There are a number of factors that a potential purchaser will want to consider when deciding which fishfinder will suit him best. Generally speaking, the bigger the screen the better, when it comes to viewing detail of the water volume beneath your transducer. However in practise the decision tends to be a trade-off between available budget and a number of additional factors:
Space
– the first consideration will be where the fishfinder is to be mounted. Most fishfinders can be either flush mounted into a dashboard or bulkhead, or mounted on a bracket. The latter option can allow the user to have a larger unit in a small boat where the dash does not have the necessary room, but for those who wish to have the security and convenience of a flush-mounted fishfinder then choosing the right casing size for the position is the first priority. Most quoted screen sizes refer to the diagonal distance across the screen.
Screen quality
– the display resolution, generally given in pixels, indicates the extent to which a screen can display fine detail. The higher the total number (width x height) the better. With other terminology an SVGA monitor is generally superior to a VGA monitor in terms of viewing quality, and a TFT screen is a widely used type of LCD flat-screen monitor. Sunlight viewability is another factor that should be considered on units that will be used in conditions of direct sunlight.
Power
– the power of a fishfinder is measured in watts, and while the higher the number the greater the depth penetration of the sonar signal, it is worth bearing in mind that there are two ways of measuring the signal strength; peak to peak and RMS. A 500W RMS (4000W peak to peak) fishfinder should have plenty of power for most coastal applications. The latest broadband fishfinders use a lot less power than their conventional alternatives, while at the same time giving far more detailed returns.
Dual vs. single frequency
– a dual frequency fishfinder emits both a high frequency (200kHz) beam that gives a high quality but narrow view of what lies below, and a lower frequency beam (generally 50k or 83Hz) that gives a broader but lower quality view to enable you to see fish further away from the boat. A dual frequency unit will general be a little more expensive.
Transducers
– the transducer sends out the actual signal into the water. If you have a dual frequency sounder then make sure you have a dual-frequency transducer to match.
There are three types of transducer, with regards to how they are mounted. The through-hull type requires a hole in the hull with the business end of the transducer fitted flush with the exterior, and sends its signal direct out into the water. The in-hull type is fitted flush against the inside of the hull, and its signal has to travel through the hull before entering the water. The transom mount version is generally used on smaller day boats and is entirely external, being mounted on an exterior bracket on the outside of the transom below the waterline. Each type has its merits, but always seek expert advice before drilling holes in your hull, particularly below the waterline.
Features
- modern fishfinders come with a wide variety of features that aim to help the angler to distinguish fish from underwater obstacles and thermal anomalies. Buyers should consider which may be applicable to the type of waters in which they fish.
Combi units
– fishfinders and chartplotters are widely available as single ‘combi’ units. These can be great space as well as money savers, and are ideal for smaller boats. If both applications are run together they will of course have to share the same screen, so purchasers may wish to opt for a larger screen than they would otherwise have chosen.
Waterproofing
– all good models should be waterproof to at least IPX7 (immersion in 1 metre of water for at least 30 minutes). This is vital for units mounted in a cockpit or any other exposed position.
Touch screen or conventional buttons
– this is really a matter of personal preference. Touch screen controls do reinforce the structural integrity of a unit, yet many people still prefer the combination of buttons, scroll wheels and on-screen menus to achieve the same multi-option effect. On the latter, back-lit buttons will aid operation of the unit after dark.
Connectivity
– those who may wish to integrate their fishfinder into a broader navigation network should select a unit that is NMEA2000 compatible. Many larger units are these days, enabling them to function as multifunction displays, but many simpler models are available that are standalone instruments.
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