VEMCO - VR2AR / VR2AR-X Manual
15 March 2019
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7.2
VR2AR related questions
7.2.1
How much detection range can I expect?
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/VR2AR range test could yield a range of 300-400 m and a V16/VR2AR 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
. McGraw-Hill, 1983.
New York.).
7.2.2
How long will my VR2AR battery last?
The VR2AR receiver will typically last 14 months on a single D-cell Tadiran lithium battery (model TL-
5930/F). An estimation of the remaining battery life is available when acoustically communicating with the
VR2AR through the VR100-200.
TIP:
Write the installation date on the battery so you know how long the
battery has been in use.
The AA Lithium battery only powers the release motor and should never need to be removed or disconnected
from the VR2AR.
7.2.3
Does receiver orientation matter?
The VR2AR must be orientated with the hydrophone looking upwards for communication with the VR100-
200. Also, receivers are commonly moored closer to the seafloor than the surface to minimize the effect of
surface noise and conditions.
