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Subel. J
6 questions
Subelement J

MF-HF Equip. and Comms:

Section 80

MF-HF Panel Controls

Which modes could be selected to receive vessel traffic lists from high seas coast radio stations:

  • AM and VHF-FM
  • Correct Answer
    SSB and FEC
  • ARQ and FEC
  • VHF-FM and SSB

Which modes could be selected to receive vessel traffic lists from high seas coast radio stations:

SSB and FEC

The SSB, single side band, radio waves focuses the effective radiation power on a part of the full wave (LSB and carrier frequencies are suppressed). Thus, the propagation can reach farther.

FEC, or the forward error correction, allows for a single transceiver to contact either one or many stations. When a message is sent, some additional data is sent that helps to catch some transmission errors. This helps with message accuracy.

Both A and D are not as effective in long-distance communication. Choice C has only two types of error detection and correction methods.

Please see Marine Insight web site, for the article What are SSB Radios?

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MF/HF Transceiver Power levels should be set:

  • To the highest possible level to ensure effective communications.
  • To the lowest possible level at all times regardless of whether communications are effective.
  • Correct Answer
    To the lowest level needed to achieve the necessary propagation radius and communications range.
  • To the highest level possible so as to ensure other stations cannot "break-in" on the channel during use.

FCC guides to use the minimum amount of effective radiating power to achieve successful communication. That is for all frequency range bands. It helps to avoid congestion of the airwaves.

As example, please view this:
FCC guidelines for reducing power of AM at night

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Which statement regarding GMDSS MF/HF Transceiver frequency set-up is true:

  • Manual keypad entries are quicker and more certain than using the database.
  • All consoles ensure that manual keypad entries are checked for legal outcomes.
  • All consoles ensure that ITU channel recall from a database produces accurate and legal outcomes.
  • Correct Answer
    Using the manufacturer’s database typically produces a more swift and certain result.

For set-ups, best to follow manufacturer's instructions and defined functions instead of manual entries to select channels.

Very useful manufacturer's operating manual

Example of manufacturer's info

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Which statement regarding GMDSS MF/HF Transceiver frequency set-up is true:

  • Correct Answer
    Some consoles allow both manual keypad entry and ITU channel recall from a database or memory.
  • Transmit and receive frequencies must always be manually entered from the keypad.
  • Transmit and receive frequencies must always be recalled from a database or memory.
  • Frequencies in the manufacturer’s databases are always accurate and legal for use.
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To set-up the MF/HF Transceiver for a TELEX call to a coast station, the operator must:

  • Select J3E mode for proper SITOR (NBDP) operations.
  • Select F1B/J2B modes or J3E mode, depending on whether ARQ or FEC is preferred.
  • Select J3E mode for ARQ and H3E mode for FEC.
  • Correct Answer
    Select F1B mode or J2B mode, depending on the equipment manufacturer.

From ITU-R M.493-01 Recommendation
DSC system for Maritime Mobile Service

"1.3 The classes of emission, frequency shifts and modulation rates are as follows:

1.3.1 F1B or J2B 170 Hz and 100 Bd for use on HF and MF channels. When frequency-shift keying is effected by applying audio signals to the input of single-sideband transmitters (J2B), the centre of the audio-frequency spectrum offered to the transmitter is 1 700 Hz."

For example of Radio Telex operating manual setup, see:

RadioTelex Operating Manual

For the table of classes of emissions § 80.207, see
Code of Federal Regulations Title 47 Telecommunications

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To set-up the MF/HF Transceiver for a voice call to a coast station, the operator must:

  • Correct Answer
    Select J3E mode for proper voice operations.
  • Select J3E mode for proper SITOR (NBDP) operations.
  • Select F1B mode or J2B mode, depending on the equipment manufacturer.
  • Select F1B/J2B modes or J3E mode, depending on whether FEC or ARQ is preferred.

The J3E mode facilitates transmission of information through the use of a single-side band in telephony or telegraphy.

For ITU use of J3E emissions for distress and safety purposes, see: ITU use of J3E

For the ITU's listing of modes of emissions for radio communication, see ITU Table of Emission Classes in pdf

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