I have a kit that lets a user tune an antenna to different frequencies, from 100 KHz to 150 KHz. I can read 125 KHz tags, but not 132.4 KHz tags. I tuned it to 134.2 KHz and read it using an oscilloscope. Any idea what the problem could be?
To answer your question, I reached out to James Heurich, the president of RFID Inc., one of the few companies that make passive low-frequency (LF) tags and readers. Here is an edited version of James' response:
"Just because the frequency is correct, that doesn't mean you can read any tags. There are different encryption and demodulation methods—the process of logic that signifies which bit is a one and which bit is a zero. Among the demodulation methods are Biphase, Manchester, amplitude shift keying (ASK), phase shift keying (PSK), frequency shift keying (FSK) or combinations of these. If a tag is encrypted with one method, it cannot be read by another. Did the 134.2 KHz tags come in the development kit? 134.2 KHz tags are either ASK or FSK (assuming they conform to ISO 11784/5). If the reader in the kit is operating Manchester, that dawg won't hunt."
—Mark Roberti, Founder and Editor, RFID Journal
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