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Marine Electronic Equipment
by Captain Tom Martin
Navigators currently have a host of dependable instruments to assist them in finding their way on rivers, lakes and around the globe. Technological advances in electroics and other areas have made these devices available and relatively inexpensive. There are user friendly GPS, Radar, Plotters, Depth Sounders, Knot meters and Logs, Wind speed and direction, VHF radios, SSB & Ham Radios, Weather Fax, Satellite Telephones, LSAT, Fluxgate compasses, Auto Pilots, EPRIB, forward scanning sonar devices and much more.
Before we review the functions and uses of the following devices a word of caution...
Manmade device may fail at any given time.
Most long distance marine navigators have years of experience and a cultivated "sea sense" that comes with time on the water in many different situations. As dependable and well made as most electronic devices are they may cease to function, so many of these individuals have "get home gear," a duplicate set of crucial instruments that will work in an emergency.
GPS Global Positioning System
Satellites supply multiple signals that are used to the track location and show the speed of a moving boat to the observer. Latitude and Longitude are displayed numerically which can be directly plotted on to nautical charts.
Specific positions or waypoints can be imputed manually and by the "mark" or "MOB" button and used as targets for course settings.
SOG (Speed Over the Ground) and average speed are available. COG (Course Over the Ground) is also available. Bearing to waypoint is displayed and can be compared to COG for corrections to steering for drift and leeway.
Alarms can be set for course and proximity to waypoint upon approach.
GPS can be connected to plotters, computers, EPIRB and VHF radio in many cases. Units are both fixed, with remote heads and handheld. Twelve satellite fixes are standard and reliability is excellent.
Radar
Radar is for or collision avoidance and poor visibility. Night time, fog and beyond the horizon for both weather, other vessels, markers and landmass location; radar is a dependable tool. Displays are both monochrome and color plus day light viewable screens are available. Automatic range and bearing lines allow onscreen distance and course monitoring of other vessels. Controls for sea and rain clutter plus gain (sensitivity) can be set to manual or automatic. Collision avoidance zones are available with audible alarms on many units. Some radars will show bearing lines to waypoints. Some radars offer main ship channel marker identification.
Watch the "Radar Plotter" video
Plotter
Plotters incorporate GPS location, speed and course on an electronic chart. Screens can be monochrome, color and daylight viewing, plus weather resistant. Fixed installations and handheld units are available. Display quality varies with brand and whether it is a CRT, TFT or LCD.
Chart details are the operator choice usually e.g. depth, lines of equal depth, latitude and longitude lines, surface features, navigational aides and more. Most plotters will hold waypoints separate from the GPS unit feeding it, while others have integral GPS. Many units offer interconnection between GPS, Radar and Plotter usually the same brand, (networking).
Depth Sounders / Fishfinders
Digital display of water depth is standard. Fishfinders display in color or monochrome depth and bottom plus in-between. All charts have depth measurements on them so navigation using a depth sounder is possible even in reduced visibility. If you have limited space or see no need for both sounder and fish finder the fish finder does offer all the information you need. Both have optional shallow or deep water alarms as well as color or monochrome displays.
Knotmeters and Logs
Both digital and analog displays are available. Speed is from a paddle wheel through hull installation generally, with some more exotic methods of reading of boat speed through the water. A note of caution, boat speed through the water is affected by currents and leeway and must be factored in when dead reckoning. Paddle wheels must be kept clean of marine growth to function properly. There are two distance logs, a trip log which is reset-able and a log for permanent record. Many network with GPS and allow comparison with SOG.
Wind speed
Anemometer measures wind speed and direction. Wind direction is available in both true and apparent wind. Apparent wind is true with the movement of the vessel through the wind factored in. Many network with auto-pilot and allow a sailboat to stay on a tack relative to the wind. Displays are digital and analog.
VHF radios
A required safety item!! VHF radio telephone is for all critical marine communications. Designated channels for distress calls, ship to ship, ship to shore, ship to bridge allow direct communications in all circumstances. Fixed installations have higher power while handheld have less, 25 watt vs. 5 watts. This is FM and line of sight. So a sailboat with an antenna atop it's mast at 65 feet will have a greater range than a power boat with an antenna some 15 feet above sea level. A handheld radio at sea level has minimal range base on the height of the person holding it. For example a sailboat with a 36 foot mast mounted antenna reached a Coast Guard antenna some 65 miles away.
SSB & HAM Radios
Single Side Band and Ham Radio are similar in use but you must be licensed to use Ham radio. Operator skill is essential for both. SSB is the standard long range communications for marine use. Signals are bounced off the ionosphere to beyond the horizon. SSB are reliable for ship to ship or ship to shore. Private patches, usually local and marine operators can hook you into a land line for a price. SSB requires a ground field and an antenna plus an antenna tuner with installation could cost as much or more than the unit. Sailboats often use a backstay for an antenna by isolating a section of the stay.
SSB and Ham Radio are both radio broadcast thus everyone can listen in. Often used for "nets" where many cruising boats can discuss things from where to get an engine part or weather. A computer can be hooked up to a SSB and with the some extra hardware and software receive weather maps and weather alert info. Limited e-mail and internet access is also available.
Weather FAX
Weather facsimile are dedicated units with separate antennas that receive both data and maps of weather. Schedules for transmissions are periodically transmitted for receiving the weather charts allowing owners to set a time table for the unit to be on. Most units are basically a dedicated SSB receiver and printer. Newer units have USB ports to download to a computer. Optional NAVTEX external receivers can also be attached, (NAVTEX are text messages of the weather on a LCD screen).
INMARSAT
Inmarsat C and Mini-M satellite systems provides text, fax, data and voice communications on a world wide basis. Geostationary satellites offer a reliable communications system. Cost is high while equipment can be expensive and require higher power and more space demands. Inmarsat C is text messaging for sending and receiving email type correspondence. You pay per character and for spaces which can add up fast. Messages are sent and received when satellite is overhead which is not always the case with only four Satellite for the entire planet. Inmarsat Mini-M offers voice, 2400bps G-III fax and data service. Rates are by the minute and the antenna is smaller.
Satellite Telephones
Two systems are available world wide for both land and sea. Iridium and Globalstar both are reliable and offer lots of extras. Bigger then a cell phone, which some can do both, they are simple to use and require no external antennas. Units are expensive and service is also costly. Often they can be interconnected with the ships phone system for ease of use.
Cellular Phones
("Users Advisory - Cellular Phone" courtesy Marine Electronics Technical Articles)
With the popularity of the cellular telephones more and more people are using them on board their boats. However, since most cellular phones are designed for land based service, the coverage offshore is limited and may change without notice. Most everyone has experienced communications out to about 25 miles at times. Yet at other times could not get through to a land based phone inside of 10 miles from shore. This might well create a communications problem in the event of an emergency at sea.
In general, cellular phones cannot provide proper communications with rescue vessels. A distress call can only be heard by the one party you call. To help remedy this problem some providers have established a code ( *CG ), which if you are in range, will connect you directly to the Coast Guard Operations Center. Keep in mind, however, that this service may only work with certain subscribed carriers.
Thus, the Coast Guard does not advocate cellular phones as a substitute for the regular maritime radio distress and safety systems recognized by the Federal Communications Commission and the International Radio Regulations, namely the VHF radio. There is very little comparison between the two as they are designed for very different services.
Cellular phones can have a place aboard as an added measure of safety. They also provide a convenient and private way to make personal calls to home, office, another boat, etc. It is a personal link with shore based phones and other cellular phones. By adding an external antenna on board for your cellular phone you can increase its performance to better suit your needs. Antennas are available in three (3'-0") foot and eight (8'-0") foot sizes.
A VHF radio is an important piece of equipment that every boat should have on board. The VHF is intended to be used on boats, ships, and other marine related installations. The VHF radios were made with safety in mind. If you are in distress, calls can be received by the Coast Guard and all other ships which may be in position to provide immediate assistance. The VHF radio will also provide up to date weather broadcasts that feature storm warnings and other important marine information broadcast. These broadcasts are announced on channel 16 and the timely receipt of these broadcasts might well be the difference that may save lives.
Cellular phone conversations are private and one to one. The VHF radio conversations are not and they are intended for everyone within range to hear your broadcast and this is a very important difference.
Telephone communications are possible with the VHF radio through the Marine Operator. These calls are not private and if one is expecting a phone call through the Marine Operator a continual monitoring of Channel 16 is required or the call will be missed.
Remember a cell phone should never be used in place of a VHF radio, but as an additional means of communication while on the water.
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VHF Marine Radio Channels and Frequencies
Channel Number
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Ship Transmit
MHz
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Ship Receive
MHz
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Use
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01A
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156.050
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156.050
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Port Operations and Commercial, VTS. Available only in New Orleans / Lower Mississippi area.
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05A
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156.250
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156.250
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Port Operations or VTS in the Houston, New Orleans and Seattle areas.
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06
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156.300
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156.300
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Intership Safety
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07A
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156.350
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156.350
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Commercial
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08
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156.400
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156.400
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Commercial (Intership only)
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09
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156.450
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156.450
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Boater Calling. Commercial and Non-Commercial.
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10
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156.500
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156.500
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Commercial
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11
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156.550
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156.550
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Commercial. VTS in selected areas.
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12
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156.600
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156.600
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Port Operations. VTS in selected areas.
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13
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156.650
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156.650
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Intership Navigation Safety (Bridge-to-bridge). Ships >20m length maintain a listening watch on this channel in US waters.
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14
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156.700
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156.700
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Port Operations. VTS in selected areas.
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15
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-
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156.750
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Environmental (Receive only). Used by Class C EPIRBs.
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16
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156.800
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156.800
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International Distress, Safety
and Calling. Ships required to carry radio, USCG, and most coast stations maintain a listening watch on this channel.
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17
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156.850
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156.850
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State Control
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18A
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156.900
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156.900
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Commercial
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19A
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156.950
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156.950
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Commercial
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20
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157.000
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161.600
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Port Operations (duplex)
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20A
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157.000
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157.000
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Port Operations
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21A
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157.050
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157.050
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U.S. Coast Guard only
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22A
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157.100
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157.100
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Coast Guard Liaison and Maritime Safety Information Broadcasts. Broadcasts announced on channel 16.
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23A
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157.150
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157.150
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U.S. Coast Guard only
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24
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157.200
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161.800
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Public Correspondence (Marine Operator)
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25
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157.250
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161.850
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Public Correspondence (Marine Operator)
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26
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157.300
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161.900
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Public Correspondence (Marine Operator)
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27
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157.350
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161.950
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Public Correspondence (Marine Operator)
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28
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157.400
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162.000
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Public Correspondence (Marine Operator)
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63A
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156.175
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156.175
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Port Operations and Commercial, VTS. Available only in New Orleans / Lower Mississippi area.
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65A
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156.275
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156.275
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Port Operations
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66A
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156.325
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156.325
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Port Operations
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67
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156.375
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156.375
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Commercial. Used for Bridge-to-bridge communications in lower Mississippi River. Intership only.
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68
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156.425
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156.425
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Non-Commercial
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69
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156.475
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156.475
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Non-Commercial
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70
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156.525
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156.525
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Digital Selective Calling (voice communications not allowed)
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71
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156.575
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156.575
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Non-Commercial
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72
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156.625
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156.625
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Non-Commercial (Intership only)
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73
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156.675
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156.675
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Port Operations
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74
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156.725
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156.725
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Port Operations
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77
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156.875
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156.875
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Port Operations (Intership only)
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78A
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156.925
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156.925
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Non-Commercial
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79A
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156.975
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156.975
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Commercial. Non-Commercial in Great Lakes only
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80A
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157.025
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157.025
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Commercial. Non-Commercial in Great Lakes only
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81A
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157.075
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157.075
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U.S. Government only - Environmental protection operations.
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82A
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157.125
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157.125
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U.S. Government only
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83A
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157.175
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157.175
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U.S. Coast Guard only
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84
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157.225
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161.825
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Public Correspondence (Marine Operator)
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85
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157.275
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161.875
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Public Correspondence (Marine Operator)
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86
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157.325
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161.925
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Public Correspondence (Marine Operator)
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87
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157.375
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161.975
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Public Correspondence (Marine Operator)
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88
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157.425
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162.025
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Public Correspondence only near Canadian border.
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88A
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157.425
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157.425
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Commercial, Intership only.
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NOAA Weather Radio Frequencies in MHz
WX1
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162.550
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WX2
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162.400
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WX3
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162.475
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WX4
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162.425
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WX5
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162.450
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WX6
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162.500
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WX7
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162.525
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See the NOAA Weather Radio Homepage
for more information.
Frequencies are in MHz.
Modulation is 16KF3E or 16KG3E.
Note that the letter "A" indicates simplex use of the ship station transmit side of an international duplex channel, and that operations are different than international operations on that channel. Some VHF transceivers are equipped with an "International - U.S." switch for that purpose. "A" channels are generally only used in the United States, and use is normally not recognized or allowed outside the U.S. The letter "B" indicates simplex use of the coast station transmit side of an international duplex channel. The U.S. does not currently use "B" channels for simplex communications in this band.
dot Boaters should normally use channels listed as Non-Commercial. Channel 16 is used for calling other stations or for distress alerting. Channel 13 should be used to contact a ship when there is danger of collision. All ships of length 20m or greater are required to guard VHF channel 13, in addition to VHF channel 16, when operating within U.S. territorial waters. Users may be fined by the FCC for improper use of these channels.
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Autopilots
An autopilot steers the vessel for you yet does not replace your legal responsibility to control the boat and have a lookout. Modern units have a variety of interfaces and low power drains. Essentially the unit depends on a sensor on the rudder gear to update position relative to a fluxgate compass or wind vane. Drift or leeway is not normally in the equation unless interfaced from a GPS. Drives vary from linear mounted on the steering gear or belt drives on the steering wheel. Your choice of the drive is the most important factor since power drain and efficiency result. The choice is relative to your boat and its limits. Remote units are available with many units allowing the helmsman to locate in a comfortable spot to maintain lookout.
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The ACR GlobalFix 406 MHz EPIRB w/ Internal GPS provides instant recognition of who and where you are when activated. The GlobalFix is considered the state of the art of EPIRBs.
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EPIRB
Emergency Position Indicating Radio Beacon; are designed to alert rescue authorities in emergencies. There are different classes of EPIRB for the many possible rescue situations. Class A, B and S are most common and have limited range. Class C is manually activated and for near shore or inland. Category I and II work on two separate frequencies for alert and locate tasks.
Open any marine catalogue and there is a mind boggling array of EPIRB and accessories. You must first decide what you intend to use it for and compare what is available. A simple radio beacon for near coastal or a satellite alert with a location beacon for offshore.
EPIRB's can be rented for offshore use. Most beacons have an ID that can be matched with information you give to authorities ahead of time.
Locating your EPIRB on your boat is important. Below decks is the wrong place. It should be topside within reach if it must be manually activated and if it is self activating you have many choices but remember it must be free to float off the boat if necessary. Most have a strobe light if yours doesn't have one available.
Sonar and Other Devices
There are a number of high tech electronic devices that are at the far end of the spectrum of electronic equipment that are available yet have limited use for most people. Forward looking sonar for one is available and allows you to see the bottom ahead as you travel. Of course if you are going at high speeds and are using it for avoiding underwater obstacles you might not become aware of and object in time to stop. If you're going very slow through uncharted waters you can make judgments on the bottom to find your way.
Radio direction finders, RDF are available but GPS has made it obsolete. Your GPS has a heading feature that reads in degrees magnetic yet a simple magnetic compass is always necessary.
A radar alarm that tells you if and from what direction you are being scanned is handy yet has limited use. A simple radar reflector will increase you radar profile to that of a much larger vessel and give another vessel ample notice of your existence.
Sources for this article and of further information: http://www.marine-electronics.net
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