High-Performance Fish Finders

When it comes to fish-finding sonar, there is game-changing technology on the market. It's called CHIRP (compressed high-intensity radar pulse), and it's a very different animal than the traditional fish finder.

Is fish finding even important to cruising skippers? Maybe it's not critical, but if marine electronics is of any interest to you at all, it can't hurt to be aware of the current technology. Especially when that technology promises to change the language and the expectations mariners have of their sonar. There are reasons to pay attention even if you only fish part of the time. It's not only hard-core anglers who benefit from a high-performance fish finder.

Easy Does It
CHIRP provides a level of accuracy and detail that is unprecedented in civilian sonar. This means even if you only use a fish finder a few times a year ? especially if you only use it a few times a year ? when you do turn the sounder on, it's going to be a whole lot easier to use and interpret.

We've all watched people who use a fish finder every day read a screen and glean information that borders on telepathic. That's because they are accustomed to decoding the lines and colors that print on the screen. But what if something made those lines and colors a lot less cryptic, requiring a lot less day-to-day experience to be useful? If that were the case, many of us with less experience could get more usable information. That's what CHIRP does.

Fishing aside, sonar is handy for reading the bottom for any number of reasons. If you are a diver, it's nice to have an accurate picture of the bottom, along with details of any reefs and wrecks, before you drop overboard.

I even spoke with a dedicated cruising sailor who says he likes to see what the bottom is doing even if it has no effect on his passage. This guy is a nut for situational awareness, and knowing he is crossing a shoaling bottom ? even when it is shoaling from 300 to 60 feet over the course of five miles ? enriches his cruising. He just wants to know what's down there.

Everything in Modulation
CHIRP technology is quite simply a modulated frequency pulse broadcast by the transducer. Instead of firing a steady 50 or 200 kHz signal beneath the boat, CHIRP technology modulates the pulse so the signal broadcast by the transducer sweeps across a range frequencies, say 28 to 60 kHz or 130 to 210 kHz or 42 to 65 kHz.

The advantage of this system is the ability to differentiate between closely spaced targets. With a single-frequency pulse, the return signal from two closely spaced targets ? like a fish holding next to a rock ? may be interpreted as a single target. With CHIRP, the ever-changing frequency will strike the individual targets at slightly different times. As a result, the return echoes will be of slightly different frequencies. This allows for better separation of the targets and yields extreme resolution and detail.

All in the 'Ducer
The heart of the technology lies in the transducer. Airmar, the dominant transducer manufacturer in the United States, developed transducers a couple of years ago that were capable of generating a modulated pulse. At that time, Steve Boucher, president of Airmar, predicted a change was coming in the sonar business. "Nobody has the sonar to handle these transducers," he said at the time. "We know some things are under development and may be out next year. By the end of 2010, the whole market will have changed."

Here and Now
Simrad demoed its CHIRP-enabled sonar, the BSM-2 ($2,495), in February at the Miami International Boat Show. It delivers up to five times greater target resolution than conventional sounders and, Simrad claims, offers bottom readings beyond 10,000 feet. Not that anyone really needs resolution that deep, but that claim makes great promises for performance at lesser depths.

"Shallow water resolution is out of this world," says Simrad's Dennis Hogan. "The advanced digital signal processing clears up a lot of the return so you get more real information instead of artifacts on the screen."

Garmin had its first CHIRP units on the water in mid-January and also demonstrated its new sounder at the Miami show. Its flagship product is the black-box sonar GSD 26 ($2,000). Garmin's name for its version of CHIRP is Spread- Spectrum technology.

"The GSD 26 will be manually tunable from 25 to 210 kHz, creating a modulated pulse across the whole range of frequencies for superb resolution and target return," says Garmin's Greg DeVries. "With traditional fish-finding sonar, when you see the bottom in deep water, you often don't see what is in the water column above it. With a modulated pulse, you get both: a good view of the bottom and an accurate look at everything between."

GeoNav says it intends to release a CHIRP sonar later this year. Furuno already has the technology in its commercial equipment but has yet to make it available in a recreational product. Raymarine, without offering any detail, states emphatically: "Raymarine will be releasing some very innovative sonar products that incorporate CHIRP technology before the end of the year."

So CHIRP sonar is here to stay, but conversions won't be a simple matter on most boats. New transducers will have to be installed, which means a haul-out for larger boats that spend their lives in the water. CHIRP sonar is also a little pricey ? it will run you between $4,000 and $5,000 just for the head and the transducer, before installation.

If you have any real interest in what's resting on the bottom or swimming beneath your boat, CHIRP will provide you a much clearer picture of what lies below.

SPOT on Phones
SPOT Connect turns smartphones into one-way satellite communicators capable of sending messages that include a GPS position to personal contacts and social networks from remote areas beyond cellular coverage.

To use it, download the SPOT Connect app, which synchronizes wirelessly via Bluetooth with smartphone operating systems such as Android. SPOT message features are then initiated using the SPOT Connect app on the phone through the satellite transceiver. ($170 plus a required annual subscription service starting at $100 per year.) findmespot.com