Login or Register for FREE!
Subelement C
Equipment Operations
Section 13
VHF Equipment Controls
What is the purpose of the INT-USA control settings on a VHF?
  • To change all VTS frequencies to Duplex so all vessels can receive maneuvering orders.
  • To change all VHF channels from Duplex to Simplex while in U.S. waters.
  • Correct Answer
    To change certain International Duplex channel assignments to simplex in the U.S. for VTS and other purposes.
  • To change to NOAA weather channels and receive weather broadcasts while in the U.S.

What is the purpose of the INT-USA control settings on a VHF?

(C). To change certain International Duplex channel assignments to simplex in the U.S. for VTS and other purposes.

For detailed info, please see The Coastal Passage site for the article on What every VHF user should already know

The goal is to inform all vessels to be able to receive maneuvering orders.

In US waters, change all VHF channels from Duplex to Simplex while in U.S. waters.

In International waters, reverse. Change all VTS frequencies to Duplex so all vessels can hear the orders.

See Wikipedia's article on Marine VHF radio

For comprehensive regulations, see Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 80 Subpart H - Frequencies

Last edited by markadlerdallas. Register to edit

Tags: none

VHF ship station transmitters must have the capability of reducing carrier power to:
  • Correct Answer
    1 watt.
  • 10 watts.
  • 25 watts.
  • 50 watts.

VHF ship station transmitters must have the capability of reducing carrier power to:

(A). 1 watt.

Code of Federal Regulations, Title 47 Chapter I Subchapter D Part 80 Subpart
E - General Technical Standards

§ 80.215 Transmitter power.

47 CFR 80.215(e) Ship stations frequencies above 27500 kHz. The maximum power must not exceed the values listed below.

  • 47 CFR 80.215(e)(1) Ship stations 156-162 MHz - 25W *

  • *Reducible to 1 watt or less, except for transmitters limited to public correspondence channels and used in an automated system.

Last edited by markadlerdallas. Register to edit

Tags: none

The Dual Watch (DW) function is used to:
  • Listen to Ch-70 at the same time while monitoring Ch-16.
  • Sequentially monitor 4 different channels.
  • Sequentially monitoring all VHF channels.
  • Correct Answer
    Listen on any selected channel while periodically monitoring Ch-16.

The Dual Watch (DW) function is used to:

(D). Listen on any selected channel while periodically monitoring Ch-16.

Dual watch is a setting which allows listening on multiple frequencies at once. Most units will require that one of the dual watch channels is 16.

For practical info, please see egmdss site for article on Dual Watch (D/W)

Last edited by markadlerdallas. Register to edit

Tags: none

Which of the following statements best describes the correct setting for manual adjustment of the squelch control?
  • Correct Answer
    Adjust squelch control to the minimum level necessary to barely suppress any background noise.
  • Always adjust squelch control to its maximum level.
  • Always adjust squelch control to its minimum level.
  • Adjust squelch control to approximately twice the minimum level necessary to barely suppress any background noise.

Which of the following statements best describes the correct setting for manual adjustment of the squelch control?

(A). Adjust squelch control to the minimum level necessary to barely suppress any background noise.

Squelch is a setting which filters out background noise being received.

Squelch is turned down such that the background noise is just audible, and then down one additional level.

But you can have too much of a good thing, and if you increase squelch, you will blank out receiving some transmission. Same works for hand-helds and CB radios.

For more info, please see Casualnavigation site, for article on How To Properly Adjust The Squelch On A VHF Radio


YouTube Video: The Emily & Clark's Adventure channel has a good overall video worth watching called How to use a Marine VHF RADIO

Last edited by markadlerdallas. Register to edit

Tags: none

The “Scan” function is used to:
  • Monitor Ch-16 continuously and switching to either Ch-70 or Ch-13 every 5 seconds.
  • Scan Ch-16 for Distress calls.
  • Scan Ch-70 for Distress alerts.
  • Correct Answer
    Sequentially scan all or selected channels.

The “Scan” function is used to:

(D). Sequentially scan all or selected channels.

Scan is a function which searches through multiple frequencies listening for transmissions.

It is a marine radio function which you must select. Also, must set frequencies (channels) to scan.

For basic info, see HowStuffWorks site for article on How Radio Scanners Work

For detailed info, see Radio-ScannerGuide article on Part 3B: Marine and Part 5: Radio Scanner Features

Last edited by markadlerdallas. Register to edit

Tags: none

Why must all VHF Distress, Urgency and Safety communications (as well as VTS traffic calls) be performed in Simplex operating mode?
  • To minimize interference from vessels engaged in routine communications.
  • Correct Answer
    To ensure that vessels not directly participating in the communications can hear both sides of the radio exchange.
  • To enable an RCC or Coast station to only hear communications from the vessel actually in distress.
  • To allow an RCC or Coast station to determine which transmissions are from other vessels and which transmissions are from the vessel actually in distress.

Why must all VHF Distress, Urgency and Safety communications (as well as VTS traffic calls) be performed in Simplex operating mode?

(B). To ensure that vessels not directly participating in the communications can hear both sides of the radio exchange.

Two objectives:

  1. To reduce signals from vessels in the range talking to each other.

  2. In Simplex, other ships can hear both sides of communications.

When operating in Simplex, the transmitting and received signals are sent on the same frequency. Therefore, only one side of the conversation can occur at a time.

Any 3rd party people tuned into the channel will be able to hear the entire conversation, as opposed to in Duplex. In Duplex, Transmit and Received signals occur on two separate frequencies, and a 3rd party may only be tuned into one of them. This will only allow them to hear half of the conversation.

For a great overall info on communications in pdf format, this will be a great reference document to download:

Principles of Maritime Mobile Service

Last edited by markadlerdallas. Register to edit

Tags: none

Go to 12 Go to 19