SUPPORT > SYSTEM SETUP > CHOOSING A MOUNTING LOCATION

Before you can start using the Starfish 450H Sonar system in the field, you will need to mount the sonar transducer to the hull of you boat. Correct mounting of the sonar is essential in order to achieve the best image results, and as each hull is different you should consider the following points when deciding on a suitable mounting location...

Avoid Creating Acoustic Shadows

The hull mounted StarFish transducer has transmitter and receiver elements located on either side of the moulding that are angled 30° down from the horizontal, and acoustically transmit sound in a "fan beam" 2° wide by 100° vertically (with most of the acoustic energy being confined to the centre of the beam).

The arrangement allows the StarFish to perform well in shallow water at long ranges, and see almost directly below it, but incorrect placement on the hull could cause "acoustic shadows" or "reflections" to be produced from the hull, keel or rudder.

In this position, mounted directly on the hull, the keel is casting a shadow on the starboard channel.	In this position, mounted on the keel, no other parts of the hull are obstructing the acoustic beams.

Acoustic shadows will create blind spots in the sonar's field of vision and may reduce its maximum working range. Reflections from the hull may create a 'ghost' or mirror image of the opposite channel on the sonar display.

Reduce Vulnerability To Grounding

When mounting the sonar on your vessel, make sure there is always a point on the hull that is lower than the transducers location. This will reduce the risk of damage to the transducer should you run aground or collide with any submerged obstacle.

In this position, the transducer is vulnerable to submerged hazards.	Above, the keel at the centre of the boat is lower than at the stern, and offers protection to the transducer.

Position In Relation To The Vessels Propeller

Ideally the StarFish transducer should be mounted to the vessels hull in front of the vessels propeller, as this introduces small air-bubbles into the water which in-turn act as reflectors of sound and degrade the range and quality of the sonar imagery.

If using an outboard motor to propel and steer your boat, ensure that the propeller does not touch the transducer when the steering is at its extremities.

Try and keep a minimum distance of 400mm between the transducer and propeller to minimise mechanical interference (noise).

If it is not possible to mount the transducer in front of the propeller, efforts should instead be made to mount the transducer lower than it, such that its turbulence does not obstruct the acoustic beams.

Avoid Cavitation & Turbulence

When mounting the transducer onto the hull of your boat, it is important that a location is chosen that under normal conditions is known to be free from turbulence and aeration. You should also ensure the transducer is angled such that cavitation and turbulence is minimised on the transmitter and receiver surfaces as this may distort or degrade the sonar imagery. The figures below illustrate this principle...

Transducer is angled up.	Transducer is level.	Transducer is angled slightly down.

Avoid mounting the transducer behind features on the hull of your vessel (such as rivets, strakes or steps) that may introduce cavitation or turbulence into the water.