Basic instructions for communicating acoustically with
a VR4-UWM while deployed are found in the Field
Communication Quick Guide.
Operating temperature:
-5 °C to 40 °C; Water in which
the VR4-UWM is deployed must not freeze.
Static depth rating: 500 meters (730 psi)
Errors encountered in transmitting data from the VR4-UWM receiver to the surface require data
to be retransmitted. If this occurs try:
z
Moving the slider closer to “Reliable” .
z
Check the
Advanced
box and make adjustments (see next point).
If you are unfamiliar with the settings necessary at a particular location, begin with the settings
shown in the sample shown at right, and make further adjustments as needed. These settings
are a good starting point.
You may need to increase both the
Power up
and
Power down
settings as the boat drifts away
from the VR4-UWM.
Do not increase the power too quickly or too strongly
, as echoes may be
created that will increase communication errors/time required.
Reduce power levels for both up and down communication if the boat is close to the receiver and communication quality is
poor.
Too much power may cause additional noise in the water
and lower the quality of communication.
If you are working in an
acoustically reflective environment
(hard bottom), avoid using high power settings as this can cause
intense reflected signals that could interfere with the direct communication signals.
Use a VR100 receiver set to 20 kHz and an omni-directional hydrophone (place hydrophone in water, below draft of boat) to
listen to the signals being transmitted between VR4-UWM and the Benthos transducer.
If you are outside acoustic range from the VR4-UWM, the commands sent from the VUE software will not be received by the
receiver. Move closer and try to send the command again.
When you change a communication setting, it takes time (two consecutive transmissions) for the VR4-UWM to receive the
command and make the change.
Be patient!
If the surface transponder is close to the VR4-UWM and communication quality is poor, reduce the baud rate to 300-600 baud.
This should reduce the communication errors caused by fewer transmission repetitions.
Status and Range
communications are short messages that are more likely to “get through” during challenging acoustic
conditions than the larger offload communication.
Use these smaller communications to help identify the settings
needed to establish “good” or “very good” communication levels.
If a VR4-UWM is stationed in an area where you expect there will be lots of tagged animals, offload the data on a more frequent
schedule to reduce the amount of time required to offload data at each visit to the site.
Record
the environmental conditions, power and bit rate settings for each VR4-UWM location. This will reduce the
communication setup time for your next visit to this location. For example, if the area has a hard flat bottom that is very
reflective to acoustic signals and requires a lower power setting, then start with the same power setting at your next visit.
Power scale:
0 dB
is the
highest
power (signal strength) and
-21 dB
is the
lowest
power level. Using a high power level when
it is not necessary can increase communication errors by saturating the area with acoustic energy.
Advanced Acoustic Communication Points
www.vemco.com
+1 902-450-1700
DOC-5461-02 (QG)
VR4-UWM Receiver
Quick Reference Guide
