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098-00208-000 Revision A – February, 2010
TimeAnalyzer 7x00 User’s Guide
31
Chapter 2 Setting Up
Connecting the GPS Antenna
Other GPS Antenna Options
In the event that the optional portable GPS antenna is not adequate for specific
applications, users can order Symmetricom GPS L1 antenna kits or provide their
own GPS antennas. See Appendix C in the TimeProvider 5000 User’s Guide for
GPS L1 antenna kits that are compatible with the TP5000 Probe.
Required Gain to GPS Engine
It is important to select the proper gain antenna and coaxial cable that accounts for
the insertion loss between the antenna and the radio receiver to avoid under-driving
or over-driving the radio receiver antenna input. The gain required at 1575 MHz for
a GPS radio receiver input is the manufacturer’s specification for the radio receiver
to acquire satellites, with some level of signal degradation allowed.
L1 Antenna gains are usually specified as the minimum effective gain. Such
antenna gains can have 4.5 to 10 dB more signal strength at different satellite
azimuths and elevations, depending on their reception pattern. The GPS engine of
the TP5000 probe requires a gain at the antenna connector input of the chassis to
be between
25 dB and 35 dB. This tolerance allows for the signal loss of the internal
coaxial cable and connectors. The optimal gain at the radio receiver input is 30 dB.
The total gain is the gain of the GPS antenna less the loss of the transient
eliminator, connectors, and cables.
Antenna Placement and Mounting
Mount the antenna outside, preferably on the roof with a clear view of the sky, as the
cable length allows.
Do not
mount the antenna near a wall or other obstruction
blocking part of the sky. Mount the antenna well above roads or parking lots.
If fixed mounting is not possible or practical for a Symmetricom GPS antenna kit or
user supplied antenna, a tripod can be used for temporary antenna mounting.
Coaxial Cable
5 meter length, double-shielded RG-174 equiv.,
low loss 0.7 dB/m
Environmental
Operating Temperature
-30 deg C to +85 deg C
Storage Temperature
-40 deg C to +90 deg C
Table 2-3. GPS Antenna Parameters
Parameter
Value