RADIO AMATEUR EXAMINATION (RAE) SAMPLE QUESTIONS FOR REVISION
1. Power supplies to RF power amplifiers should:
a) be open wires
b) be AF filtered
c) be RF filtered
d) be inductively coupled
2. The value of a resistor to drop 100 volt with a current of 0.8 miliampere is:
a) 125 ohm c) 1250 ohm
b) 125 kilohm d) 1.25 kilohm
3. If a current of 2 amperes flows through a 50-ohm resistor, what is the voltage across the resistor?
a) 25 volts c) 100 volts
b) 52 volts d) 200 volts
The effective resistance of three 24 Ohm resistors connected in parallel is:
a) 8 ohms b) 12 ohms
c) 36 ohms d) 72 ohms
4. An electric current passing through a wire will produce around the conductor:
a) An electric field c) a superconductor
b) A magnetic field d) a semiconductor
5. The unit of impedance is the:
a) ampere c) Henry
b) farad d) ohm
6. One kilohm is:
a) 10 ohm c) 0.001 ohm
b) 0.01 ohm d) 1000 ohm
7. The watt is the unit of :
a) power c) electromagnetic field
strength
b) magnetic flux d) breakdown voltage
8. The unit of resistance is the:
a) farad c) ohm
b) watt d) resistor
9. Radio wave polarization is defined by the orientation of the radiated:
a) magnetic field b) electric field
c) inductive field d) capacitive field
10. The voltage drop across a germanium diode when conducting is about:
a) 0.3V b) 0.6V
c) 0.7V d) 1.3V
11. A 50 hertz current in a wire means that:
a) A potential difference of 50 volts exists across the wire
b) The current flowing in the wire is 50 amperes
c) The power dissipated in the wire is 50 watts
d) A cycle is completed 50 times in each second
12. Starting at a positive peak, how many times does a sine wave cross the zero axis in one complete cycle:
a) 180 times c) 2 times
b) 4 times d) 360 times
13 What is a wave called that abruptly changes back
and forth between two voltage levels and remains an equal time at each level?
a) A sine wave c) a square wave
b) A cosine wave d) a sawtooth wave
14. What would be the most accurate way of determining the RMS voltage of a complex waveform?
a) By using a grid dip meter
b) By measuring the voltage with a D’Arsonval meter
c) By using an absorption wavemeter
d) By measuring the heating effect in a known resistor
15 What are three good electrical conductors
a) Copper, gold, mica
b) Gold, silver, wood
c) gold, silver, aluminium
d) copper, aluminium, paper
17. An isolating transformer is used to
a) Ensure that faulty equipment connected to it will blow a fuse in the distribution board
b) Ensure that no voltage is developed between either output lead and ground
c) Ensure that no voltage is developed between the output leads
d) Step down the mains voltage to a safe value
17. What device is used to store electrical energy in an electrostatic field:
a) A battery c) a capacitor
b) A transformer d) an inductor
18. What dies a variable resistor or potentiometer do:
a) Its resistance changes when AC is applied to it
b) It transforms a variable voltage into a constant voltage
c) Its resistance changes when its slide or contact is moved
d) To create an open circuit when there is too much current in a circuit
19. Which component can amplify a small signal using low voltages:
a) PNP transistor
b) an electrolytic capacitor
c) A variable resistor
d) a multiple-cell battery
 |
FIGURE N6-1
20. In figure N6-1, which symbol represents a fixed resistor:
a) Symbol 2 c) Symbol 4
b) Symbol 3 d) Symbol 5
In figure N6-1, which symbol represents a fuse
a) Symbol 1 c) Symbol 5
b) Symbol 3 d) Symbol 7
In figure N6-1, which symbol represents a single-cell battery
a) Symbol 7 b) Symbol 5
a) Symbol 1 d) Symbol 4
21 In figure N6-1, which symbol represents an earth ground:
a) Symbol 2 b) Symbol 5
c) Symbol 6 d) Symbol 8
22 In figure N6-1, which symbol represents an antenna
a) Symbol 2 b) Symbol 3
c) Symbol 6 d) Symbol 7
23 In figure N6-2, which symbol represents a single-pole, single-throw switch
 |
FIGURE N6-2
b) Symbol 1 c) Symbol 3
c) Symbol 2 d) Symbol 4
24 What does a capacitor do:
a) It stores energy electrochemically and opposes a change in current
b) It stores energy electrostatically and opposes a change in voltage
c) It stores energy electromagnetically and opposes a change in current
d) It stores energy electromechanically and opposes a change in voltage
25 The mains transformer in a transmitter is fitted with an internal screen. To minimize the possibility of introducing mains-borne interference it should be connected to:
a) the chassis
b) the VFO output
c) the live side of the mains
d) left floating
26 The total capacitance of two or more capacitors in series is :
a) always less than that of the smallest capacitor
b) always greater than hat of the largest capacitor
c) found by adding each of the capacitances together
d) found by adding the capacitances together and dividing by their total number
27 An absorption wavemeter is useful for:
a) Checking exact transmission frequency
b) Checking frequency drift
c) Checking peak modulation index
d) Checking for harmonic radiation
28 How does a spectrum analyzer differ from a conventional time-domain oscilloscope
a) A spectrum analyzer measures ionospheric reflection; an oscilloscope displays electrical signals
b) A spectrum analyser displays signals in the time domain; an oscilloscope displays signals in the frequency domain
c) A spectrum analyzer displays signals in the frequency domain; an oscilloscope displays signals in the time domain
d) A spectrum analyzer displays radio frequencies; an oscilloscope displays audio frequencies
29 How is an ammeter usually connected to a circuit under test
a) In series with the circuit
b) in quadrature with the circuit
c) In parallel with the circuit
d) a phase with the circuit
30 What might happen if you switch a multimeter to measure resistance while you have it connected to measure voltage
a) The multimeter would read half the actual voltage
b) It would probably destroy the meter circuitry
c) The multimeter would read twice the actual voltage
d) Nothing unusual would happen; the multimeter would measure the circuit’s resistance
31 Which instrument would you use to measure electric current:
a) an ohmmeter b) a wavemeter
c) a voltmeter d) an ammeter
32 What instrument can be used to determine the horizontal radiation pattern of an antenna
a) a field-strength meter
b) a grid-dip meter
c) an oscilloscope
d) a signal tracer & an audio amplifier
33 An absorption wavemeter can be used to check for:
a) Over-modulation
b) Receiver overloading
c) Band edge signals
d) Correct selection of harmonic from a multiplier circuit
34 Which of the following is NOT something you would determine with a spectrum analyzer
a) The degree of isolation between the input and output ports of a 2-meter duplexer
b) Whether a crystal is operating on its fundamental or overtone
c) The speed at which a transceiver switches from transmit to receive when being used for packet radio
d) The spectral output of a transmitter
35 What can a logic probe indicate about a digital logic circuit
a) a short-circuit fault
b) an open-circuit fault
c) the resistance between logic modules
d) the high & low logic states
36 The wavelength of a signal in free space with a frequency of 100 MHz is:
a) 30mm b) 0.3m
c) 3m d) 30m
37 What does a frequency counter do
a) It makes frequency measurements
b) It produces a reference frequency
c) It measures FM transmitter deviation
d) It generates broadband white noise
38 What does a dip-meter do
a) It accurately indicates signal strength
b) It measures frequency accurately
c) It measures transmitter output power accurately
d) It gives an indication of the resonant frequency of a circuit
39 The following unit in a DC power supply performs a smoothing operation
a) an electrolytic capacitor
b) a fuse
c) a crowbar
d) a full-wave diode bridge
40 A mains operated DC power supply
a) Converts DC from the mains into AC of the same voltage
b) Converts energy from the mains into DC for operating electronic equipment
c) Is a diode-capacitor device for measuring mains power
d) Is a diode-choked device for measuring inductance power
41 A low pass filter will:
a) suppress sub-harmonics
b) reduce harmonics
c) always eliminate interference
d) improve harmonic radiation
42 A power supply is to power a solid-state transceiver. A suitable over-voltage protection device is a
a) Crowbar across the regulator output
b) 100uF capacitor across the transformer output
c) fuse in parallel with the regulator output
d) zener diode in series with the regulator
43 AGC stands for:
a) Amplified gain control
b) auxiliary gain cut-off
c) automatic ganging control
d) automatic gain control
44 Over driving a power amplifier will:
a) give a high SWR
b) give minimum distortion on receive
c) generate excessive harmonics
d) minimize power output
45 VHF and UHF bands are frequently used for satellite communication because
a) Waves at these frequencies travel to & from the satellite relatively unaffected by the ionosphere
b) The Doppler frequency change caused by satellite motion is much less than at HF
c) Satellites move too fast for HF waves to follow
d) The Doppler effect would cause HF waves to be shifted into the VHF and UHF bands
46 When using voice, which of the following modes of transmissions required the least bandwidth?
a) single sideband
b) amplitude modulation
c) frequency modulation
d) phase modulation
47 The sensitivity of a receiver can be degraded by:
a) strong RF signals on a nearby frequency
b) removing all crystals
c) good RF filtering
d) incorrect adjustment of the volume control
48 Radio wave polarisation is defined by the orientation of the radiated
a) magnetic field b) electric field
c) inductive field d) capacitive field
49 For long distance propagation, the radiation angle of energy from the antenna should be:
a) less than 30 degrees
b) more than 30 degrees but less than 45
c) more than 45 degrees but less than 90
d) 90 degrees
50 The ability of a receiver to separate signals close in frequency is called its:
a) noise figure b) sensitivity
c) bandwidth d) selectivity
51 What is the primary source of noise that can be heard in a VHF/UHF-band receiver with an antenna connected?
a) receiver front-end noise
b) man-made noise
c) atmospheric noise
d) detector noise
52 Which of the following antenna arrangements is least likely to radiate harmonics:
a) a dipole fed with coaxial cable
b) a dipole fed with balanced feeder
c) an inverted L-Marconi with vertical feeder
d) a trap dipole
53 A stage in a receiver with input and output circuits tuned to the received frequency is the :
a) RF amplifier
b) local oscillator
c) audio frequency amplifier
d) detector
54 A communication receiver may have several IF filters of different bandwidths. The operator selects one to:
a) improve the S-meter readings
b) improve the receiver sensitivity
c) improve the reception of different types of signal
d) increase the noise received
55 To obtain high frequency stability in a transmitter, the VFO should be:
a) Run from a non-regulated AC supply
b) powered from a regulated DC supply
c) In a plastic box
d) able to change frequency with temperature
56 The side of quad antenna is:
a) a quarter wavelength
b) a half wavelength
c) three quarter of a wavelength
d) a full wavelength
57 The driver stage of a transmitter is located:
a) Before the power amplifier
b) with the frequency multiplier
c) Between oscillator and buffer
d) after the output low-pass filter circuit
58 The process of modulation allows
a) Information to be impresses on to a carrier
b) Information to be removed from a carrier
c) Voice and Morse code to be combined
d) None of these
59 The output power rating of a linear amplifier is a SSB transmitter is a specified by the
a) peak DC input power
b) mean AC input power
c) peak envelope power
d) unmodulated carrier power
 |
FIGURE N7-2
60 In figure N7-2, if block 1 is a transceiver and block 3 is an antenna switch, what is block 2
a) a terminal-node switch
b) an SWR meter
c) a dipole antenna
d) a high-pass filter
61 Harmonic frequencies are
a) Always lower in the frequency than the fundamental frequency
b) At multiples of the fundamental frequency
c) Any unwanted frequency above the fundamental frequency
d) Any frequency causing TVI
62 A parasitic oscillation
a) Is an unwanted signal developed in a transmitter
b) Is generated by parasitic elements of a Yagi beam
c) Does not cause any radio interference
d) Is produced in a transmitter oscillator stage
63 Parasitic oscillations can cause interference. They are
a) Always the same frequency as the mains supply
b) Always twice the operating frequency
c) Not related to the operating frequency
d) Three times the operating frequency
64 Unwanted signals from a radio transmitter which cause harmful interference to other users are known as
a) Rectified signals
b) Re-radiation signals
c) Reflected signals
d) Harmonic signals and spurious signals
65 To reduce the harmonic output from a high frequency transmitter, the following filter is usually installed at the transmitter
a) band pass b) low pass
c) high pass d) active filter
66 Test should be made on one’s equipment to check for harmonic radiation. These should be
a) from time to time
b) every 6 months
c) at the time of renewal of the license
d) weekly
67 A harmonic is
a) a whole number multiple of a frequency
b) a sub multiple of a frequency
e) any frequency greater than the fundamental frequency
f) any frequency causing interference
68 Which of the following sets of components are used to make RF filters?
a) Diodes and resistors
b) Zener diodes and inductors
c) LEDs and capacitors
d) Inductors capacitors
69 Earth return circuits should always be:
a) high impedance b) highly reactive
c) low impedance d) inductive
70 What is a folded dipole antenna
a) a dipole one-quarter wavelength long
b) a type of ground-plane antenna
c) a dipole whose ends are connected by a one-half wavelength piece of wire
d) a hypothetical antenna used in theoretical discussions to replace the radiation resistance
71 What is meant by antenna gain
a) the numerical ratio relating the radiated signal strength of an antenna to that of another antenna
b) the numerical ratio of the signal in the forward direction to the signal in the back direction
c) the numerical ratio of the amount of power radiated by an antenna compared tot eh transmitter output power
d) the final amplifier gain minus the transmission-line losses (including any phasing lines present)
72 A neighbour using a TV set top antenna complains of interference when you are transmitting at VHF. As a first step to eliminating this problem you could suggest:
a) better coaxial cable on their antenna
b) they use a preamplifier
c) they use a roof mounted antenna
d) their set is no good
73 Which of the following does not rely on a magnetic field:
a) a dynamic microphone
b) a loudspeaker
c) a carbon microphone
d) a transformer
74 The main purpose of a Varactor Diode is:
a) tuning b) rectification
c) voltage regulation d) display
75 An antenna which transmits well is one direction is a
a) dipole with a reflector only
b) quarterwave grounder vertical
c) a yagi
d) none of the above
76 The purpose of a balun in a transmitting antenna system is to
a) balance harmonic radiation
b) reduce unbalanced standing waves
c) protect the antenna system from lightning strikes
d) match unbalanced and balanced transmission lines
77 The main characteristic of a vertical antenna is that it
a) requires few insulators
b) is very sensitive to signals coming from horizontal aerials
c) receives signals from all points around it equally well
d) is easy to feed with TV ribbon feeder
78 A noise blanker on a receiver is most effective to reduce:
a) 50 Hz power supply hum
b) noise originating from the mixer stage of the receiver
c) ignition noise
d) noise originating from the RF stage of the receiver
79 What does an antenna tuner do
a) it matches a transceiver output impedance to the antenna system impedance
b) it helps a receiver automatically tune in stations that are far away
c) it switches an antenna system to a transceiver when sending and to a receiver when listening
d) it switches a transceiver between different kinds of antennas connected to one feed line
80 How is a Yagi antenna constructed
a) two or more straight, parallel elements are fixed in line with each other
b) two or more square or circular loops are fixed in line with each other
c) two or more square or circular loops are stacked inside each other
d) a straight element is fixed in the center of three or more elements that angle toward the ground
81 When operating a mobile HF set at home from a battery supply and using the base antenna there is no interference problem. When using the same arrangement but with an earthed battery charger connected interference occurs on an electronic organ. The possible cause is:
a) the production of sub-harmonics at the transmitter
b) very strong received signal
c) poor RF earthing
d) that the RF earthing is too good
82 Yagi antenna is said to have a power gain over a dipole antenna for the same frequency band because
a) it radiates more power than a dipole
b) more powerful transmitters can use it
c) it concentrates the radiation in one direction
d) it can be used for more than one band
83 The bandwidth of a beam antenna is dependent on:
a) radiation resistance of the dipole
b) spacing of directors and reflectors
c) feed cable impedance
d) propagation conditions
84 What is a loop antenna
a) a large circularly-polarised antenna
b) a small coil of wire tightly wound around a toraidal ferrite core
c) several turns of wire wound in the shape of a large open coil
d) any antenna coupled to a feed line through an inductive loop of wire
85 What phenomenon has the most effect on radio communication beyond ground-wave or line-of-sight ranges
a) solar activity
b) lunar tidal effects
c) the F1 region of the ionosphere
d) the F2 region of the ionosphere
86 An antenna which transmits equally well in all compass directions is a
a) dipole with a reflector only
b) quarterwave grounded vertical
c) dipole with director only
d) half-wave horizontal dipole
87 What pattern is desirable for a direction-finding antenna
a) one which is non-cardioids
b) one with good front-to-back and front-to-side ratios
c) one with good top-to-bottom and side-to-side ratios
d) one with shallow nulls
88 To check for harmonics in a radiated signal, which of the following could be used?
a) an SWR meter
b) an absorption wave meter
c) a digital frequency meter
d) an AVO meter
89 Radio wave polarisation is defined by the orientation of the radiated:
a) magnetic field c) inductive field
b) electric field d) capacitive field
90 For long distance propagation, the radiation angle of energy from the antenna should be
a) less than 30 degrees
b) more than 30 degrees but less than 45
c) more than 45 degrees but less than 90
d) 90 degrees
91 A band pass filter following a VHF transmitter will:
a) stop all transmitting frequencies
b) allow all harmonics to be radiated
c) allow all sub-harmonics to be radiated
d) pass the desired frequency range with minimum loss
92 The ionosphere layer mainly responsible for long distance communication at HF is:
a) D b) E
c) F2 d) F1
93 High frequency long-distance propagation is most dependent on
a) ionospheric reflection
c) tropospheric reflection
d) ground reflection
d) inverted reflection
94 A low pass filter will
a) suppress sub-harmonics
b) reduce harmonics
c) always eliminate interference
d) improve harmonic radiation
95 To prevent unwanted radiation in the shack, RF connections between units should be by
a) open wire feeder
b) good quality coaxidel cable
c) bell wire
d) mains type cable
96 The coaxial cable from an SWR meter to an antenna at HF develops a fault so that no power reaches the antenna. The SWR meter will read:
a) zero b) 1:1
c) high d) very low
97 What is the proper procedure for suppressing electrical noise in a mobile transceiver
a) apply shielding and filtering where necessary
b) insulate all place sheet metal surfaces from each other
c) apply antistatic spray liberally to all non-metallic surfaces
d) install filter capacitors in series with all DC wiring
98 The resonant frequency of a tuned circuit can be checked by:
a) a DC Voltmeter
b) a DIP Oscillator
c) a Digital Frequency Meter
d) an Ohm-Meter
a) by connecting the radio’s power leads to the battery by the longest possible path
b) by connecting the radio’s power leads to the battery by the shortest possible path
c) by installing a high-pass filter in series with the radio’s DC power lead to the vehicle’s electrical system
d) by installing filter capacitors in series with the DC power lead
100 A corroded connector on a neighbour’s TV receiving antenna may cause:
a) unwanted mixing products due to it exhibiting diode properties
b) mains rectification
c) enhanced signal reception due to its fitering properties
d) increased amplification
101 A band pass filter will
a) pass frequencies each side of a band
b) attenuate low frequencies but not high
c) attenuate frequencies each side of a band
d) attenuate high frequencies but not low
102 If the VFO of a transmitter is subject to varying temperatures, this might cause:
a) chrip
b) drift
c) harmonic generation
d) no problems
103 A braid-breaking choke in a TV antenna down load will block:
a) all AC signals
b) out phase interfering signals
c) in phase interfering signals
d) mains hum
104 When operating at HF, interference is caused on a TV. The most likely route for the interfering signal is:
a) via the earth
b) through the transmitter power supply
c) by the TV antenna coaxial cable screen and/or IF stages
d) by frequency multiplication in free space
105 To reduce strong signals from a 21 MHz transmitter reaching a TV via antenna down lead, one could fit:
a) a high pass filter in the TV down lead
b) a low pass filter in the TV down lead
c) a UHF amplifier in the TV down lead
d) a band reject filter at the TV channel frequency
106 A good dummy load for RF is constructed from:
a) light bulbs
b) a column of water
c) wire wound resistors
d) non-reactive resistors
107 Which of the following components could be attached to a moving coil meter in an attempt to measure power?
a) resistor b) thermistor
c) thermocouple d) thimble
108 When transmitting Morse code, key clicks can be prevented by a
a) resistor in series with the key, and a choke across the key contacts
b) choke in series with the key, and a capacitor across the key contacts
c) choke across the key contacts, and a capacitor in series with the key
d) capacitor and choke in series with the key contacts
109 It is not a good practice to:
a) use double insulated cable on EHT circuits
b) use a separate RF earth
c) use a gas pipe for the earth connection
d) have safety switches
110 How much electrical current flowing through the human body will probably be fatal
a) as little as 1/10 of an ampere
b) approximately 10 amperes
c) more than 20 amperes
d) current through the human body is never fatal
111 What could happen to your transceiver if you replace its blown 5 amp AC line fuse with a 30 amp fuse
a) a 30-amp fuse would better protect your transceiver from using too much current
b) the transceiver would run cooler
c) the transceiver could use more current than 5 amps and a fire could occur
d) the transceiver would not be able to produce as much RF output
112 How can amateur station equipment best be protected from lighting damage
a) use heavy insulation on the wiring
b) never turn off the equipment
c) disconnect the ground system from all radios
d) disconnect all equipment from the power lines and antenna cables
113 Which of the following is the best way to install your antenna in relation to overhead electric power lines
a) always be sure your antenna wire is higher than the power line, and crosses it at a 90-degree angle
b) always be sure your antenna and feed line are well clear of any power lines
c) always be sure your antenna is lower than the power line, and crosses it at a small angle
d) only use vertical antennas within 100 feet of a power line
114 ‘VOX’ stands for
a) volume operated extension speaker
b) variable oscillator transmitter
b) voice operated transmit
d) voice operated expander
115 The figure in a receiver’s specifications which indicates its sensitivity is the
a) bandwidth of the IF in kilohertz
b) signal plus noise to noise ratio
c) audio output in watts
d) number of RF amplifiers
116 The abbreviation AGC means:
a) attenuating gain capacitor
b) anode-grid capacitor
c) automatic gain control
d) amplified grid conductance
117 The coaxial cable from an SWR meter to an antenna at HF develops a fault so that no power reaches the antenna. The SWR meter will read:
a) zero b) 1:1
c) high d) very low
118 Define Peak Envelope Power
a) means power supplied to an antenna by a radio receiver in a condition of no modulation
b) means the average power supplied to the antenna transmission lines by a transmitter during one radio-frequency cycle at the highest crest of the modulation envelope taken under conditions of normal operation
c) means the average power that is supplied to the antenna transmission lines in a condition of no modulation
d) means the average power that is supplied to the antenna in a condition where such power does not create a danger to life
119 Identify the correct statements
i All equipment should be controlled by one master switch, the position of which should be known to others in the house or club
ii All equipment should be properly connected to a good and permanent earth
iii PVC water main pipes are commonly used as permanent earth
iv Indicator lamps should be installed showing that the equipment is live
v Indicator lamps should be clearly visible at the operating and test position
vi Faulty indicator lamps should be replaced immediately
vii Filament lamps are more reliable than gas-filled (neon) lamps
viii Antennas should always be connected to mains or other hot source
a) i, ii & iv c) v, vi & vii
b) ii, iii & v d) iii, vii & viii
120 For your safety, before checking a fault in a mains operated power supply unit, first
a) short the leads of the filter capacitor
b) turn off the power and remove the power plug
c) check the action of the capacitor bleeder resistance
d) remove and check the fuse in the power supply
121 Wires carrying high voltages in a transmitter should be well insulated to avoid
a) short circuits c) over modulation
b) overheating d) SWR effects
122 The purpose of using three wires in the mains power cord and plug on amateur radio equipment is to
a) make it inconvenient to use
b) prevent the chassis from becoming live in case of an internal short to the chassis
c) prevent the plug from being reversed in the wall outlet
d) prevent short circuits
123 When switching on the power to your transmitter, for safety reasons ensure that
a) the other callsign followed by your own callsign
b) you callsign followed by the other callsign
c) your own callsign, repeated twice
d) the other callsign, repeated twice
124 The following should always be included as a standard protection device in any power supply
a) a saturating transformer
b) a fuse in the mains lead
c) a zener diode bridge limiter
d) a fuse in the filter capacitor negative lead
125 For equipment safety, before switching on your amateur radio equipment, check that the equipment is connected to
a) an unregulated power supply unit
b) an antenna or a dummy load
c) check that your license is valid
d) answer a & b above
126 Two 10K Ohm resistors are connected in parallel across a 5V DC supply. Total current taken is:
a) 5uA
b) 1mA
c) 0.5mA
d) 1A
127 A 50 Ohm dummy loads are made from eleven 560 Ohm carbon resistors each of 5W rating. Total safe power that can be dissipated is:
a) 0.5W b) 5.0W
c) 27.5W d) 55W
128 When monitoring the frequency of an un-modulated carrier, the readout of a digital frequency counter should show:
a) the carrier frequency plus the number of significant harmonics present
b) how many sidebands there are
c) nothing
d) the constant carrier frequency
129 At 3.5MHz, a wire 40 meters long corresponds to:
a) a quarter wavelength
b) half wavelength
c) one wavelength
d) two wavelength
130 You can operate this number of identical lamps, each drawing a current of 250 mA, from a 5A supply:
a) 50 b) 30
c) 20 d) 5
Tiada ulasan:
Catat Ulasan