Vemco VR100 - In the Field Operations; Manual Tracking Procedures; Hydrophone Deployment Tips

VEMCO – VR100 Manual 28 May 2018 28
4 In the Field
There are two major tasks that are usually performed in the field. One of those tasks is manually tracking a
tag using a directional hydrophone. The other popular task is using the VR100 as a deck-box to communicate
with a VEMCO receiver capable of acoustic communication.
4.1 Manual Tracking
Manually tracking a tag in the field refers to using a directional hydrophone, such as the VH110, to follow the
direction in which the tag signal is strongest. Manual tracking can follow a continuous tag or a coded tag,
although continuous tags are easier to follow because they don’t have long delays between pings as coded
tags do.
4.1.1 Hydrophone Deployment Facts/Tips
Hydrophone Type
Deployment Tip
Omni-directional
(VH165, VH180, VHTx)
Attach an omni-directional hydrophone to a weighted rope to counteract
buoyancy and to put the hydrophone to the desired depth. Do not put
strain on hydrophone cable! The amount of weight needed depends on
the flow rate in the area. Transponding hydrophones are weighted but
may need additional weight in high-flow areas.
Both
For better results, turn off the boat motor and the depth sounder to reduce
acoustic interference when using the VR100.
Directional
(VH110, VH180-D)
The attachment hole on a directional hydrophone is 11/16” diameter. The
figure below shows one method used to mount the hydrophone to a pole.
Directional
(VH110, VH180-D)
Mark the top of the pole to correspond with the location of the element as
the element will be submerged while tracking. The direction the element
is facing when the strongest signal is detected is the direction of the tag.
Directional
(VH110, VH180-D)
If the animal being tracked is operating in deeper water, then adjust the
angle of the directional hydrophone so it’s pointing downward as you get
closer to the tag. If you don’t adjust the angle, you might miss the animal
because the hydrophone is looking at the surface of the water instead of
into its depth.
The VR100 can be used while it is plugged in to an external power
source, but this does introduce additional noise into the receiver and is
slightly less effective than using the VR100 with battery power.