Northstar has been a leader in the US marine electronics industry for over 35 years, and now offers a range of solutions that combine navigation, radar, and entertainment functionality. Boat builders and boat owners alike value Northstar's systems.
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Basics & Buying Guide
The type of radar most commonly found on recreational boats is termed X band radar, operating in the 8 to 12 GHz frequency range. Because the X band operates on a higher frequency than other types, the wavelength is small (2.5 to 4 cm) and is more sensitive. This allows it to detect smaller particles such as rain, making the X band a valuable tool for weather tracking. Because the signal at these high frequencies is scattered and absorbed easily, it is generally used for short ranges.
Boaters usually think of using radar in limited visibility conditions such as at night or in fog or heavy rain. But radar can also be used as an extra set of eyes in good weather conditions, allowing you to "see" distant objects.
The type of radar most commonly found on recreational boats is termed X band radar, operating in the 8 to 12 GHz frequency range.
Because the X band operates on a higher frequency than other types, the wavelength is small (2.5 to 4 cm) and is more sensitive. This allows it to detect smaller particles such as rain, making the X band a valuable tool for weather tracking. Because the signal at these high frequencies is scattered and absorbed easily, it is generally used for short ranges.
A radar consists of a display, a transceiver (transmitter and receiver) and an antenna or scanner.
Radio frequency energy (RF), generated by the transceiver, is emitted by a rotating antenna, bounces off reflective objects and is returned. The time it takes for the RF energy to arrive at the target and return is measured by the transceiver, which calculates the distance to the target. The transceiver also computes which direction the antenna is pointing on each rotation and determines a target bearing. The size, shape, distance and bearing of the target are then displayed on a screen.
Display screens are measured on the diagonal like TV screens and can range in size from 5.5 to 15 inches. They may be either color or several levels of monochrome. Screen size, type, resolution and contrast are factors that will influence how well you can read the screen in a variety of light conditions. High-resolution and high-contrast monochrome displays with back lighting offer good visibility in a variety of lighting conditions but all displays are best used in subdued lighting. Another contributory factor to visibility is the screen type, LCD or CRT.
LCD (Liquid Crystal Display) screens are available in either monochrome or color, but the color display will have readability limitations in daylight conditions, especially direct sunlight. Because LCDs are thin and lightweight, they're suited to locations where space is at a premium. Most LCDs are described in the manufacturer's specifications as either full VGA (Video Graphics Adapter) or ¼ VGA. Full VGA consists of 640 X 480 pixels and is usually found in larger displays such as radar or permanently mounted chartplotters. The ¼ VGA units offer only 320 X 240 pixels and are typically found on handheld and portable chartplotters. The LCD monochrome screen is a good choice for use most lighting conditions.
CRT (Cathode Ray Tube) displays have a higher pixel count (full VGA) than LCD screens, and have bright, high-contrast screens that are readable in most light conditions except bright sunlight. CRT displays take up more space and use more power than LCD displays.
The shape and width of the antenna, or scanner, determines the shape of the radar's beam. Most antennas available to recreational boaters are either the more popular radome (closed array) or the open array type. In addition to the shape, the transmit power determines the signal strength or "visibility" range of your radar unit. This is important in weather conditions that require you to use your radar to begin with since fog and rain absorb RF energy, reducing range. RF energy emissions by radar are line-of-sight, making the mounting height a consideration. Follow the manufacturer's recommendations on this.
The narrower antenna found in radomes produces a wider horizontal beamwidth which runs from about 4 to 7 degrees, producing less separated targets. A radome encloses the moving parts of the antenna within a plastic housing to protect them. These are primarily found mast-mounted on sailboats or on smaller powerboats where it's difficult to find an out-of-the-way mounting location.
Open array antennas are wider, as much as 8 feet, and produce a narrower horizontal beamwidth, usually less than 3.5 degrees. This enables the antenna to focus the transmitted RF energy, and provides better target separation and a longer range than the radomes. Because the antenna rotates without the protection of a cover, it must be mounted clear of obstructions and crew.
Like high frequency radios,radar uses its own language and it's important to know the basic language in order to understand what you're buying. Below are the more common terms used.,
Attenuation is the loss of signal on either side of the transmit pattern. Sidelobes can be reflected back as interference and the radar's capability to suppress this interference is listed by the manufacturer as a negative number relative to the main transmission signal's positive number; the lower the negative number the better.
Bearing Accuracy should be within +/- 1 to 2 degrees and are relative to your boat's position only.
Clutter is unwanted signals, echoes or images that radar picks up and displays, interfering with reading of the desired signals.
EBL, Electronics Bearing Line, measures the relative bearing of a target from your location.
Gain Control is an adjustment for the sensitivity of the receiver allowing you to adjust the intensity of the return signals for the best image.
Horizontal Beam Width should be as small as possible. Radar emissions measured in the horizontal plane determine resolution; the smaller the horizontal beamwidth, the better the resolution.
Interference Rejection disregards signals caused by other radars operating in the immediate area.
Maximum Range is determined primarily by the transmit power, antenna height, and pulse length. Other factors contribute such as the transceiver's sensitivity, weather, and the size, shape and reflectivity of the target.
Minimum Range is the shortest distance where the signals transmitted don't interfere with the signals being bounced back. This distance is determined primarily by the mounting height and the vertical beam width. As the antenna mounting height is increased, the minimum range is increased.
Overall Noise Figure is the number that determines the usable display
area near the center of the screen. A low overall noise figure provides
for a larger usable display area picking up smaller targets with
weak return signals.
Rain Clutter Control allows you to optimize the image for weather conditions by suppressing the reflected RF energy from rain, minimizing the loss of targets in the clutter. Unlike other radars else on the recreational boating market the Company "Northstar" has introduced a revolutionary new radar system - "solid-state".
Radar system that provides superior target separation and detection. In additional low power consumption and mount anywhere.
Range Discrimination is the distance that radar is able to distinguish two broadside targets that are in line with each other. The transmitted pulse length determines range discrimination. The smaller the range discrimination, the better. If two targets are closer than the range discrimination, you will not be able to tell them apart.
Sea State Clutter Control permits you to enhance the image by minimizing the reflection of echoes from waves in a seaway.
Transmit or Output Power is designated in kW, usually 2 or 4 kW for most recreational marine radars. This figure is the maximum peak power transmitted. A higher transmit power produces a longer signal range with cleaner, clearer return signals.
Vertical Beam Width; radar emissions measured in the vertical plane.
VRM, Variable Range Marker, or range ring, measures the distance to a target. Zoom allows you to enlarge any area on the display for greater detail.
There are many other terms used in the language of radar and your manufacturer's instruction manual will define those terms and tell you how they relate to operating the radar and getting the most out of it.
If you plan to buy, purchase a radar system with an antenna that fits your boat and your boating style. For instance, open array antennas are usually not the best choi for sailboats.
Keep the maximum height of your antenna installation in mind when buying a radar. Since the signals are line of sight, antenna height is directly connected to maximum range. Buying a 32-mile radar to mount 10 feet above the water is a waste of money.
Buy the largest, highest resolution display you can afford.
A 2 kW transmit power usually provides enough signal strength for the average boater. If you boat in an area that typically has dense fog or heavy rain the majority of the time, consider purchasing a higher transmit power.
There are many videos on the marine market that instruct you on both how to use and how to read radar, purchase one when you purchase your radar.
Installation is for professionals unless you're knowledgeable with electronics. The unit must be tuned after installation. If you do this yourself, pay to have the dealer you purchased it from check out both the tuning and installation to avoid warranty problems later.
Practice using your new radar in good conditions until you become familiar with the way targets display on the radar screen. Then when poor visibility strikes, you will know what the display is showing you.
A radar consists of a display, a transceiver (transmitter and receiver) and an antenna or scanner. Radio frequency energy (RF), generated by the transceiver, is emitted by a rotating antenna, bounces off reflective objects and is returned. The time it takes for the RF energy to arrive at the target and return is measured by the transceiver, which calculates the distance to the target. The transceiver also computes which direction the antenna is pointing on each rotation and determines a target bearing. The size, shape, distance and bearing of the target are then displayed on a screen.