| Autopilots The first self-steering gear was | | | | "birdcage" around the globe, they are |
| introduced in the 1920's to control model | | | | positioned in such a way that at any place on |
| yachts but it was not until 1948 that the | | | | the earth's surface a direct line of sight |
| principle was applied to full scale yachts. | | | | can be established to a minimum of 4 |
| Standing at the helm for lengthy periods, | | | | satellites. A fix is obtained by measuring |
| monitoring instruments and keeping a good | | | | accurately the distance between a satellite |
| look out can be very tiring. An autopilot | | | | and the GPS receiver at a precise time. |
| relieves the helmsman from steering the | | | | Because the exact position of the satellite |
| correct course leaving him free to maintain a | | | | is known, these distances provide position |
| proper watch. The autopilot can be set to | | | | lines which are converted by a microprocessor |
| either steer a compass course or a course | | | | within the GPS receiver to read outs of |
| relative to the wind. A fluxgate compass or | | | | latitude and longitude.The log is used to |
| electronic wind indicator feeds information | | | | measure the boats speed through the water. A |
| to a microprocessor which then makes the | | | | paddle wheel or impeller, mounted below the |
| necessary rudder movements to return the | | | | waterline is turned by the flow of water, |
| vessel to it's required course. The | | | | this generates electrical impulses that are |
| mechanical power is applied to the rudder by | | | | fed to a microprocessor that displays both |
| either electric linear activators, hydraulic | | | | speed and distance run.Inverters - On most |
| pumps or rotary drives. GPS/Chart plotters | | | | boats today you will find domestic equipment |
| can be used to input navigational | | | | of one sort or another. For on board |
| instructions to the autopilot.Battery | | | | entertainment there are televisions and |
| Chargers will keep batteries fully charged | | | | stereo systems. With the popularity of chart |
| thereby extending their working life.Chart | | | | plotters comes the PC or laptop. Maintenance |
| Plotters Typically a chart plotter consists | | | | often requires the use of power tools. |
| of an antenna, mounted high on the boat, to | | | | Liveaboards might have a washing machine, |
| track GPS signals and a display unit sited | | | | dishwasher or microwave. Can take 12v, 24v or |
| either at the at the navigation station or | | | | 48v supply and convert it to a stable 110 v |
| the helm of the vessel. The vessels position | | | | or 220v AC supply.Navtex can perhaps best be |
| is sent from the antenna to the display unit | | | | described as a continuously updated telex |
| which in turn shows it graphically on the | | | | service providing navigation and weather |
| chart. The Chart itself will look similar to | | | | information within specified areas. An on |
| it's paper equivalent and show depth, land | | | | board receiver, tuned to 518kHz, the |
| mass, navigational aids such as bouys and | | | | worldwide Navtex frequency, if left turned on |
| potential dangers in the form of wrecks and | | | | will either print out or display the latest |
| obstructions. The user can add way points to | | | | massages sent from a local station. The |
| the chart and zoom in and out of the display. | | | | service is available up to 400 miles from the |
| Chart plotters can be connected to drive an | | | | coast.Radar enables you to see what otherwise |
| autopilot and/or send GPS data to a fish | | | | would be invisible. They offer greatest |
| finder or radar. They can also interface with | | | | benefit at night and in fog or rain and are |
| a laptop enabling complex passage planning to | | | | of particular value when close to shore or in |
| be done away from the boat and then entered | | | | busy shipping lanes. They consist of an |
| into the chart plotter after arriving at the | | | | antenna and a display. The antenna sends out |
| boat.Magnetic Transmitting Compasses work | | | | a stream of RF energy which is reflected back |
| like traditional compasses using magnets to | | | | off hard objects. When this energy is bounced |
| determine the vessels orientation to the | | | | back it is converted to a signal which |
| earth's magnetic field they then transmit the | | | | displayed to the user. The antenna rotates |
| boats heading to an electronic display. They | | | | every few seconds, the display continuously |
| make steering easier than with conventional | | | | calculates the direction of the antenna and |
| compasses because they display steadier | | | | so a precise bearing to the target is |
| headings and do not suffer from the "lag" | | | | calculated. The time is measured for the |
| that occurs when making a turn. They can | | | | energy to be reflected and so the distance of |
| interface with chart plotters, autopilots and | | | | the target is also displayed.Satellite Phones |
| radar. Fluxgate Compasses consist of two | | | | consist of an antenna, a modem and a normal |
| pieces of readily saturated magnetic material | | | | handset. They are powered by an iridium |
| with coils wound round them in opposing | | | | battery. Their range is anywhere covered by |
| directions. AC current is passed through the | | | | in Inmarsat Mini-M satellite. Voice, fax, |
| coils and the material is saturated in one | | | | email and data can be transmitted.Satellite |
| direction and then the other. The earth's | | | | TV requires an antenna and of course a |
| magnetic field affects slightly the time at | | | | television. Reception is available within a |
| which saturation occurs, earlier in one coil | | | | "footprint" which is based on EIRP (Effective |
| and later in the other. The difference is | | | | Isotropic Radiated Power) of a transmitting |
| then calculated giving an output proportional | | | | satellite. The EUTELSAT together with the two |
| to the earth's magnetic field. They are | | | | ASTRA satellites cover Europe. NILESAT and |
| accurate to 0.1 of a degree. Their output can | | | | the two ARABSATs cover Africa and the Middle |
| be displayed digitally to the helmsman or | | | | East. Good coverage is also available in |
| they can interface with autopilots, chart | | | | North, Central and Southern America.SSB Radio |
| plotters and radar.Echo Sounders work on the | | | | has a range of several thousand miles. You |
| same principle as sonar. A transducer emits a | | | | will need an FFC license, or the equivalent |
| narrow beam of high frequency sound. This is | | | | in whichever country you plan to operate it. |
| reflected by any solid objects and the time | | | | Power consumption is a consideration. Up to |
| between transmission and receipt of the echo | | | | 100 Watts may be required for transmission. |
| is measured. The speed of sound through water | | | | SSB radio requires several items of |
| is know and so the range or distance to the | | | | equipment. A transceiver capable of SSB |
| sea bed can be calculated. That is then | | | | operation, An antenna, this must be 8 metres |
| displayed in metres. Forward Looking Sonar | | | | long and in practice most boats use a |
| (FLS) enables you to see the underwater | | | | backstay or shroud for the purpose having |
| hazards before you're actually on top of | | | | fitted the necessary insulators. An antenna |
| them. A typical range for a FLS is 150 | | | | tuner matched to the transceiver model. If |
| metres.An Emergency Position Indicating Radio | | | | you want to send email you will also need and |
| Beacon (EPIRB) is a piece of equipment | | | | radio modem and computer.VHF Radio The power |
| designed to float free of a vessel in | | | | required to transmit is minimal, all sets |
| distress. It then sends a radio signal that | | | | have the option of transmitting on either 1 |
| can be detected by Search and Rescue | | | | Watt or 25 Watts and the lower power should |
| Satellite Aided Tracking (SARSAT) satellites. | | | | be used whenever possible. Unlike telephones |
| They relay a message to a ground station that | | | | that allow you to both talk and hear at the |
| in turn can instigate a search and rescue | | | | same time most VHF sets require you to press |
| operation.Fish Finders use the same | | | | a transmit button prior to talking. This is |
| technology as sonar. A narrow beam of high | | | | known as simplex. Duplex sets are available |
| frequency sound is transmitted by a | | | | but are much more expensive. VHF radio waves |
| transducer, this is reflected by solid | | | | travel in straight lines so the aerial should |
| objects such as the sea bed. By developing | | | | be mounted as high as possible, preferably at |
| this technology fishfinders provide displays | | | | the masthead.Ken Jones runs a Sailing Site. |
| that show where the fish are and they can | | | | |
| differentiate between bait fish and larger | | | | More information about marine electronics |
| speciesGlobal Positioning System (GPS | | | | can be found here |
| Receivers) - This system was originally | | | | |
| designed for military purposes and is owned | | | | To find manufacturers or suppliers of marine |
| and operated by the United States Department | | | | electronics in your area visit the Marine |
| of Defence. 24 satellites are arranged in a | | | | Directory. |