Spectracom Model 8225 GPS Antenna Installation Guide
Rev D, June 2012 / PN 8225-5000-0050
Page 2 of 5
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Antenna Cable for Outdoor Antenna
When using the Model 8225 GPS outdoor antenna, Spectracom recommends
using LMR-400 (or equivalent) low loss type cable for the GPS antenna cable.
To simplify the installation process, Spectracom offers GPS cable assemblies
terminated with Type N Male connectors. Standard lengths are 25, 50, 100,
150 and 200 feet.
If the antenna cable is purchased locally, select coax suitable for outdoor use.
Consider the cable's weather ability, temperature range, UV resistance, and
attenuation characteristics.
Do not allow the antenna cable to be placed in standing water, as water may
permeate through the coax jacket over time. On flat roof installations, the coax
can be suspended by cable hangers or placed in sealed PVC conduit. Apply a
weather proofing sealant or tape over all outdoor connections.
Installation of a surge protection device in the antenna line is recommended to
protect the GPS receiver and connected devices from lightning damage.
Spectracom offers the Model 8226 Impulse Suppressor to shunt potentially
damaging voltages on the antenna coax to ground. Note the Model 8226
surge suppressor is only compatible with the Model 8225 GPS antenna. It is
not compatible with the TSAT dome antenna.
Cable Lengths
For the Model 8225 antenna, the maximum recommended antenna cable
length, when installed without a preamplifier, is 300 feet of LMR 400 or
equivalent cable with a maximum attenuation (loss) of 16 dB (Figure 2-1).
When selecting alternate antenna cable sources, the attenuation
characteristics at the GPS frequency of 1575.42 MHz must be known. To
ensure optimum receiver performance, the total antenna cable attenuation
must not exceed 16 dB regardless of cable length. Cable attenuation of greater
than 16 dB requires the use of a Model 8227 Inline Amplifier (Figure 2-2).
Model 8224 GPS Splitter
The GPS Antenna Splitter, Model 8224, is designed for use with an existing
antenna/cable setup. It eliminates the need and expense for a second
antenna/cable run when two synchronization systems are desirable. The
Model 8224 should be installed indoors.
Model 8226 Impulse Suppressor
Spectracom recommends the use of an inline coaxial protector for all products
with an outside antenna. Spectracom offers the Model 8226, Impulse
Suppressor, to protect the receiver from damaging voltages occurring on the
antenna coax. Voltages exceeding the impulse suppresser trip point are
shunted to the system ground. The Model 8226 is designed to withstand
multiple surges.
Two LMR-400 field-installable N type connectors are provided with the Model 8226 to splice in the surge suppressor
wherever it must be placed. However, the recommended method to avoid having to cut the antenna cable is to determine
the desired location of the Model 8226 ahead of time and then order two lengths of pre-terminated cables instead of just
one long cable that spans the entire distance between the antenna and the Spectracom GPS Receiver.
Mount the suppressor indoors, preferably where the coax enters the building. Install the suppressor on a grounding panel
or bulkhead as shown in Figure 2-3. Refer to the Model 8226 Manual for proper installation.
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