What is the maximum distance that an RFID tag can be used effectively?
With standard ultrahigh-frequency (UHF) systems, tags can be read from approximately 30 feet under ideal conditions. I have seen a passive UHF tag read from a distance of more than 300 feet, by Mojix's STAR system, which uses highly sensitive phased array antennas and e-nodes that energize the tag from a much closer distance.
Active RFID tags have a power source that enables them to broadcast a signal to an interrogator, rather than reflecting back energy from the reader. This allows for much longer read ranges—typically, 100 meters (328 feet). Some companies, such as Identec Solutions, have taken this further, by increasing the reader's sensitivity to pick up a tag from even longer distances: up to 500 meters (1,640 feet).
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