User's Manual

SPSx80 Smart GPS Antenna User Guide 41
Setting up the Receiver 5
Figure 5.1 SPSx50 receiver permanent installation
Setting up a base station for daily site use: T-Bar
For construction applications where a daily setup and takedown of equipment is
required for security reasons, Trimble recommends that you use a T-Bar setup.
The T-Bar consists of a post mounted in concrete (so it cannot move), which has a
solid metal T-Bar mounted to it to provide lateral separation between the GPS antenna
and radio antenna. The T piece of the T-Bar has a vertical rod at each end. Each end
terminates in a 5/8"×11 thread to which the antennas can be mounted. Trimble
recommends that one end is clearly marked GPS and the other end is clearly marked
Radio so that at each daily setup, the GPS and radio antennas are mounted at the
same location. Switching antennas by mistake introduces a position error in all
resulting measurements. You can buy the parts you need to make a T-Bar from any
reputable hardware store. Make certain that the T-Bar cannot rotate after
construction. Rotation of the T-Bar can introduce a position error into all subsequent
measurements.
On the upright post, mount either a bracket (to which the GPS receiver can be
mounted), or a well-ventilated lockbox (in which the GPS receiver itself can be
secured).