Electronic – How to send one bit one mile with one battery

If you have the RFID readers connected to a network, you could do this pretty easily.

You need to separate your project into two parts - getting the rfid info into a processor/microprocessor of some sort, and then moving the data to another location. Both are pretty easily solved with off-the-shelf parts.

The problem I think is that you're asking/googlinh about transmitting "RFID Information" in particular. Once you scan a tag, you basically get data. Data is pretty generic. People spend a lot of time working on moving data around. Once the tag information is in the computer, it's just a string you need to send over some sort of medium, and if your medium supports data, it probably supports any actual data contents, RFID or not.

I'm not too sure how many of these things you want to make; an easy if not cheap solution would be to just slap an RFID reader on an Arduino, together with a GSM module (for cellular communication), or a WiFi module. However, this is a bring-your-own-code solution. If you're hoping for something off-the-shelf, short of using an full-on desktop/laptop computer for each node, I think you're out of luck.

If you already have a lot of RFID readers, there are plenty of serial/analog/whatever bus to wireless adapters out there, but they're not going to be labeled RFID-specific. Again, think data, not RFID.

Build a simple detector with some diodes:

^{simulate this circuit – Schematic created using CircuitLab}

If you just want to know if there is some signal, and aren't concerned with accurately measuring its strength, or demodulating it, you can throw this together with just about any components and it will work. Ideally the diodes have a low forward voltage, so they are Schottky diodes, like 1N60, or 1N5711, or a germanium diode. If you don't have any of those, probably an ordinary 1N4148 works too. Use whatever you have.

The capacitor is also not terribly critical. A cheap ceramic disk capacitor will work fine; whatever value you have.

The antenna is just a piece of wire. Connect the ground to something else, like your Arduino's ground, or the case, or another piece of wire. Not especially critical.

The hardest part is probably the ammeter. This needs to be a very sensitive meter -- on the order of microamps. Ideally, an analog meter, since it will be easier to see the changes in signal strength. A digital meter will work also, if it has a low enough range. It will just be harder to read.

Test the circuit by putting the antenna near a source of noise, like a computer monitor, or a motor, or your wireless access point, or your laptop's WiFi antenna, or any other radio transmitter you have that you know works.

Then, put it near your RF transmitter. Try transmitting something. If the ammeter moves, it's transmitting something.