rfid long range reader problems

hi all,i'm trying to design a long range reader operating in 13.56Mhz ,and have a external PA,i'm sure that it's no problem for transmit link ,and the wave are all the same with the referrence document,but it can't read card at all,and i also change various antenna to void carry wave saturation,but no effect,i guess receiver link have problem but don't konw how to do it,can anybody help me ?thank you !or you have different advice about it ?

You don't provide much information at all.

- involved RFID standard?
- utilized reader chip?
- did you measure the field strength at the card's location with a test coil? (A test coil is basically an oscilloscope probe with a wire loop of known area)
- did you see any load modulation (card response) with the test coil?

hi

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