RC3000 Antenna Controller Appendix HGPS Hemisphere GPS Compass
HGPS-3
2.0 INSTALLATION
This section details specific installation procedures applicable only to the HGPS compass option.
Proceed with all other installation steps as described in the baseline RC3000 manual and any other
applicable appendices.
The following installation steps described in the baseline manual are superceded by those described in
this appendix:
GPS mounting (2.1.2)
Compass mounting 2.1.3
Navigation sensor wiring (2.2.6)
Navigation sensor communication (2.3.8)
Compass calibration (2.4.1)
2.1.2 GPS Receiver Mounting
The HGPS compass option consists of a circuit card containing the GPS compass engine and two high
performance GPS antennas. Coax cables will connect the RC3000 to the two GPS antennas. Multiple
factors must be considered when positioning the 2 antennas (antenna array).
1) The two GPS antennas may be positioned between 0.5 and 2.0 meters apart. The further the
antennas are placed (up to 2 meters), the better the theoretical performance of the heading solution will
be. The distance between the antennas will need to be precisely measured and programmed into the
RC3000 during the calibration procedure discussed later.
2) The two antennas must be placed where they both have unobstructed views of the sky. Do not
sacrifice either antenna's view of the sky though in order to obtain a longer baseline. No structure
associated with the satellite antenna system should rise more than 10 degrees above the horizon of the
GPS antenna array. This restriction also applies to external structures within the area that the antenna
array will be functioning. If the 10 degree and above view cannot be achieved, the elevation_mask
parameter must be changed (see 3.3.2.9 GPS Compass Calibration).
3) Coax cables should be limited to lengths that would realize 15 dB of loss or less at GPS L1 (1.575
GHz). This limits the length of RG58 cable (0.78 dB/m) to approximately 10 m. when connector loss is
included. RG8 material (0.36 dB/m) may be used to about 20m.
4) The antennas should also be placed where the vector between the two will be as close to parallel to
the ground (level) as possible when the antenna controller polls the GPS engine for a heading reading.
The suggestion to have the antenna array within 10 degrees of level allows the heading algorithm to
disregard some possible mathematically correct heading solutions for antenna array tilts greater than 10
degrees. The engine compass will be programmed to assume this level situation exists. If level
operation cannot be achieved, the level_operation parameter must be changed (see 3.3.2.9 GPS
Compass Calibration).
2.1.3 Compass Mounting
Since the compass function is contained within the HGPS compass unit, no additional mounting beyond
that described in 2.1.2 are required.
2.2.6 Navigation Sensor Wiring
The two GPS antennas will be connected via TNC connectors labeled "Primary" and "Secondary."
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