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Innovative tracking solutions since 2003

Building a LF PIT Tag System


A PIT tag monitoring site consists of an RFID reader, a power source and an antenna. The simplest system is a reader with a large deep cycle marine battery. Two batteries can usually power the reader for 7-10 days, depending on the antenna design. Other field power sources can be used to supply 12 volts DC at 2 amps (per reader). The power source needs to be electrically quiet with low ripple. Other recommended power sources are found in the link on the left.

Antennas

Antennas for low frequency RFID must be a loop of wire to generate a magnetic field. The easiest HDX antenna is a loop of wire suspended from a rope pulled across the water. The lower half of the loop is held on the bottom with rocks or anchors.



Antennas can be mounted inside plastic pipe to provide a structure for the loop. FDX antennas require a watertight air gap around the antenna wire when the loop will be in water.



Poorly designed antennas can only read tags at a short distance from the wire and often consume excessive amounts of power. It is easier to make antennas for large tags since their signals are relatively strong. The weaker signal from small tags usually requires a well designed antenna. Contact us if you are having problems getting the read range you need.

The most critical factor when designing an antenna is the choice of wire. The size and stranding have a direct effect on how well an antenna will perform. The wrong wire can cause excessive power levels to build at the antenna that can erase firmware and in extreme cases burn up a circuit board.


Circuit board burned due to wrong antenna wire