Vector Sensor Reference Manual 36
2.3 Vector Antenna Array Placement
When considering various locations to mount or place the Vector Antenna Array unit, consider
the following recommendations closely.
• The primary GPS engine inside the Vector Sensor computes a position based upon measurements from
each satellite to the internal GPS antenna element. Mount the Antenna Array in the location for which
you desire a position.
• When choosing a location to mount the antenna, please ensure that there is an unobstructed
hemisphere of sky available to the Antenna Array. This will ensure that GPS and SBAS satellites are not
masked by obstructions, potentially reducing system performance.
• It’s important to locate any transmitting antennas away from the Antenna Array by at least a few feet.
This will ensure that tracking performance of the Vector Sensor is not compromised, giving you the best
performance possible.
• Make sure that there is sufficient length of the extension cable available to install the Vector Sensor in
the desired location
• Do not locate the antenna where environmental conditions exceed those specified in Section 2.4.
• The Vector Sensor System has a loss budget of approximately 15 dB to accommodate cable losses.
Please ensure that the correct cable material is chosen in order to maintain an overall loss of less than
15 dB based upon the length of cable needed.
2.3.1 MBL-3 Placement and Beacon Reception
When using the Vector Sensor’s internal beacon receiver as the correction source, selecting an
appropriate location for installation of the MBL-3 antenna will influence beacon receiver
performance. The following list provides some general guidelines for deciding upon an MBL-3
beacon antenna location.
• Ensure that the antenna is as far as possible from all other equipment that emits Electromagnetic
Interference (EMI), including DC motors, alternators, solenoids, radios, power cables, display units, and
other electronic devices
• If you are installing the antenna on a vessel (using DGPS beacon corrections), mount the MBL-3 beacon
antenna as high as possible, considering maintenance and accessibility. In addition, ensure that the
antenna is lower than the highest metal object on the vessel.
• If a radar system is present, mount the antenna outside the path of the radar beam
The Vector Sensor’s internal beacon receiver calculates a Signal to Noise Ratio (SNR), measured in
dB (Decibels) that indicates the receiver’s performance. The SNR is height of the signal above the
noise floor. The higher the SNR, the better your beacon receiver is demodulating the signal. The
optimum antenna location will be a position where your average SNR is highest. You should turn
on all accessories that you intend to use during normal operation when locating the best position
for the antenna. The SNR is available in the $CRMSS NMEA message described in Chapter 6.
Note - You do not have to install the MBL-3 beacon antenna in the same location as
the Vector Antenna Array. The best location for the MBL-3 antenna is likely in a
different region of the vessel considering that beacon reception is very susceptible to
man-made sources of noise in the 283.5 to 325 kHz band.
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