Thanks Mike.
Grumpy_Mike:
If you do the latter you have to know if the reader has a parallel LC tuned circuit or a series one, so you know how to add more capacitance.
This is kinda where things fall down with the RDM reader -- they just don't give you much to go on, to get your coil design right. I'm looking forward to getting my hands on the ID-2 since they do spell out this aspect of the design. Unfortunately they appear to be back ordered.
...and thanks Mark.
markB:
In you're case you'll be looking at a 30-35 cm coil.
...
You'll want the coil voltage to be sitting at about 300v peak to peak.
Can you mention which reader circuit Robert is referring to here? EM4095 or U2270B something else? I'm not above wiring up my own reader using one of these chips, but I am not keen on ordering them all the way from Oz.