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