Texas Boating

True Green
January 1, 2014
Paul’s Tips
January 1, 2014

Looking Up, Down, and All Around


Side-scanning sonar has now been around for several years, down-scanning units have come to incorporate CHIRP technology, and for 2014 even more new ways to find those fish have been released on the market. Is this stuff worth buying, or are we just being bombarded by more marketing ploys designed to separate you and your hard-earned dollar?

If this stuff is worthwhile, which one of these technologies should you invest in? There’s a lot of confusion surrounding scanners vs. sonar, so let’s cut through the BS and figure out where and if it’s money well spent. Every “Truth” you’ll read below is IMHO, and some manufacturers and some anglers are bound to disagree—but this is what I’ve discovered, through hands-on experience.


Side-Scanners: Tech

Side-scanning (called Side Imaging or Structure Scan depending on which manufacturer you’re looking at) uses very high frequency fan-shaped beams to look out to either side of your boat. While traditional finders commonly use frequencies in the low 200-kHz range and in the 50-kHz range (for very deep water), these side-finding beams are in the 455- and 800-kHz range. As a result they have much higher detail levels, but range is limited to 150 feet or so and can be notably less in unfavorable conditions.


Side-Scanners: Truth

Yes, they do work and yes, they are worth the investment. But don’t get giddy over seeing sideways just yet. Although they are excellent for finding structure, the 455- and 800-kHz beams don’t seem to show fish as well as an old-fashioned 210-kHz beam does. They often appear as specks or blips instead of hard arches, and it can be much harder to differentiate fish from clutter. That said, in many fishing situations, finding the structure is really what you need to do—the fish will be there.

One other item to bear in mind is that the screen size of your unit has a huge bearing on just how well side-scanning works for you. On very large screens (10 inches or bigger) it’s much easier to pick out the fish and judge what type of structure you see. Often you’ll want to split the screen between a traditional down-looker and side-scanning, or between your chartplotter and side-scanning, and in these cases having a large screen becomes that much more important. When you buy one of these, push the envelope to get as large a screen as you can afford—you won’t regret it.


Side-Scanners: News

Garmin has just introduced their own version of side-scanning, called SideVu. It will be available on stand-alone units, as well as in a black-box form (the GVC 10). It will work with echoMAP 70, 700, 800, and 1000 series units, though a (free) software update may be necessary. Look for them to start showing up in stores this winter or spring.


Down-Scanners: Tech

Down-scan “imagers” use the same type of high-frequency beams as side-scanners. Again, you get much higher detail at the cost of range. One of the newer models, the Dragonfly from Raymarine, incorporates CHIRP technology to get a range boost. CHIRP sends out a blast of sonar waves spread through a band of frequencies instead of a single frequency. The Dragonfly has a more limited frequency spread than full-blown (and much more expensive) CHIRP units, so call it CHIRP-light.


Down-Scanners: Truth

Detail levels are magnificent; you can see everything from sprigs of weed to individual tree-limbs, and you’ll know exactly what you’re looking at. True, there’s a loss of range, but realistically most of us are usually fishing in depths well under 100 feet—so the “cost” of limiting range to 150 feet is irrelevant for many anglers. Those who do need additional depth range can consider CHIRP-light. When it comes to this type of down-scanning, depth range increases significantly. Raymarine says that in ideal conditions it can see all the way down to 600 feet, though when I’ve had the Dragonfly offshore, range was closer to 400 feet.

As mentioned earlier, fish often don’t show up as well when seen with the high-frequency beams. This isn’t as big a problem as it might be since most down-scanners also shoot out a traditional beam frequency, and you can use a split screen or flip back and forth between the two, as necessary. I’d beware, however, of very inexpensive stand-alone imagers that don’t include a traditional down-looker and/or those with very small screens that can’t realistically be split. CHIRP-light eliminates this problem, since the frequency spread shows fish quite well.


Down-Scanners: News

Very soon, the Dragonfly will have some company in the world of CHIRP down-scanning fishfinders. If you favor a competitor’s units but you want this type of down-scanner it would be smart to sit tight for a few months. At the time of this writing they haven’t made an announcement yet, and manufacturers get very upset when this sort of news leaks out too early, so I’m not going to name names. But stay tuned.


All-Around Scanners: Tech

Again utilizing those very high frequencies, a couple of manufacturers have looked for ways to let you see all around the boat. But they’ve taken two different paths, to do so. In the case of Humminbird, 360 Imaging seeks to paint a picture 360-degrees around. You get a circular view on-screen, with your boat in the middle, and you can also isolate a “sweep area”. Lowrance, on the other hand, developed SpotlightScan Sonar, which was just released a few months ago. It’s pretty much what it sounds like from the name. With a trolling-motor-mounted transducer, you get lateral viewing ability, but with a unidirectional, spotlight-like beam.


All-Around Scanners: Truth

These systems more or less take side-scanning technology and apply it a bit differently. So the results are similar, just with a different view. That said, one thing should be noted with the 360. Instead of mounting a transducer on the transom or through the hull, this system requires a “transom pod” that raises and lowers the transducer. When deployed, it does stick down below the boat and creates an obstruction. As far as SpotlightScan goes, the unit’s so new I haven’t been able to give it a hands-on test just yet. I wonder about boat steering vs. scanning conflicts since you point the motor to point the transducer, but again, stay tuned.


All-Around Scanners: News

At the moment, the real news in this category of scanners is the actual release of the SpotlightScan. If history is any indication, other competitors will follow with versions of their own in the next year or two.

So, which one of these technologies should you spend your hard-earned money on? That depends on the type of fishing you do, and what type of system you already have at the helm. Now that you’re familiar with the nuts and bolts of each, the truths about them, what’s new and what’s coming soon, you’ll be able to make the right decision.



Contact Lenny Rudow at
[email protected]

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