DL 240L Spring 2014
Name:_____________________________
VHF/ VHF DSC Lab Worksheet
You can use your notes, manuals, Pub. 117 and any other reference material
available to answer the following questions
1. List two U.S. government agencies that regulate/monitor marine VHF radios. (Lab Reference VHF)
The FCC regulates marine communications in cooperation with the U.S. Coast Guard, which
monitors marine distress frequencies continuously to protect life and property. All users of
marine radio, whether voluntary or compulsory, are responsible for observing both FCC and
Coast Guard requirements.
2. In a marine emergency, why should cell phones be used with caution? (Lab Reference - VHF)
Cellular phones generally cannot provide ship to ship safety communications or communications
with rescue vessels. If you make a distress call on a cellular phone, only the one party you call
will be able to hear you.
Most cellular phones are designed for a land-based service. Their coverage offshore is limited,
and may change without notice.
Locating a cellular caller is hard to do. If you don't know precisely where you are, the Coast
Guard will have difficulty finding your location on the water.
3. Describe Sea Area A1. (Pub.117 / Notes)
An area within the radiotelephone coverage of at least one VHF coast station in which
continuous digital selective calling (Ch.70/156.525 MHz) alerting and radiotelephony services
are available. Such an area could extend typically 30 nautical miles (56 km) to 40 nautical miles
(74 km) from the Coast Station.
4. What is the typical range of your marine VHF radio? (Notes)
Line of sight.
DL 240L Spring 2014
Name:_____________________________
5. With the advent of the GMDSS and DSC technology, is a listening watch on VHF Ch. 16 still
necessary?
Yes
6. What condition(s) can result in much greater ranges with your VHF radio?
Atmospheric ducting.
7. Explain the unwanted effect of turning a VHF radio’s squelch too high.
Limits effective receiving range.
8. What is the emissions class designation for VHF voice and DSC? What does the designation
indicate? (Pub.117 pg. IV)
Voice – F3E, DSC- G2B
9. What is the mandatory GMDSS VHF DSC watch channel/frequency? (Pub.117 / Notes)
Ch. 70, 156.525 MHz.
DL 240L Spring 2014
Name:_____________________________
10. List the minimum voice VHF channels required under the GMDSS:
16, 6, 13 and 70.
11. What does the term follow-on channel or frequency mean when referring to DSC calling?
The channel where the actual information is exchanged.
12. Briefly describe Rescue 21. (Lab Reference – VHF / Notes)
Rescue 21 is an advanced maritime computing, command, control, and communications (C4)
system designed to manage communications for the United States Coast Guard.
13. What types of radio communications are prohibited by the FCC? (Lab Reference – VHF)
False distress or emergency messages. Messages containing obscene, indecent, or
profane words or meaning. General calls, signals, or messages on channel 16, except in
an emergency or if you are testing your radio (these are messages not addressed to a
particular station), or When your ship is on land (for example, while the ship is on a
trailer).
DL 240L Spring 2014
Name:_____________________________
14. What may happen if you violate the United State’s Communications Act or FCC rules? (Lab
Reference – VHF)
If the FCC finds that you have willfully or repeatedly violated the Communications Act or
the rules, your authorization to use the radio may be revoked and you may be fined or
sent to prison.
15. Explain the difference between an Alpha VHF channel and an International VHF channel. Why is
it important to understand the difference? (Notes)
Note that the letter "A" indicates simplex use of the ship station transmit side of an
international duplex channel, and that operations are different than international operations on
that channel. Some VHF transceivers are equipped with an "International - U.S." switch for that
purpose. "A" channels are generally only used in the United States, and use is normally not
recognized or allowed outside the U.S. The letter "B" indicates simplex use of the coast station
transmit side of an international duplex channel. The U.S. does not currently use "B" channels
for simplex communications in this band.
16. What is an MMSI / MID? (Lab Reference – VHF)
A Maritime Mobile Service Identity (MMSI) is a series of nine digits which are sent in digital form
over a radio frequency channel in order to uniquely identify ship stations, ship earth stations,
coast stations, coast earth stations, and group calls. These identities are formed in such a way
that the identity or part thereof can be used by telephone and telex subscribers connected to
the general telecommunications network to call ships automatically.
There are now six kinds of maritime mobile service identities:






Ship station identities,
Group ship station identities,
Coast station identities,
Group coast station identities.
SAR aircraft
Navigational aids and craft associated with a parent ship
Maritime identification digits (MID)
DL 240L Spring 2014
Name:_____________________________
An MID consists of three digits, always starting with a number from 2 to 7 (assigned regionally).
A second MID can be assigned once the first or subsequently allocated MID is more than 80%
exhausted, and the rate of assignments is such that 90% exhaustion is foreseen. A listing of MIDs
assigned to each country is written in Table 1 of ITU Radio Regulations Appendix 43.
17.
What is the MF DSC MMSI for Kodiak AK? Explain why Pub. 117 does not list VHF DSC MMSI’s
for the U.S. (Pub.117)
003669899
At publication the U.S. did not have a designated Sea Area A1.
18. What is the format for a group MMSI? (Lab Reference – VHF)
Group ship station call identities for calling simultaneously more than one ship are formed as
follows:
0MIDxxxxx
19. What is the format for an AIS SART MMSI? (Lab Reference – VHF)
AIS Search and Rescue Transmitters (AIS-SART) have an identifier related to the
manufacturer, rather than a country's MID:[1]
970YYxxxx
DL 240L Spring 2014
Name:_____________________________
20. What are the priority of call types? Include the procedural words. (Lab Reference – VHF)
Distress – Mayday x 3
Urgency – Pan Pan x 3
Security – Sécurité x 3
21. What are the time limitations on making a voice call using your VHF radio on Ch. 16? (Lab
Reference – VHF)
Limits on calling. You must not call the same station for more than 30 seconds at a time.
If you do not get a reply, wait at least two minutes before calling again. After three
calling periods, wait at least 15 minutes before calling again.
22. Explain why your VHF radio has two power settings? Are the power settings mandated
internationally? (Lab Reference – VHF)
1W and 25 W max. Calls should be attempted on 1W unless there is no reply. Keep power as low
as possible to reduce channel crowding.
23. When is ok to only identify your station by ship name only? (Lab Reference – VHF)
Ch. 13
DL 240L Spring 2014
Name:_____________________________
24. When must you say your ship’s name and call sign when making a voice call on your VHF radio?
(Lab Reference – VHF)
Station identification. Identify, in English, your station by your FCC call sign, ship name,
the state registration number or official number at the beginning and end of each
message.
25. What is the designated VHF DSC watch channel and corresponding frequency?
Ch. 70 / Ch. 16
26. Can a distress DSC call be made as a test? (Lab Reference – VHF)
No
27. How is an inadvertent DSC Distress alert cancelled? (Pub.117)
28. Can DSC be used to relay a VHF DSC distress alert? (Pub.117)
Only to a single RCC or CRS.
29. How must a VHF DSC distress alert be acknowledged by a station other than a RCC? (Pub.117)
By voice or using DSC with the explicite permission from the RCC or CRS.
DL 240L Spring 2014
Name:_____________________________
30. When may a DSC Distress alert be acknowledged by a station other than a RCC (ship station)?
(Pub.117)
By voice or using DSC with the explicite permission from the RCC or CRS.
31. What are your obligations under the IMO flow chart (Actions by Ship’s Upon Reception of
VHF/MF DSC Distress Alert in Pub. 117) after receiving a VHF DSC Distress alert? (Pub.117)
32. Considering the IMO flow chart (Actions by Ship’s Upon Reception of VHF/MF DSC Distress Alert)
why are VHF and MF procedures located on the same chart separate from HF procedures?
(Pub.117)
Both are close range. If you receives someone’s MF DSC they are likely to be within a 100 nm or
so. You will most likely be the closest vessel if in open ocean.
33. Locate the bridge alarm panel and describe its function. (Simulator / Manual)