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Marine Radar Information

Radar FAQ's
Understanding Your Radar
Typical Radar Screen with "Lollipop" Indicator
Typical Radar Screen with Pop-Up Sub-Window

Radar FAQ's

Q: What is radar?

A: Radar is an acronym meaning RAdio Detection And Ranging. It is a device which measures not only the time it takes for a pulsed signal to be reflected back from an appropriate object, but also determines its bearing relative to your position. Once the time and bearing are measured, these targets or echoes are calculated and displayed on your radar display. This will give you a birds eye view of where other targets are relative to you, even when you can not see them with your eyes due to low visibility.

Q: What can radar do for me?

A: With radar acting as your eyes, you have the ability to see objects (targets) such as landmasses, weather systems and other vessels to assist you in the navigation of your vessel.

Q: What kind of features should I consider when choosing a radar?

A: There are many things to consider when buying a radar. Here are a few:

1. Boat Size -- Radars are available in various sizes and configurations. Consulting with an authorized Furuno dealer is the best way to ensure that you choose the right radar for your particular vessel.

2. Transmitter Power Output -- A higher power output level increases the chances that your radar will receive signals reflecting off objects and showing them as targets on your display. A higher-powered radar will also have a better chance of "punching through" fog and precipitation, allowing you to see objects around your vessel.

3. Beam Angle -- This specification is related to the length of your antenna. The longer the antenna is, the narrower the beam angle. This narrow beam angle increases the radars bearing resolution allowing you to discriminate easily between two objects that are close together. It also shows land mass contours and inlets with much greater resolution.

4. Display Preference (CRT vs. LCD) -- There are two display types to choose from; CRT (Cathode Ray Tube) or LCD (Liquid Crystal Display.) Each type has different advantages that need to be considered when choosing a radar. A CRT is similar to a television screen. It has high contrast in normal to low light, allowing for bright and clear targets to be shown on the display. Bright sunlight will tend to make the CRT display fade. CRT radars work best in an environment that is either covered or out of direct sunlight. LCD units are more compact and usually waterproof. The viewable area of a LCD is actually larger than its CRT counterpart, because it has a flat screen surface. The contrast on a LCD display is increased when it is back-lit or front-lit. In most cases the view-ability will actually increase in direct sunlight.

Q: What is a Guard Alarm?

A: A guard alarm alerts you when targets enter a designated area or when your vessel is approaching a dangerous area. The guard alarm area, or zone, can be set for a specified distance in front of your vessel or expanded to a 360° circle around your vessel. When targets such as other vessels, landmasses and buoys enter the zone, an audible alarm sounds to alert the operator.

Q: What are target trails and how do they help me navigate?

A: The echo trail feature indicates target movement by leaving an afterglow, showing where a target used to be. It is useful for quickly assessing the movement of targets relative to your own vessel. For example, if you were observing a moving vessel while the target trail feature was enabled, the radar display would show the moving vessel as a bright green target with a darker green trail where it had been. The length of this trail would depend upon the "trail time" setting, which is adjustable from 30 seconds to several minutes. Some radars also have the capability of showing the true or relative movement of targets providing increased safety at sea.

Q: How can I navigate with radar?

A: Fishing vessels and pleasure boats continually use radar to help them navigate to their favorite fishing spots. When heading to a particular spot, the forces of wind and current combine to shift the vessel off its intended course. To determine your position and to counter vessel drift, use the VRM (Variable Range Marker) and the EBL (Electronic Bearing Line) to mark range and bearing to fixed targets.

Q: What is a VRM?

A: VRM stands for Variable Range Marker. It is an electronic mark or ring that can be placed over any target on your radar display. An on-screen digital readout will let you know the precise range, in nautical miles, between the target and you.

Q: How does my radar determine range?

A: Suitable targets within its range will reflect the radar pulse transmitted by your antenna. The total time interval of the pulse divided by two (2) will tell us the targets exact range in nautical miles. The following screen shots show how radar targets are displayed on a typical Plan Position Indicator (PPI). The PPI is essentially a polar diagram, with the transmitting vessel's position at the center. Target echoes are received and displayed at their relative bearing to the vessel and at their exact distances from the PPI center.

Understanding Your Radar


Radar, The "Mandatory" Option. With all of the advances made in small boat radars, it has gradually become a "mandatory" option when outfitting a new boat. Affordable prices and user-friendly systems have also caused owners looking to re-outfit their "experienced" hulls to consider adding radar to their electronics arsenal. The biggest challenge facing many first-time radar users is to select the appropriate unit for their particular application from a long list of options that includes CRT or LCD screens, monochrome or color format, supported by either an enclosed radome or open array antenna.

The LCD Revolution. The introduction of high-resolution, small footprint LCD screens has enabled many pleasure boat operators to experience the benefits of radar previously enjoyed by only larger boats. LCD Radars, like the Furuno 1621MK2 and the M800 series, offer pleasure boat operators the best combination of features that will not only hold up to the elements with a totally waterproof case and keyboard, but also offer a backlit, high-resolution LCD screen that is easy to see in almost any ambient lighting condition.

For those boaters who have more room at the helm and a dedicated area to mount their electronics arsenal out of the weather, Furuno's M1701 CRT radar series offers the sharp, crisp depth and detail that only a high-definition monochrome screen can produce. Although historically, boaters were only offered a monochrome format when choosing a radar screen, all that has changed with Furuno's exciting new FRS1000 series of four-in-one integrated navigation systems, which produce vivid pictures, on a bright 10.4" TFT LCD color screen.

Choose Your Antenna. Most Furuno radars offer a variety of antenna choices. The enclosed radome type is very popular with both sailors and anglers, since it keeps all moving parts away from outrigger halyards, working lines, rigging and anything else that might work its way near the antenna. In addition, the fiberglass dome keeps moisture and salt out and away from critical components. The open array antenna typically is larger than the radome types and requires mounting on top of a larger vessel with a flybridge or tower, but offers increased range and enhanced target detail in return.

The bottom line is that no matter what type of Radar you need, Furuno has an affordable unit that will enhance the safety for all those aboard.

Typical Radar Screen with "Lollipop" Indicator


Typical Radar Screen image with Lollipop Indicator

Typical Radar Screen with "Lollipop" Indicator

A Range of radar display.

B Land Mass.

C "Lollipop" indication of selected waypoint.

D Position of boat in a head-up display.

E Auto anti-clutter is activated.

F Heading of boat.

G Heading line shows direction of boats path.

H Selectable fixed range rings.

I Waypoint bearing.

Typical Radar Screen with Pop-Up Sub-Window


Typical Radar Screen image with Pop-up Sub-window

Typical Radar Screen with Pop-Up Sub-Window

A Range of radar display.

B Heading line shows direction of boat's path.

C EBL -- Electronic Bearing Line.

D Pop-up sub-window in zoom mode.

E Radius of VRM marker.

F Heading of boat.

G VRM -- Variable Range Marker.

H Cursor shows range and bearing of specific targets.

I Selectable fixed range rings.

J Land Mass.

K Direction of EBL.


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