If you use a wire or PCB trace antenna, the simples way to optimize performance without expensive instruments is to make the antenna intentionally to long. Then measure range and repeat range measurement for shorter and shorter antenna. The range can be measured by either packet error at a fixed distance or RSSI readings. These measurement should give a poor performance at too long and too short antenna. Somewhere in-between there should be an optimal point.
Last Update: August 8, 2017