Moog Crossbow NAV440 Series - Manual (Page 36)

Page 36
NAV440 User Manual
7430‐0131‐01 Rev. F
J2—GPS Antenna Connector
The GPS receiver needs to receive signals from as many satellites as possible. A GPS receiver does not work properly
in narrow streets and underground parking lots or if objects or human beings cover the antenna. Poor visibility may
result in position drift or a prolonged Time‐To‐First‐Fix (TTFF). A good sky visibility is therefore a prerequisite.
Even the best receiver cannot compensate for signal loss due to a poor antenna, in‐band jamming or a poor RF cable.
The unit ships with an external active antenna that must be connected properly to SMA jack on the unit case. Placing
the antenna on a 16 square inch or larger ground plane is highly recommended.
I/O Port Interface
Port A: User (computer), RS232 serial data interface
The serial interface is standard RS‐232, 9600, 19200, 38400, or 57600 baud, 8 data bits, 1 start bit, 1 stop bit, no
parity, and no flow control and will output at a user configurable output rate. These settings allow interaction via a
standard PC serial port.
Port B: GPS Interface, RS232 serial interface
Port B can be applied to internal or external GPS interface.
Internal GPS
The internal GPS receiver of the NAV440 outputs data in NMEA‐0183 format as defined by the National Marine
Electronics Association (NMEA), Standard For Interfacing Marine Electronic Devices, Version 2.20, January 1, 1997.
no flow control. The packets are sent at 9600 Baud, 8 data bits, 1 start bit, 1 stop bit, no parity bit, and
GPS messages are delivered in NMEA message format. For more information, refer to Appendix A. NMEA Message
Format on page 103.
External GPS
External GPS is supported via VG440 and AHRS440 functions. For the 440 Series unit to interface with an external
GPS receiver, the GPS receiver must be configured to output data in a format compatible with the 440 Series unit.
ormats are described in the next section: F External GPS Aiding (Port B, VG440 and AHRS440) on page 37.
Cable Field Requirements
The 440 Series is shipped with an EMI filter attached to the DB‐15 Connector. This connector must remain in place
to ensure proper shielding from EMI interference.
CAUTION: The cable sent with the unit is intended to provide the user with the ability to test the unit right out of the
box, and will not provide adequate shielding for all environments. Case ground must be used to provide full
EMI protection, and ensure the cable shield is grounded on only one end of the cable.
Case Grounding
The case is electrically connected to Pin 5 of the DB‐15 connector. The Pin 5 should be electrically connected to the
user’s cable shield, especially if the chassis does not make good ground contact. The case should be bolted to a good
conducting surface that is grounded.