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5/25/2007
Document number: 060-FSA-ABQ-AAS-AGZ
Rev. 001
The S14WI includes an option to monitor the status of the application’s active antenna and to
provide an alarm indication if the antenna’s current is not within a specified range. The default
current window for the S14WI is 15mA to 150mA (e.g. antenna current below 15mA indicates an
open circuit, above 150mA indicates a short circuit); however, for large volume orders, the
antenna current window may be specified to meet the customer’s specific requirements.
The S14WI samples the antenna current 16 times per second. So long as the average of four
samples are within the specified antenna current window, the S14WI will continue to operate
normally, passing the DC voltage applied to lowest number RF output on to the RF input. In this
mode, DC voltages applied to the remaining RF outputs are switched to 200Ohm DC loads. If
the average of four antenna current samples falls outside of the specified antenna monitor
current window, the DC voltage to the antenna is removed (open circuit) and all DC inputs are
switch to Pass DC. Since the DC path to the antenna has been opened, the DC current on all
four DC inputs will be at or near zero (less than 0.5mA for the passive configuration and less
than 5mA each for the active). In this alarm condition, all GPS receivers connected to the RF
outputs will also see very low antenna current draw, resulting in corresponding antenna alarm
conditions within each receiver.
Once in the alarm condition, the S14WI will periodically (every 60 seconds) attempt to re-
connect DC power to the antenna. If the antenna failure condition persists, the S14WI will re-
enter the fault condition, repeating this cycle until the fault condition is removed.
Surge Arrestor System
The S14WI includes standard Gas Discharge Tubes and Transient Voltage Suppressors on
each RF input/output. Furthermore, provisions for high current grounding are included in the
metal enclosure of the device. The Surge Arrestor System is intended to provide a limited
capability to survive power line surges and voltage surges that may be induced by “near miss”
lighting strikes. Protection is rated to 4KA, according the IEC-61000-4-5. In order to ensure
proper protection of the device, the S14WI must be connected via a (8 AWG minimum) ground
cable to a low impedance ground.
Connecting the S14WI
When installing the S14WI, connect the coaxial cable feeding the active GPS antenna prior to
connecting RF outputs. Once the antenna coaxial cable is attached, coaxial cables with or
without DC voltages may be connected to the outputs. Note that at least one coaxial cable
connected any output of the device must provide a DC voltage suitable for operating the active
GPS antenna and the S14WI.
Note that in some instances, upon initial connection of the DC voltage, the S14WI may power
up in the “Antenna Fault” mode which will prevent DC voltage from being applied to the active
antenna. If this behavior is observed immediately after power up, wait for approximately one
minute. Proper operation should be restored by this time. If after 1 minute proper operation is
not observed, ensure that a “known-good” active GPS antenna that sinks a DC current within
the specified range is connected to the IN port of the S14WI via a “known-good” RF coaxial
cable.
