Lessons

Radar bacic components

Radar systems comprise three basic components: A transmitter and a receiver unit, also called a transceiver, an antenna, also known as a scanner, and a display unit. In many radar units the transceiver is located in the scanner. Radar signals...

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Radar controls general

This is a radar display unit. The display unit has controls for the following purposes: The function control. Range selector. The brilliance control. The tuning control. The tuning indicator. The gain control. The anti-sea clutter control and the...

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The function control

The function control has five positions, which are: Radar off position. At this position the radar is not in operation and there is no power supplied to the display or to the scanner. Standby position. In this position the radar can be brought...

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Other radar controls

Range selector position. The range selector is used to select the range that the radar will cover. There are five positions, indicated in miles: 1½, 3, 6, 12, and 24 miles. When the range is selected, the distance between the rings is determined...

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Introduction

The weight of air pressing down on the earth is called the air pressure. Air pressure is caused by the earth’s gravity, which acts like a downward force. Pressure can be measured by a barometer and can be recorded by a barograph. Pressure...

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Aneroid barometer

Small vessels most often use an aneroid barometer. Although it is not as accurate as a mercury barometer, it is more robust, compact and affordable. The aneroid barometer consists of a corrugated container nearly exhausted of air, with a spring...

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Barograph

A barograph is a type of aneroid barometer, and as you see here, the pointer is replaced by a pen. It also has a drum and bellows. Every seven days the drum makes one revolution. A chart, which is affixed to the drum, is graduated in time on one...

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Introduction

In former times, before wind measuring equipment was available, the Beaufort Scale was the only device available to determine the wind force. The scale was invented in the year 1805 by Sir Francis Beaufort and officially adopted in 1838. Sir...

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Description

Let’s have a closer look at a modern Beaufort Scale. The scale contains a column with: the Beaufort Wind Force, the Mean Wind Speed in knots, the Descriptive Term, the State of Sea, and the probable Height of Waves in meters. The column...

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Introduction

An air mass is a huge dome of air whose temperature and humidity characteristics remain fairly constant over a horizontal distance. This horizontal distance can extend up to hundreds or thousands of kilometers. Air masses are classified according...

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Introduction

Clouds are often very important indicators of imminent weather changes. When they are observed at various times and regular intervals, even an approaching mid-latitude storm can be recognized. In an approaching storm, a change of cloud structure...

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How clouds are formed

The cloud formations of interest to the mariner are formed in the Troposphere. The Troposphere is a layer of the earth’s atmosphere that extends from the earth’s surface to about 24.000 feet (7.300 meters) above the poles, and to...

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Classification

Clouds are classified by their general appearance and level. Cloud names are Cirrus, Stratus and Cumulus. To indicate the level of a cloud, a prefix is given to the cloud name, like Cirro and Alto. Cirro indicates high clouds with bases above...

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High clouds

High clouds are Cirrus, Cirrostratus and Cirrocumulus. Cirrus clouds are thin wispy clouds, composed predominantly of ice crystals. Thick patches of Cirrus clouds indicate that showers are nearby. Cirrus clouds that are shaped like commas...

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Mid level clouds

Mid-level clouds are Altostratus and Altocumulus. Altostratus clouds are usually grayish clouds that cover part or all of the sky. These clouds are composed of water droplets or ice crystals. At sea, Altostratus clouds are an important weather...

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Low clouds 1

Low clouds are Nimbostratus, Stratus, Stratocumulus, Cumulus and Cumulonimbus. Nimbostratus clouds are dark and quite homogeneous clouds. These clouds are associated with heavy downpours, high winds and sea conditions that are hazardous for small...

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Low clouds 2

Cumulus clouds are cauliflower-like clouds whose contours change constantly. Cumulus clouds can have slight or extensive height. With little vertical growth, these clouds indicate fair weather. With a large vertical extent, these clouds are...

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