GPS-Tracker icon indicating copy to clipboard operation
GPS-Tracker copied to clipboard

Published 20 hours ago • verified publisher icon mohamedboubaker

Add GPS Bias Tee circuit

Open mohamedboubaker opened this issue 2 years ago • 1 comments

The current version of the PCB has a GPS antenna issue. The GPS signal is not strong enough for the SIM808 to get a GPS fix. Probable root cause: lack of DC bias on the antenna line to activate the active GPS Antenna.

DC signal in the antenna line should be introduced and turned on and off using a transistor (or other switch) connected to a GPIO on the MCU. It should be activated and deactivated by software to control power consumption of the Active antenna.

mohamedboubaker avatar Dec 27 '22 10:12 mohamedboubaker

This hardware bug can be fixed by manually hooking the active antenna amplifier circuit to the power line 3.6V. It seems that the SIM808 antenna input is tolerant to DC offset.

However it is best to include the Bias Tee circuit.

image

mohamedboubaker avatar Dec 28 '22 22:12 mohamedboubaker