From how far away would an interrogator be able to read a tag?
—Name withheld
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It depends on the type of RFID system being used. A high-frequency (HF) reader based on the ISO 14443 air-interface protocol standard, designed for short-range transmission, has a maximum read range of about 18 inches. An active RFID system can read tags from 1,500 feet away or more, as the tags broadcast a signal and the systems are designed for longer-range applications.
Even within one type of RFID, however, there can be a wide array of read ranges. A passive ultrahigh-frequency (UHF) handheld reader has a range of about 10 feet, while a model using a beam-steerable phased-array antenna can interrogate passive tags at a distance of 600 feet or more.
Keep in mind that the reader is only half of the story. A very small passive tag with a small antenna harvests less energy from and reflects less energy back to a reader. It, therefore, has a shorter read range than a tag with a much larger antenna. I have seen small passive UHF tags that can be read by an ordinary fixed reader at a distance of only 2 or 3 feet, and I have seen passive tags that can be interrogated at a range of 80 feet.
—Mark Roberti, Founder and Editor, RFID Journal
