EchoSonde EX.220-B is our dual-frequency echo sounder for working boats. It was designed around trawler requirements and then found a second life on general cargo tonnage, where it is fitted purely as a depth reference rather than as a fish-finding tool. The two uses pull the design in different directions, and the B revision is where we stopped pretending they did not.
Two frequencies, two jobs
The lower frequency gives depth in water that the higher one cannot reach; the higher gives discrimination that the lower one cannot resolve. Running both simultaneously rather than switching between them means the display can show a hard bottom return and the softer layer above it at the same time. For a skipper reading ground, that distinction is the whole point. For a mate on a cargo ship wanting to know how much water is under the keel on the approach to Elefsina, only the hard return matters, and the unit can be configured to suppress the rest.
Keel offset
Every installation needs the transducer’s position relative to the keel entered before the displayed figure means anything. The EX.220-B accepts a keel offset compensation range of −4.5 m to +12.0 m, which covers everything from a shallow-draught coaster with a hull-mounted transducer to a deep trawler with the sensor in a blister well below the waterline. The offset is stored in the head unit, not the transducer, so replacing a damaged transducer does not silently reset the calibration.
Transducer and fairing
The transducer ships with a moulded fairing matched to the hull deadrise. Getting this wrong is the single most common cause of a sounder that works alongside and goes blind at twelve knots: an unfaired or badly faired transducer sits in its own turbulence and reads nothing but bubbles. We supply the fairing as part of the installation rather than as an accessory, and we will not quote a fit without a hull survey.
Environment
The head unit is sealed for a wheelhouse that leaks, which most working wheelhouses eventually do. Salt, condensation and the occasional direct hit of spray through an open window are all within what the enclosure is rated for. The connectors are the weak point on any sounder, and they are the part we specify most conservatively.
What it does not do
It is not a multibeam and it is not a survey instrument. It measures depth beneath the transducer, along one axis, and reports it honestly. Customers occasionally ask whether it can be used to build a bottom profile for a chartlet; it cannot, and any vendor telling you otherwise about a unit in this class is selling you the display software rather than the sounder.
Maintenance
The transducer face needs cleaning at every dry-docking. Marine growth on the face attenuates the signal long before it stops it altogether, which means the failure mode is a slow loss of range that nobody notices until it is severe.