Interference is a problem when trying to build a diy repeater.
You might be able to build a patch cord with a control curcit in the middle. However it is a hevey lift unless you have guru status. I built a repeater with two Midland data radios, burned up two radios, tried different types of radios, controller's, cheap duplexer, Celwave duplexer, many hours, lots of dollars ($1,000 plus). I tell myself it was fun?
A Midland or Retevis repeater would be quicker, cheaper, and possibly more efficient.
Just a thought from a hobbyists.
Good luck on your journey.
WRJA397