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Subelement J
MF-HF Equip. and Comms:
Section 83
MF-HF Voice and Telex Channel Separation
Which statement regarding bandwidth and channel spacing is correct:
  • Bandwidth values are a function of channel spacing values.
  • Channel spacing values are not a function of bandwidth values.
  • Correct Answer
    Channel spacing values are a function of bandwidth values.
  • Bandwidth & channel values do not vary with emission mode.

(C). Channel spacing values are a function of bandwidth values.

Channel width, or band width is the range of frequencies assigned for a specific purpose. Then, channel spacing is the allocation of channel widths for specific purposes.

In US, FCC created a "road map" of channels (channel widths) and where on the overall all radio spectrum the channels are located. See FCC Frequency and Channel Maps

Wide channels of large number of assigned frequencies produces better sound quality, but you end up with fewer channels. Narrow band width channels allow a lot more channels (and types of user) but the sound quality is not as good.

For more details, well explained, please see
Radio Academy: Introduction to Channel Spacing

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The purpose of ITU channel spacing is:
  • To minimize the number of voice & TELEX channels available.
  • To make most efficient use of the radio spectrum, by using voice channels rather than TELEX channels.
  • To make most efficient use of the radio spectrum, by using TELEX channels rather than voice channels.
  • Correct Answer
    To minimize the possibility of interference from adjacent channels.

(D). To minimize the possibility of interference from adjacent channels.

Any arrangement of channel spacing for dedicated use will assist in preventing unintended use, reducing interference by the user who should be on other channels.

Channel width, or band width is the range of frequencies assigned for a specific purpose. Then, channel spacing is the allocation of channel widths for specific purposes.

In US, FCC created a "road map" of channels (channel widths) and where on the overall all radio spectrum the channels are located. See FCC Frequency and Channel Maps

Wide channels of large number of assigned frequencies produces better sound quality, but you end up with fewer channels. Narrow band width channels allow a lot more channels (and types of user) but the sound quality is not as good.

For more details, well explained, please see
Radio Academy: Introduction to Channel Spacing

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Which statement regarding channel spacing and bandwidth is true?
  • Correct Answer
    Both TELEX bandwidth and channel spacing values are less than voice bandwidth and channel spacing values.
  • Voice bandwidth is greater than TELEX bandwidth and therefore voice channel spacing values are less than TELEX channel spacing values.
  • TELEX bandwidth is greater than voice bandwidth and therefore TELEX channel spacing values are less than voice channel spacing values.
  • Both TELEX bandwidth and channel spacing values are greater than voice bandwidth and channel spacing values.

(A). Both TELEX bandwidth and channel spacing values are less than voice bandwidth and channel spacing values.

For TELEX bandwidth map in pdf please see
World Wide Telex Band Chart

You can have narrower channels for texting of lower sound quality, but you need greater width channels for better voice sound quality.

Wide channels of large number of assigned frequencies produces better sound quality, but you end up with fewer channels. Narrow band width channels allow a lot more channels (and types of user) but the sound quality is not as good.

For more details, well explained, please see
Radio Academy: Introduction to Channel Spacing

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The proper sequence of channel spacing from narrow to widest is:
  • SSB voice, SITOR (NBDP), VHF-FM voice.
  • Correct Answer
    SITOR (NBDP), SSB-voice, VHF-FM voice.
  • VHF-FM voice, SITOR (NBDP), SSB-voice.
  • SITOR (NBDP), VHF-FM voice, SSB-voice.

(B). SITOR (NBDP), SSB-voice, VHF-FM voice.

SITOR, or sImplex teletype over radio was designed to send text messages, like SMS texting. To modulate radio waves, it uses FSK, or frequency-shift keying, and it contains functions for error detection, and retransmission, so it is more reliable than the RTTY system it improved on. Because it is texting use, it needs only a narrow band, as voice quality is not as big issue as in SSB-voice, or VHF-FM voice.

Wide channels of large number of assigned frequencies produces better sound quality, but you end up with fewer channels. Narrow band width channels allow a lot more channels (and types of user) but the sound quality is not as good.

In US, FCC created a "road map" of channels (channel widths) and where on the overall all radio spectrum the channels are located. See FCC Frequency and Channel Maps

For more details, well explained, please see
Radio Academy: Introduction to Channel Spacing

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Communications with an emission of F1B/J2B would typically have a channel spacing of:
  • 0.3 kHz
  • Correct Answer
    0.5 kHz
  • 2.8 kHz
  • 3.0 kHz

Communications with an emission of F1B/J2B would typically have a channel spacing of 0.5 kHz

Class of EmissionAuthorized bandwidth (kHz)
  F1B         0.5
  J2B        0.5

Radiotelegraphy (4000-27500 kHz) bandwidth is for: Manual A1A, J2A, J2B, J2D
DSC F1B, J2B
Facsimile F1C, F3C, J2C, J3C

For an excellent document of channel frequency assignments, please see:

Coast and Ship Station Equipment Operating in the Maritime Service in the Frequency Range

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Communications with an emission of J3E would typically have a channel spacing of:
  • 0.5 kHz
  • 0.3 kHz
  • Correct Answer
    3.0 kHz
  • 2.8 kHz

Communications with an emission of J3E would typically have a channel spacing of 3.0 kHz

Although not specified by name in the table in the document listed below, the table states that "For all other emission types" the range is 3.0 kHz.

Radiotelegraphy (4000-27500 kHz) bandwidth is for: Manual A1A, J2A, J2B, J2D
DSC F1B, J2B
Facsimile F1C, F3C, J2C, J3C

For an excellent document of channel frequency assignments, please see:

Coast and Ship Station Equipment Operating in the Maritime Service in the Frequency Range

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