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Soup up your fishfinder: transducer output makes a big difference.

For the past decade or more industry standard for a recreational fishfinder has been 500 watts of power output shot through a dual frequency transducer. These units were affordable but of limited utility in depths beyond 500 feet or so.


So how do you boost the performance of your fishfinder without spending the thousands of dollars it takes to outfit with Spread Spectrum or CHIRP technology? Simple, upgrade your transducer. Most late model fishfinders and multifunction displays coupled to a black box sounder are capable of using a 1,000-watt transducer.

Changing over to the beefier, more powerful unit will significantly enhance your fishfinder performance both in shallow and deep water. The holdup to switching over has been the size, cost, and availability of mounting options for a 1,000-watt transducer.

Nowadays all mounting options are available including thru-hull, in-hull, and transom. The latter is most important for small boat owners for two reasons, cost and space. Many small boats simply don't have the space to access and mount a large transducer internally, making a transom mount the only viable option. Plus, the cost to mount on the transom is much less than doing an internal or thru-hull mount. For most of us, a transom mount is a money-saving DIY project. Yes, a 1,000-watt transducer still costs several hundred dollars more than a 500-watt unit, but that still makes it less expensive than moving to newer technology while getting a huge performance boost.

Is a 1,000-watt transducer really that much better than a 500-watt unit? Well, let's do a quick review of transducer basics first and then compare a couple of units. First, we must know that a transducer shoots out a sound signal in somewhat the same pattern as a flashlight shoots out light. The pattern starts small and expands as depth increases; the amount of pattern spread is known as beamwidth. The transducer also listens for some of the signal return as it is reflected off fish, structure, and bottom.

Now let's compare the Airmar P66, which is a top performing 600-watt transom mount used by several electronics makers, to the recently released Airmar TM260, a 1,000-watt transom mount unit [otherwise same specifications as the thru-hull 8260 unit in the illustration, left]. Both of these transducers operate at 50 kHz and 200 kHz.

One thousand watts versus 600 doesn't sound like a big difference, but there is much more in play here.

For 200 kHz operation, both units use a single element. However because the TM260 element is larger, it can generate a narrower beam (counterintuitive, but true)--6 degrees versus 11 degrees for the P66, concentrating the ping for better depth penetration. Again, because of its larger element the TM260 is also 13 times more sensitive to the returning signal. This translates into superior echo presentation.

Differences are even more dramatic at 50 kHz. The P66 uses a single element with a beamwidth of 45 degrees while the TM260 uses 7 elements that narrow the beam to 19 degrees and provide 50 times the sensitivity to the returning signal.

The upgrade to a 1,000-watt transducer gives a massive increase in results.

More Transducer Options

* The latest sonar technology, CHIRP or Spread Spectrum, uses special transducers capable of a long duration pulse of energy over a range of frequencies. Coupled to the appropriate network sounder, these units are capable of painting bottom in depths up to 10,000 feet. They also offer finer target resolution to more easily distinguish bait, fish, structure and bottom. Black box sounders available from Garmin, Simrad and Raymarine are capable of using the latest generation Airmar CHIRP transducers.


* Side-looking and Down Imaging fishfinders use higher frequencies than traditional shoot down transducers to significantly increase detail and target definition. Images sometimes appear to be near photo quality. The tradeoff is limited range, normally about 300 feet. Humminbird and Lowrance are the two big players in this arena.
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Title Annotation:ELECTRONICS
Author:Herum, Al
Publication:Florida Sportsman
Date:Sep 1, 2012
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