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Maritime mobile amateur radio is an amateur radio transmission license that allows maritime operators to install and use radio while they operating at sea. The call sign of operators is extended by adding the suffix "MM" when transmitting at sea.
 | The examples and perspective in this section deal primarily with the United Kingdom and do not represent a worldwide view of the subject.(June 2017) |
The following notes are made with regard to the UK "Full" amateur radio licence terms, provisions and limitations, [1] and so may vary slightly from other amateur licences.
Maritime mobile operation is defined as operating a transmitter that is located on any vessel at sea. This means any manned structure afloat outside the high-water mark. Operating on vessels on inland waterways is defined as mobile work, and so requires /M to be added to the callsign, not /MM as for maritime mobile operations. [1]
There is a requirement that the amateur radio equipment must only be installed with the written permission of the vessel's master. This does not affect those who intend to install a transceiver on their own boat, but is relevant to anyone who intends to make transmissions from a ferry or other passenger ship. In such cases, the master of the ship has the right to demand radio silence from the amateur operator. There is no requirement to keep a log of calls, but a written record of information about frequencies, times, operators and their callsigns can be valuable. [1]
It is not a requirement that the station transmits its location, but of course, this is advisable, and easy to do with on-board GPS location. UK amateurs have a system of regional secondary locators that they must use within UK territorial waters (e.g. adding D for the Isle of Man, M for Scotland etc. in the second position in their callsign). In international waters, this is not necessary. When in the territorial waters of other countries, CEPT rules apply and these can get complex. The normal procedure is to prepend the national locator of the host country to the normal callsign, separated with another slash. So, amateur station A0AA, operating from a vessel within the territorial tidal waters of a country identified by the prefix B, would identify itself as B/A0AA/MM when transmitting. [1]
In international waters, amateur licensees must only use frequency bands allocated internationally in each of the three ITU Regions. [2] In any country's territorial waters, they should abide by the frequency allocations and bandplans applicable to the host country. [1]
Many long-standing and sophisticated radio nets are regularly operated by shore-based amateur volunteers for seafaring operators.
| Frequency (MHz) | Time(s) (UTC) | Operator(s) | Notes | |
|---|---|---|---|---|
| Transatlantic maritime mobile net [3] [4] | 21.400 | 1300 | Trudi (8P6QM) | Based in Barbados, Atlantic crossing |
| Worldwide weather net [5] [6] | 21.303 | 1300 | Neville (G3LMO), Richard (KT4UW), Don (6Y5DA) | |
| UK maritime mobile net [7] [8] | 14.303 (14.306) | 0800 1800 | Bill (G4FRN, sk [9] ), Bruce (G4YZH), Tony (G0IAD) and others. | 2E0NWE (Owen) is seeking volunteers to reestablish the Net. Pse contact him via QRZ.com to volunteer. |
| Mississauga maritime net [3] [6] | 14.121 | 0745 local time, i.e. 1145 (Canadian summer time) or 1245 GMT | Doug (VE3NBL), Ernie (VE3EGM) | Based in Canada, Atlantic crossing |
| Caribbean maritime mobile net [10] | 7.241 | 1100 | Lou (KV4JC) | Caribbean cruising |
| Caribbean weather net [11] [12] | 7.086 | 1120 | George (KP2G) | Caribbean weather information |
| INTERMAR German maritime mobile service net [13] | 14.313 | 0800 1630 | Klaus (DJ3CD), Armin (DL8AH), Ruettger (DL8MEZ), Ruediger (DJ9UE) | daily all Oceans |
| PIN - COSTA RICA PANAMA PACIFIC ISLAND NET [14] | 14.135 | 0200 | Gunter (TI7WGI) | Pacific Atlantic |
| The Maritime Mobile Service Network [3] | 14.300 | 1700-0300 (winter) 1600-0200 (summer) | Net Manager is Jeff Savasta, KB4JKL, with over 70 net controllers | Atlantic, Caribbean and E. Pacific. Position reports posted on request. |
| ANAVRE Spanish maritime mobile service net [15] | 14.323 | 1630 2230 | Ignacio (EA4FZZ), Manel (EA3CBQ) | daily Med. & Northeast Atlantic |
| South African Maritime Mobile Net (SAMMNet) | 7.120 14.316 | 0635 1135 0630 1130 | Peter Wolf (ZS1CH), Woody Collett (ZS3WL), Marjoke Schuitemaker (ZS5V), Johan Smith (ZS6WZ), | Marine weather bulletins for coastal areas (40 m band) and the high seas (METAREA VII) (20 m band), Maritime Mobile station communication, |
There are some special considerations when installing and using amateur radio transmitters and receivers afloat. These include power supply, RF earth, antenna design and EMC (electromagnetic compatibility) with other electronic equipment aboard.
For MF and HF use, the most common antenna design is to add two RF insulators into the backstay of the mast and feed it from the transceiver using a sintered bronze earthing plate, bolted to the outside of the hull, well under the waterline, as an earth. On metal-hulled boats, the earth plate can be dispensed with, and the whole hull used as a ground. In this case, the thickness of any paint layer is entirely negligible at RF. On a yacht with twin backstays, if insulators are placed in both of them, and they are fed from the masthead, they may be usable as an "inverted vee" avoiding the need to feed the antenna against ground. Either format will require the use of an ATU (Antenna Tuning Unit) to achieve resonance for the HF frequency in use, as the physical length of the antenna will almost invariably be incorrect at the frequency of choice. A few twin-masted sailing vessels have the space to erect a "Tee" antenna or an inverted "L" between masts. These antenna configurations are more common on merchant ships.
For VHF and UHF operation, one option is to mount a small Yagi antenna to a pole 1–2 m (3–6 ft) long and haul this to the masthead using a flag halyard. If the halyard is correctly knotted to the middle and bottom of the pole, it is easy enough to make the antenna project above the clutter at the masthead into clear air. The problem is in rotating it - it usually needs to be lowered and re-raised to alter the direction of its beam. For the safety of masthead fittings and lights it is better if these yagis are light in weight and made largely of, for example, plastic tubes supporting internal wire conductors. Operating in this way is best reserved for when in harbour or at anchor, to avoid interfering with the operation of the boat. Repeated loss of signal due to rolling and pitching would make it impractical for useful communication at sea anyway.
For FM operation on the 2 m band, the masthead vertical whip that is normally installed for marine VHF operation will provide good omni-directional, vertically polarised signals. The frequency of operation around 145 MHz is close enough to the antenna's design frequency of 156 MHz that most amateur transceivers will not need an ATU and will not suffer unduly from a poor (high) SWR.
For a single-ended HF antenna, a good electrical earth connection is essential. It is also necessary from the points of view of safety and EMC considerations on any radio transmitter installation on a boat or ship. As mentioned above, metal-hulled vessels have a natural advantage in that, especially at HF and lower frequencies, the hull can be considered to be in contact with the water, as the insulating properties of the paint layer against the water is a capacitance that presents very little electrical impedance to the RF currents. For fibreglass and wooden hulls and HF transmission, the usual solution is to attach a sintered bronze plate to the outside of the hull for RF earthing. [16] The construction of a sintered bronze plate is porous to water so that although the plate may be only a square foot or two and an inch thick, the actual surface area of metal in electrical contact with the water is very many times that.
Once a good connection to the sea water has been established, it is necessary to make a good RF connection from the transceiver and ATU to the grounding system. While it might seem that a good, thick wire is all that is needed, for large RF currents it is usually recommended that copper grounding tape is used. [16] This is not because thick wires will not be able to support the currents involved, but because it is more likely that RF currents will remain flowing along something that has a wide surface area without re-transmitting themselves along the way due to skin effect.[ citation needed ] The key pathway from the ATU of a single-ended antenna system to the earthing plate, or the hull earth-point, should be as short and as straight as possible. This should be considered from the start when deciding where to mount the various components within the hull. There is not much that the installer can do about the losses in, and the efficiencies of, the transceiver, the ATU, the antenna or its feed, but extra effort put into the efficiency of the earthing paths will pay much bigger dividends, in terms of radiated power and freedom from EMC problems later, than any other single aspect of the installation. The salty sea makes an exceptionally good ground plane, and effort put into achieving a good connection to it will be handsomely repaid.
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A modern sailing boat, or any other modern seagoing craft, is a much more complex electronic environment than ever in the past, and even more so than a normal home-based amateur radio "shack". The vessel will probably have electronic navigation instruments, one or more GPS receivers, electronic automatic steering, domestic radio and perhaps television receivers as well as probably radar and VHF transmitters and receivers too. It may have various GMDSS devices too, such as a Navtex receiver and an AIS system. Many of these items are computerised and many of them are networked together with data, RF and power connections. All of this is crammed into a very compact, three-dimensional space and that space is shared by not only the radio operator, but perhaps several other crew or family members. Safety and EMC issues have never been so important.
One important fact to bear in mind is that the antenna lead, from the point where it leaves the relevant terminal on the HF ATU is a transmitting antenna. There is nothing that can or should be done to prevent RF radiation from this lead. It should be a specialist, high-voltage insulated, single-core wire and it should be rigidly mounted, well away from any other wiring, outside of any conducting faraday cage, in the shortest, straightest possible route to the point where it will connect to the external antenna, be that a whip or an insulated part of the standing rigging.
As discussed above, good earthing is essential in the installation of transmitting equipment, and good RF management will also pay dividends in terms of the ability to use other electronic equipment while transmitting, without damage to the other gear, or debilitating interference in the other gear during transmissions. It may be possible to disengage electronic steering and switch off or do without navigation instruments while the radio operator aboard makes a scheduled call, but others aboard will be much more grateful if this is not necessary and life aboard can continue as normal while people gather around the transceiver to hear news from ashore and from other boats, as well as weather or other important routing information.
Software-defined radio (SDR) is a radio communication system where components that conventionally have been implemented in analog hardware are instead implemented by means of software on a computer or embedded system. While the concept of SDR is not new, the rapidly evolving capabilities of digital electronics render practical many processes which were once only theoretically possible.
Medium frequency (MF) is the ITU designation for radio frequencies (RF) in the range of 300 kilohertz (kHz) to 3 megahertz (MHz). Part of this band is the medium wave (MW) AM broadcast band. The MF band is also known as the hectometer band as the wavelengths range from ten to one hectometers. Frequencies immediately below MF are denoted as low frequency (LF), while the first band of higher frequencies is known as high frequency (HF). MF is mostly used for AM radio broadcasting, navigational radio beacons, maritime ship-to-shore communication, and transoceanic air traffic control.
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for amateur radio communications, international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems.
A walkie-talkie, more formally known as a handheld transceiver (HT), is a hand-held, portable, two-way radio transceiver. Its development during the Second World War has been variously credited to Donald Hings, radio engineer Alfred J. Gross, Henryk Magnuski and engineering teams at Motorola. First used for infantry, similar designs were created for field artillery and tank units, and after the war, walkie-talkies spread to public safety and eventually commercial and jobsite work.
Marine VHF radio is a worldwide system of two way radio transceivers on ships and watercraft used for bidirectional voice communication from ship-to-ship, ship-to-shore, and in certain circumstances ship-to-aircraft. It uses FM channels in the very high frequency (VHF) radio band in the frequency range between 156 and 174 MHz, inclusive, designated by the International Telecommunication Union as 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. Transmitter power is limited to 25 watts, giving them a range of about 100 kilometres.
An antenna tuner, a matchbox, transmatch, antenna tuning unit (ATU), antenna coupler, or feedline coupler is a device connected between a radio transmitter or receiver and its antenna to improve power transfer between them by matching the impedance of the radio to the antenna's feedline. Antenna tuners are particularly important for use with transmitters. Transmitters feed power into a resistive load, very often 50 ohms, for which the transmitter is optimally designed for power output, efficiency, and low distortion. If the load seen by the transmitter departs from this design value due to improper tuning of the antenna/feedline combination the power output will change, distortion may occur and the transmitter may overheat.
The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3 Hz to 3,000 GHz (3 THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication. To prevent interference between different users, the generation and transmission of radio waves is strictly regulated by national laws, coordinated by an international body, the International Telecommunication Union (ITU).
The 2-meter amateur radio band is a portion of the VHF radio spectrum that comprises frequencies stretching from 144 MHz to 148 MHz in International Telecommunication Union region (ITU) Regions 2 and 3 and from 144 MHz to 146 MHz in ITU Region 1 . The license privileges of amateur radio operators include the use of frequencies within this band for telecommunication, usually conducted locally with a line-of-sight range of about 100 miles (160 km).
The 80 meter or 3.5 MHz band is a span of radio frequencies allocated for amateur use, from 3.5–4.0 MHz in North and South America ; generally 3.5–3.8 MHz in Europe, Africa, and northern Asia (Region 1); and 3.5–3.9 MHz in south and east Asia and the eastern Pacific (Region 3). The upper portion of the band, which is usually used for phone (voice), is sometimes referred to as 75 meters; however, in Europe, "75 m" is used to name an overlapping shortwave broadcast band between 3.9–4.0 MHz used by a number of national radio services.
The automatic identification system (AIS) is an automatic tracking system that uses transceivers on ships and is used by vessel traffic services (VTS). When satellites are used to receive AIS signatures, the term Satellite-AIS (S-AIS) is used. AIS information supplements marine radar, which continues to be the primary method of collision avoidance for water transport. Although technically and operationally distinct, the ADS-B system is analogous to AIS and performs a similar function for aircraft.
The R. L. Drake Company is a manufacturer of electronic communications equipment located in Springboro, Ohio. It is also known for its line of equipment for amateur radio and shortwave listening, built in the 1950s through the 1980s. The company operates as a separate entity owned by Blonder Tongue Laboratories, Inc.
A land mobile radio system (LMRS) is a person-to-person voice communication system consisting of two-way radio transceivers which can be stationary, mobile, or portable.
Single operator two radios (SO2R) is an operating practice employed by some competitors in the sport of amateur radio contesting. By using two transceivers attached to separate antennas, competitors can listen to one amateur radio band while transmitting on another. This capability enables the operator to more efficiently locate other amateur radio stations participating in the competition with which to make contact and score points.
An amateur radio station is a radio station designed to provide radiocommunications in the amateur radio service for an amateur radio operator. Radio amateurs build and operate several types of amateur radio stations, including fixed ground stations, mobile stations, space stations, and temporary field stations. A slang term often used for an amateur station's location is the shack, named after the small enclosures added to the upperworks of naval ships to hold early radio equipment and batteries.
An amateur radio repeater is an electronic device that receives a weak or low-level amateur radio signal and retransmits it at a higher level or higher power, so that the signal can cover longer distances without degradation. Many repeaters are located on hilltops or on tall buildings as the higher location increases their coverage area, sometimes referred to as the radio horizon, or "footprint". Amateur radio repeaters are similar in concept to those used by public safety entities, businesses, government, military, and more. Amateur radio repeaters may even use commercially packaged repeater systems that have been adjusted to operate within amateur radio frequency bands, but more often amateur repeaters are assembled from receivers, transmitters, controllers, power supplies, antennas, and other components, from various sources.
D-STAR is a digital voice and data protocol specification for amateur radio. The system was developed in the late 1990s by the Japan Amateur Radio League and uses minimum-shift keying in its packet-based standard. There are other digital modes that have been adapted for use by amateurs, but D-STAR was the first that was designed specifically for amateur radio.
Clansman is the name of a combat net radio system (CNR) used by the British Army from 1976 to 2010.
A radio communication station is a set of equipment necessary to carry on communication via radio waves. Generally, it is a receiver or transmitter or transceiver, an antenna, and some smaller additional equipment necessary to operate them. They play a vital role in communication technology as they are heavily relied on to transfer data and information across the world.
Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates oscillating electrical energy, often characterized as a wave. They can be received by other antennas connected to a radio receiver, this is the fundamental principle of radio communication. In addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications.
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