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16 SPAN-CPT User Manual Rev 8
Chapter 2 SPAN-CPT Installation
2.2.3 Connect the GNSS Antenna
Connect the antenna cable from the connector on the GNSS antenna to the antenna port on the
SPAN-CPT. See Typical SPAN-CPT Set Up on page 14.
For best performance, use a high quality coaxial cable. An appropriate coaxial cable is one that matches
the impedances of the antenna and receiver (50 ohms) and has a line loss that does not exceed 10.0 dB.
If the limit is exceeded, excessive signal degradation may occur and the receiver may not meet
performance specifications.
If your application requires the use of cable longer than 30 m, refer to application note APN-003 RF
Equipment Selection and Installation, available at www.novatel.com/support/manuals/.
2.2.4 Connect Power
The SPAN-CPT receiver requires an input supply voltage of +9 VDC to +18 VDC. The receiver has an
internal power module that does the following:
• filters and regulates the supply voltage
• protects against over voltage, over current, and high temperature conditions
• provides automatic reset circuit protection
Power input pins are located on the multi-purpose I/O connector. Be sure to connect the power with the
correct polarity and ensure the power source is within specifications. See Appendix A, Technical
Specifications on page 48 for the multi-purpose I/O connector pin out and the power input requirements.
There is always a drop in voltage between the power source and the power port due to cable loss.
Improper selection of wire gauge can lead to an unacceptable voltage drop at the SPAN-CPT system. A
paired wire run represents a feed and return line. Therefore, a 2 m wire pair represents a total wire path
of 4 m. For a SPAN-CPT system operating from a 12 V system, a power cable longer than 2.1 m (7 ft.)
should not use a wire diameter smaller than 24 AWG.
If the SPAN-CPT is installed in a vehicle, NovAtel recommends a backup battery be placed between the
receiver and its voltage supply to act as a power buffer. When a vehicle engine is started, power can dip
or cut out to ancillary equipment causing the receiver and IMU to lose lock and calibration settings.
The SPAN-CPT can supply power for the antenna Low Noise Amplifier (LNA) through the
antenna port center conductor. The SPAN-CPT provides +5 VDC ±5% at a maximum of 100
mA.
NovAtel offers several coaxial cables to meet your GNSS antenna interconnection
requirements, including 5, 15 and 30 m antenna cable with TNC connectors on both ends
(NovAtel part numbers GPS-C006, GPS-C016 and GPS-C032).
The power supply used to power the SPAN-CPT must be monotonic during power on to
ensure internal logic blocks are initialized appropriately and proceed to valid operating
states. If the power supply is not monotonic during power on, the accelerometer status in
the IMU status may show a failure and the accelerometer measurements in the RAWIMUS
log will be zero (see the RAWIMUS log description in the SPAN on OEM6 Family Firmware
Reference Manual (OM-20000144)). Power cycling with a monotonic power up clears this
error state.
The SPAN-CPT contains a breaker which can be tripped if using an incorrect power supply.
Manually power cycle the SPAN-CPT to reset the breaker and reconnect to a properly
supported power supply.