2 – Hardware Configuration
GPStation™ User Manual
11
USER-SUPPLIED RADIO OR MODEM
When using the GPStation as a DGPS base station, it needs to be connected to user-supplied equipment that will
propagate the differential corrections to remote stations. Whether this equipment is a modem that sends the corrections
over telecommunication channels, or radio transmitting equipment that sends the corrections through an atmospheric
path, the only requirement is that it have an RS-232C serial data interface through which data can be exchanged with
either the COM1 or COM2 port of the GPStation.
NOTE:
When using radio transmitting equipment, please ensure that you comply with all applicable government
regulations (such as obtaining a license, and obtaining approval before operating a transmitter or setting up an antenna
near an airport).
When using a radio transmitter to disseminate the differential corrections, keep in mind that its maximum “line-of-sight”
range will primarily be influenced by the effective radiated power (determined, in turn, by the transmitter’s power output,
the gain of its antenna, and any losses in the transmitting subsystem), the height of the transmitting antenna, and the
height of the receiving antenna. The documentation supplied with the radio equipment should contain the information
needed to design an effective radio network.
OVEN-CONTROLLED CRYSTAL OSCILLATOR (OCXO)
The built-in, high-stability OCXO enables the GPStation to generate highly accurate differential corrections. The OCXO
section of Appendix A summarizes the operating characteristics of this oscillator. It is important to remember that the
OCXO requires 3-5 minutes after power-up to stabilize its temperature; differential corrections should not be sent until
after this stabilization has occurred. The GPStation power requirements increase when the OCXO heater switches on; see
the Power Requirements section of Appendix A.
NOTE:
The accuracy of the OCXO is impaired by vibration and shock, so it is essential that the GPStation be at rest
on a stable and secure surface during operation. The GPStation has rubber feet in order to reduce the effect of vibration.
