Novatel OM-20000077 user manual Installation Considerations, Power Connection, Antenna Location

Installation Chapter 3

3.2.2Power Connection

The input range for a SUPERSTAR II card is either 3.3 VDC or 5 VDC depending on your model. The input range required for the FlexPak-SSII is +6 to +18 VDC.

3.3Installation Considerations

The FlexPak receiver is waterproof. The SUPERSTAR II bare card must be mounted in a dry location. Locate your receiver where it is convenient for cables to run to the power source, display device, and antenna. Form drip loops in the cables to prevent moisture from running down the cables and into the receiver.

Mount the receiver several feet away from radio transmission equipment.

3.3.1Antenna Location

Many GPS reception problems can be reduced, to some degree, by careful antenna site selection. Of primary importance is to place the antenna so that unobstructed line-of-sight reception is possible from horizon to horizon and at all bearings and elevation angles from the antenna. This is, of course, the ideal situation, which may not be possible under actual operating conditions.

1.Try to place the antenna as far as possible from obvious reflective objects, especially reflective objects that are above the antenna’s radiation pattern horizon. Close-in reflections cause strong multipath signals. For a detailed discussion on multipath and site selection, see Section G.4, Multipath starting on Page 71.

2.Care should also be taken to avoid coiling the antenna cable around the mounting base and pinching the antenna cable in window or door jambs.

By default, the SUPERSTAR II uses satellites above 4.5 degrees elevation. The mask angle can be set to use a different cut-off, as low as zero degrees (all in view), using Message ID# 81, Set Mask Angle (refer to the L1 GPS Firmware Reference Manual for more message details).

3.3.2Base Station Location

Your receiver must be a BASE model to act as a base station. A list of models is in Appendix A of the L1 GPS Firmware Reference Manual and in our Price List available from the Sales side menu of our website at www.novatel.com.

1.The base station must be located on a site that is above all obscuring elements on the surrounding terrain in order to have all satellites above the horizon visible at the base station’s antenna. The intent is to have all satellites that are visible at the roving unit’s antenna to be visible at the base station as well.

2.Multipath interference must be minimized as much as possible. Multipath is defined as the interaction of the GPS satellite signal and its reflections. This causes errors mainly on the GPS code, and less so on the GPS carrier. Even though the receiver uses carrier phase measurements, it can revert to code differential GPS operation if carrier phase differential GPS cannot be performed. Hence, the base station’s antenna must be far from any reflecting elements.

3.The position of the base station’s antenna must be surveyed using appropriate surveying equipment. This position must then be programmed in the base station using Message ID# 80, Set User’s Position/Operating Mode (refer to the L1 GPS Firmware Reference Manual). Any error in the base station’s position will be reflected in the roving unit’s computed position.

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