I recently bought the 13.56MHz module (RDM880) together with a key fob and finally got around to try it out. Unfortunately, the range I am getting is about 1/16 of an inch, and only if I put the fob into one of the corners of the antenna.
Between the Arduino and the RDM880 I am using the Serial connection and I can properly read the serial number of the module as well as of the fob, when in really close proximity. The module is powered with 5V from a USB connection. I tried reversing the polarity of the antenna, too.
However, whatever I do, the range where the module can recognize the fob remains abysmal, to say the least. The antenna is mounted freestanding, and the only way i can recognize the fob is by putting it inside the hole of the antenna and move it into either corner. Not even passing it through the center will recognize it.
Either I must be doing something, or there is something wrong with one of the components. Does anybody know what else I could try?