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OVERALL TEST

B L Englisch 76 Karten

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  1. 1Purpose of a receiver?To convert EM energy into usable energy
  2. 23 Requirements of an effective receiver?Select the wanted signal
    Extract the intelligence
    Produce an output of sufficient power
  3. 34 Receiver characteristics?Sensitivity
    Selectivity
    Stability
    Noise
  4. 4Expand and define RF?Radio Frequency
    (The carrier, raw state, no information)
  5. 5Expand and define AF?Audio Frequency
    Frequency audible to the average human ear
  6. 6Expand and define IF?Intermediate Frequency
    RF is shifted to to produce an AF
  7. 7What is heterodyning?Two frequencies are mixed and multiplied to create two new frequencies
  8. 85 Types of filter?High pass
    Low pass
    Band pass
    Notch
    Band reject
  9. 9How do you work out Rx bandwidth?Higher frequency level - lower frequency level
  10. 10Define squelch?Used to suppress the audio of a receiver in the absence of a sufficiently strong and desired input signal
  11. 11Define modulation?The process where information is superimposed upon the RF (Carrier wave)
  12. 12What is the modulating wave?The waveform of the original intelligence
  13. 13What is the carrier wave?The wave that is used to carry the modulating wave
    (To gain further distance)
  14. 14What is the modulated wave?The waveform that is transmitted
  15. 15What is AM?(Amplitude modulation)
    Method in which the amplitude of the modulated wave is varied in accordance with the amplitude of the modulating wave.
  16. 16If the amplitude of the transmission stays the same it is said to have a..... envelope?Constant
  17. 17If the amplitude of the transmission varies in a repetitive manner it is said to have a...... envelope?Periodic
  18. 18How would you work out AM transmission bandwidth?2 x modulating frequency
  19. 19How would you work out depth of modulation?Peak AF voltage/ Peak RF voltage
    Answer X 100 = %
    (80% is best)
  20. 20What is the result from a modulation value of over 100%?Distortion
  21. 21What is a double sideband?The method of operation where both side bands of frequencies are transmitted equally.
  22. 22Speech frequency range is?300Hertz - 3400Hertz
  23. 23Describe an erect sideband?The higher the RF, the higher the AF.
  24. 24Describe an inverted sideband?The lower the RF, the higher the AF.
  25. 253 DSB disadvantages?1- Waste of transmitter power
    2- Excessive bandwidth
    3- Prone to selective fading
  26. 26What is a single sideband?Where only the upper or lower sideband is transmitted, and one sideband is completely attenuated.
  27. 272 Disadvantages of SSB?Carrier needs to be re-inserted
    SSB equipment must be stable
  28. 28What is FM?The frequency of the carrier wave is varied in accordance with the amplitude of the modulating wave.
  29. 29Define centre frequency?The frequency occupied by the carrier when in an un-modulated state.
  30. 30Define frequency deviation?The amount of change in frequency from the centre frequency.
  31. 31What is carrier/frequency swing?The difference between the highest and lowest frequencies the modulated wave can attain.
  32. 32What is the deivation ratio?The ratio of the maximum frequency deviation and the highest permissible modulating frequency.
  33. 33What is the modulation index?The decimal number representing the ratio of the frequency deviation and the highest frequency of the modulating wave.
  34. 34How would you work out FM bandwidth?Carsons bandwidth.
    2x (fd+fm)
  35. 35Expand and define FSK?Frequency shift keying
    RF carrier if shifted between two or more discreet frequency values.
  36. 36Define shift?Difference between adjacent frequency levels.
  37. 37Define Excursion?Difference between the highest and lowest frequency levels
  38. 38How would you work out FSK bandwidth?Carsons bandwidth
    Shift(Excursion) + bauds
  39. 39Expand and define OOK?On-Off keying
    Simplest form of AM, a carrier is keyed on or off a voltage according to a pre-arranged code.
  40. 40Define telegraphic structure?The arrangement and polarity of elements.
  41. 41Define element?A function of time, its polarity may be mark or space.
    (1's and 0's)
  42. 42Define mark and space?Mark = Voltage high/ binary 1
    Space = Voltage low/ binary 0
  43. 43What is a baud?A unit of telegraphic speed (Number of elements per second)
  44. 44Expand and explain ETD?Element time duration
    Time taken for one element to be transmitted.
    (Expressed in Bauds, (B) )
  45. 45How is ETD calculated?1000/Bauds
  46. 46Expand and explain the FKFFundamental keying frequency
    same as modulating frequency
  47. 47How is the FKF calculated?Bauds/2 = Hertz
  48. 48How is OOK Tx BW calculated?5 x Bauds
  49. 49How is OOK Rx BW calculated?3 x Bauds
  50. 50Expand and explain MFSK?Multi level frequency shift keying
    Number of levels and states the signal can change to is increased.
  51. 512 Advantages of MFSK signalling?- Higher information rate
    - Variable information rate
  52. 522 Disadvantages of MFSK signalling?- Susceptible to drift due to narrow spacing
    - More Rx and Tx processing needed
  53. 53What is the data rate?The number of bits received as data by the receiving equipment
    (Quoted in bps) (Bits per second)
  54. 54Expand and explain MSK?Minimum shift keying
    FSK transmission that has a baud speed of exactly twice the value of the shift.
  55. 55Expand and explain MFC?Multiple frequency coding
    Method of FSK where each frequency level represents partial or whole characters.
  56. 56How many levels can be common in MFC and why?36, one per alphabet letter =26
    one per number 0-9 = 10
    26+10=36
  57. 57Common MFCs?11 MFC
    7 MFC
  58. 58How can an MFC be recognised?Sounds slow
    Not in binary
  59. 59Expand and explain PM?Phase modulation.
    The phase of the carrier in changed in accordance with the amplitude of the modulating wave.
  60. 60What is phase deviation?The amount of phase change produced by the modulating wave.
  61. 61Expand and explain PSK?Phase shift keying.
    The carrier phase is shifted between discreet phase values.
  62. 62The drop from the major lobe to the minor lobe in PSK = ?13.7dB
  63. 63The drop from the major lobe to the minor lobe in MSK = ?23.7dB
  64. 64What is an initial phase reference?Used to counter initial phase problems
  65. 65Expand and explain DPSK?Differential Phase shift keying
    'Changes on a 1'
  66. 66Explain abolute PSK?'Changes on a change'
    (1-0 OR 0-1)
  67. 67What is a polar plot?Diagram used to show which pases are being used and permits the operator to determine the quality of a demodulated signal.
  68. 68Expand and explain BPSK?Bi-Phase shift keying
    Carrier is shifted between two discreet phase values.
  69. 69Expand and explain QPSK?Quadrature- Phase shift keying
    Carrier is shifted between four discreet phase values.
    (Di-bits)
  70. 70Explain Eight PSK?8PSK
    Carrier is shifted between 8 discreet phase values.
    (Tri-bits)
  71. 71Expand and explain QAM?Quadrature amplitude modulation.
  72. 72Define amplitude ring?An imaginary circle that denotes the clusters that share a common amplitude.
  73. 73Define signal states?The total number of amplitude and phase combinations a signal can attain.
  74. 74Define phase states?Data is represented by the phase of the signal in relation to a reference.
  75. 75Explain the V.29 modem8 Phase states
    4 Amplitude levels
    16 signal states
  76. 762 Benefits of QAM?1- High data rate
    2- Improved adaptability

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Karteikarten am OVERALL TEST, erstellt von B L am 26/02/2017.
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