© 2020 Radiodetection Ltd
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Small stethoscope antenna
The small stethoscope antenna has a 25mm (2”)
concave head at the end of a 2m (6½ ft) lead. The small
stethoscope can be screwed into an extension rod or
used at the end of several extension rods joined together
for identifying inaccessible small cables.
Miniature hi-gain stethoscope
The miniature stethoscope is similar to the small
stethoscope but has no handle or facility for extension
rods.
The miniature stethoscope can also be used as a
miniature antenna for locations where the bulk of the
locator makes it inconvenient for use, such as locating
pipes or cables in walls.
CD stethoscope
In restricted areas, the CD stethoscope can be used to
obtain current direction but not current measurement.
12.8 Submersible antenna
When to use a submersible 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 locator
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
(300ft).
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
locator is used in a surface vessel. It is crucial to have
effective communication between the operator with the
locator 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 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 the
accessory socket of the locator. The locator is used
onboard a boat, which should by positioned directly over
the line. The transmitting signal should be applied by
Direct Connection with the strongest possible signal and
at the frequency that the submersible antenna is
calibrated to. Make a ground connection about 50m
(160ft) 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 a submersible antenna:
The user in the boat should be a specialist or have
considerable experience using a locator so that they can
give concise instructions to the diver.
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 blindfolded receiving directions from the user with
the locator out of sight of the line and the diver.
Because of rapid signal loss and a combination of large
surface area and very conductive soil there may be
problems applying a suitable signal for tracing a large
diameter pipe. It may be necessary to use a high power,
low frequency tracing signal.
It is necessary to define a method of recording target line
position and depth before starting work in the boat or on
the seabed.
Figure 12.14: Using a submersible antenna
WARNING! Only properly licensed and experienced
divers should attempt to use the submersible antenna.
12.9 Phone/Tablet mount
When using a mobile device running a compatible
application, such as RD Map for Android, you can use
the Phone or Tablet mount to conveniently hold your
device next to the locator and have immediate visual
feedback on the survey measurement points you are
marking.
