Installation manual

Trawl hydrophone installation
101
851-165187 / Rev.A
Dual hydrophone installation
The PI54 system trawl hydrophones receive horizontally and
vertically within 50 and 30 degree sectors respectively. Signals
transmitted from sensors attached to towed gear must be able to
be received on both sides of a vessel’s keel under normal
operating conditions. When a single hydrophone is installed, it
must therefore be mounted no more than five centimetres higher
than the lowest point on the keel to ensure proper coverage on
both sides of the vessel. Hydrophones that protrude from the
hull in this manner are often subject to damage when for
example dry-docking and special precautions should be taken to
safeguard their protection.
Simrad recommends the use of two hydrophones t o ensure the
necessary horizontal and vertical coverage for proper system
operation. This also allow the respective coverage areas of t he
hydrophones located on opposite sides of the hull to overlap
each other providing the system with the ability to be optimized
for a specific type and method of fishing. The use of dual
hydrophones have the following benefits:
• They provide a larger area of coverage with the ability to
receive signals even when the trawl is being substantially set.
• The hydrophone on the lee side of the vessel can provide
better signals in heavy weather.
• Hydrophone placement can be optimized without having to
take into account signal clearance over the vessel’s keel.
• Each hydrophone can be placed at a different distance from
the bow if there is any doubt about which configuration is
best.
• The hyprophones can be tilted individually to optimise
performance when trawling in deep or shallow water and to
provide wider overall coverage.