Advanced trial exam

  1. The approximate forward bias value for a germanium transistor is
    1. 0.2 volt
    2. 0.6 volt
    3. 0.9 volt
    4. 1 volt
  2. To convert microfarads to nanofarads requires
    1. multiplication by 1,000
    2. division by 1,000
    3. multiplication by 10,000
    4. division by 10,000
  3. RF radiation from transmitting equipment
    1. increases in danger with increase in frequency
    2. can cause tissue damage in the short term
    3. can cause cumulative eye damage
    4. all of the above
  4. The frequency of an electromagnetic wave which has a single cycle duration of 2.25 nanoseconds is approximately
    1. 28MHz
    2. 54MHz
    3. 144MHz
    4. 444MHz
  5. In satellite communications, Doppler effect causes an apparent
    1. frequency increase as the satellite moves towards the ground station
    2. frequency decrease as the satellite moves towards the ground station
    3. frequency doubling at the point of closest approach
    4. frequency increase as the satellite moves away from the ground station
  6. The standard colour code used to identify the earth conductor of a flexible 3-core AC power cord is
    1. green/yellow
    2. red/yellow
    3. brown
    4. blue
  7. A half wave dipole antenna resonant at 28 MHz, would have an approximate length of
    1. 5 metres
    2. 10 metres
    3. 38 metres
    4. 56 metres
  8. A single side band transmitter could cause interference to stations on adjacent frequencies if it
    1. had shorted turns in the tank coil
    2. had ripple on the power supply
    3. had leakage of RF into the mains cable
    4. was overdriven
  9. The depth of modulation of a transmitter may easily be monitored by means of an oscilloscope. The following displays, from left to right, show approximate modulation percentages of
    1. 0% 100% over 100%
    2. 30% 100% over 100%
    3. 80% 0% -10%
    4. 60% 0% 10%
  10. When tuning a mobile antenna the test instrument being used to measure the amount of RF radiated is a
    1. noise bridge
    2. antenna impedance meter
    3. field strength meter
    4. digital frequency meter
  11. The term "horizontally polarised electromagnetic wave" refers to a wave in which the
    1. magnetic component oscillates vertically
    2. electric component oscillates vertically
    3. magnetic component has been eliminated
    4. electric component has been eliminated
  12. If the voltage across a resistor is tripled the power dissipated is multiplied by
    1. 2
    2. 3
    3. 4
    4. 9
  13. A 120 watts 21.1 MHz frequency shift keyed radioteletype transmitter has a duty cycle of
    1. 1
    2. 2
    3. 3
    4. 4
  14. The sensitivity of a meter with a full scale deflection (FSD) of 300V and an internal resistance of 300,000 ohms is
    1. 100 ohms/volt
    2. 300 ohms/volt
    3. 1,000 ohms/volt
    4. 3,000 ohms/volt
  15. An unterminated long wire "V" beam antenna has a radiation pattern which is
    1. omnidirectional
    2. bidirectional
    3. dependent on the ionosphere
    4. unidirectional
  16. A semiconductor has
    1. very high resistance
    2. high conductivity
    3. less conductivity than an insulator
    4. greater conductivity than an insulator
  17. Filter capacitors in power supplies are sometimes connected in series to
    1. resonate the filter circuit
    2. increase the total capacity
    3. reduce the ripple voltage further
    4. withstand a greater voltage than a single capacitor
  18. This block diagram represents a
    1. balanced modulator
    2. discriminator
    3. PLL synthesizer
    4. triple conversion superheterodyne receiver
  19. Which of the following statements is incorrect in relation to a full wave bridge rectifier circuit
    1. its transformer does not require a centre tap
    2. the circuit requires two diodes
    3. all diodes conduct at the same time
    4. the output ripple frequency is 100Hz
  20. To increase the efficiency of a simple electromechanical relay the relay coil (motor) is wound on
    1. aluminium
    2. soft iron
    3. ceramic
    4. lead
  21. The bias used in this amplifier circuit is
    1. fixed bias
    2. grid leak bias
    3. cathode bias
    4. combination bias
  22. The voltage across terminals A, B is
    1. 0 volts
    2. 3 volts
    3. 6 volts
    4. 10 volts
  23. The time constant of a 500 microhenry inductor and a 50 ohm resistance is
    1. 0.2 microsecond
    2. 5 microseconds
    3. 10 microseconds
    4. 125 microseconds
  24. The maximum frequency deviation in an FM transmitter is 3000Hz. The modulation index, when the highest modulating audio frequency is 1000Hz is
    1. 0.3
    2. 1
    3. 3
    4. 30
  25. A pi-coupling network used at the output of the final power amplifier stage in a transmitter
    1. doubles the output frequency and improves neutralisation
    2. suppresses parasitic oscillations and enhances spurious sidebands
    3. matches the P.A. output impedance to the antenna load and suppresses harmonics
    4. enables a half-wave dipole antenna to be voltage fed at
  26. When comparing series and switching voltage regulators, the major disadvantage of the series regulator is its
    1. higher power dissipation
    2. difficulty in adjustment
    3. lower power dissipation
    4. instability
  27. The total effective capacitance of this circuit is
    1. 400 picofarads
    2. 800 picofarads
    3. 200 picofarads
    4. 3200 picofarads
  28. A 10.7MHz first stage IF is commonly used in VHF receivers to
    1. provide a high degree of adjacent channel selectivity
    2. reduce noise generated in the receiver
    3. achieve the high gain required
    4. provide an adequate degree of image rejection
  29. Interference seen as "cross-hatching" on a TV screen occurs when
    1. the front end is overloaded
    2. harmonics of an amateur transmission beat with the sound carrier
    3. an SSB signal is demodulated by the TV set
    4. an interfering carrier signal beats with the picture carrier
  30. The three electrodes of the Silicon Controlled Rectifier (SCR) are
    1. source, emitter and base
    2. anode, cathode and grid
    3. anode, cathode and gate
    4. source, drain and gate
  31. Critical frequency is defined as
    1. the highest frequency on which it is possible to communicate with another station
    2. the highest frequency at which waves sent vertically are returned to earth
    3. the frequency of the greatest skip distance
    4. the highest frequency with which a station may be contacted by ground wave
  32. The AGC system in an AM receiver works by sampling the level of the
    1. carrier
    2. modulation
    3. frequency
    4. deviation
  33. A five-eighth wave length antenna is made with a loading coil at its base to make the antenna electrically three-quarters of a wavelength long. The reason for the antenna being electrically three-quarters of a wavelength long is to
    1. allow for easy matching to a 50 ohm transmission line
    2. increase the radiation angle
    3. decrease the radiation angle
    4. increase the bandwidth of the antenna
  34. Tropospheric ducting may
    1. cause high frequency signals to fade suddenly
    2. allow long distance VHF communications
    3. occur as a result of meteor showers or auroral activity
    4. occur more frequently at HF than at VHF
  35. In an SSB transmitter the balanced modulator suppresses
    1. both sidebands
    2. the carrier an one sideband
    3. one side band
    4. the carrier
  36. On entry to a power supply the active lead of the mains should be connected to a
    1. indicator lamp
    2. filter capacitor
    3. transformer
    4. fuse
  37. An oscillator that slowly moves in frequency of "its own accord" is said to
    1. over modulate
    2. drift
    3. have distortion
    4. chirp
  38. Two tone tests are done to test the
    1. linearity of an FM transmitter
    2. power output of a CW transmitter
    3. linearity of an SSB transmitter
    4. symmetry of an FSK transmitter
  39. A capacity hat or capacitive top loading is used on a vertical antenna to
    1. to increase the bandwidth of the antenna
    2. make the antenna more stable in high winds
    3. to decrease the electrical length of the antenna
    4. to increase the electrical length of the antenna
  40. A linear repeater station accepts
    1. FM signals only
    2. SSB signals onlys
    3. SSB, FM and CW signals
    4. RTTY signals only
  41. The approximate wavelength of the second harmonic of a 144 MHz transmission is
    1. 1 metre
    2. 2 metres
    3. 3 metres
    4. 4 metres
  42. In this circuit R1 dissipates 10 watts. What power is dissipated in R2?
    1. 10 watts
    2. 5 watts
    3. 2.5 watts
    4. 20 watts
  43. A power gain of 30 dB is an equivalent power ratio of
    1. 1,000
    2. 10,000
    3. 100,000
    4. 10
  44. The hfe or beta of a transistor is
    1. noise figure
    2. current gain
    3. operating speed
    4. breakdown voltage
  45. Spurious emissions from a amateur transmitter may be caused by
    1. ripple on the power supply
    2. under modulation
    3. oscillation of the RF power amplifier stage
    4. the antenna being too near the ground
  46. Image interference in a superheterodyne communications receiver is caused by an unwanted signal operating on
    1. half the frequency to which the receiver is tuned
    2. the same frequency as the local oscillator in a dual conversion receiver
    3. twice the frequency to which the receiver is tuned
    4. twice the intermediate-frequency away from the desired signal frequency
  47. A television receiver suffers ghosting interference, a possible cure for this is to
    1. fit a high pass filter to the receiver antenna input
    2. change the direction of the antenna
    3. install an RF choke to the antenna lead
    4. use a small by-pass capacitor across the antenna
  48. Distortion occurring in a non-linear device driven by a signal containing more than one frequency is called
    1. frequency distortion
    2. phase distortion
    3. harmonic distortion
    4. intermodulation distortion
  49. Which of the following solid state devices has the highest input impedance?
    1. PNP bipolar transistor
    2. JFET
    3. NPN bipolar transistor
    4. MOSFET
  50. The transistor circuit used to match a high impedance source to a low impedance is the
    1. common emitter
    2. common gate
    3. emitter follower
    4. common base