This GPS module I have broke (just gets hot and won't work) so I took it apart and am amazed to see all of this circuitry under the ceramic antenna but only two connections (gnd and signal). When tested there is ~3v between the signal and ground wires. So how does it work to send power over the wire and then also get signal back along the same wire ?
GPS Antenna – How Does It Work with Only Two Connections?
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Best Answer
All that circuitry operates from DC power sent along the signal cable from a DC power supply. The received GPS signal is amplified by the circuitry and sent along the signal cable as a radio frequency (RF) signal to the connected GPS equipment.
The DC power and RF signals are combined and separated by circuits known as bias-tees. A bias-tee built in to the GPS aerial feeds DC power from the signal cable to the supply rails of the circuitry and connects the received RF signal to the cable. At the equipment end another bias-tee allows DC power to be fed to the cable and connects the RF signal to the GPS receiver. This bias-tee can either be built into the equipment or provided as a separate (small) box.