Standard trial exam

  1. A device used to couple a co-axial transmission line to a balanced antenna is known as a
    1. converter
    2. feed-line
    3. co-axial connector
    4. balun
  2. Parasitic oscillations are usually generated by
    1. a frequency which is an exact multiple of the transmitted frequency
    2. excessive drive or excitation to the power amplifier
    3. accidental resonant frequencies in the power amplifier
    4. a mismatch between the power amplifier and transmission line
  3. The ability of a communication receiver to distinguish between signals that are close in frequency is known as
    1. realiability
    2. stability
    3. selectivity
    4. sensitivity
  4. A correctly biased NPN transistor will conduct when
    1. the emitter is more positive than the collector
    2. emitter and collector are at the same potential
    3. the collector is more positive than the emitter
    4. emitter and base are at the same potential
  5. The capacitive reactance of a capacitor will
    1. fall as the applied frequency increases
    2. remain the same at all frequencies
    3. rises as the capacitance is increased
    4. increases as the applied frequency increases
  6. Resolving interference problems with neighbours requires
    1. tell the neighbour you have a licence and can continue to transmit anyway
    2. suggest because their equipment is unlicensed it is their problem
    3. refer the matter instantly to a community dispute resolution centre
    4. the exercise of diplomacy
  7. Adjusting a tuned circuit's frequency can done by altering the DC voltage across
    1. variable capacitor
    2. a trimmer capacitor
    3. a varicap
    4. an electrolytic capacitor
  8. Compared with an amplititude modulated signal, a single sideband signal modulated with the same audio frequency
    1. occupies the same bandwidth
    2. occupies approximately half the bandwidth
    3. occupies twice the bandwidth
    4. occupies twice the peak bandwidth
  9. A transmitter is more likely to cause interference to TV reception when it is
    1. 100 per cent modulated
    2. 50 per cent modulated
    3. unmodulated
    4. over-modulated
  10. The third harmonic of a 21.15MHz tranmission is
    1. 63.45MHz
    2. 10.57MHz
    3. 31.72MHz
    4. 42.30MHz
  11. The radiation resistance of a half-wave dipole is about
    1. 36.6 ohms
    2. 73 ohms
    3. 146 ohms
    4. 300 ohms
  12. Two 300 ohm resistors are connected in parallel. The total resistance is
    1. 600 ohms
    2. 300 ohms
    3. 150 ohms
    4. 200 ohms
  13. This symbol represents a
    1. NPN bipolar transistor
    2. PNP bipolar transistor
    3. N channel field effect transistor
    4. P channel field effect transistor
  14. A radio wave which propagates via the ionosphere is called
    1. surface wave
    2. sky wave
    3. ground wave
    4. direct wave
  15. The unit of electrical potential difference is the
    1. watt
    2. volt
    3. ohm
    4. ampere
  16. The highest frequency that will be reflected back to earth by the ionosphere at any given time is known as the
    1. UHF
    2. MUF
    3. OWF
    4. LUF
  17. The velocity factor for commonly used co-axial transmission line is approximately
    1. 0.66
    2. 1.66
    3. 50
    4. 75
  18. The purpose of AGC in superhetrodyne receivers is to
    1. keep the local oscillator frequency constant
    2. maintain constant power supply current drain
    3. provide a small variation in receiver tuning
    4. maintain a constant output level with wide input variations
  19. A correctly biased PNP transistor will conduct when the
    1. emitter is more negative than the collector
    2. collector is more positive than the emitter
    3. collector is more negative than the emitter
    4. emitter and base are at the same potentail
  20. In this bridge rectifier circuit, when point A is positive with respect to point B, which doides conduct?
    1. D1 and D3
    2. D1 and D2
    3. D3 and D4
    4. D2 and D4
  21. What is the peak-inverse-voltage rating of a power-supply rectifier?
    1. the maximum transient voltage the rectifier will handle in the conducting direction
    2. 1.4 times the AC frequency
    3. the maximum voltage the rectifier will handle in the non-conducting direction
    4. 2.8 times the AC frequency
  22. A Yagi beam antenna usually consists of a driven element, a reflector and additional elements called
    1. refractors
    2. directors
    3. radiators
    4. rejectors
  23. A frequency multiplier will not oscillate because
    1. its input and output frequencies are different
    2. there are no tuned circuits in a frequency multiplier
    3. its output and input frequencies are the same
    4. transistors cannot be used as frequency multipliers
  24. The standard color code used to identify the active conductor of a flexible 3-core AC power cable is
    1. yellow
    2. green
    3. brown
    4. blue
  25. The main advantage of ground wave propagation is that it
    1. reduces power requirements
    2. requires a small antenna array
    3. is not affected by ionospheric disturbances
    4. has highly directional properties
  26. In an SSB transmitter the sideband filter is normally placed
    1. between the balanced modulator and mixer stages
    2. in the speech amplifier stage
    3. as close as possible to the final stage
    4. in the variable frequency (VFO) stage
  27. The purpose of the capacitor in this filter circuit is to
    1. pass the low frequency
    2. attenuate the low frequencies
    3. bypass the high frequencies
    4. amplify the high frequencies
  28. To measure resistance using a moving coil meter the minimum extra componants needed are
    1. diode and battery
    2. resistor and battery
    3. resistor, capacitor and diode
    4. resistor, diode and battery
  29. In an SSB transmitter the output from the Balanced Modulator is
    1. one sideband and no carrier
    2. both sidebands with a suppressed carrier
    3. one sideband with carrier
    4. both sidebands and no carrier
  30. Improvement to the RF immunity of an electronic device can include
    1. replacement of its mains power lead to industrial rather than domestic standard
    2. the use of non-metallic adhesive tap
    3. a high pass filter on the out of the nearby radio transmitter
    4. use of a filter in combination with the electronic device
  31. The best way to eliminate TV set front-end overload caused by a nearby 80, 15 and 10 metre amateur transmitter is to
    1. use a low-pass filter on the transmitter
    2. install a wave-trap in the TV set's feedline
    3. install a power-line filter
    4. use a high-pass filter on the TV receiver
  32. The ripple frequency of a full-wave bridge rectifier is
    1. one-half of the frequency which is rectified
    2. equal to the frequency that is rectified
    3. twice the frequency that is rectified
    4. unrelated to the frequency which is rectified
  33. To extend the range of an ammeter you should use a
    1. resistor in parrallel with the meter
    2. resistor in series with the meter
    3. rectifier in series with the meter
    4. capacitor in parallel with the meter
  34. The approximate forward bias values for germanium and silicon diodes are
    1. germanium 0.2 volt, silicon 0.6 volt
    2. germanium 0.6 volt, silicon 0.2 volt
    3. germanium 0.6 volt, silicon 1.6 volt
    4. germanium 1.6 volt, silicon 1.6 volt
  35. The stages in a superhetrodyne receiver which are normally tuned simultaneously are the
    1. IF stage and detector
    2. local oscillator and detector
    3. RF stage and local oscillator
    4. RF and IF stages
  36. The most reliable amateur band for communication over a path of 160 kilometres during daytime hours is
    1. 10 metres
    2. 15 metres
    3. 20 metres
    4. 80 metres
  37. Single sideband SSB transmissionss
    1. occupy about twice the bandwidth of AM transmissions
    2. contain more information than AM transmissions
    3. occupy about half the bandwidth of AM transmissions
    4. can also be detected by an FM receiver
  38. If the frequency of the AC supply is increased, the current through the inductor L will
    1. increase
    2. decrease
    3. remain the same
    4. be zero
  39. To lower the resonant frequency of an antenna requires
    1. lengthening the antenna
    2. centre feeding the antenna with TV ribbon
    3. shortening the antenna
    4. insertion of a variable capacitor
  40. In this transmitter block diagram, the Power Amplifier
    1. Increases the mains voltage to drive the antenna
    2. Amplifies the audio frequency component of the signal
    3. Amplifies the selected signal band to a suitable level
    4. Amplifies the RF signal to a suitable level
  41. An instrument to check whether RF power is being fed into an antenna transmission line is
    1. a Standing Wave Radio Meter
    2. an Antenna Tuner
    3. dummy Load or Artificial Antenna
    4. an ohmmeter or continuity checker
  42. This diagram represents a
    1. high pass filter
    2. low pass filter
    3. band pass filter
    4. band stop filter
  43. Capacitors may be connected in series to
    1. increase the total capacitance
    2. decrease the total reactance
    3. decrease the voltage rating
    4. increase the total voltage rating
  44. Interference to home entertainment equipment can enter via
    1. the mains power and power lead
    2. unshielded speaker leads
    3. RF and IF stages
    4. all of the above
  45. The process of mixing audio and radio frequency voltages is called
    1. amplification
    2. impedance matching
    3. neutralisation
    4. modulation
  46. The IF stage in a superheterodyne receiver
    1. mixes the received signal for the Detector
    2. rejects the unwanted sideband
    3. amplifies a fixed narrow band of frequencies
    4. purely provides a buffer for the RF stage
  47. When a current of 20 millamps flows through a 50 ohm resistor the voltage drop across the resistor will be
    1. 100 millivolts
    2. 10 millivolts
    3. 1 volt
    4. 10 volts
  48. The best conductor on the following list is
    1. iron
    2. silver
    3. carbon
    4. glass
  49. The ratio of the collector current Ic to the base current Ib of a transistor is called
    1. resistance gain
    2. voltage gain
    3. power gain
    4. current gain
  50. Two capacitors of 400 microfarad are connected in series, their total effective capacitance is
    1. 200 microfarad
    2. 800 microfarad
    3. 400 microfarad
    4. 4,000 microfarad