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