Hello,
Please check the wiki page that Marcelo provided. Additionally, there are posts on the forum about RUTX12 antennas, such as this one:
RUTX12 - External antennas to improve wifi AP range? - #4 by JuliusL.
Kindly review the community posts, and if you still need assistance, please provide more details, and I will do my best to help you.
Best regards,