VEMCO - VR2W Manual
41
7.2
VR2W related questions
7.2.1
How much detection range can I expect from my tags and receivers?
Detection range depends on so many factors that it is difficult to estimate without knowledge of the
environment and prior experience with telemetry. Range depends on transmission power, signal absorption,
line of sight, reflection/refraction, multipath and environmental noise (man-made & natural), and the
receiving quality of the receiver/hydrophone. Typically areas that have clear water, sand or silt flat bottoms
and low current exhibit the greatest ranges. Conversely, areas with turbid water, complex rocky bottom
topography and high current exhibit low ranges. In all cases, extreme weather events and periods of high
wind (waves) may significantly reduce range.
In most cases greater transmission power output (dB) results in greater range. For example, in good
conditions a V7-VR2W range test could yield a range of 300-400 m and a V16-VR2W test could yield ranges
of 800-1200 m. There are some exceptions where high power and a reflective and low noise environment
may cause detection breakdowns.
Please try our range calculator at
www.vemco.com/customer-service/?cs-tutorials
, but only use the results as
a guide. One should always perform range testing to determine appropriate receiver spacing. For the
enthusiast who wants to learn more about sound propagation try the widely accepted reference on underwater
sound by Urick (1983). (Urick, Robert J. Principles of Underwater Sound, 3rd Edition. New York. McGraw-
Hill, 1983.).
7.2.2
How long will my VR2W battery last?
The VR2W-69kHz receiver will typically last 15 months on a single Tadiran lithium battery (model TL-
5930/F). The VR2W-180kHz receiver will last 8 months on a single Tadiran lithium battery.
TIP: Write the installation date on the battery so you know how long the battery has been in use.
7.2.3
Does receiver orientation matter?
Generally, in most cases we recommend that a VR2W should be orientated with the hydrophone looking
upwards. This is typically because receivers are commonly moored closer to the seafloor than the surface. In
some situations it may be beneficial to mount the receiver with the hydrophone pointing towards the sea floor.
If a receiver is mounted near the surface or a considerable distance from the sea floor and if the researcher is
monitoring benthic creatures a bottom looking receiver may perform better because your tagged animals will
not be in a shadow zone (under the receiver). If receiver orientation is a concern we recommend that you
perform range tests using both orientations.
7.2.4
At low tide my VR2W receiver will be exposed to direct sunlight,
does this matter?
The VR2W receiver has a recommended operating temperature of between -5 to 40°C. If there is a chance
that your receiver will exceed either of these temperatures please consider another location for the receiver.
Keep in mind that direct sunlight on the black case can cause the receiver’s internal temperature to be much
higher than the ambient temperature.
