Linear multicode gate opener schematic needed

[emptech]

I have a linear multicode gate opener with poor sensitivity, could be off frequency.  It works but only when the transmitter is up close, the issue is not the transmitter.  I can spend some time reverse engineering the pcb but hoping somebody else has already done it.  I don't care about the codes, I'm interested in the rf area.  It is on 300 MHz.

For what it's worth, the part number on the pcb is 221421-01D

Jim