Marine VHF radio
Marine VHF radio refers to the radio frequency range between 156 and 174 MHz, inclusive. The "VHF" signifies the high frequency of the range. In the official language of the International Telecommunication Union the band is called the VHF maritime mobile band. In some countries additional channels are used, such as the L and F channels for leisure and fishing vessels in the Nordic countries. Marine VHF radio equipment is installed on most seagoing small craft, it is used, with different regulation, on rivers and lakes. It is used for a wide variety of purposes, including summoning rescue services and communicating with harbours, locks and marinas. A marine VHF set is a combined transmitter and receiver and only operates on standard, international frequencies known as channels. Channel 16 is the international distress channel. Transmission power ranges between 1 and 25 watts, giving a maximum range of up to about 60 nautical miles between aerials mounted on tall ships and hills, 5 nautical miles between aerials mounted on small boats at sea level.
Frequency modulation is used, with vertical polarization, meaning that antennas have to be vertical in order to have good reception. Modern-day marine VHF radios offer not only basic receive capabilities. Permanently mounted marine VHF radios on seagoing vessels are required to have certification of some level of "Digital Selective Calling" capability, to allow a distress signal to be sent with a single button press. Marine VHF uses "half-duplex" transmission, where communication is over a single radio frequency, only one of the parties can transmit at a time; the transceiver is in receive mode. Some channels, are "full duplex" transmission channels where communication can take place in both directions when the equipment on both ends allow it; each full-duplex channel has two frequency assignments. Duplex channels can be used to place calls over the public telephone network for a fee via a marine operator; when full-duplex is used, the call is similar to one using a mobile landline. When half-duplex is used, voice is only carried one way at a time and the party on the boat must press the transmit button only when speaking.
This facility is still available in some areas, though its use has died out with the advent of mobile and satellite phones. Marine VHF radios can receive weather radio broadcasts, where they are available. Sets can be fixed or portable. A fixed set has the advantages of a more reliable power source, higher transmit power, a larger and more effective aerial and a bigger display and buttons. A portable set can be carried on a kayak, or to a lifeboat in an emergency, has its own power source and is waterproof if GMDSS-approved. A few portable VHFs are approved to be used as emergency radios in environments requiring intrinsically safe equipment. Marine radios can be "voice-only" or can include "Digital Selective Calling". Voice-only equipment is the traditional type, which relies on the human voice for calling and communicating. Digital Selective Calling equipment, a part of the Global Maritime Distress Safety System, provides all the functionality of voice-only equipment and, allows several other features: a transmitter can automatically call a receiver equipped with Digital Selective Calling, using a telephone-type number known as a Maritime Mobile Service Identity.
The DSC information is sent on the reserved Channel 70. When the receiver picks up the call, their active channel is automatically switched to the transmitter's channel and normal voice communication can proceed. A distress button, which automatically sends a digital distress signal identifying the calling vessel and the nature of the emergency a connection to a GPS receiver allowing the digital distress message to contain the distressed vessel's positionThe MMSI is used for seagoing vessels and consists of a nine-digit number identifying a VHF set or group of sets; the left hand digits of MMSI indicate the type of station. For example, here are MMSI prefixes of four station types: Ship: 232, 233, 234 or 235 are the United Kingdom – e.g. a UK ship: 232003556 Coastal station: 00 – e.g. Solent Coastguard: 002320011 Group of stations: 0 – e.g. 023207823 Portable DSC equipment: for UK 2359 - e.g. 235900498Here is an external link where you can find different countries' MMSI Numbers http://www.vtexplorer.com/vessel-tracking-mmsi-mid-codes.html For use on the inland waterways within continental Europe, a compulsory Automatic Transmitter Identification System transmission conveys the vessel's identity after each voice transmission.
This is a ten-digit code, either an encoded version of the ship's alphanumeric call sign, or for vessels from outside the region, the ship MMSI prefixed with "9". The requirement to use ATIS in Europe, which VHF channels may be used, are regulated, most by the Basel agreements. Half-duplex channels here are listed with the B frequencies the same; the frequencies and some of their purposes are governed by the ITU. For an authoritative list see; the original allocation of channels consisted of only channels 1 to 28 with 50 kHz spacing between channels, the second frequency for full-duplex operation 4.6 MHz higher. Improvements in radio technology meant that the channel spacing could be reduced to 25 kHz with channels 60 to 88 interspersed between the original channels. Chann
A yacht is a watercraft used for pleasure or sports. The term originates from the Dutch word jacht, was referencing light fast sailing vessels that the Dutch Republic navy used to pursue pirates and other transgressors around and into the shallow waters of the Low Countries; the yacht was popularized by Charles II of England as a pleasure or recreation vessel following his restoration in 1660. Today's yachts differ from other vessels by their leisure purpose. A yacht is any power vessel used for pleasure, cruising or racing. A yacht does not have to have luxury accommodations to be a yacht, in fact many racing yachts are stripped out vessels with the minimum of accommodations; the term'sailboat' is sometimes used in America to differentiate sail from powerboat. See also'yachting'. There are about 6,500 yacht over 24m on the market. Charter yachts are a subset of yachts used for pleasure, cruising or racing, but run as a business for profit. Ownership can be corporate; the paid crews of these vessels call themselves'yachties'.
Yacht lengths range from 7 metres up to dozens of meters. A luxury craft smaller than 12 metres is more called a cabin cruiser or a cruiser. A superyacht refers to any yacht above 24 m and a megayacht refers to any yacht over 50 metres. A few countries have a special flag worn by recreational boats or ships, which indicates the nationality of the ship. Although inspired by the national flag, the yacht ensign does not always correspond with the civil or merchant ensign of the state in question; the US yacht ensign for example, has a circle of 13 stars and a fouled anchor in the canton instead of the 50 stars, being quite different from the ensign of the United States, the flag of the United States. Yacht ensigns differ from merchant ensigns in order to signal that the yacht is not carrying cargo that requires a customs declaration. Carrying commercial cargo on a boat with a yacht ensign is deemed to be smuggling in many jurisdictions; until the 1950s all yachts were made of wood or steel, but a much wider range of materials is used today.
Although wood hulls are still in production, the most common construction material is fibreglass, followed by aluminium, carbon fibre, ferrocement. The use of wood has changed and is no longer limited to traditional board-based methods, but include modern products such as plywood, skinned balsa and epoxy resins. Wood is used by hobbyists or wooden boat purists when building an individual boat. Apart from materials like carbon fibre and aramid fibre, spruce veneers laminated with epoxy resins have the best weight-to-strength ratios of all boatbuilding materials. Sailing yachts can range in overall length from about 6 metres to well over 30 metres, where the distinction between a yacht and a ship becomes blurred. Most owned yachts fall in the range of about 7 metres -14 metres. In the United States, sailors tend to refer to smaller yachts as sailboats, while referring to the general sport of sailing as yachting. Within the limited context of sailboat racing, a yacht is any sailing vessel taking part in a race, regardless of size.
Many modern racing sail yachts have efficient sail-plans, most notably the Bermuda rig, that allow them to sail close to the wind. This capability is the result of a hull design oriented towards this capability. Day sailing yachts are small, at under 6 metres in length. Sometimes called sailing dinghies, they have a retractable keel, centreboard, or daggerboard. Most day sailing yachts do not have a cabin, as they are designed for hourly or daily use and not for overnight journeys, they may have a'cuddy' cabin, where the front part of the hull has a raised solid roof to provide a place to store equipment or to offer shelter from wind or spray. Weekender yachts are larger, at under 9.5 metres in length. They may have twin keels or lifting keels such as in trailer sailers; this allows them to operate in shallow waters, if needed "dry out"—become beached as the tide falls. This is important in UK waters; the hull shape allows the boat to sit upright. Such boats are designed to undertake short journeys lasting more than 2 or 3 days.
In coastal areas, long trips may be undertaken in a series of short hops. Weekenders have only a simple cabin consisting of a single "saloon" with bedspace for two to four people. Clever use of ergonomics allows space in the saloon for a galley and navigation equipment. There is limited space for stores of food. Most are single-masted "Bermuda sloops", with a single foresail of the jib or genoa type and a single mainsail; some are gaff rigged. The smallest of this type called pocket yachts or pocket cruisers, trailer sailers can be transported on special trailers. Cruising yachts are by far the most common yacht in private use, making up most of the 7–14-metre range; these vessels can be quite complex in design, as they need a balance between docile handling qualities, interior space, good light-wind performance and on-board comfort. The huge range of such craft, from dozens of builders worldwide, makes it hard to give a single illustrative description. However, most favor a teardrop-planform hull, with a fine bow, a wide, flat bottom and deep single-fin keel with ample beam to give good stability.
Most are single-masted Bermuda rigged sloops, with a single fo
The radio frequency 2182 kHz is one of the international calling and distress frequencies for maritime radiocommunication in a frequency band allocated to the mobile service on primary basis for distress and calling operations. Transmissions on 2182 kHz use single-sideband modulation. However, amplitude modulation and some variants such as vestigial sideband are still in use by vessels with older equipment and by some coastal stations in an attempt to ensure compatibility with older and less sophisticated receivers. Frequency allocation 2173.5–2190.5 kHz 2182 kHz is analogous to channel 16 on the marine VHF band, but unlike VHF, limited to ranges of about 20 to 50 nautical miles depending on antenna height, communications on 2182 kHz and nearby frequencies have a reliable range of around 50 to 100 nautical miles during the day and 150 to 300 nautical miles or sometimes more at night. The reception range of a well-equipped station can be limited in summer because of static caused by lightning.
All stations using 2182 kHz were required to maintain a enforced three-minute silence and listening period twice each hour, starting at h+00, h+30. This allowed any station with distress, urgent or safety traffic the best chance of being heard at that time if they were at some distance from other stations, operating on reduced battery power or reduced antenna efficiency, as for example from a dismasted vessel; as a visual aide-memoire, a typical clock in a ship's radio room would have these silence periods marked by shading the sectors from h+00 to h+03 and from h+30 to h+33 in green. Similar sectors were marked in red for what used to be the corresponding silence and listening period on 500 kHz between h+15 and h+18 and from h+45 to h+48; these silence periods are no longer required as the introduction of GMDSS has produced alternative automatic watchkeeping systems and the 500 kHz band is no longer in use for maritime traffic. In order to operate a marine radio transmitter on 2182 kHz, the operator must hold a GMDSS General Operating Certificate for mandatory installations, a Long Range Certificate for voluntary ones, or other equivalent and recognised radio operator's qualifications.
Both these certificates have a wider syllabus than those of the GMDSS Restricted Operators Course or the RYA Short Range Certificate, necessary for marine VHF use. In practice, an unqualified operator would not be prosecuted for the use of either transmitter in what turns out to be a genuine distress situation. 2182 kHz forms an essential part of the Global Maritime Distress Safety System. It has an associated DSC frequency at 2187.5 kHz. Other international distress frequencies, in use as of 2008, include: 121.5 MHz and 243.0 MHz - civil aircraft emergency frequency 243 MHz - military aircraft emergency frequency 156.8 MHz - Marine VHF radio channel 16, short range maritime use 406 MHz / 406.1 MHz - Cospas-Sarsat international satellite-based search and rescue distress alert detection and information distribution system 500 kHz Morse code is no longer monitored. 121.5 or 243 MHz locators. Effective 1 August 2013, the U. S. Coast Guard terminated its radio guard of the international voice distress and calling frequency 2182 kHz and the international digital selective calling distress and safety frequency 2187.5 kHz.
Additionally, marine information and weather broadcasts transmitted on 2670 kHz terminated concurrently. The U. S. Coast Guard continues to monitor HF marine distress/safety/calling voice and DSC frequencies. Distress signal Marine VHF radio Mayday Pan-pan Sécurité Global Maritime Distress Safety System 500 kHz International Telecommunication Union Maritime and Coastguard Agency Merchant Shipping Regulations
Morse code is a character encoding scheme used in telecommunication that encodes text characters as standardized sequences of two different signal durations called dots and dashes or dits and dahs. Morse code is named for Samuel F. B. Morse, an inventor of the telegraph; the International Morse Code encodes the 26 English letters A through Z, some non-English letters, the Arabic numerals and a small set of punctuation and procedural signals. There is no distinction between lower case letters; each Morse code symbol is formed by a sequence of dashes. The dot duration is the basic unit of time measurement in Morse code transmission; the duration of a dash is three times the duration of a dot. Each dot or dash within a character is followed by period of signal absence, called a space, equal to the dot duration; the letters of a word are separated by a space of duration equal to three dots, the words are separated by a space equal to seven dots. To increase the efficiency of encoding, Morse code was designed so that the length of each symbol is inverse to the frequency of occurrence in text of the English language character that it represents.
Thus the most common letter in English, the letter "E", has the shortest code: a single dot. Because the Morse code elements are specified by proportion rather than specific time durations, the code is transmitted at the highest rate that the receiver is capable of decoding; the Morse code transmission rate is specified in groups per minute referred to as words per minute. Morse code is transmitted by on-off keying of an information carrying medium such as electric current, radio waves, visible light or sound waves; the current or wave is present during time period of the dot or dash and absent during the time between dots and dashes. Morse code can be memorized, Morse code signalling in a form perceptible to the human senses, such as sound waves or visible light, can be directly interpreted by persons trained in the skill; because many non-English natural languages use other than the 26 Roman letters, Morse alphabets have been developed for those languages. In an emergency, Morse code can be generated by improvised methods such as turning a light on and off, tapping on an object or sounding a horn or whistle, making it one of the simplest and most versatile methods of telecommunication.
The most common distress signal is SOS – three dots, three dashes, three dots – internationally recognized by treaty. Early in the nineteenth century, European experimenters made progress with electrical signaling systems, using a variety of techniques including static electricity and electricity from Voltaic piles producing electrochemical and electromagnetic changes; these numerous ingenious experimental designs were precursors to practical telegraphic applications. Following the discovery of electromagnetism by Hans Christian Ørsted in 1820 and the invention of the electromagnet by William Sturgeon in 1824, there were developments in electromagnetic telegraphy in Europe and America. Pulses of electric current were sent along wires to control an electromagnet in the receiving instrument. Many of the earliest telegraph systems used a single-needle system which gave a simple and robust instrument. However, it was slow, as the receiving operator had to alternate between looking at the needle and writing down the message.
In Morse code, a deflection of the needle to the left corresponded to a dot and a deflection to the right to a dash. By making the two clicks sound different with one ivory and one metal stop, the single needle device became an audible instrument, which led in turn to the Double Plate Sounder System; the American artist Samuel F. B. Morse, the American physicist Joseph Henry, Alfred Vail developed an electrical telegraph system, it needed a method to transmit natural language using only electrical pulses and the silence between them. Around 1837, therefore, developed an early forerunner to the modern International Morse code. William Cooke and Charles Wheatstone in England developed an electrical telegraph that used electromagnets in its receivers, they obtained an English patent in June 1837 and demonstrated it on the London and Birmingham Railway, making it the first commercial telegraph. Carl Friedrich Gauss and Wilhelm Eduard Weber as well as Carl August von Steinheil used codes with varying word lengths for their telegraphs.
In 1841, Cooke and Wheatstone built a telegraph that printed the letters from a wheel of typefaces struck by a hammer. The Morse system for telegraphy, first used in about 1844, was designed to make indentations on a paper tape when electric currents were received. Morse's original telegraph receiver used a mechanical clockwork to move a paper tape; when an electrical current was received, an electromagnet engaged an armature that pushed a stylus onto the moving paper tape, making an indentation on the tape. When the current was interrupted, a spring retracted the stylus and that portion of the moving tape remained unmarked. Morse code was developed so that operators could translate the indentations marked on the paper tape into text messages. In his earliest code, Morse had planned to transmit only numerals and to use a codebook to look up each word according to the number, sent. However, the code was soon expanded by Alfred Vail in 1840 to include letters and special characters so it could be used more generally.
Vail estimated the frequency of use of letters in the English language by counting the movable type he found in the type-cases of a local newspaper in Morristown. The shorter marks were called "dots" and the longer ones "dashes", the letters most used were assigned the shorter sequences of dots and dashes; this code was used since 1844 and became known as Morse lan