Which types of devices will make transmissions unreadable?
Generally speaking, any device that emits radio waves at the same frequency as an RFID system will cause interference with the reading of RFID tags and vice versa. Low-frequency (LF) and high-frequency (HF) tags operate at short range and at frequencies that are used almost exclusively by RFID systems, so interference from other RF devices is rarely an issue. Active systems operate at 433 MHz, 915 MHz and 2.45 GHz. Because they broadcast a signal, much like a cell phone, they are less prone to interference.
So it's mainly passive UHF systems that experience problems with electromagnetic interference (EMI). UHF systems operate at 860 MHz to 960 MHz around the world, and there are many more RF devices and communications systems that operate in the same general area of the spectrum. It's not possible to provide a list, but anything that operates in this spectrum could be a problem. Machines can also throw off electromagnetic interference and might need to be shielded. I have heard of rare instances in which fluorescent lighting created some problems as well.
—Mark Roberti, Founder and Editor, RFID Journal
Previous Post How Does Backscatter Modulation Take Place in RFID? »