This is a question I saw on another blog…

“I’ve seen a lot of people talk about the range of passive and active RFID tags. But what is the range for these two kinds of tags? Anybody know how far it truly can go?”

Basically passive RFID tags have a very small range because they have no internal power supply. The variance between passive RFID tags varies greatly and can be as little as a few mm to about 18 feet.

This makes them a great choice for tagging merchandise in a store—allowing a retail outlet to track their merch all the way to the parking lot.

Active RFID tags are bigger, more expensive, and have a much bigger range. They generally use high frequencies to be read at a range up to 300 feet. Whether RFID tags will get much farther depends on the technological advances that come down the line. Right now high frequency and microwave frequencies travel the longest—but will it be long before satellite technology allows you to track things globally. Who knows?

Check out active tags for more info on RFID tag ranges.

Just wanted to include something i wrote for the newsletter here at work…

The history of RFID tags is as shadowy as the technology it uses. Many believe that Leon Theremin invented the RFID tag in use with espionage work for the Russian government. They would be wrong. What Theremin created was more of a way to listen in on conversations—and as everybody knows there isn’t much listening done with an RFID tag on a shirt from the Gap.

Perhaps the oldest instance of RFID technology is the IFF Transponder stuff used in the Second World War. This ‘friend or foe’ technology allowed the British to identify allied planes much more easily—an important feature considering how crude radio signal technology was at this time.

It took 30 more years before the RFID technology became honed to the state it is today. But many saw it coming. Harry Stockman delivered a paper in 1948 in which he predicted the next great wave of scientific radio technology will be in the field of “reflected-power-communication.” (Notice the word power in that description.)

For more info>..http://www.de220.com/Electronics/Antennas/Antennas.htm