Hi,

About change "region":
I implement the reader U107 (JRD-4035) with an USB to serial TTL UART interface (a TTL-232R-5V-PCB fron FTDI Chip) and can drive this reader with a serial terminal software as RealTerm (that supports frame of hex bytes) for simple tests (with Pyserial for a more evolved application).
Then it is possible to check active "region" parameter, by send the command frame: 0xBB 0x00 0x08 0x00 0x00 0x08 0x7E. After a power On, the response is: BB 01 08 00 01 01 0B 7E corresponding to "China 900MHz" (01).
We have to send the command: 0xBB 0x00 0x07 0x00 0x01 0x03 0x0B 0x7E to pass in "EU region", the reponse after the command: 0xBB 0x00 0x08 0x00 0x00 0x08 0x7E, is BB 01 08 00 01 03 0D 7E region parameter has well switched to "EU region" (03).
(note: if the USB dongle is unplugged then plugged, the region parameter returns to '01')

About documentation on this reader: I used this manual "https://m5stack.oss-cn-shenzhen.aliyuncs.com/resource/docs/datasheet/unit/uhf_rfid/MagicRF M100%26QM100_Firmware_manual_cn.pdf" and "translate Google tool" (the en version of the manual is not sufficient).

Best,
Thierry

PS: the link between U107 and the FTDI interface module is: TXD/U107 to RXD/FTDI, RXD/U107 to TXD/FTDI, 5V to VCC and GND to GND.

Hello,
I begin with this RFID UHF reader (U107), and i encountered the same issue to solve, i.e. to optimize the read distance when "Europe work location" is selected.
The patch antenna within the U107 seems fitted to 900MHz band, and as this antenna is very small therefore the bandwith is really narrow. The read performance at 868MHz are then degraded.
The solution I found is to modify the patch antenna like this: you have to remove the box to access the top of the patch antenna, and you have to remove the white adhesive protective sheet and stick in place a square of aluminiun adhesive tape above/againts the roof of the integrated patch antenna.
The size of about 30mm by 30mm seems close to the best ... but you can try other sizes and see. You can also try cropping the opposite angle along the diagonal passing between the two feed points (not a lot !).
Best regards,
Thierry