Telemetry radio distance issue in outside

I am using mRo 915 MHz telemetry radio for my rover. When I connect my rover in mission planner, it gets full signal but when I open base station antenna, the signal level in mission planner gets too low. How to solve the issue?

Not sure what you are asking. The range on a Rover with those radios is limited. Much less than a Multirotor or Plane.

I have found that when my base station antenna is connected, the signal strength level that shows is mission planner decreases but when base station antenna is not connected, the signal stays in almost 100%.