Long-Range RFID Reader for the Arduino?

Hello, I'm new to the Arduino, and this forum, so I hope I didn't post this in the wrong section.

I want to setup a system that uses RFID tags, a reader, the Arduino, and some external event, like unlocking a door, etc. There are plenty of code snippets on how to make the reader work, and I don't think I'd have a problem adapting the code to do whatever I want. However, none of the RFID readers I've seen used have a range over about 3 inches. This is useless to me, as taking the time to reach in my pocket, pull out the RFID device, then pass it over the reader, is almost as time-consuming as just pulling out a key and unlocking the door like we've been doing for a few centuries.

What I need is a reader with a range of at least 3 feet, and preferably something like 10-15 feet. Then I could walk near the door, push a button, have it scan for a valid card, then if it finds one nearby, lock or unlock the door as needed. It would also need to detect multiple cards at once, so if there are 3 people with cards, it would send all 3 IDs to the Arduino to be checked. This would not only allow me to leave the key in my pocket, but would also allow me to save power consumption by only activating the reader for the couple seconds I'm actually using it a few times per day, rather than drawing power all day, every day, futilely scanning a billion times just to see if there might happen to be a tag in the vicinity.

Does anyone know of a reader like this that interfaces with the Arduino (preferably via serial, as I already know how to do that), that doesn't cost hundreds or thousands of dollars? Alternately, is there a way to just make a more sensitive antenna for an existing reader that doesn't involve me knowing the quantum mechanics of everything?

Thanks, Michael

Hmm, not the answer I'd hoped to hear, but thanks for the info.

What I need is a reader with a range of at least 3 feet, and preferably something like 10-15 feet.

Yes a lot of people want that. Unfortunately physics gets in the way. Most RFID tags are passive, that is they use the received RF signal to power the field modulator or transmitter. This severely limits the range to about 20cm maximum, even that takes a good design to do. However there are systems with active tags, that is a tag with a built in battery. These last about two years before needing a new battery.

the technology, it appears that RFID readers are still somewhat of a black (or maybe just gray) art

RFID technology has been around for about 30 years, but because of it's security aspect there is little information published. However there are some books, this is good but pricey:- http://www.amazon.co.uk/RFID-Handbook-Applications-Technology-Security/dp/1420054996/ref=sr_1_6?s=books&ie=UTF8&qid=1291631508&sr=1-6