Global Positioning System (GPS Receivers) - This system was originally designed for military purposes and is owned and operated by the United States Department of Defence. 24 satellites are arranged in a "birdcage" around the globe, they are positioned in such a way that at any place on the earth's surface a direct line of sight can be established to a minimum of 4 satellites. A fix is obtained by measuring accurately the distance between a satellite and the GPS receiver at a precise time. Because the exact position of the satellite is known, these distances provide position lines which are converted by a microprocessor within the GPS receiver to read outs of latitude and longitude.
The log is used to measure the boats speed through the water. A paddle wheel or impeller, mounted below the waterline is turned by the flow of water, this generates electrical impulses that are fed to a microprocessor that displays both speed and distance run.
Inverters - On most boats today you will find domestic equipment of one sort or another. For on board entertainment there are televisions and stereo systems. With the popularity of chart plotters comes the PC or laptop. Maintenance often requires the use of power tools. Liveaboards might have a washing machine, dishwasher or microwave. Can take 12v, 24v or 48v supply and convert it to a stable 110 v or 220v AC supply.
Navtex can perhaps best be described as a continuously updated telex service providing navigation and weather information within specified areas. An on board receiver, tuned to 518kHz, the worldwide Navtex frequency, if left turned on will either print out or display the latest massages sent from a local station. The service is available up to 400 miles from the coast.
Radar enables you to see what otherwise would be invisible. They offer greatest benefit at night and in fog or rain and are of particular value when close to shore or in busy shipping lanes. They consist of an antenna and a display. The antenna sends out a stream of RF energy which is reflected back off hard objects. When this energy is bounced back it is converted to a signal which displayed to the user. The antenna rotates every few seconds, the display continuously calculates the direction of the antenna and so a precise bearing to the target is calculated. The time is measured for the energy to be reflected and so the distance of the target is also displayed.
Satellite Phones consist of an antenna, a modem and a normal handset. They are powered by an iridium battery. Their range is anywhere covered by in Inmarsat Mini-M satellite. Voice, fax, email and data can be transmitted. A satellite cell phone can also be a cost-effective option if you only need voice capabilities.
Satellite TV requires an antenna and of course a television. Reception is available within a "footprint" which is based on EIRP (Effective Isotropic Radiated Power) of a transmitting satellite. The EUTELSAT together with the two ASTRA satellites cover Europe. NILESAT and the two ARABSATs cover Africa and the Middle East. Good coverage is also available in North, Central and Southern America.
SSB Radio has a range of several thousand miles. You will need an FFC license, or the equivalent in whichever country you plan to operate it. Power consumption is a consideration. Up to 100 Watts may be required for transmission. SSB radio requires several items of equipment. A transceiver capable of SSB operation, An antenna, this must be 8 metres long and in practice most boats use a backstay or shroud for the purpose having fitted the necessary insulators. An antenna tuner matched to the transceiver model. If you want to send email you will also need and radio modem and computer.
VHF Radio The power required to transmit is minimal, all sets have the option of transmitting on either 1 Watt or 25 Watts and the lower power should be used whenever possible. Unlike telephones that allow you to both talk and hear at the same time most VHF sets require you to press a transmit button prior to talking. This is known as simplex. Duplex sets are available but are much more expensive. VHF radio waves travel in straight lines so the aerial should be mounted as high as possible, preferably at the masthead.