MANUAL P/N 900000108 REV D
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Location
Several factors must be considered when installing the GPS antenna. In most cases, the antenna is
mounted externally (outdoor) and is exposed to the elements. A good quality coaxial cable of 50 ohm
impedance is required to connect the GPS antenna to the ENTA. The cable provides two functions,
which are to conduct the GPS RF signals (1575.42 MHz) that are received from the GPS antenna to
the ENTA and to conduct the DC bias voltage (5 VDC) provided by the ENTA to the LNA (low noise
amplifier) contained inside of the GPS antenna. The antenna should be mounted securely, have a
clear view of the sky, and have the top of the antenna pointing upward. For some installations, it may
not be possible to mount the antenna such that the antenna has a clear (360 degree) view of the sky.
For these cases, pick the location with the best view of the sky.
Exposure to High RF Fields
Some antenna installations may occur in locations where a variety of high power transmitters and
antennas are located. The GPS antenna should not be directly exposed to or bombarded with high
level RF energy. In such cases, it is better to place the antenna either above, below, or to the side of
high power RF transmission antennas.
Lightning Protection
The ENTA does not provide any inherent protection against lightning strikes. In general, lightning
protection (when desired or needed) is provided by an externally mounted protection device designed
to shunt the high voltage transient to a well established earth ground. Lightning arresting devices
designed for use in GPS antenna systems are available at Brandywine Communications (P/N
001000914).
Antenna Cable Factors
Other factors affecting the antenna mounting location deal with the cable length required to provide
connection between the GPS antenna and ENTA.
