Equal to the product of the two inductances divided by their sum
  • The sum of the individual inductances
  • Zero
  • None of the above
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What is the total reactance of a series AC circuit, with no resistance and equal inductance and capacitive reactances?
  • The two reactances cancel being equal and opposite
  • Net impedance is purely resistive and contains no reactive component
  • The total reactance is zero at the resonant frequency
  • Correct Answer
    All of the above
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The total inductance of two coils in series without any mutual coupling is:
  • Correct Answer
    The sum of the individual inductances
  • The product of the individual inductances divided by their sum
  • Infinite
  • None of the above
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One wave-length is:
  • The distance a wave will travel in the time for one cycle
  • Centimeter wavelength = 30,000 / frequency MHz
  • Correct Answer
    A and B
  • Neither A or B
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In an AC circuit, a series inductance acting alone:
  • Correct Answer
    Causes the current to lag the applied voltage by 90 degrees
  • Causes the current to lead the applied voltage by 90 degrees
  • Causes the current to lag the applied voltage by 45 degrees
  • Causes the current to lead the applied voltage by 45 degrees
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Shock excitation into an L-C circuit is the result of:
  • A voltage being momentarily introduced
  • The capacitor may be charged
  • The inductor may have a voltage induced
  • Correct Answer
    All of the above
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The term cathode ray usually applies to:
  • Correct Answer
    A fairly high velocity electron beam
  • Background noise
  • The logarithm gain of an electron beam
  • None of the above
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Shielding an RF inductance:
  • Increases the losses of the inductance
  • Lowers the inductance value and the Q
  • Increases the coil capacity to the shield
  • Correct Answer
    All of the above
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The tendency of a tank circuit to keep oscillating for a time after the excitation energy has been removed is:
  • Push-pull effect
  • Correct Answer
    Flywheel effect
  • Polarizing effect
  • Parasitic oscillation
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Power factor is defined as:
  • The ratio between the resistance and the impedance in a circuit
  • The ratio between the true power and the apparent power of a circuit
  • Correct Answer
    Both A&B
  • None of the above
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High or low frequency oscillations occurring in circuits other than the original tank desired output frequencies are:
  • Harmonics
  • Correct Answer
    Parasitic oscillations
  • Hysteresis
  • Eddy currents
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What are effects of parasitic oscillations?
  • Change of bias
  • Reduced efficiency of the amplifier tube
  • Distortion of the modulated wave
  • Correct Answer
    All of the above
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The velocity of propagation of radio frequency waves in free space is:
  • 300,000 meters / second
  • 186,284 miles / second
  • The same as the velocity of light in free space
  • Correct Answer
    All of the above
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To double the resonant frequency of a resonant circuit:
  • Make C one third of its original value
  • Correct Answer
    Make L and C both half their original values
  • Decreasing the value of both L and C in any proportion so that their product will be one-half of the original values
  • None of the above
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How may the Q of a parallel resonant circuit be increased?
  • Increasing coupling to the resonant circuit
  • Using coil and capacitor supports of special low - loss materials
  • Correct Answer
    Both A and B
  • Decreasing coupling to the resonant circuit
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If L and C in a parallel resonant circuit resonants at 1000 kHz are so varied that their product remains constant, what will be the resulting resonant frequency?
  • 10,000 kHz
  • 100 kHz
  • Correct Answer
    1 MHz
  • None of the above
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What is the resonant frequency of a tuned circuit consisting of a 500 picofarad capacitor, a 150 microfarad tuning coil, and 10 ohms resistance?
  • Correct Answer
    581 kHz
  • 753 kHz
  • 498 kHz
  • None of the above
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What is voltage regulation as applied to power supplies?
  • Correct Answer
    The ratio of change in voltage between no load and full load to the full-load voltage output
  • The ratio of output to input voltage
  • Voltage output of the power supply under full load
  • The ratio of input to output voltage
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An EMF may be generated by sound waves by what principle?
  • Electrostatic
  • Piezo-electric
  • Resistance change
  • Correct Answer
    All of the above
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How can you correct power factor in an electrical circuit?
  • Inductance is used to correct a leading angle
  • Capacitance is used to correct a lagging angle
  • Neither A or B
  • Correct Answer
    Both A and B
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Permeability is:
  • The magnetic field created by a conductor wound on a laminated core and carrying any electric current
  • Correct Answer
    The ratio of magnetic flux density in a substance to the magnetizing force which produces it
  • Polarized molecular alignment in a ferromagnetic material while under the influence of a magnetizing force
  • Both A and C
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The time in seconds for a capacitor to attain 63.2 % of the applied voltage across its terminals is:
  • Twice the natural period of oscillation of the circuit
  • Varactance
  • Correct Answer
    Time constant
  • Equal to the ohmic resistance of the circuit
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What is the reactance of a 2-henry choke at 3000 Hz?
  • 5300 ohms
  • Correct Answer
    37,680 ohms
  • 376,800 ohms
  • 53,000 ohms
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If there is no resistance in either leg of a circuit with an inductance of 5 henrys in parallel with a capacitance of 1 microfarad, what is the equivalent impedance of the parallel network circuit?
  • Zero
  • Correct Answer
    Infinite
  • Median
  • None of the above
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What is the total impedance of a series AC circuit having a resistance of 6 ohms, an inductive reactance of 17 ohms, and zero capacitive reactance?
  • 15 ohms
  • 27 ohms
  • Correct Answer
    18 ohms
  • 5 ohms
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The total impedance of a series AC circuit with an inductive reactance of 24 ohms, a resistance of 16 ohms, and a capacitive reactance of 16 ohms is:
  • 20 ohms
  • Correct Answer
    16 ohms
  • 10 ohms
  • None of the above
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Essentials for making a good solder connection are:
  • Bright, clean parts
  • Plenty of heat with the minimum amount of solder used
  • Discontinue operating on high power
  • Correct Answer
    None of the above
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For protection of personnel handling a transmitter:
  • Correct Answer
    Ground all exposed metal parts
  • Transmitter is equipped to shunt grounded faults
  • Discontinue operating on high power
  • None of the above
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The ratio of peak-to-effective voltage values of a sign wave are:
  • 1.414 to 1
  • 1 to 0.707
  • Correct Answer
    Both A and B
  • Neither A or B
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The opposition to the creation of magnetic lines of force in a magnetic circuit is known as:
  • Correct Answer
    Reluctance
  • Hysteresis
  • Permeability
  • Eddy currents
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The ratio of magnetic flux density to the field strength is known as:
  • Residual magnetism
  • Correct Answer
    Permeability
  • Reluctance
  • None of the above
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The magnetic force which remains in a substance after the original magnetizing force has been removed is known as:
  • Reluctance
  • Correct Answer
    Residual magnetism
  • Permeability
  • Hysteresis
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The direction of electron flow through a coil and the manner of winding the turns:
  • Correct Answer
    Influence the direction of magnetic line of force generated by an electromagnet
  • Are determined by the left-hand status rule
  • Are determined by the diameter of the wire and length
  • Both A and C
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Adding an iron core to an air-core inductance:
  • Correct Answer
    Increases the inductance
  • Decreases the inductance
  • Does not affect the inductance
  • Causes parasitic oscillations in the inductor
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Electromagnets are used in:
  • loudspeakers
  • meters
  • motors
  • Correct Answer
    All of the above
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What will be the effect of a small increase in the number of turns upon the field strength of a single layer solenoid?
  • Decrease in field strength if the coil length is increased
  • Unchanged if the spacing is reduced to keep the length constant
  • Correct Answer
    Both A and B
  • None of the above
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Can a transformer be used with direct current?
  • In general, no
  • If the DC current is periodically interrupted it would be possible to use an original DC voltage source
  • Correct Answer
    Both A and B
  • None of the above
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A tube containing either a filament or cathode structure, grid, and a plate is a:
  • Correct Answer
    Triode
  • Tetrode
  • Pentode
  • Diode
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A tube similar to a triode with the addition of a spirally wound screen grid between the plate and control grid is a:
  • Diode
  • Correct Answer
    Tetrode
  • Pentode
  • Triode
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Theoretical gain of a tube. The ratio of a small change in plate voltage to give a certain small change in plate current to a change in grid which would cause the same current:
  • Correct Answer
    Amplification factor
  • Power factor
  • Maximum inverse plate voltage
  • None of the above
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Effectiveness of the grid in causing changes of plate current:
  • Transconductance
  • Mutual conductance
  • Plate resistance
  • Correct Answer
    A & B
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The maximum negative anode voltage with respect to the cathode. It equals the DC voltage at the input to the plus the peak AC voltage applied during the nonconducting portion of the cycle of operation of the tube:
  • Correct Answer
    Maximum inverse plate voltage
  • Mutual conductance
  • Both A & B
  • None of the above
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What is the primary purpose of the control grid of the triode?
  • Correct Answer
    To provide a means of obtaining amplification
  • To neutralize RF amplifiers
  • Blocks passage of electrons
  • None of the above
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What is the primary purpose of the screen grid of the tetrode?
  • Reduces the grid to plate capacitance, making it unnecessary to neutralize RF amplifiers except at very high frequencies
  • Makes the plate current substantially independent of plate voltage, permitting much higher values of amplification
  • Correct Answer
    Both A & B
  • None of the above
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What is the primary purpose of the suppressor grid of a pentode?
  • Correct Answer
    Is highly negative with respect to the plate and returns secondary emission to the plate, increasing the permissible gain and the tube efficiency
  • Reduces interelectrode capacitance between control grid and plate making plate efficiency about 10% greater than a triode
  • Both A & B
  • Neither of the above
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Thoriated tungsten is usually used to make:
  • Correct Answer
    Filaments
  • Heaters
  • Cathodes
  • None of the above
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In what types of circuits do beam power vacuum tubes find application?
  • As audio amplifier in the output and power stages of circuits having low to moderately high output ratings
  • As an RF power amplifier
  • Correct Answer
    Both A & B
  • None of the above
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When free electrons in a conductor acquire sufficient energy to leave the conductor and pass into the surrounding space, it is expressed as:
  • Secondary emission
  • Correct Answer
    Electron emission
  • Primary electron release
  • None of the above
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The emission of electrons from a material due to the impact of high-velocity electrons on its surface is:
  • Primary electron emission
  • Correct Answer
    Secondary emission
  • Mimetic emission
  • None of the above
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Characteristics of a vacuum tube operating as a class A amplifier:
  • Correct Answer
    Low plate circuit efficiency, about 25%; practically no grid driving power; plate current flowing for 360 degrees of each cycle; practically no distortion of the output waveshape
  • Plate circuit efficiency, about 50-60%; plate current flows slightly more than 180 degrees of each cycle, medium power output
  • High efficiency, up to 80%; plate current drawn in bursts; great distortion of output waveshape
  • None of the above
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Characteristics of a vacuum tube operating as a class B amplifier:
  • Low plate circuit efficiency, about 25%; practically no grid driving power; plate current flowing for 360 degrees of each cycle; practically no distortion of the output waveshape
  • Correct Answer
    Plate circuit efficiency, about 50-60%; plate current flows slightly more than 180 degrees of each cycle, medium power output
  • High efficiency, up to 80%; plate current drawn in bursts; great distortion of output waveshape
  • None of the above
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Factors which determine bios voltage of a vacuum tube:
  • Class of operation, plate supply voltage, permissible distortion
  • Grid signal magnitude, permissible plate dissipation, desired amplification factor
  • The no-signal plate current desired, the desirability of drawing grid current
  • Correct Answer
    All of the above
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In the usual Class A amplifier:
  • Correct Answer
    There is no grid current
  • Plate current flows slightly more than 180 degrees of each cycle
  • Biased to twice
  • None of the above
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The DC bias in a Class A amplifier:
  • Correct Answer
    Usually is negative as measured at the grid with respect to cathode
  • Usually is positive as measured at the grid with respect to cathode
  • Cannot be determined
  • None of the above
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What is the effect of incorrect grid bias in a Class A amplifier?
  • Distortion of the output waveshape
  • Possible excessive plate dissipation if the bias is too low
  • Correct Answer
    Both A & B
  • None of the above
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The approximate efficiency of a Class A vacuum tube amplifier:
  • Correct Answer
    20%-30%
  • 60%
  • 85%
  • 100%
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The approximate efficiency of a Class B vacuum tube amplifier:
  • 20%-30%
  • Correct Answer
    60%
  • 85%
  • 100%
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The approximate efficiency of a Class C vacuum tube amplifier:
  • 20%-30%
  • 60%
  • Correct Answer
    85%
  • 100%
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A charge due to the accumulation of negative electrons because the plate potential cannot attract all of the electrons leaving the emitter:
  • Getter
  • Correct Answer
    Space charge
  • Plate saturation
  • None of the above
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A material flashed by the application of heat after the tube is evacuated that absorbs any gases remaining inside the tube:
  • Space charge
  • Correct Answer
    Getter
  • Collector
  • Emitter
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What types of vacuum tube filaments are reactivated:
  • Barium berylliate
  • Correct Answer
    Thoriated tungsten
  • Nickel
  • Thorium oxide
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A tungsten filament is operated at ____ temperature than a thoriated tungsten filament:
  • Correct Answer
    A higher
  • A lower
  • The same
  • Unknown
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The presence of gas within a tube is indicated:
  • Correct Answer
    By a blue glow
  • By a red glow
  • By a yellow glow
  • None of the above
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The cathode of an indirectly heated type of vacuum tube should be maintained at nearly the same potential as the heater circuit:
  • To reduce hum pickup into the cathode
  • To prevent breakdown of the insulation between the heater and cathode
  • Correct Answer
    A & B
  • None of the above
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Transmitting tube filaments should be maintained at recommended voltages:
  • To realize the greatest life-expectancy
  • If the filament voltage is too low, the emission will be reduced and operation of the circuit may be adversely affected
  • If the voltage is too high, the filament may burn out
  • Correct Answer
    All of the above
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Use of an AC filament supply is desirable:
  • Correct Answer
    Mostly for practical reasons. It is easily obtainable
  • Hum may be introduced into the amplifier
  • A & B
  • None of the above
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If a DC filament supply is used, it is advisable to periodically reverse the polarity of the filament potential:
  • Correct Answer
    To lengthen the life of the filament
  • To lengthen the life of the power source
  • Both A & B
  • None of the above
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Bias voltage on the grid of an AF amplifier tube:
  • Determines the operating conditions of the tube
  • The correct value is essential for undistorted Class A output
  • In power amplifiers the plate current must be limited to safe value not to exceed the rated plate dissipation of the tube
  • Correct Answer
    All of the above
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The screen grid in a vacuum tube:
  • Makes it unnecessary to neutralize RF amplifiers except at very high frequencies,
  • Makes it possible to obtain much higher values of amplification than with triodes
  • Correct Answer
    A & B
  • None of the above
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The suppressor grid in a multielement vacuum tube:
  • Is highly negative with respect to the plate
  • Returns secondary electrons to the plate
  • Increases the permissible gain and the efficiency of the tube
  • Correct Answer
    All of the above
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The gain of a triode audio amplifier is a function of:
  • Tube transconduction
  • Plate load impedance
  • Transformer step-up (if used)
  • Correct Answer
    All of the above
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"Load" on a vacuum tube commonly refers to:
  • The impedance through which plate current flows to produce a useful output
  • Increases as the load impedance approaches the internal plate impedance in value
  • Correct Answer
    A & B
  • None of the above
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A case in which the grid is held at an excessively negative value for a period of time thereby cutting off plate current:
  • Correct Answer
    Blocked grid
  • Blocked plate
  • Motorboating
  • Tuned grid
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The maximum power that can be safely and continuously dissipated in heat on the plate:
  • Correct Answer
    Maximum plate dissipation
  • Maximum power dissipation
  • Continuous plate dissipation
  • Plate heat dissipation
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Occurs when plate current equals electron emission for any given filament or cathode temperature:
  • Correct Answer
    Plate saturation
  • Electron saturation
  • Filament saturation
  • None of the above
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The most desirable factor in the choice of a vacuum tube for a voltage amplifier:
  • A low value of transconductance
  • Correct Answer
    A high value of transconductance
  • High output tube capacitance
  • None of the above
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Lack of requirement for neutralizing, except at ultra high frequencies, is an advantage of a tetrode over ____:
  • Correct Answer
    A Triode
  • A Pentode
  • A & B
  • None of the above
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Characteristics of a vacuum tube operating as a Class C amplifier:
  • Low plate circuit efficiency, about 25%; practically no grid driving power; plate current flowing for 360 degrees of each cycle; practically no distortion of the output waveshape
  • Plate circuit efficiency, about 50-60%; plate current flows slightly more than 180 degrees of each cycle; medium power output
  • Correct Answer
    High plate circuit efficiency, up to 80%; plate current drawn in bursts; great distortion of output waveshape
  • None of the above
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Plate current flows for less than 180 degrees (about 120 degrees when the grid bias is about twice cutoff value) in what class amplifier?
  • A
  • B
  • Correct Answer
    C
  • AB
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Tubes operated as Class C amplifiers are not suited for audio-frequency amplifiers:
  • Correct Answer
    Because of excessive distortion
  • Because of current requirement
  • Because of reduced life expectancy of the filament
  • None of the above
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Low plate current may be caused by:
  • Low filament emission and voltage
  • Excessive bias value, shorted screen by-pass capacitor
  • Open grid circuit, low screen grid supply voltage
  • Correct Answer
    All of the above
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A tuned circuit made up of inductance and capacitance is:
  • Correct Answer
    An oscillator
  • A neutralizer
  • Voltage divider
  • None of the above
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Some radio-frequency amplifiers must be neutralized:
  • To maintain linear operation
  • Correct Answer
    To prevent sustained oscillations from occurring in the amplifier
  • Sustain feedback
  • None of the above
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Cavity resonators are:
  • A form of resonant tank circuit
  • Consist of a hollow metal cylinder bead on all sides
  • Have a very high Q and selectivity
  • Correct Answer
    All of the above
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The diode detector:
  • Is square law on weak signals
  • Is practically linear on strong signals
  • Is square law on strong signals
  • Correct Answer
    A & B
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The functioning of a grid-leak detector:
  • Depends on the ability of the grid leak and capacitor to follow the average grid current variations which are directly proportioned to the modulation envelope
  • Depends on second harmonic distortion
  • Very sensitive to weak signals
  • Correct Answer
    A & C
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Characteristic of a square law type of vacuum tube detector:
  • High sensitivity is provided due to the audio output signal amplitude being proportioned to the square of the radio frequency voltage
  • High percentage of second harmonic distortion
  • Works on weak signals only
  • Correct Answer
    All of the above
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A diode detector ordinarily produces ____ overall distortion of the audio output wave than does a triode detector:
  • Correct Answer
    Lower
  • Higher
  • Practically the same
  • Either A or B
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Operating conditions for determining that a tube is being used as a power detector:
  • Bias at about cutoff
  • High input grid resistance
  • Plate circuit rectification
  • Correct Answer
    All of the above
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Why is a center top usually provided for vacuum tube plate and grid return circuits when and AC filament supply is used?
  • Correct Answer
    To prevent hum voltage from modulating the normal signals
  • To allow more filament current
  • A & B
  • None of the above
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How would you determine the cathode-bias resistance necessary to provide correct grid bias for an amplifier?
  • Bias equals the IR drop across the cathode
  • Bias is found by dividing the desired DC bias voltage by the total no-signal cathode current
  • For a tetrode or pentode, the screen current must be added to the plate current
  • Correct Answer
    All of the above
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Given the following vacuum tube constants: Gp = 1000 V, Ip = 150 mA, Ig = 10 mA, Grid leaks = 5000 ohms. What would be the grid bias voltage?
  • Correct Answer
    50 V
  • 100 V
  • 25 V
  • None of the above
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What currents will be indicated by a milliammeter connected between the center top of the filament transformer of a tetrode and negative high voltage?
  • Plate current
  • Screen grid current
  • Correct Answer
    Combined plate and screen grid currents
  • None of the above
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A dynatron oscillator is a ____ which depends upon the negative resistance characteristic of a tetrode tube for its operation:
  • Correct Answer
    Tuned circuit operation
  • Diode detector
  • Magnetron oscillator
  • Meystron oscillator
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Materials which can be used as crystal detectors:
  • Silicon, galena
  • Carborundum, iron pyrites
  • Silicon, iron pyrites
  • Correct Answer
    All of the above
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A power detector may be operated:
  • As a square law detector
  • As a linear detector
  • Correct Answer
    As either a square law detector or a linear detector
  • None of the above
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Used to multiply the fundamental frequency by two:
  • Correct Answer
    Frequency doubler
  • Harmonic generator with a suitable resonant circuit
  • A & B
  • None of the above
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When used as an RF amplifier, a pentode vacuum tube:
  • Usually does not require neutralization
  • Usually requires neutralization
  • May require neutralization at ultra-high frequencies
  • Correct Answer
    A & C
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A quartz crystal in a radio transmitter:
  • Is used to provide a high degree of master-oscillator frequency stability
  • May be the sole tuned circuit in the oscillator
  • Correct Answer
    A & B
  • None of the above
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Advantage of crystal control over tuned circuit oscillators:
  • Very high Q
  • Compact size
  • Excellent frequency stability
  • Correct Answer
    All of the above
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If the crystal will undergo very small changes in its operating frequency with relatively large temperature variations:
  • A high-temperature coefficient crystal
  • Correct Answer
    A low-temperature coefficient crystal
  • A constant-temperature coefficient crystal
  • None of the above
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A separate source of power is sometimes desirable for crystal-oscillator units in a transmitter:
  • Correct Answer
    To prevent dynamic instability of the crystal oscillator
  • To prevent thermocoupling of the crystal oscillator
  • To prevent overtuning of the crystal oscillator
  • To cause dynamic instability of the crystal oscillator
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"The temperature coefficient of an x-cut crystal is negative":
  • The operating frequency of the crystal will decrease as the temperature decreases
  • The operating frequency of the crystal will decrease as the temperature increases
  • The operating frequency of the crystal will increase as the temperature decreases
  • Correct Answer
    B & C
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If you apply DC voltage to the opposite plane surfaces of a quartz crystal:
  • The crystal plate will always undergo a physical distortion
  • The crystal might crack under the strain of displacement caused by too much voltage
  • Correct Answer
    A & B
  • None of the above
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"The temperature coefficient of a y-cut crystal is positive" means:
  • The operating frequency of the crystal will decrease as the temperature decreases
  • The operating frequency of the crystal will increase as the temperature increases
  • The operating frequency of the crystal will decrease as the temperature increases
  • Correct Answer
    A & B
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Two dissimilar metals joined together and producing a current between them when the junction is heated is:
  • A point contact type transistor
  • Correct Answer
    A thermocouple
  • A junction contact type transistor
  • A solenoid
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Waveguides:
  • A type of transmission line
  • Hollow rectangular or circular pipe
  • Fine application as transmission lines
  • Correct Answer
    All of the above
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Transistors may be compared to a conventional triode vacuum tube functionally:
  • Emitter corresponds to the cathode
  • Collector corresponds to the plate
  • Base corresponds to the grid
  • Correct Answer
    All of the above
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Types of transistors:
  • Point-contact
  • Junction
  • Correct Answer
    Both A & B
  • NPP
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When using and storing crystal microphones:
  • They should be protected from shock and vibration
  • They should be protected from humidity
  • They should be protected from high temperatures
  • Correct Answer
    All of the above
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What effect does a change in the dielectric constant of a capacitor dielectric material have upon the capacitance of a capacitor:
  • Correct Answer
    Capacity varies directly with the dielectric constant
  • Capacity may fluctuate wildly
  • There is no effect upon the capacitance
  • None of the above
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Increasing the number of plates of a capacitor:
  • Correct Answer
    Will increase the capacitance
  • Will decrease the capacitance
  • Will have no effect on the capacitance
  • Will make the capacitance fluctuate
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If the dielectric constants of a capacitor dielectric material between the capacitor plates were changed from 1 to 1:
  • Correct Answer
    The capacitance would be twice its original value
  • The capacitance would be half its original value
  • The capacitance would decay rapidly
  • None of the above
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Contacts which slide together on opening and closing:
  • Are butt joined
  • Are known as self-wiping
  • Keep the contacts clean by their action
  • Correct Answer
    B & C
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Permanent magnets used in head telephones:
  • Place the diaphragms under tension so that the sensitivity of the telephones will be increased
  • Improve the frequency response
  • Prevents production of second harmonics in the telephones
  • Correct Answer
    All of the above
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Emergency repairs to an inductance coil having burned or charred insulation:
  • Correct Answer
    Are generally impractical, short of rewinding the coil with good wire
  • Are always practical if repaired by coating the bad turns with insulating varnish
  • A & B
  • None of the above
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Indications of a defective vacuum tube in a transmitter:
  • Gas blow within the tube, excessive plate color due to overheating
  • No light from the filament, insufficient plate current, reduced output
  • Excessive plate current, possible internal arcing, fluctuating plate or grid current
  • Correct Answer
    All of the above
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The breakdown voltage rating of a capacitor are determined by:
  • The type of dielectric material used
  • The thickness of the dielectric material
  • Correct Answer
    A & B
  • None of the above
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Crystal surfaces should be free of dirt of grease to operate properly:
  • Do not touch the faces of the crystal with the fingers
  • Clean the faces with soap and water
  • Clean the faces with carbon tetrachloride
  • Correct Answer
    All of the above
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A purplish glow from within a tube indicates:
  • A soft tube
  • A hard tube
  • Air or undesired gases within the tube
  • Correct Answer
    A & C
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Given a solenoid with a resistance of 5 ohms and 0.34 through the winding when 1108 at 60 Hz is applied. What is the impedance?
  • Correct Answer
    367 ohms
  • 350 ohms
  • 360 ohms
  • None of the above
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Use of a low pass filter network:
  • Ripple filter in power supplies, harmonic suppression filters in antenna systems
  • Line noise filters, tone control systems
  • Crossover networks, output filters of detector circuits
  • Correct Answer
    All of the above
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A special type of power supply filter choke whose inductance is inversely proportioned to values of DC within specified limits is:
  • Smoothing choke
  • Correct Answer
    Swinging choke
  • Radio frequency choke
  • Audio frequency choke
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The best suited material for use as an antenna strain insulator exposed to the elements:
  • Correct Answer
    Glazed porcelain
  • Glass
  • Graphite composite
  • Rubber
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Materials frequently used for relay contacts:
  • Tungsten
  • Silver
  • Gold
  • Correct Answer
    All of the above
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Why is rosin used as a soldering flux?
  • It is noncorrosive
  • It allows a perfect soldering bond to be made
  • It possesses good insulation qualities
  • Correct Answer
    All of the above
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What substance is the most widely used in crystal oscillators?
  • Correct Answer
    Quartz
  • Galena
  • Silicon
  • Tourmaline
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Why is an oscillator crystal operated at a constant temperature?
  • Just because, stupid!
  • Correct Answer
    To maintain a constant frequency output from the oscillator
  • Constant temperature allows easier frequency change
  • None of the above
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The advantage of a single-button carbon microphone:
  • High output voltage
  • Sensitivity
  • Low cost
  • Correct Answer
    All of the above
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A carbon microphone should not be:
  • Jarred while in operation
  • Tapped while in operation
  • Subjected to violent sound intensities
  • Correct Answer
    All of the above
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In connecting head telephones directly in the plate circuit of a vacuum tube one should observe the proper polarity:
  • Correct Answer
    To maintain maximum sensitivity in the headphones
  • So its current flows opposed to the field strength of the permanent magnet
  • A & B
  • None of the above
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What should the plate current do in the operation of a Class B audio amplifier?
  • Correct Answer
    Fluctuate
  • Remain Steady
  • Increase
  • None of the above
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What turns ratio does a transformer need to match a source impedance of 500 ohms to a load of 10 ohms?
  • Correct Answer
    7.1 to 1
  • 7 to 1
  • 14 to 1
  • None of the above
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What microphones have a high impedance output?
  • Crystal
  • Dynamic
  • Correct Answer
    Any
  • None of the above
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How may low impedance (75 ohm) head telephones be connected to the output of a vacuum tube?
  • By using an impedance matching transformer in the output stage
  • Connect them as a cathode bias resistor in the output stage
  • Correct Answer
    Either A or B
  • None of the above
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Why do headphones usually have high-impedance windings?
  • They can usually be operated without an impedance matching transformer
  • They represent a closer match to the plate load impedance for the tube delivering necessary driving power than low impedance planes
  • Correct Answer
    A & B
  • None of the above
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A "choke" coil:
  • Offers a relatively high impedance to AC currents
  • Has a high "Q" (low RF losses)
  • Offers a low resistance to DC currents
  • Correct Answer
    All of the above
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Why is correct grid bias necessary for audio frequency amplifier?
  • To minimize distortion
  • To set the operating conditions for determining the class of amplifications
  • So as not to exceed the rated plate dissipation of the tube
  • Correct Answer
    All of the above
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When a tube is used as a Class B amplifier what portion of the excitation voltage cycle does plate current flow?
  • Correct Answer
    Slightly more than 180 degrees
  • Slightly less than 180 degrees
  • 360 degrees
  • None of the above
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A properly operated Class A audio amplifier:
  • Correct Answer
    Produces no serious modification of the input waveform
  • Serious distortion is present
  • A & B
  • All of the above
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What is the main advantage obtained by using two triodes in push-pull in a Class a audio frequency amplifier?
  • Increased power output
  • Cancellation of even harmonic distortion in the output
  • Elimination of DC saturation, elimination of cathode by-pass capacitor
  • Correct Answer
    All of the above
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What is the maximum permissible RMS value of audio voltage which can be applied to the grid of a Class A audio amplifier which has a grid bias of 10 V?
  • Correct Answer
    7.07 V
  • 8 V
  • 10 V
  • 14.14 V
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Distortion in a Class A amplifier can be caused by:
  • Insufficient plate and screen potentials, incorrect grid bias defective rube
  • Leaky or shorted input coupling capacitor
  • Excessive anokutyde if grid signal, incorrect value of load impedance
  • Correct Answer
    All of the above
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Vacuum tubes operating as Class A amplifiers may be used as:
  • Audio power amplifiers, audio voltage amplifiers, microphones amplifiers, line amplifiers
  • Oscilloscope amplifiers, modulators
  • Phonograph amplifiers
  • Correct Answer
    All of the above
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Why is a push-pull audio frequency amplifier preferable to a single-tube stage?
  • Correct Answer
    When compared with a single-tube stage, power output is doubled
  • When compared with a single-tube stage, power output is the same
  • When compared with a single-tube stage, power output is cut in half
  • None of the above
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What is the DC plate voltage of a resistance-coupled amplifier state with a plate-supply voltage of 260 V, a plate current of 1 mA, and a plate load resistance of 100,000 ohms?
  • Correct Answer
    160 V
  • 100 V
  • 200 V
  • 60 V
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Why is it necessary to use two tubes in a Class B audio amplifier?
  • Correct Answer
    To prevent the excessive distortion which would result from the use of only one tube in Class B
  • To eliminate hum
  • A & B
  • None of the above
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If the coupling capacitor leaked in a resistance-coupled audio frequency amplifier:
  • Excessive plate current would result
  • A large value of grid current would result
  • There would be extreme distortion, and very low gain
  • Correct Answer
    All of the above
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A vacuum tube operated Class C audio amplifier is not feasible, either in single or push-pull:
  • Since the plate current only flows 120 degrees, even in push-pull, only 2/3 of the cycle is reproduced and the resultant distortion would be unacceptable for audio
  • Tank circuits, which replace the missing portions of the cycle, can't be used in an audio amplifier because they only operate on one frequency
  • Correct Answer
    A & B
  • None of the above
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Even harmonics may be reduced in the output of an audio frequency amplifier:
  • By operating the state push-pull
  • In a single tube amplifier, by operating the stage only on the linear part of the tube's characteristic curve
  • Correct Answer
    A & B
  • None of the above
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The main advantage of a tuned audio frequency amplifier in a receiver used for the reception of CW:
  • Correct Answer
    A reduction in interference from unwanted signals
  • The desired audio beat frequency is attenuates
  • A & B
  • None of the above
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Decoupling networks in the plate circuit of a multistage audio amplifier:
  • Correct Answer
    Prevents oscillations from occurring in the amplifier
  • Result in oscillations in the amplifier
  • Allow variable oscillations in the amplifier
  • None of the above
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An audio-transformer is seldom used as the output device in the plate circuit of a tetrode audio-amplifier stage:
  • Correct Answer
    Because an ordinary transformer cannot supply enough impedance to the plate circuit
  • Because an ordinary transformer supplies too much impedance to the plate circuit
  • Because an ordinary transformer would be too costly
  • None of the above
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The chief advantage of Class A audio operation is compared to the other classes of audio-frequency amplifiers:
  • Hum currents are in phase
  • Correct Answer
    Low distortion of the output signal
  • Tendency for regeneration is increased
  • Elimination of cathode bypass capacitors
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Which is not the principle advantage of transformer coupling compared to resistance coupling in audio-frequency amplifiers?
  • Greater gain per stage
  • Can provide necessary impedance matching
  • A & B
  • Correct Answer
    A transformer is expensive, heavy, and bulky
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Efficiency of a power transformer is determined by:
  • Eddy current losses
  • Hysteresis losses
  • Copper losses
  • Correct Answer
    All of the above
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The ratios of primary and secondary currents in a power transformer:
  • Are approximately in inverse ratio to the turns ratio
  • Is to some extent affected by the diameter of the primary and secondary wire
  • The current ratio is in inverse proportion to the voltage ratio
  • Correct Answer
    All of the above
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A transformer has a primary voltage of 100, primary turns = 200, and secondary turns = 40. What is the secondary voltage?
  • Correct Answer
    20 V
  • 240 V
  • 140 V
  • 340 V
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What factors determine the no-load voltage ratio of a power transformer?
  • Power ratio
  • Correct Answer
    Turns ratio
  • Voltage ratio
  • Power factor
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The turns ratio of a transformer varies:
  • Correct Answer
    As the square root of the impedance ratio
  • As the square of the impedance ratio
  • As one-half the impedance ratio
  • As twice the impedance ratio
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Primary cells:
  • Can be recharged
  • Cannot be recharged
  • An attempt to recharge it would not restore the eroded electrode
  • Correct Answer
    B & D
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Secondary cells:
  • Can be recharged
  • Cannot be recharged
  • The products of the chemical change are not soluble in the electrolyte
  • Correct Answer
    A & C
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The formation of hydrogen gas around the positive electrode of a primary cell is:
  • Depolarization
  • Correct Answer
    Polarization
  • Manganese dioxide
  • None of the above
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A dry cell may be tested:
  • Must be tested under normal load condition
  • May be tested under no load condition
  • May be taken by any conventional voltmeter
  • Correct Answer
    A & C
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In the usual type dry cell:
  • The negative electrode is made of zinc
  • The positive electrode is made of carbon
  • The negative electrode is made of zinc
  • Correct Answer
    A & B
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"A", "B", and "C" batteries are alike, but specifically constructed for a particular function. Explain:
  • "B" battery is for plate and screen power
  • "C" battery for grid bias voltage
  • "A" battery for filament power
  • Correct Answer
    All of the above
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The condition of a dry "B" battery may be determined:
  • By measuring the voltage under normal load
  • By measuring the voltage under no load
  • A loss of 20 % of the voltage under normal load indicates that the battery should be replaced
  • Correct Answer
    A & C
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Spare "B" batteries should be stored:
  • Correct Answer
    In a dry place
  • In a hot place
  • Anywhere
  • A & C
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A means of comparing the weight of a volume of liquid with the same volume of distilled water:
  • Correct Answer
    Specific gravity
  • Specific mass
  • Specific volume
  • None of the above
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Edison type batteries:
  • Have plates up nickel
  • Have plates of iron
  • Have plates of compounds of nickel and iron
  • Correct Answer
    All of the above
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The electrolyte of a lead-acid storage cell:
  • Concentrated sulfuric acid
  • Dilute sulfuric acid
  • Has a specific gravity about 1.3 fully charged
  • Correct Answer
    B & C
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The negative plate of a lead-acid storage cell:
  • Correct Answer
    Is composed of pure spongy lead
  • Is composed of lead peroxide
  • Is composed of a compound of pure spongy lead and lead peroxide
  • None of the above
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The positive plate of a lead-acid storage cell:
  • Is composed of pure spongy lead
  • Correct Answer
    Is composed of lead peroxide
  • Is composed of a compound of pure spongy lead and lead peroxide
  • None of the above
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The chemical composition of the electrolyte in an Edison-type storage cell:
  • Is contained in a nickel-plated sheet steel tank
  • Has a specific gravity of about 1.200
  • Is a 21% solution of potassium and lithium hydroxides in distilled water
  • Correct Answer
    All of the above
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The negative plate of an Edison-type storage cell is:
  • Correct Answer
    Finely powdered pure iron
  • Green oxide of nickel
  • Potassium oxide
  • None of the above
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The positive plate of an Edison-type storage cell is:
  • Finely powdered pure iron
  • Correct Answer
    Green oxide of nickel
  • Lithium oxide
  • None of the above
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The average fully-charged voltage of an Edison storage cell is:
  • Correct Answer
    1.2 V
  • 1.5 V
  • 2 V
  • 1 V
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Decrease in capacity of an Edison-type storage cell can be caused by:
  • Frequent overheating, and operating conditions over 115 degrees fahrenheit
  • Charging at less than the normal rate
  • Adding impure water to the electrolyte, or a weak or aged electrolyte
  • Correct Answer
    All of the above
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The average fully charged voltage of a lead-acid cell is:
  • 1.0 V
  • 1.56 V
  • Correct Answer
    2.06 V
  • 2.5 V
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To increase the power output of a storage cell:
  • Correct Answer
    Low internal resistance is desirable
  • High internal resistance is desirable
  • Low terminal voltage under load is desirable
  • None of the above
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The condition of charge of an Edison cell can be determined:
  • By reading the terminal voltage under load
  • By checking the voltage against a standard discharge curve
  • Correct Answer
    Both A & B
  • Checking the specific gravity
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The charge of a lead-acid storage cell:
  • May be determined by hydrometer readings
  • By measuring voltage under a heavy load
  • Correct Answer
    A or B
  • None of the above
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Sulfation:
  • Reduces terminal voltage
  • Increases internal resistance
  • Reduces power output
  • Correct Answer
    All of the above
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If the polarity is reversed when charging a storage cell:
  • No damage in a lead-acid cell unless excessive
  • Damage in an Edison-cell
  • No damage in an Edison-cell if temperatures below 115 degrees Fahrenheit
  • Correct Answer
    A & C
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You may measure the voltage of a battery under heavy load:
  • Correct Answer
    To determine its condition of charge
  • To determine its polarity
  • To determine its age
  • None of the above
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If the voltage of some cells in a battery are found to be reversed, what is indicated?
  • Correct Answer
    Polarity was reversed while charging
  • Polarity was doubled while charging
  • Polarity has no influence of charging
  • Polarity was correct while charging
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Distilled water should be added to a lead-acid storage cell:
  • To keep the electrolyte 1/4 inch above the to of the plates
  • To keep the useful plate area sufficient to maintain the full capacity of the cell
  • None of the above
  • Correct Answer
    A & B
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Local action in a lead-acid storage cell:
  • Causes a slow discharge in the cell
  • Forms a very hard sulfate on the plates
  • May be reduced by trickle charging when the battery is not in actual use
  • Correct Answer
    All of the above
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To maintain a group of storage cells in good operating condition:
  • Observe correct charge and discharge rates
  • Overcharge about once a month to remove sulfation
  • Keep all terminal corrections clean and tight
  • Correct Answer
    All of the above
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What may cause the plates of a lead-acid call to buckle?
  • Excessive sulfation
  • Overheating
  • Overdischarging of the battery
  • Correct Answer
    All of the above
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What may cause sulfation of a lead-acid cell?
  • It is a normal process
  • Overdischarging
  • Local action with improper charging
  • Correct Answer
    All of the above
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What may be used to neutralize an acid electrolyte?
  • Ammonium hydroxide
  • Baking soda
  • Washing soda
  • Correct Answer
    All of the above
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To prevent corrosion of battery terminals:
  • Correct Answer
    Occasionally clean and coat them with Vaseline or other suitable lubricants
  • Use only brass terminals
  • Use only stainless steel terminals
  • Keep battery on trickles charge
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Why should there be ventilation to the room housing a large group of storage cells?
  • To prevent gas accumulation
  • To prevent overheating
  • To prevent the terminals from shorting
  • Correct Answer
    A & B
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Radio equipment on which electrolyte may be used:
  • Electrolyte capacitor
  • Electrolyte rectifier
  • Electrolyte detector
  • Correct Answer
    All of the above
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What is the effect of low temperature on the operation of a lead-acid storage battery?
  • Electrolyte may freeze and split the battery if sg too low
  • The capacity is decreased
  • Correct Answer
    A & B
  • None of the above
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What form of energy is stored in a lead-acid storage battery?
  • Correct Answer
    Chemical
  • Mechanical
  • Heat
  • Light
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How may polarity of a storage battery be determined?
  • Voltmeter
  • Salt water method
  • Correct Answer
    A & B
  • None of the above
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A battery with a terminal voltage of 12.5 V is to be trickle-charged at a 0.5 A rate. What resistance should be connected in series with the battery to charge from a 110 V line?
  • Correct Answer
    195 ohms
  • 300 ohms
  • 95 ohms
  • None of the above
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A discharged storage battery of 3 cells has an open circuit voltage of 1.8 V per cell and an internal resistance of 0.1 ohm per cell. What voltage is needed to give an initial charging rate of 10 A?
  • Correct Answer
    8.4 V
  • 10 V
  • 15 V
  • 12.5 V
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What capacity in amperes of storage battery is required to operate a 50 W emergency transmitter for 6 hr.? Assume a continuous transmitter load of 70% of the key-locked demand of 40 A, and an emergency light load of 1.5 A.
  • A battery rated greater than 177 amperhours
  • A battery rated at least 177 amperhours
  • Correct Answer
    A & B
  • None of the above
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If a receiver storage A battery could not be kept charged, and maintain the required watch period, what should you do?
  • Correct Answer
    Increase the charging rate
  • Get a new battery
  • Discontinue the required watch period
  • B & C
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Abnormally low input power terminal voltage of a lifeboat radiotelegraph transmitter while in operation could be caused by:
  • Reversed polarity
  • Excessive overload
  • A partially discharged battery
  • Correct Answer
    B & C
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If a battery has 12.4 V on open circuit and 12.2 V when its charging circuit is closed:
  • Correct Answer
    Could have polarity reversed
  • Could be overloaded
  • A & B
  • None of the above

When charging, voltage should increase.

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The tops of lead-acid batteries should be kept dry:
  • To prevent slow discharge of the battery
  • To prevent terminal overload
  • To reduce the formation of terminal corrosion
  • Correct Answer
    A & C
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When lead-acid cells are subject to low temperatures they should:
  • To prevent freezing
  • To provide the maximum capacity
  • Correct Answer
    A & B
  • None of the above
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If an electrolyte in a lead-acid storage cell becomes low due to evaporation:
  • Correct Answer
    The level should be brought to about 1/4 inch above the tops of the plates with pure water
  • The level should be brought to about 1/4 inch above the tops of the plates with tap water
  • The level should be brought to about 1/4 inch above the tops of the plates with salt water
  • None of the above
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An Edison storage battery should not be charged at less than the manufacturer's specified rate:
  • In order that the capacity of the battery shall be maximum after charge
  • The chemical reactions of the Edison-type cell
  • Correct Answer
    A & B
  • None of the above
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Your emergency battery has a specific gravity reading of 1.120. What should be done?
  • Place the battery on charge at once
  • Bring the electrolyte level to about 1/4 inch above the top of the plates
  • The battery will be fully charged when the specific gravity reads 1.280 to 1.300
  • Correct Answer
    All of the above
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What care should be taken with selecting water to add to a storage cell?
  • Correct Answer
    It should be chemically pure or distilled
  • It should be only sea water
  • Tap water is as good as any
  • None of the above
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If the circuit breakers refuse to stay closed when you place the emergency batteries on charge, what is the trouble?
  • Internally shorted cells
  • Reversed charging polarity
  • Grounded circuit connections
  • Correct Answer
    Any of the above
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Heat developed within a storage cell under charge or discharge conditions is caused by:
  • I2R losses
  • Energy transfer due to chemical reactions
  • Correct Answer
    A & B
  • None of the above
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How would you connect a group of similar cells in a storage battery to obtain the maximum zero resistance current?
  • Correct Answer
    In parallel
  • In series
  • In series/parallel
  • None of the above
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How would you connect a group of similar cells in a storage battery to obtain the maximum no-bond output voltage?
  • In parallel
  • Correct Answer
    In series
  • In series/parallel
  • None of the above
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What current will flow in a 6 V storage battery with an internal resistance of 0.01 ohms, when a 3 W, 6 V lamp is connected?
  • Correct Answer
    0.4995 A
  • 0.4885 A
  • 0.5566 A
  • 0.5795 A
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The charging rate of a storage cell charged from a fixed voltage source decreases as the charging progresses opposition to the charging voltage?
  • Because as cell voltages increase, offering more opposition to the charging voltage
  • When the effective charging potential is reduced, the charging current is decreased
  • Correct Answer
    Both A & B
  • None of the above
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The principal function of the filter in a power supply:
  • To remove the variations in amplitude of the rectifier output
  • To provide a relatively unvarying DC voltage for use in the various circuits
  • Correct Answer
    Either A or B
  • None of the above
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Advantages of capacitor input and choke-input filters when used with rectifiers:
  • Capacitor-input filter provides higher output voltage under reasonably light load conditions
  • Choke-input filter offers better voltage regulations
  • Correct Answer
    A & B
  • None of the above
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A high-resistance fixed resistor is shunted across each unit of a high voltage series capacitor bank in the power-supply filter circuit to:
  • Correct Answer
    Insure that the correct voltage appears across each unit
  • Discharge the capacitors
  • Does not insure the correct voltage across each unit
  • None of the above
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Part of the secondary winding of a transmitters power transformer is accidentally shorted. What should be the immediate effect?
  • Correct Answer
    The current would rise to an excessive value and trip the circuit breaker
  • The short would burn the transformer
  • The current in the secondary winding would decrease
  • None of the above
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Bleeder resistors are used in power supplies:
  • To improve the output voltage regulation
  • They also discharge the filter capacitor when the power is turned off
  • Correct Answer
    Either A or B
  • None of the above
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The ratio of the frequencies of the output and input circuits of a single-phase full-wave rectifier:
  • 1 to 1
  • Correct Answer
    2 to 1
  • 1 to 2
  • None of the above
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A capacitor is sometimes placed in series with the primary of a power transformer:
  • Correct Answer
    To improve the power factor
  • To improve output voltage regulation
  • To rectify the primary windings
  • None of the above
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What is the maximum allowable secondary voltage of a transformer used as a center-tapped full-wave rectifier with tubes having a peak inverse voltage rating of 10,000 V?
  • Correct Answer
    7070 V
  • 14140 V
  • 10000 V
  • 5000 V
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If a 60 Hz transformer is connected to a 120 Hz source of the same voltage:
  • The impedance of the transformers would be greater
  • The current would be reduced
  • There would be a decrease in power delivered to the load
  • Correct Answer
    All the above
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If a 500 Hz transformer is connected to a 60 Hz source of the same voltage:
  • The primary would draw excessive current
  • The transformer would overheat
  • The primary might burn out
  • Correct Answer
    All of the above
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A 500 Hz AC plate supply, rectified by a full-wave, unfiltered rectifier circuit. What would the emission be?
  • A modulated continuous wave of 500 Hz
  • A modulated continuous wave of 1000 Hz
  • A-2
  • Correct Answer
    All of the above
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The purpose of an air gap in a filter choke coil core. Which is the incorrect answer?
  • Correct Answer
    To decrease the effective inductance for the AC component of current by increasing the DC saturation
  • To increase the effective inductance for the AC component of current by decreasing the DC saturation
  • The inductance of the coil in general's decreased
  • All of the above
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Loose laminations in a filter choke:
  • Make it impossible to firmly connect the choke in a circuit
  • A & C
  • Correct Answer
    Cause a buzzing or chattering sound
  • None of the above
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Poor regulation in a power supply may be caused by:
  • No bleeder resistance
  • High resistance filter chokes
  • Insufficient filter capacity
  • Correct Answer
    All of the above
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Why should the case of a high-voltage transformer be grounded?
  • To protect personnel handling the equipment from shock
  • To prevent high static voltages building up between the case and grounds
  • Correct Answer
    A & B
  • None of the above
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When connecting electrolytic capacitors in series:
  • Correct Answer
    Observe the polarity marked on the component
  • There is no polarity to observe
  • Connect anode to anode
  • Connect cathode to cathode
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Full wave rectification has ____ than half-wave:
  • Better output voltage regulation
  • Smaller filter components for a given ripple percentage
  • Correct Answer
    A and B
  • None of the above
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Voltage regulation is ____ with a high resistance choke:
  • Correct Answer
    Made worse
  • Made better
  • The same
  • None of the above
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Electrolyte capacitors are desirable over other types because:
  • A large capacitance may be obtained with small physical dimensions
  • They have a cathode
  • The wet-type electrolytic capacitor is "self-healing"
  • Correct Answer
    A & C
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The most common values of chokes range from:
  • Correct Answer
    5 H to 30 H
  • 30 H-100 H
  • 1 H to 100 H
  • 100 H to 1000 H
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The power transformer and rectifier of a radio receiver are designed to supply a plate voltage of 250 V when operating from a 110 V 60 Hz supply, if the transformer is connected to 110 VDC what will happen?
  • The secondary would burn out
  • The primary would overheat and burn out
  • The circuit breaker would open to protect the circuit
  • Correct Answer
    Either A or B
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A shunt-wound DC motor:
  • Correct Answer
    Has a practically constant speed under widely varying load conditions
  • Has poor speed regulation under varying load conditions
  • High starting torque
  • None of the above
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A series DC motor has:
  • Maximum torque at low speed
  • Quick starting
  • Poor speed regulation under varying loads
  • Correct Answer
    All of the above
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This partially counteracts the line voltage and so limits the armature current in a DC motor:
  • EMF
  • Correct Answer
    Counter EMF
  • Opposition EMF
  • None of the above
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A compound-wound DC motor:
  • Has constant speed under changing load conditions
  • Low starting torque
  • High starting torque
  • Correct Answer
    A & B
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Laminated iron is used in armature and field construction to:
  • Reduce eddy current losses
  • Offer a number of high-resistance paths to Eddy currents
  • Correct Answer
    A or B
  • None of the above
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The ____ of a DC motor periodically change the armature coils to maintain one direction of rotation:
  • Field coils
  • Correct Answer
    Connector
  • Brushes
  • Auxiliary speed control
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The speed of a series DC motor may increase and destroy the motor by centrifugal action:
  • Correct Answer
    When operated without a load
  • When operated on AC
  • When operated under varying load
  • None of the above
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When the field of a shunt-wound DC motor opens while the machine is operating under no load:
  • Correct Answer
    The motor would race, and if unchoked, might destroy itself
  • The motor would quit running without damage
  • The motor would burn out the field coils
  • None of the above
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____ are used in a DC motor to reduce brush sparking without moving the brushes:
  • Interpoles
  • Commutating poles
  • Correct Answer
    Either A or B
  • None of the above
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A short in the armature coils of a DC motor causes:
  • No excessive sparking at the commutator brushes
  • No overheating of the motor
  • Correct Answer
    Reduction of speed under load, and excessive armature current
  • All of the above
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The motor-field rheostat should be ____ when starting a DC motor generator set:
  • Minimum resistance in the armature circuit
  • Correct Answer
    Minimum resistance in the field circuit
  • Maximum resistance in the field circuit
  • None of the above
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If a motor generator fails to start when the start button is depressed, the trouble may be:
  • Blown fuse or tripped circuit breaker
  • Open armature or motor-field rheostat
  • Broken connections, defective brushes
  • Correct Answer
    All of the above
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When increased output is desired from a motor-generator, what is the usual procedure?
  • Correct Answer
    Decrease the resistance after rheostat in series with the generator field
  • Increase the resistance of the rheostat in series with the generator field
  • Output cannot be easily increased
  • Shut down the motor-generator and restart under full load
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A dynamotor is:
  • A combination motor-generator which utilizes a common field winding
  • Usually run by battery power
  • A higher efficiency than a motor-generator
  • Correct Answer
    All of the above
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Output voltage of a dynamotor may be regulated:
  • Only by changing the speed of the motor
  • A series resistance in the output line could be used to reduce the available output voltage
  • Correct Answer
    Either A or B
  • None of the above
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What disadvantage is there to a dynamotor?
  • Compactness
  • Operating efficiency
  • It can be operated from batteries
  • Correct Answer
    Its output voltage is dependent on the source voltage stability
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Causes of excessive sparking at the brushes of a DC motor or generator include:
  • Brushes not properly set at neutral point, dirt on commutator, motor overloaded
  • Weak spring tension on brushes, brushes worn, commutator worn eccentric
  • High mica-insulation between bars, commutator bars of uneven height
  • Correct Answer
    All of the above
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By-pass capacitors are often connected across the brushes of a high-voltage DC generator:
  • To regulate the voltage
  • To protect the generator winding from high voltage surges
  • To reduce RF interference
  • Correct Answer
    B & C
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Causes of motor-generator bearing overheating include:
  • Incorrect kind of lubrication, lack of ventilation
  • Constant overload, dirt in bearings
  • Misalignment
  • Correct Answer
    All of the above
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RF interference may be minimized:
  • By the use of brush by-pass capacitors
  • Low frequency filters
  • Shielding of long connecting leads
  • Correct Answer
    All of the above
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Emery cloth should never be used to clean the commutator of a motor or generator:
  • Correct Answer
    Because it contains particles which may lodge between commutator segments and cause short circuits
  • Because it may polish the commutator too smooth for good brush contact
  • Because it may decrease the insulating quality of its mica between the interpoles
  • None of the above
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A 3 HP 100 V DC motor is 85% efficient when developing its rated output. What is the current?
  • Correct Answer
    23.93 A
  • 25 A
  • 20 A
  • 8.5 A
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The speed of a synchronous motor is determined:
  • By the number of pairs of poles
  • By the line frequency
  • By the load
  • Correct Answer
    A & B
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The speed of an induction motor is determined:
  • By the number of pairs of poles
  • By the line frequency
  • By the load
  • Correct Answer
    All of the above
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The speed of a DC series motor is determined:
  • Correct Answer
    By the load
  • By the number of pairs of poles
  • By the commutator
  • None of the above
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What is the line current of a 7 HP motor operating on 120 V at full load, a power factor of 0.8, and 95% efficiency?
  • 56 A
  • Correct Answer
    57.2 A
  • 58 A
  • None of the above
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Alternators are usually rated in:
  • Correct Answer
    Volt-amperes output
  • Watts
  • Amperes
  • ***<This answer left blank by the FCC>
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What conditions must be met before two AC generators can be operated in parallel?
  • Output voltages must be equal, frequencies must match
  • Phase rotation, and relative phase positions must match
  • Correct Answer
    A & B
  • None of the above
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The voltage of an alternator will:
  • Correct Answer
    Decrease under load
  • Increase under load
  • Load has no effect on voltage
  • None of the above
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What effect will high coupling between the plate and grid circuits of a quartz-crystal oscillator have?
  • The grid to plate capacitance will be destroyed
  • The oscillation will be higher because of higher Q
  • Correct Answer
    Overheating of the crystal and possible breakage
  • Overmodulation
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The operation of a dynatron oscillator depends on what?
  • The positive emission from the anode
  • Correct Answer
    The secondary emission from the anode
  • Cathode being in saturation
  • Positive resistance characteristic of the tetrode tube
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To provide additional feedback voltage in a crystal oscillator what is sometimes needed?
  • Correct Answer
    An additional plate grid feedback capacitor
  • Adding a coupling circuit in series with the plate resistors
  • An astable multivibrator
  • A monostable multivibrator
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What is the primary reason for the use of a crystal controlled oscillator for use as a transmitter?
  • No cross-modulation
  • Increase in gain
  • Correct Answer
    Frequency stability
  • Impedance gain and wider bandpass
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What is are the advantages of self excited oscillator and master-oscillator power-amplifier transmitters?
  • The master-oscillator has fewer parts than the self-excited and is simpler to construct
  • Correct Answer
    The self-excited oscillator transmitter is simpler to construct and has fewer parts than the master-oscillator
  • Either A or B
  • Neither
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The primary function of the power-amplifier stage of a marine radiotelegraph transmitter is:
  • To transmit messages concerning the safety and health of the ship personnel
  • To transmit messages concerning the weather and safety of upcoming storms
  • Both A and B
  • Correct Answer
    To improve the frequency stability of the oscillator
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The buffer amplifier stage of a transmitter:
  • To hold any discriminator signals until verified by the varactor diode circuits
  • Buffers any signals that may have been imposed upon the carrier signal
  • Correct Answer
    To improve the frequency stability of the oscillator
  • Both A and C
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Which class of amplifier is used in the final amplifier stage for maximum plate efficiency?
  • Class A
  • Class B
  • Correct Answer
    Class C
  • Filtered Class D
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What class of amplifier is used as linear in order not to distort the modulation components?
  • Class A
  • Correct Answer
    Class B
  • Class C
  • None of the above
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If a class B linear final R-F amplifier were in saturation and no modulation what would happen when modulated?
  • The carrier frequency would override the grid-plate current and the result would be positive shift resulting in amplification
  • The Class B linear amplifier only modulates below cut-off
  • Correct Answer
    A condition of negative carrier shift would be the result
  • Both A and B
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A class C amplifier:
  • Has an output for the entire input signal cycle
  • Output is present for less than 180 degrees of the input cycle
  • Bias is set well beyond cutoff
  • Correct Answer
    Both B and C

Note that HamStudy rearranges the order of answers with each test, so the "Both B and C" answer won't always refer to the correct answers -- but this is the correct choice for the question.

The two correct answers are these:

B) Output is present for less than 180 degrees of the input cycle. A low drive cycle is characteristic of Class C amplifiers. The output element drives for less than 180 degrees of the input cycle, and that attribute causes the distortion for which that Class C amps are known.

C) Bias is set well beyond cutoff. The output element (usually a transistor) is biased so that it doesn't conduct for most of the input signal's duration.

Answers B) and C) might be re-numbered incorrectly when taking the test on HamStudy.

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What effect would insufficient radio-frequency excitation have on Class C modulated amplifier output?
  • Correct Answer
    A negative carrier shift
  • A positive carrier shift
  • Both A and B
  • None of the above
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The second harmonic of a 380 kHz frequency is:
  • 1520 kHz
  • Correct Answer
    760 kHz
  • 190 kHz
  • 2

The second harmonic is always double the fundamental frequency. In this question, the fundamental frequency is 380 kHz. Doubling this value yields the correct answer, 760 kHz.

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Two effects of over-excitation of a Class B amplifier grid circuit are:
  • Increased plate efficiency, decreased power output
  • Decreased plate efficiency, excessive grid current
  • Excessive plate current, excessive distortion
  • Correct Answer
    Both B and C
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Three main factors to consider about grid-leak in a vacuum tube transmitter:
  • The value of grid leak current and grid leak anode to grid
  • The value of grid leak resistance and duration of time the grid current is flowing
  • Internal resistance of the tube between the grid and cathode
  • Correct Answer
    Both B and C
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How can an R-F amplifier stage be neutralized?
  • Correct Answer
    Vary the tuning of the plate tank circuit while observing the amp. meter
  • Vary the tuning of the plate tank circuit while observing the SWR meter
  • Neutralization is done by circuit design either by increasing the input impedance or lowering the inductance value
  • Both A and C are correct
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What is the purpose of a speech amplifier in connection with the modulator of a transmitter?
  • Used to raise the gain of signal after filtering
  • Correct Answer
    To raise the signal-to-noise ratio and the output voltage of microphones
  • To feed the mixer where signal-to-noise ratio is raised
  • To pre-amp the weaker of the two signals received
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When the first speech-amplifier of a transmitter were overexcited, but the modulation capabilities were not exceeded what would be the effect on the output?
  • The waveform would be sawtooth causing undermodulation
  • The waveform would be square wave creating cross-modulation
  • Correct Answer
    The output would be distorted
  • Both A and C
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The bias of a grid-modulated R-F stage is adjusted:
  • Below cut-off frequency
  • At grid saturation
  • At bias
  • Correct Answer
    1 and half to 3 times plate current cutoff value
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Given the following: (1) audio power for 100% modulation equals 50% of DC input power to RF modulated amplifier, (2) load presented to the modulated tube consists of the DC plate impedance of the modulated amplifier, (3) constant grid excitation voltage, very lot distortion, what type of modulation?
  • Grid
  • Correct Answer
    Plate
  • Cathode
  • Anode
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Modulation occurring in an RF stage other than the final power amplifier:
  • High level
  • Correct Answer
    Low level
  • Pre-emphasis
  • Plate
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The efficiency of a grid-bias modulated stage should be:
  • Maximum at complete modulation
  • Minimum at zero modulation
  • Correct Answer
    Either A or B
  • None of the above
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Does grid current flow in a grid-bias modulated stage under modulated conditions?
  • Grid current may exist during the positive porions of the AF cycle
  • Grid current may cause distortion
  • Correct Answer
    A and B
  • None of the above
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What might be the cause of a positive shift in carrier amplitude during modulation?
  • Parasitic oscillations, excessive audio drive
  • Incorrect tuning of final amplifier
  • Insufficient RF excitation, incorrect neutralization
  • Correct Answer
    All of the above
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For 100% modulation, DC power input to the modulated RF amplifier should:
  • Be the same as the AC power from the modulation
  • Correct Answer
    Be 1/2 the AC power from the modulation
  • Be 1/4 the AC power from the modulation
  • None of the above
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When a radiotelephone transmitter is 100% modulated by sinusoidal waveform , how much antenna current will be observed?
  • Correct Answer
    22.5 % increase
  • 22.5 % decrease
  • 12.25% increase
  • No change in antenna current
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What can be done in a Heising modulation system to obtain 100% modulation?
  • Correct Answer
    Use a series resistor between the amplifier and modulator in the DC plate supply
  • Nothing needs to be done
  • Use a series capacitor between amplifier and modulator in the DC grid supply
  • Both A and C
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A plate choke in a Heising modulator:
  • Builds up audio modulating voltages
  • Feeds audio modulating voltages to the plate of the RF modulated amplifier to produce plate modulation
  • Correct Answer
    A and B
  • None of the above
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What value of sinusoidal audio power is required to insure 100% modulation when the DC plate input to a modulated Class C amplifier has an efficiency of 60 % , and is 200 W?
  • Correct Answer
    100 W
  • 50 W
  • 25 W
  • 12 W
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What would be the antenna current when a transmitter has an antenna current of 8 amp, under A -1, even if it is 100% modulated by sinusoidal modulation?
  • 9.8 amp
  • The antenna current will increase by 22.5%
  • Correct Answer
    Either A or B
  • None of the above
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If a transmitter is adjusted for maximum power for telegraph, what must be done to be amplitude modulated?
  • The plate voltage must be reduced
  • The plate voltage must be increased
  • Tubes would have to dissipate 1.5 times as much power if the plate voltage were not reduced
  • Correct Answer
    Both A and C
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A series-fed plate circuit of a vacuum tube amplifier has a short circuit of the plate bypass capacitor. What happened?
  • It would short out the power supply
  • It would remove the plate voltage
  • It would possibly damage the power supply
  • Correct Answer
    All of the above
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A shunt-fed plate circuit of a vacuum tube amplifier has a short circuit of the plate RF choke. What happens?
  • The plate tank circuit would be effectively shorted
  • The DC plate current would increase, possibly to excess
  • No RF output could be expected
  • Correct Answer
    All of the above
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The total bandwidth of a transmitter using A-2 emission with a modulating frequency of 800 Hz and a carrier frequency of 500 kHz is:
  • Correct Answer
    1600 Hz
  • 1.6 kHz
  • 800 kHz
  • 1000 kHz
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Given a vacuum tube of the following characteristics: plate voltage 1000 V, plate current 127 ma, filament current 5.4 amp, mutual conductance 8000 microvolts, and amplification factor of 25. What is the correct volume of negative grid bias for Class B amplifier?
  • Correct Answer
    40 V
  • 50 V
  • 30 V
  • 60 V
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When the relative amplitudes of the positive and negative modulation peaks are unsymmetrical:
  • Correct Answer
    Carrier shift
  • Frequency shift
  • Amplifier shift
  • None of the above
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What may be used as indicating devices in neutralizing an RF amplifier stage?
  • Neon bulb, sensitive wavemeter
  • A flashlight bulb connected to a small loop of wire, a sensitive thermocoupler either attached to a small loop of wire
  • Amplifier grid current meter, a thermocouple meter connected in series with the plate tank
  • Correct Answer
    All of the above
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Important factors in the operation of the vacuum tube as a frequency doubler are:
  • Plate tank should be tuned to twice the grid circuit frequency
  • The grid bias should be very large, the grid driving voltage must be very large, the plate voltage should be comparatively high
  • The plate tank circuit should have a low C to L ratio
  • Correct Answer
    All of the above
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If a 1500 kHz radio wave is modulated by a 2000 Hz sine wave tone, what frequencies does the modulated wave contain?
  • Correct Answer
    1500 kHz , 1502 kHz , 1498 kHz
  • 1500 MHz , 1502 MHz , 1498 MHz
  • 1500 Hz , 1502 Hz , 1498 Hz
  • None of the above
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To avoid damage to components what precautions should be observed in tuning a transmitter?
  • Correct Answer
    It should be adjusted at reduced power
  • It should be adjusted under normal power
  • Plate tank circuits are tuned for maximum DC current
  • None of the above
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A transmitter has a master-oscillator, intermediate amplifier, and final amplifier. In what order should the circuit be adjusted in putting the transmitter in operation?
  • Correct Answer
    Master-oscillator, intermediate amplifier, final amplifier, antenna circuit
  • Antenna circuit, master-oscillator, intermediate amplifier, final amplifier
  • Final amplifier, antenna circuit, master-oscillator, intermediate amplifier
  • Master-oscillator, intermediate amplifier, antenna circuit, final amplifier
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