Monday, November 3, 2008

Lesson 46: Radiotelephone


VHF and SSB Radiotelephone

The VHF (Very High Frequency) marine radio uses a FM (Frequency Modulated) signal band of 152 – 156 mHz (mega-Hertz) with switched or set frequencies (channels). All VHF radios used aboard boats are limited to a maximum of 25 watts of transmitting power. VHF radiotelephone distances are usually 10 -15 miles for ship-to-ship communications while ship-to-coast station is generally about 20 – 30 miles. When operating on VHF channel 13 (Bridge-to-Bridge Radiotelephone) wattage is limited to 1 watt.

When operating at greater distances, SSB radiotelephone equipment is used. This type of equipment uses AM (Amplitude Modulated) with a maximum of 150 watts of transmitting power on the 2 to 4 kHz (kilo-Hertz) band. Typical daytime transmitting range is about: 100 miles, at dusk expect about 300 miles and over 600 miles at night.

Radio Licenses

The regulations requires most operators of commercial vessels to carry a radio or to have an individual license to operate VHF marine radios (with or without digital selective calling capability), or any type of radar.

Users of VHF marine radio equipped with digital selective calling will need to obtain a maritime mobile service identity (MMSI) number from the FCC. It is unlawful to use digital selective calling (VHF channel 70) without obtaining this identity.

Vessels required to be licensed:

Vessels that use MF/HF single side-band radio, satellite communications, or telegraphy,
Power Driven vessels over 65.6 feet/20 meters in length.
Vessels used for commercial purposes including:
Vessels documented for commercial use, including commercial fishing vessels.
CG inspected vessels carrying more than 6 passengers.
Towboats more than 25.7 feet/7.8 meters in length.
Vessels of more than 100 tons certified to carry at least 1 passenger.
Cargo ships over 300 tons.
Dredges –floating plants engaged in or near a channel or fairway.
Any vessel, including a recreational vessel, on an international voyage.

Radio Listening Watch

In general, any vessel equipped with a VHF marine radiotelephone (whether voluntarily or required to) must maintain a watch on channel 16 (156.800 MHz) whenever the radiotelephone is not being used to communicate.
In addition, every power-driven vessel of 20 meters or over in length or of 100 tons and upwards carrying one or more passengers for hire, or a towing vessel of 26 feet or over in length, as well, as every dredge and floating plant operating near a channel or fairway, must also maintain a watch on channel 13 (156.650 MHz) -- channel 67 (156.375 MHz) if operating on the lower Mississippi River-- ; while navigating on U.S. waters (which include the territorial sea, internal waters that are subject to tidal influence, and, those not subject to tidal influence but that are used or are determined to be capable of being used for substantial interstate or foreign commerce). Sequential monitoring techniques (scanners) alone cannot be used to meet this requirement; two radios (including portable radios, i.e. handhelds) or one radio with two receivers, are required. These vessels must also maintain a watch on the designated Vessel Traffic Service (VTS) frequency, in lieu of maintaining watch on channel 16, while transiting within a VTS area.

Radiotelephone operators must be able to understand and speak English. Radio logs are kept for one (1) year with the day starting and ending at 0000 (mid-night). Logs containing Distress entries must be kept for three (3) years. All entries must be corrected by the individual who made the original entry by striking out the incorrect entry, dating, and initialing.

Distress Call Procedures

Make sure radio is on
Select VHF Channel 16, SSB 2182 kHz
Press/Hold the transmit button
Also give:

Vessel Name and/or Description
Position and/or Location
Nature of Emergency
Number of People on Board

Release transmit button
Wait for 10 seconds – If no response Repeat "MAYDAY" Call.
Try other channels – frequencies if no response

False Distress Alerts

It is unlawful to intentionally transmit a false distress alert, or to unintentionally transmit a false distress alert without taking steps to cancel that alert.

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