In one embodiment, a diagnostic device determines signal strengths of two antennas of a multi-antenna device. When the signal strength of each of the two antennas is unacceptable, the diagnostic device provides a recommendation to adjust each of the two antennas. Alternatively, when the signal strength of a first antenna of the two antennas is unacceptable while the signal strength of a second antenna of the two antennas is acceptable, the diagnostic device provides a recommendation to adjust the first antenna. However, when the signal strength of each of the two antennas is acceptable, but a difference between the signal strength of a first antenna and a second antenna of the two antennas is greater than a threshold, then the diagnostic device determines a weaker antenna with weaker signal strength between the first antenna and the second antenna, and provides a recommendation to adjust the weaker antenna.