When using a radio one should bear the following in mind: Unlike your telephone it is not a private circuit. Anyone who has a radio covering the same frequency can listen in. There may be many users waiting to use the same circuit. Your use of the radio must be brief and to the point.…
The use of the safety signal implies that the station making the call has an important navigational or meteorological warning to transmit. All stations hearing the safety signal shall listen to the safety message until they are satisfied that the message is of no concern to them. It should take the form of the following…
An urgency message indicates that the station making it has a very urgent message to transmit concerning the safety of the mobile unit or person. It is only sent on the authority of the master or person responsible for the ship. The urgency signal will have priority over all other communications except Distress. All stations…
A distress call and message is sent when a vessel is in grave and imminent danger. They are only sent on the authority of the master or person responsible for the vessel. A distress call has priority over all other transmissions. All stations receiving a distress call and message must immediately cease any transmissions that…
Distress frequencies. For the purposes of safety and distress there are certain frequencies that have been specially reserved for their exclusive use internationally. They are the following: Medium frequency (MF) 518 kHz. Used by coast radio stations to transmit meteorological and navigation warnings and urgent information to ships using the international NAVTEX system of narrow…
General. Technology has changed the way we communicate at sea quite considerably. In grade 12 you will be introduced to the Global Maritime Distress and Safety System (GMDSS) but during grade 11 we will be discussing distress and safety communications outside of the new automated system. The old system relied heavily on telegraphy using the…
Types of current. Unlike tidal currents, ocean currents are not dependent on gravitational effect produced by the interaction of sun and moon. They are caused by the differences in level, or in salinity/density, or in temperature between various masses of water, in which case they are called stream currents, or by the wind blowing continuously…
Nature. Tropical storms are violent storms with very strong winds and heavy seas. Origin. They occur mostly in the late summer and early autumn (December to April in the southern hemisphere). They originate in the tropics between latitude 5° and latitude 10° north or south and develop only over the oceans. Named. Tropical storms are…
Life Cycle of a frontal depression. Warm air moves faster than cold and every now and again, it forces its way into the cold air, making a bulge in the polar front. This is the commencement of a frontal depression, since as the warm, less dense air pushes into the cold denser air, the pressure…
Air masses are large areas of air which have the same characteristics throughout. They may be warm or cold, depending upon where they originated, ie tropical or polar. They are further classified as either continental or maritime. When two different air masses meet they form a boundary which is known as a front. Most fronts…