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