When to use: Use to determine the required Bi-Directional Amplifier (BDA) gain for in-building public safety coverage systems. Enter the donor signal level, cable losses, antenna gains, and building penetration loss. The calculator determines the minimum BDA gain needed to achieve NFPA 1221 / IFC Section 510 compliant inbound RSSI at a portable radio (default −95 dBm, DAQ 3.0). FCC limits BDA gain to 100 dB maximum.