Chapter 11 Marine

Communication

PART 2 Communication of Distress Signals

REVISION OF PART ONE

What does GMDSS stand for? What’s Function of GMDSS? What does EPIRB stand for? What’ function of EPIRB?

Global Maritime Distress Safety System (GMDSS)

GMDSS consists of several systems, some of which are new, but many of which have been in operation for many years. The system is intended to perform the following functions: alerting (including position determination of the unit in distress), search and rescue coordination, locating (homing), maritime safety information broadcasts, general communications, and bridge-to-bridge communications.

EPIRB (Emergency Position Indicating Radio Beacon)

An EPIRB (Emergency Position Indicating

Radio Beacon) is a device which, in the event of an emergency, transmits a signal that alerts search and rescue (SAR) authorities and enables rescue units to home in on the scene of the accident.

SART&DSC Search and Rescue Transponder The GMDSS installation on ships include one or more

Search and Rescue Transponder (SART) devices which are used to locate survival craft or distressed vessels by creating a series of dots on a rescuing ship's 3 cm radar display. The detection range between these devices and ships, dependent upon the height of the ship's radar mast and the height of the SART, is normally about 15 km (8 nautical miles).

Digital Selective Calling The IMO also introduced Digital Selective Calling (DSC) on MF,

HF and VHF maritime radios as part of the GMDSS system. DSC is primarily intended to initiate ship-to-ship, ship-to-shore and shore-to-ship radiotelephone and MF/HF radio telex calls.

Translation

Ask students to translate some sentences of part one:

A small, low-cost and self-contained "smart" printing rareceiver is installed on the bridge, or the place from where the ship is navigated, and checks each incoming message to see if it has been received during an earlier transmission,

or if it is of a category of no interest to the ship's master… 一部小型的 , 廉价的并且自带智能无线打印接收机被安装在

驾驶台上或操纵船舶的地方 , 检查每条刚接收的信息判断该信息是否是在前期发射期间收到的 , 或该信息是否对船长毫无利益。

TRANSLATION

The types of INMARSAT ship earth station terminals recognized by the GMDSS are: INMARSAT B, C and F77.

被全球海上遇险与安全系统认可的国际海事卫星船舶地面终端类型是 :国际海事卫星的 B 站 ,C 站和 F77 站。 (77 代表天线是 77 厘米 )

The detection range between these devices and ships, dependent upon the height of the ship's radar mast and the height of the SART, is normally about 15 km (8 nautical miles). Note that a marine radar may

not detect a SART even within this distance, if the radar settings are not optimized for SART detection.

这些装置 (SART) 与船舶之间的探测距离通常有 15 千米 (8 海里 ), 并且探测距离取决于船舶雷达的天线高度以及搜救雷达应答器 (SART) 放置的高度。 值得注意的是 : 如果一台雷达没有调节到探测搜救雷达应答器的最佳状态 , 即使在雷达探测范围内 , 也有可能探测不到它。

VHF—Very High Frequency

A marine VHF set is a combined transmitter and receiver and only operates on standard, international frequencies known as channels. Channel 16 (156.8 MHz) is the international calling and distress channel. Channel 9 can also be used in some places as a secondary call and distress channel.

Chapter 11 Part 2 VHF.doc

NAVAREA Warnings, Coastal Warnings and Local Warnings

Many navigational warnings are of a temporary nature, but others remain in force for several months or may be succeeded by Notices to Mariners.

Details of All Radio Navigational Warnings system are given in Admiralty List of Radio Signals Vol.5. See also Annual Summary of Admiralty Notices to Mariners.

NAVAREA Warnings are promulgated by the World-wide Navigational Warning Service (WWNWS), established jointly by IHO and IMO. The service divides the world into 16 NAVAREA, identified by Roman numerals.

A marine VHF set is a combined transmitter and receiver and only operates on standard, international frequencies known as channels. Channel 16 (156.8 MHz) is the international calling and distress channel. Channel 9 can also be used in some places as a secondary call and distress channel. Transmission power ranges between 1 and 25 watts, giving a maximum range of up to about 60 nautical miles (111 km) between aerials mounted on tall ships and hills, and 5 nautical miles (9 km) between aerials mounted on small boats at sea-level. Frequency modulation is used, with vertical polarization, meaning that antennas have to be vertical in order to have good reception.

VHF & VHFDSC

甚高频只能直线传播，受视距限制，理论上约 100 海里，实际正常范围 30~50海里左右。为避免相互干扰， 一般限制发射功率： 船台： 25W/1W

Marine VHF mostly uses "simplex" transmission, where communication can only take place in one direction at a time. A transmit button on the set or microphone determines whether it is operating as a transmitter or a receiver. The majority of channels, however, are set aside for "duplex" transmissions channels where communication can take place in both directions simultaneously. Each duplex channel has two frequency assignments.

单工（ SIMP）： 单工方式：通信双方交替进行发射

同频单工：收发频率相同 异频单工：收发频率不同

船舶间通信只能工作在同频单工方式。单工方式工作时，同一方的收发机是交替工作的。

船用 VHF 设备的单工操作是由送受话器上的按压开关 PTT（ PUSH TO TALK ）控制的，按下时天线与发射机相接，并开始工作；接收机与天线断开；对着话筒讲话，即可把信息发出。松开 PTT 开关，发射机关闭不工作，天线接入接收机，接收机工作，收听对方讲话。

Notes 1. If the installation is a “simplex” radio, speaking and li

stening cannot be done simultaneously. 如果甚高频是单工模式的无线电，则说和听不能同时

进行。 2. This is mainly because, in the days before mobile

phones became widespread, the duplex channels could be used to place calls on the public telephone system for a fee via a marine operator.

这主要是因为在移动电话普及之前，双工模式可通过付费经海上话务员呼叫公共电话系统。

Vocabulary simplex ['] adj. 单一的 simultaneously [] adv. 同时地 consequence [] n. 后果 , 结果 marina [] n. 小游艇船坞 contentious [] adj. 有争议的 , 好争吵的 , 引起争论的， modulation [] n. 调整，调节； ( 声调的 ) 抑扬，变化； frequency modulation 频率调制，调频 vertical [] adj. 垂直的 polarization [] n. 两极分化 , 【物、天】极化；极化强度 antennas [] n. 【无线电】天线〔英国常用 aerial 〕 hailer [] n. ( 海军船舰等上的 ) 手提扩音器 scrambler [] n. 【无线电】扰频器；倒频器；保密器 (scrambler phone 防窃听电话 )

duplex [] adj. 双向 ( 通讯 ) 的 Bluetooth [] n. 蓝牙