Transducer Tech

Is Broadband Best?

FSF Staff October 11, 2010

It is no secret that technology is advancing at breakneck speeds. Although the progression is astounding, your newly purchased marine electronics package may already be outdated. To get the inside scoop on what’s turning heads and if the latest developments really offer a worthy advantage, we turned to the professionals at Electronics Unlimited. For over 35-years they have been selling and installing marine electronics packages for vessels of all shapes and sizes and their dedicated team of certified FCC/NMEA/CMET personnel is ready to provide solutions to fit any and all of your needs.

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FSF: It seems that the whole world is focused on HD. From our TVs, consumer video cameras, radars, AV source units and GPS chartplotters one can only ask…what’s next?
ELECTRONICS UNLIMITED: The newest HD technology incorporates broadband transducers. Airmar is the leader in transducer technology and they’ve developed advanced units that increase bandwidth without decreasing acoustic sensitivity.

FSF: You hear a lot of talk about frequency, bandwidth and beamwidth. What do these terms mean?
ELECTRONICS UNLIMITED: The technical definition of frequency is the number of complete cycles that occur within a period of time, typically one second. Higher frequencies have more cycles per second and a shorter wavelength, which limits range. For example, 200kHz typically only sounds 700 to 1,000-feet. Low frequency, such as 50kHz, can sound deeper but has less resolution. Bandwidth is the transducer’s usable frequency range without compromising sensitivity. This will become more important as fishfinders are able to truly utilize the bandwidth of broadband transducers. At this time, most fishfinders operate at a dedicated frequency—typically 50kHz or 200kHz. Beamwidth is also referred to as cone angle and refers to the angle of coverage under the vessel.

FSF: How does broadband technology increase a fishfinder’s performance?
ELECTRONICS UNLIMITED: All transducers have a Q factor, which describes the amount of ringing after the transmit pulse. Broadband transducers greatly improve fishfinder performance because they have a low Q. The lower the Q, the more bandwidth a transducer can provide, which in turn results in excellent target definition. As broadband technology increases anglers can look forward to detailed seafloor characteristics and accurate fish identification.

FSF: It’s pretty safe to say that anglers who combine the latest broadband transducer technology with advanced fishfinders can look forward to some pretty cool features.
ELECTRONICS UNLIMITED: Absolutely. With the continuous frequency spectrum of a broadband transducer, fishfinders will soon be able to dial in a certain frequency. When it comes to frequency, higher frequencies provide narrower beams and greater image quality in regards to smaller objects. If you’re targeting game fish in 200-feet of water a high frequency will reveal crisp bottom detail. Lower frequencies produce wider beams and penetrate deeper depths.

FSF: What about shallow water performance?
ELECTRONICS UNLIMITED: Putting broadband aside for a moment, Lowrance has a new technology called DownScan Imaging. It utilizes somewhat different technology, but results in much higher resolution. The clarity comes from the way the transducer spans the digital signal. Because the returns are so clear, anglers can easily learn to differentiate and recognize variations in bottom topography. The only downfalls are that the boat must be stable and the performance does have depth limitations. Lowrance’s DownScan Imaging utilizes high frequency transducers with exclusive down-looking and side-looking crystals. Offering transom-mount transducers, there’s also a trolling motor-mount bracket option.

FSF: Let’s talk installation. How important is transducer selection and placement in regards to overall performance and clarity?
ELECTRONICS UNLIMITED: It’s extremely important. The newest broadband transducers are available in thru-hull, in-hull and tilted element variations. Thru-hull transducers are highly effective because the face of the transducer is in direct contact with the water. However, with the increasing popularity of high-speed center consoles, it’s not very practical to place a transducer with a big fairing block on the bottom of one of these hulls. This setup can get in the way if you trailer or store your boat on a lift. To combat this issue, some manufacturers actually glass the transducer flush to the keel. While this method is more expensive, it’s the best way to install a thru-hull transducer and will result in optimum performance. Tilted element transducers are yet another way to avoid a faring block. With in-hull transducers you lose about 15% range shooting through the hull, although this can be overcome with a more powerful transducer. Many of our customers like this approach because there’s nothing to hinder the vessel’s performance.

FSF: How about performance at speed? Is that increased with the frequency of a broadband transducer?
ELECTRONICS UNLIMITED: Being able to read the bottom at speed is a direct result of having clean water flow over the face of the transducer. If you have any air bubbles generated due to the shape of the hull or placement of the transducer you will not get a reliable return. Stepped hulls have a very noisy bottom so they don’t work well at speed. We’ve done installations on sportfishers with transducers in the keel that can read bottom at 40-knots. A transducer that’s placed in a clean environment works very well. Ultimately, you get to a point where you start overcoming the signal by the speed of the boat before you get a chance to process it.

High performance transducers are a key element to your overall success on the water and in the near future recreational units may be able to simultaneously pick up multiple frequencies. For now broadband transducers offer the ultimate in underwater awareness, but with marine electronic manufacturers hardly ever standing still, who knows what’s in store for the future.

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