5 ms·
RFID works at very close range (think swipe cards to get into an office). Readers with larger ranges do exist, but they get very pricey.
by giarc 12y ago
RFID works at very close range (think swipe cards to get into an office). Readers with larger ranges do exist, but they get very pricey.
- mikeash 12y agoRFID is basically an application of radar, and as such suffers from an inverse fourth power dropoff with range. Radio is inverse square, but when you reflect it off something, you suffer that inverse square twice. So while doubling the range drops your received radio power by a factor of 4, it drops your received RFID response power by a factor of 16. To have more than a tiny range, you need a lot of transmitting power and a really good receiver.
- imaginenore 12y agoNo, my father designs RFID readers and antennas. The long-range UHF readers reach 9-15 feet (with passive credit-card size tags).
- giarc 12y agoThe cost of that type of system would be no where close to acceptable for personal use.
- MacsHeadroom 12y agoYeah, but how big is the reader? A lot bigger and stronger (rf) than my cellphone- I'm sure.