Increase range of 125khz RFID Reader
The range of a RFID reader with a (round) coil with diameter D is approximately D/sqrt(2). So you need a (round) coil with approximativ D=15cm to get more than 10cm reading distance. But as the inductance needs to be the same, you have to reduce the winding turns of the coil accordingly. How to? The total length of the wire of the new coil needs to stay the same as with the old coil in the photo above. Also the wire thickness needs to stay the same.