9
1.6.6 Antenna Specifications
The active antenna used with the GPS 15xH/15xL should have the following specifications:
Gain:
Antenna should provide between 10 dB to 30 dB net gain between the
antenna feed point and the connection to the GPS 15xH/15xL. All
amplifier gains, filter losses, cable losses, etc. must be considered
when calculating the gain.
RF Connection:
GPS 15xH/15xL RF Connection: MCX Female connector (on the
GPS 15xH/15xL board)
Antenna Connection: MCX Male connector (on the end of the antenna
cable)
Garmin Antenna:
GA 25 MCX (Garmin Part Number 010-10702-00) provides the required
MCX Male connector. Other Garmin antennas terminated in a BNC
Male connector may also be used if a Garmin MCX to BNC Adapter
Cable (Garmin Part Number 010-10121-00) is used. Place the MCX to
BNC Adapter Cable between the connector on the end of the antenna
cable and the connector on the GPS 15xH/15xL.
Noise Figure/Gain:
The total noise on the external antenna should be less than
3 dB with a
gain between 10 dB and 30 dB.
Should be properly biased by your choice of:
Power from on-board source:
3.0 Vdc minus the voltage drop across a 7.2 ohm series
resistance due to the current drawn by the antenna. The antenna
must not draw more than 60 mA.
Power from external source: From 3.5 Vdc to 8.0 Vdc bias through the series combination of
an on-board ~5.6 Ohm current sensing resistance, a saturated
PNP silicon transistor and a Schottky diode. The antenna must
not draw more than 60 mA. The external source of antenna bias
voltage should not have any significant noise or interference
power in the GPS band (20 MHz bandwidth centered at 1.57542
GHz).