Operation Manual

B Using Radios with GPS
46 SiteNet 450 Operation Manual
B.1 Introduction
Note – For more information, refer to the Trimble publication “Using
Radio Communication Systems with GPS Surveying Receivers”
(PN 1-612-0082-2/94).
“GPS receiver, antenna, tripod, tribrach, tape, cones, flagging,
radio...”, such is the checklist of most GPS surveyors preparing for a
day of observations. But a truly successful survey is not just a matter
of making sure that you have all of the equipment; you must also
ensure that you optimize the usage of these new tools for the highest
productivity.
The GPS receiver is trying to measure very faint radio signals from
satellites orbiting at 22,000 kilometers in space. There are many
factors that can hinder the receiver’s ability to perform. For example,
placing your hand over the antenna or setting up the antenna under a
tree are factors that have already proven to interfere with GPS signal
reception.
As GPS receivers developed, their processors have become more
sensitive to incoming data flow. This provides an increase in accuracy
by extracting more information out of the GPS radio signal. But with
this gain in accuracy, there is an increased susceptibility to other radio
signals. The receiver is now more sensitive to the incoming GPS
signal, and consequently it is also more sensitive to other incoming
radio signals. This means that communications radios, such as those
commonly used by surveyors, can sometimes create difficulty with the
GPS signal reception.
There are some very simple steps you can follow to remove the effects
of radio interference on the GPS receiver. First, you should be aware
of the type of communications equipment you buy and understand its
characteristics. Secondly, a little care in using communications radios
can greatly decrease your chances of experiencing any interference
with satellite tracking.
SN450.book Page 46 Friday, October 5, 2001 5:01 PM