RD4000 Locating System User Manual
Page 60
Submersible double depth antenna
When to use the submersible double depth antenna
Tracing buried pipes and cables across waterways and estuaries
are frequent and critical locating applications. Less frequent but
equally important is tracing and locating lines between the
mainland and offshore islands. When locating pipes and cables
the receiver sensing antennas should be as close as possible to
the target line so it is not practical to locate lines buried under a
river or seabed from the surface. In most cases, it is necessary
to measure the depth of cover to ensure the line is protected
from dragging anchors or other underwater hazards.
The submersible, double depth antenna is suitable for use under water for tracing pipes or cables. There is a
weight at the bottom of the antenna for stability and the unit has been pressure tested to IP68 to a depth of 100m.
The antenna is supplied with 10m of submersible marine umbilical cable as standard, but lengths of up to 100m
can be supplied. The extra length enables the antenna to be carried by a diver on a riverbed or seabed while
the receiver is used in a surface vessel. It is crucial to have effective communication between the operator with
the receiver and the diver with the antenna.
Alternatively the antenna can be fastened to the end of a non-metallic boom from a barge and lowered to the
riverbed or seabed.
How to use a submersible double depth antenna
.
Apply the transmitter signal to the target line at an access point
on the shore. The submersible antenna line for tracing the line
underwater is plugged into accessory socket of the receiver,
which is on used on board a boat, which is positioned directly
over the line. The transmitting signal should be by direct
connection with the strongest possible signal and a low
frequency (less than 1kHz). Make a ground connection about
100 paces from the transmitter. Test the quality of signal on the
line before locating on the water.
Note: The submersible antenna is calibrated to work at one
frequency.
Tips for using the submersible double depth antenna
The user in the boat should be a specialist or have considerable experience using a receiver so that he or she
can give concise instructions to the diver and avoid needless waste of expensive time in trial and error.
It is prudent for the pair to practice working together on dry land before attempting to locate underwater. Using
the antenna the diver should locate and trace a known line blindfold receiving directions from the user with the
receiver out of sight of the line and the diver.
