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Subel. J
6 questions
Subelement J

MF-HF Equip. and Comms:

Section 91

MF-HF ARQ Operation - OP Codes & Procedures

What sequence of ARQ codes matches the following: manual over, end of message text, end of connection to land destination terminal?

  • NNNN, KKKK, GA+
  • KKKK, DIRTLX, NNNN
  • Correct Answer
    +?, NNNN, KKKK
  • +?, . . . . ., BRK+
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What sequence of ARQ codes matches the following: request establishment of a landline, end radio link after traffic is done, request connection for AMVER messages?

  • NNNN, KKKK, AMV+
  • KKKK, BRK+, AMV+
  • BRK+, DIRTLX+, AMV+
  • Correct Answer
    DIRTLX, BRK+, AMV+
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What sequence of ARQ codes matches the following: Send synoptic weather, switch control from a station currently transmitting over to the receiving station, terminate phasing with coast station.

  • Correct Answer
    OBS+, +?, BRK+
  • OBS+, WRU then Here is, BRK+
  • OBS+, GA+?, KKKK
  • AMV+, +?, KKKK
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A manual ship-ship ARQ message would typically begin with what sequence of ARQ procedures?

  • Initiate call with CS selcal, observe exchange of answer-backs (WRU-AAB), send message.
  • Correct Answer
    Initiate call with ship selcal, enter “HERE IS” then “WRU” commands and send message.
  • After phasing with the other vessel, observe exchange of answer-backs (WRU-AAB), send message and then KKKK to end the transmission.
  • After phasing with the other vessel then send GA+? to determine if they are ready to receive your message.

This is referred to as a "Handshake" when two stations are linked together. This ship makes a call to shore using duplex channel for the station. It then determines if the station is busy by sending out a signal back in Morse code.

Once heard, a 4 digit selcall number is used. The handshake is complete. The terminal indicates "connected" or "locked" then Automatic Answer Back or AAB codes are exchanged. The shore self-identifies first, to the vessel and uses "WRU" function to request ship calling to send ID.

The ARQ system sends a group of three characters, if everything on shore checks out, it then asks to send another group of three characters. If any characters fail, Auto Repeat reQuest (ARQ) is initiated, re-sending the three characters.

Repeated request for the same group of characters results in the station breaking the connection.

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What sequence of ARQ codes matches the following: shore station indicates it is awaiting instructions from the vessel, vessel requests a live connection to a land telex number, vessel indicates it is done with the coast station?

  • WRU-AAB, DIRTLX, NNNN
  • Correct Answer
    GA+?, DIRTLX, BRK+
  • GA+?, DIRTLX, KKKK
  • WRU-AAB, DIRTLX, .....
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All country codes which are transmitted by MF/HF SITOR (NBDP) are preceded by which character(s)?

  • 00
  • +
  • Correct Answer
    0
  • DIR
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