Huge Area RFID Reader

Hello everyone
I’m trying to make a RFID reader with diameter of 1.5 meters.
So far i managed to work 125kHz RFID reader with 12 cm diameters.
But yesterday i tried coil antenna with 35cm diameter and amplitude of coil antenna’s signal didn’t dropped much almost 200mV.

And there wasn’t anything on the output.
So i think the signal strength is the problem.
Any ideas and advice?
Thank you