A common mistake is too over-adjust the A/C SEA control so that the surface clutter is com- pletely removed. By rotating the control fully clockwise, you will see how dangerous this can be; a dark zone will be created near the center of the screen, causing a loss of close-in targets. This dark zone is even more dangerous if the gain has not been properly adjusted. Always leave a little surface clutter visible on the screen. If no clutter is observed (on very calm waters), set the control at the fully counterclockwise position.

1.12 Suppressing Rain Clutter

In adverse weather conditions, clouds, rain or snow produce a lot of spray-like spurious echoes and impairs target detection over a long distance. This situation can be improved by using a Func- tion key that is so programmed. If the Function key fails to effectively suppress rain clutter, use the A/C RAIN control.

The A/C RAIN control adjusts the receiver sen- sitivity as the A/C SEA control does but rather in a longer time period (longer range). Clockwise rotation of this control increases the anti-clutter effect.

Appearance of rain

A/C RAIN control adjusted;

clutter on the display

rain clutter suppressed

Figure 1-10 Effect of A/C RAIN control

1.13The Heading and North Markers

The heading marker indicates the ship's heading in all presentation modes. It appears at zero de- grees on the bearing scale in the Head-up mode, in any direction depending on the ship orienta- tion in North-up and True Motion modes. The north marker appears as a short dashed line. In the Head-up mode, the north marker moves around the bearing scale in accordance with the compass signal.

To temporarily extinguish the heading marker to look at targets existing dead ahead of own ship, press the HM OFF (PUSH) control. The heading marker reappears when the key is released.

1.14 Measuring the Range

There are three ways to measure the range to a target: by the range rings, by the cursor and by the VRM (Variable Range Marker).

Measuring range by the range rings

Use the range rings to obtain a rough estimate of the range to a target. They are concentric circles around own ship, or the sweep origin. The num- ber of rings is automatically determined by the selected range scale and their interval is displayed at the upper-left position of the screen. Press the RINGS (PUSH) control to show the range rings if they are not displayed. Successive presses of the RINGS (PUSH) control gradually increase the brightness of the rings in four steps and a fifth press erases the rings.

Measuring range by the cursor

Rotate the trackball to place the cursor on the in- side edge of the target. The range to the cursor appears at the bottom of the display.

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Furuno FR-8251 Suppressing Rain Clutter, Heading and North Markers, Measuring the Range, Measuring range by the cursor
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FR-8251, FR-8111 specifications

Furuno has long been a leader in marine electronics, and its FR-8251 and FR-8111 radar systems continue that tradition. Both are advanced systems designed specifically for professional mariners who demand high performance, reliability, and technological sophistication in their navigational tools.

The Furuno FR-8251 is a powerful radar system that boasts a range of features tailored for commercial vessels. With a 25 kW transmitter, the FR-8251 delivers exceptional performance, providing a clearer and more detailed image of the maritime environment. It is equipped with advanced signal processing technology, including the Doppler processing feature, which allows for the detection of moving targets. This is highly beneficial for collision avoidance, as it provides accurate information regarding the speed and direction of other vessels.

Another noteworthy feature of the FR-8251 is its large, high-resolution display that enhances visibility and ease of use, even in challenging weather conditions. The user interface is straightforward, allowing for quick adjustments and easy navigation through the various settings. It supports a variety of display formats and allows for customization, enabling operators to tailor the information presented according to their specific needs.

On the other hand, the Furuno FR-8111 is equally impressive and designed as a more compact solution without sacrificing performance. This model comes with a 12 kW output and is specifically crafted for smaller vessels, yet it still delivers high-quality radar coverage. Utilizing Furuno’s renowned Automatic Target Tracker (ATT) technology, the FR-8111 enables mariners to efficiently track multiple targets, significantly enhancing situational awareness.

Additionally, both the FR-8251 and FR-8111 come with integrated ARPA (Automatic Radar Plotting Aid), providing users with sophisticated tools for navigation and collision avoidance. The presence of multiple target tracking empowers operators to make informed decisions, optimizing safety at sea.

Furuno’s commitment to reliability and durability is evident in both models, which are designed to withstand the harsh marine environment. Their robust build quality ensures longevity, while their advanced technologies offer peace of mind.

Both the Furuno FR-8251 and FR-8111 are excellent choices for professional mariners seeking cutting-edge radar systems. With their impressive performance, user-friendly interfaces, and advanced technologies, these radar systems set the standard in marine navigation, providing essential support for safe and efficient voyages.
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