Features November 1, 2000 Issue

Raytheon Dominates Radar
Testing; JRC 1500 Is A Best Buy

JRC's $999 LCD radar performed admirably, but Raytheon’s RL70 Series, with interchangeable scanners and display screens, offers unmatched pairing power.

Small-boat radar has advanced considerably over the past few years. Liquid crystal displays (LCDs) have gone from being a poor compromise to the standard of performance. Manufacturers have added features, increased performance and decreased cost.

We mounted the scanners on a 7-foot platform on
the banks of the Delaware River, a location with
a variety of targets, including buoys and a bridge.

Early radar units tended to be bulky, with large antennas turned by correspondingly large motors and hard-to-read phosphor-coated displays. The introduction of raster scan technology marked the first major advance in radar displays. Raster scan displays are monochrome, usually green. They convert signals from the radar antenna into a video image that can be displayed on a TV monitor. The image stays on the screen without fading for a full rotation.

The addition of an inexpensive microprocessor enabled a raster scan radar to become a full-featured navigational computer. It became feasible to display accurate bearings and distances to targets, and the display could be frozen, offset or zoomed to study a particular situation. It was also possible to show additional information from GPS, Loran and wind instruments. Some new models now allow electronic charts to be displayed on the same screen.

Despite these advances, radar displays remained quite bulky. This limitation made waterproofing difficult and relegated displays to mostly belowdecks installation, requiring crew to relay information to the helm.

LCDs, as opposed to the standard CRT (cathode ray tube) displays, solved this last problem. Early LCD radar, such as the Apelco LDR9910, lacked clear resolution, had very poor contrast, were easily affected by heat and cold, and could display images at only one brightness level, making it impossible to differentiate between strong and weak echoes (radar waves reflected from an object, appearing as a spot of light on the screen).

The evolution of laptop computers brought about great advances in LCD technology. These new displays can reproduce virtually any image that can be shown on a color CRT.

LCDs use less power, can be made flatter than CRT displays, don’t require high operating voltages and can be made weather-resistant.

What Matters
The only radar specification many boater owners look at is maximum range. How better to impress your boating friends than to have a 48-mile range radar! However, you probably won’t ever need to see that far. What matters more are some of the radar’s other specifications. An explanation of these follows:

Maximum Range. A radar’s maximum range is only attainable if it is mounted sufficiently high to see that far, which isn’t feasible on most small boats. A 16- or 24-mile-range radar set, such as those reviewed in this article, will probably be sufficient for most people.

Minimum Range. When dealing with targets that are too close, the signal transmitted by a radar installation interferes with the signal being bounced back. The shortest distance at which a radar can function effectively is described as its minimum range. Minimum range becomes extremely important when you’re passing between two objects. For example, if your minimum range is 30 meters, you could not use your radar to navigate in a heavy fog between buoys that are, say, 36 meters apart. (When between them, you could never see both at once.)

A radar’s minimum effective range is partly dependent on its height above the water, as well as its vertical beam width and the amount of noise that appears in the center of the screen. The higher a radar is installed above the water, the more its minimum range is increased. Clearly, the shorter the minimum range, the better.

Range Discrimination. This is the distance at which a radar can distinguish two broadside targets in line with each other. For example, if a tugboat and its barge are closer than the “range discrimination” specification, you won’t be able to tell them apart. A radar’s range discrimination is dependent on the length of the radar pulses it emits. A smaller range discrimination ability is better than a larger one.

Bearing Accuracy. Radar should be able to produce relative bearings with an accuracy of +/- 1° to 2°. Remember that the bearings are relative to the position of your boat and are neither magnetic nor true bearings.

Horizontal Beam Width. The signal transmitted by your radar is shaped by its antenna. This beam should be as small as possible. However, concentrating the signal into a narrower beam requires a larger antenna. A narrower beam width allows you to differentiate targets that are closer together. This is why commercial vessels have 8'-wide or even larger radar antennas. The compact design of the models in our test limits their ability to separate adjacent targets. When approaching a narrow channel, two boats may appear as one until you get close enough.

A problem with using a larger antenna to decrease beam width is that a larger antenna makes the target appear smaller on the display. With a very large antenna, small objects like buoys will simply disappear from your display unless you have the type of huge display common on commercial vessels.

Antenna Sidelobe Attenuation. Some of the signal from the antenna escapes on either side of the intended pattern. These signals are called sidelobes. When looking at large targets, some of these sidelobes may be reflected back and appear as interference. The ability of the radar to suppress these emissions is listed as a negative number (for example, -21 dB) in relation to the main signal. The lower this number, the better. (-21 dB is better than -18 dB.)

Output Power. This is the maximum peak power transmitted. Higher power is necessary to produce longer range. And higher power also produces crisper, clearer echoes.

Overall Noise Figure. A radar receiver listens to noise it generates internally in its surroundings. This noise accounts for the bright area seen in the center of the screen. A radar with a small overall noise figure will have more usable screen and will be better able to see smaller targets with weak echoes.

The Tests
Our last report on LCD radar was in the August 1, 1998 issue. This time around, we tested 11 radar units from five manufacturers: Raytheon, JRC, Si-Tex, Simrad and Furuno (unfortunately, not its new color LCD model, which we may report on in a future issue). All were LCDs except for the two Si-Tex models. Si-Tex has discontinued its LCD model, so we decided to test its CRT units instead. We were able to test four radar units from Raytheon’s RL70 Series because we swapped two scanners (antennas) and two displays (one was color, one black and white).

Click here to view the LCD Radar Value Guide.

The manufacturers have improved display resolution and decreased prices. Their antennas and attached transceivers, however, have remained essentially unchanged.

Testing was done under two different controlled conditions. First the units were mounted on a platform 7 feet high on the shore of the Delaware River in a location that provided multiple targets, such as buoys both near and far, and a distant bridge.

We set up each unit and noted its ability to see both standard and radar-reflective buoys. Also noted was the shape of the coastlines. Then, on land, two simulated buoys (large metal trash cans) with radar reflectors mounted on top were set 60' apart on an abandoned airport runway. These buoys were used to measure the radar’s accuracy. Each unit was disassembled and examined for overall quality and durability.

Raytheon SL72
The SL72 is Raytheon’s latest entry-level radar. Unlike its other models, the SL72 is sold as a package that includes a 7" (diagonal) screen and 2kW radome scanner. The 18" scanner weighs 14.3 lbs. The SL72’s controls include 10 push-buttons, a two-way range rocker and four soft keys along the bottom of its display dedicated to the less frequently used set-up and tuning functions. A four-way track pad controls the cursor.

The SL72 is extremely straightforward to operate. Its controls are well-designed, and the layout still allows easy access to secondary functions. As expected from Raytheon, the included manual is well-written, with fully explained operating instructions. In addition, excellent installation instructions and radar background information is included.

The Raytheon SL72 is very well-constructed, with many nice touches such as O ring-gasketed and molded connectors, which provide protection from water intrusion.

During testing, this model performed very well in comparison with the other 2 kW radars, although naturally not as good as the more powerful (and more expensive) models. Target resolution was good, and the radar presented an accurate representation of conditions.

Bottom Line: The Raytheon SL72 is a very good entry-level radar; we highly recommend it.

Raytheon RL70 Series
Raytheon has chosen a novel but very logical approach to marketing its upper-end RL70 series. Until now, small-boat radar was purchased as a package that included a matched display and scanner. Raytheon’s idea, however, is to sell its displays and scanners separately. This makes sense, especially considering that Raytheon’s HSB (High Speed Bus) allows multiple displays, or even a CRT display, to be connected to a single scanner. This mix-and-match philosophy allows you to pair your choice of display with either a 2 kW or 4 kW radome, or a 4 kW or professional level 10 kW open array antenna. Additionally, Raytheon offers the RL70 displays with an optional (about $600) chart plotter function.

The basic RL70 display and controls are identical to the SL72’s. However, it includes additional connectors on the back for the HSB, Raytheon’s Sea-Talk data bus and a NMEA output. With the chart plotter option, a dual C-map cartridge slot is included under a cover on the display’s left side.

The RL70C substitutes a TFT (thin film transistor) color display for the basic RL70’s LCD. To accommodate and power this display, the RL70C is slightly thicker and considerably heavier than its counterpart. All operating controls otherwise remain the same.

In addition to the 2 kW, Raytheon offers three other scanners for its RL70 radars: a 4 kW, 48-mile range radome; the S5 4 kW, 48", 72-mile open array; and a 48", 10 kW high-power array. For this review, we tested the two 4 kW units with open antennas.

Both of Raytheon’s RL70 displays are identical in appearance and operation. Operation is extremely easy, manuals are very comprehensive and both displays and scanners are well-constructed. The heavy, open array scanner includes a stay to hold its casing open for servicing and an on/off safety switch so it can be disabled if you need to work near it. This lessens the possibility of the antenna striking a crew member or exposing anyone to its radiation at close range if the radar were accidentally activated. We like this feature; radiation from radar isn’t a health problem if you’re 5-10 feet away from the antenna, but it could be if you spend time close to it while it’s operating.

All RL70 configurations performed extremely well. Even the enclosed array showed consistent targets as far away as 12 miles. This was very good. (Range is 1.144 x square root of the antenna’s height. Longer distances depend on height of the target. ) The 48", 4 kW open array rivaled the performance of much more expensive professional radars we’ve used.

Raytheon’s displays show very little glare in bright sunlight, making for good visibility. We also were impressed by its effective contrast and wide viewing angle.

The RL70RC color display, sharper than the monochrome display, is impressive. The use of color greatly increases its ease of use and makes text much easier to read. Small targets, especially when distant, are more readily visible with the color display. The use of color seems to somewhat clarify the abstractness of the radar image and allows you to more quickly figure out what’s on the screen.

Bottom Line: Raytheon’s well-made, state-of-the-art R70 radars performed superbly. We recommend them very enthusiastically.

JRC 1500
The 2kW JRC 1500, an upgrade of its JRC 1000 1.5 kW model, was the least expensive radar tested. It includes an 18" radome and a 6" LCD screen designed to fit into a snap-in pedestal mount, ideal for small open boats. Disconnecting the 1500’s power and scanner cables and removing it from the mount can easily be accomplished in less than one minute. This was the only model with this feature. Five push-buttons and a joystick operate the unit. We appreciate JRC’s incorporation of its “J-Dial” for selecting and adjusting range, rain clutter, sea state and gain. Most provide automatic controls for these functions. Sometimes, however, you can get a better picture through manual adjustment.

JRC’s scanner utilizes a patch antenna and weighs 11 lbs. The manual should include more background information. Both the scanner and display are well-made and performed well during testing. Display contrast was good, but glare was a bit on the high side. Target definition was good, with consistent targets showing at 7.5 miles away. Our only complaint is that the 1500’s display is a bit small.

Bottom Line: The JRC 1500 is a very good entry-level radar, a perfect choice for small-boat owners. With its low price and good performance, it’s our Best Buy.

Si-Tex T175 & T185
The Si-Tex T175 and T185 both have a 7" CRT display. The T175 includes an 11", 2 kW, 24-mile enclosed radome antenna (the smallest tested), while the T185 is supplied with an 18", 4 kW, 32-mile version.

Controls consist of 12 push-buttons, two knobs and a track ball. Unlike the others tested, the T175 & T185 are not waterproof. Additionally, as expected because of its CRT, the display is considerably deeper (10") than relatively thin LCD displays. A plastic viewing hood helps the user see the screen in bright sunlight.

Both scanners use a slotted waveguide antenna. On the larger T185 unit, one of the endcaps on the antenna had become detached and the other end cap could easily be removed by hand. Apparently the adhesive used to hold them in place failed on this particular unit. The T175’s antenna is of a similar design but did not have this problem.

Si-Tex’s manual is fair. Explanatory text is missing from its many drawings.

Both Si-Tex models performed poorly. The T175’s antenna is simply too small to produce a sufficiently detailed radar image. Both models exhibited mediocre target resolution. Some nearby buoys faded on and off the radar image. A spurious ring echo was very noticeable on lower range scales. Si-Tex’s video processing seemed crude by current standards. Numerous phantom echoes appeared at random during our testing.

Bottom Line: The two Si-Tex CRT models lacked many of the improvements noted in the newer LCD models tested. They did not perform as well as the others.

Furuno 1622
The entry-level Furuno 1622 LCD radar is supplied with a 6" LCD and a 15", 2.2 kW, 16-mile radome scanner. Both units are well-designed and well-built. The 1622’s controls, located to the right of its display, include 15 push-buttons and a four-way “TrackDisk” control pad. Furuno supplies separate manual and installation booklets, both well-written and well-illustrated. The installation portion includes some basic adjustment procedures that might be needed.

Unlike other models featuring patch antennas, which have several rows of patches in their arrays, the 1622 has only one row of patches, supplemented by aluminum focusing reflectors. This approach undoubtedly lowers Furuno’s manufacturing cost but also adversely effects the radar's performance, in our opinion.

The Furuno 1622 can be awkward to operate. Adjustments are not readily evident without reference to the manual. We had difficulty properly adjusting its rain clutter level.

During testing, the Furuno 1622 performed poorly. Target resolution was the worst of all models.

Bottom Line: The Furuno 1622 was disappointing. It’s also more expensive than the JRC 1500, which clearly outperformed it.

Furuno 851
The Furuno 851 serves as the company’s mid- to upper-level LCD pleasure boat radar. Its 8" display is slightly larger and much more visible than the Furuno 1622. It is supplied with a 4 kW, 48-mile, 42" open array scanner. The 861 model comes with a 6 kW scanner.

Furuno’s well-made display and scanner are controlled by 15 push-buttons, a two-way range selector rocker and a four-way button pad. The 851 is somewhat easier to operate than Furuno’s entry-level model and (unlike the 1622) includes a provision for tuning its receiver. Furuno’s manual is easy to understand.

The 851 performed adequately. Target resolution was good, with consistent targets seen at 8 miles. The amount of visible clutter was somewhat higher than expected and not easily adjusted off the radar image. Display brightness was very good, and we had no problems seeing it in bright sunlight.

Bottom Line: The Furuno 851 is a high-quality machine and performed well—but not as well as the JRC or Raytheon units.

Simrad/Anritsu RA40
This is Simrad’s second offering in the LCD radar marketplace. It is supplied with a 10" display and 16", 2 kW, 24-mile range scanner that utilizes an egg-shaped antenna. The RA40 is operated using 18 push-buttons, a four-way cursor key and a spinning control knob. Seven of its push-buttons are operated as soft keys with their current function shown along the display’s right edge. Despite the space taken up by these functions, the Simrad still has the largest display. We found the RA40 easy to operate, although the sun produced a good amount of glare on its display.

The manual’s text is fine, but we thought the illustrations were only fair.

This model performed as expected, with good target resolution. However, targets often appeared larger and not as defined as with other models. This is consistent with Simrad’s choice of a parabolic antenna design. Parabolic radar antennas do not perform as well as patch antennas because they have inferior sidelobe and interference rejection.

Bottom Line: The Simrad/Anritsu RA40 is an improvement over the older Simrad RA40 we tested earlier but did not perform as well as some of the other less-expensive models.

Conclusion
We strongly favor Raytheon’s mix-and-match approach to its higher-end models, which makes it easier to choose the right model for your boat. Raytheon’s radars also performed extremely well.

Furuno’s current models did not perform as well as expected

Si-Tex models are outdated, in our opinion.

Simrad has shown improvement, but its unit seems to lag behind in both design and performance.

The real surprise is the JRC 1500. For about $1,000, this model performed exceptionally well and is our recommended entry-level radar. The Raytheon SL72 performed slightly better than the JRC 1500 but costs $500 more.

Raytheon’s RL70 series is unquestionably our top choice based on its performance and comprehensive features.

 

Contacts- Furuno, 4400 NW Pacific Rim Blvd., Camas WA 98607; 360/834-9300, www.furuno.com. JRC (Japan Radio Corp.), 1011 SW Klickitat Way, Bldg. B, Ste. 100, Seattle, WA 98134; 206/654-5644. Raytheon, 22 Cotton Road, Nashua, NH 03063; 603/881-5200, www.raymarine.com. Simrad, 19210 33rd Ave., W., Lynnwood, WA 98036; 425/778-8821, www.simrad.com. Si-Tex, 11001 Roosevelt Blvd., #800, St. Petersburg, FL 33716; 727/576-5995.

Comments (0)

Be the first to comment on this post using the section below.

New to Practical Sailor?
Register for Free!

Already Registered?
Log In