CHAPTER TWO
2.2.3 REDUCED AIR FLOW - The equipment has no cooling fans and depends on
convection for cooling. Installation in a rack may cause an excessive heat rise if sufficient air
flow is not available. Installation should be such that the amount of air flow required for safe
operation of the equipment is not compromised.
2.2.4 MECHANICAL LOADING – Mounting of the equipment in the rack should be such
that a hazardous condition is not achieved due to uneven mechanical loading.
2.2.5 CIRCUIT OVERLOADING – Consideration should be given to the connection of the
equipment to the supply circuit and the effect that overloading of circuits might have on
over current protection and supply wiring. Appropriate consideration of equipment
nameplate ratings should be used when addressing this concern.
2.2.6 RELIABLE EARTHING – Reliable earthing of rack-mounted equipment should be
maintained. Particular attention should be given to supply connections other than direct
connections to the branch circuit (e.g., use power strips).
2.3 ANTENNA/PREAMP INSTALLATION
The antenna/preamp is enclosed in a weatherproof housing suitable for permanent installation in
an exposed location. The unit should be located with an unobstructed view of the horizon for
optimum tracking conditions. The signal will not penetrate foliage. Multi-path signals may be
generated from vertical surfaces, which are above the plane of the base of the antenna/preamp.
The antenna/preamp, which is designed for fixed ground or marine applications, requires no
special ground plane, but a large metal surface below the antenna/preamp may reduce multi-path
effects. The unit may be mounted on any level surface or on a vertical pipe having ¾ - 14 NPT
threads. See Figures 2-1, and 2-4, “Antenna/Preamp Installation,” for mounting.
*** CAUTION ***
A high powered radar beamed directly at the antenna/preamp may damage it and a signal
within a few MHz of the carrier frequency may jam the GPS RPU.
2.4 ANTENNA/PREAMP INTERFACE CONNECTIONS
A fifty foot long RG-58A/U coaxial cable is provided to connect the antenna/preamp to the GPS
Timing Unit. For cable lengths greater than seventy-five feet, an optional low loss coaxial cable
(such as Belden 9913) must be used.
Note: The GPS antenna and cable described in this manual have been replaced as described in
“Appendix D: Antenna Replacement Kit” on page D-1.
2-2 ET6xxx ExacTime GPS TC & FG (Rev C) Symmetricom Inc
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