Gpsstix modifications

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This page contains modifications which are specific to the GPS portion of the gpsstix. See the Audiostix2 modifications for some additional modifications that are applicable to the audiostix portion of the board.

Using an Active Antenna

As shipped, the gpsstix is configured to use a passive antenna (V_ANT - pin 19 - is connected to ground). To use an active antenna, the datasheet suggests conecting V_ANT (pin 19) to VCC_RF (pin 18) using a 10 ohm, 1/4 watt resistor.

This photo shows the location of pins 18 and 19, along with the ground trace which must be cut:

To make the modification, you should first cut the trace indicated by the circle. You should verify that the trace has been cut using multimeter. Be aware that the metal housing containing the GPS module is also connected to ground, so make sure that your probe is only touching pin 19, and not the case.

This photo shows the 10 ohm resistor added:

I used my flush cutters to remove the excess ground pin, which blocks access to pin 18. I recommend checking all of the connections with a multimeter to ensure that there aren't any unexpected shorts. The resistor is a big 1210 resistor. Most 0603 resistors are only rated for 1/10 watt or so.

When powering up the gpsstix, you should now be able to measure about 3v between the antenna center connector and ground.

Warning (from page 66 of the ANTARIS 4 GPS Modules System Integration Manual)

Antennas should only be connected to the receiver when the receiver is not powered. Do not connect or disconnect the Antenna when the ANTARIS^®4 GPS receiver is running as the receiver calibrates the noise floor on power-up. Connecting the antenna after power-up can result in prolonged acquisition time.