Five ways a BDA system fails, and how each gets fixed

What the code checks. The annual test runs batteries and power supplies under load for at least one hour "to verify that they will properly operate during an actual power outage," and extends the test hour by hour if the battery shows signs of failure (IFC 510.6.1 item 3). The system must be able to run 12 hours at full capacity on backup (IFC 510.4.2.3; NFPA 1225 18.13.2).

Why it happens. Batteries age. A failed charger also leaves a battery flat after the next outage; that is why charger failure is its own alarm (NFPA 1225 18.14.1.2(3)(b)).

The fix. Replace the battery or charger, then re-run the load test. Do not ignore a charger failure or low battery signal; see monitoring.

What the code checks. Signal boosters must have built-in oscillation detection and control (NFPA 1225 18.3.2; IFC 510.4.2.4 item 5), must send a supervisory signal when they detect it (NFPA 1225 18.3.2.1), and are checked with a spectrum analyzer at installation and "at subsequent annual inspections" (IFC 510.5.4 item 7).

Why it happens. Oscillation is feedback: the indoor antennas leak signal back to the outdoor donor antenna. The codes require at least 20 dB more isolation between them than the system's gain (NFPA 1225 18.3.3.2; IFC 510.4.2.4 item 4). NFPA notes that building damage can reduce that isolation (NFPA 1225 A.18.3.2), and the same logic applies to anything that changes the path between the antennas. When a booster oscillates it can cut its gain or shut down, and it can interfere with the public safety radio system itself. The FCC can require added filtering when a booster causes harmful interference (47 CFR 90.219(d)(6)).

The fix. The vendor finds what changed, restores isolation (antenna position, shielding, gain settings) and documents the new settings. NFPA 1225 expects gain settings to be recorded with the as-built documents (A.18.9.3).

What the code checks. The donor antenna must be permanently fixed to the building, or mounted on a movable sled with a sign saying "Movement or repositioning of this antenna is prohibited without approval from the AHJ" (NFPA 1225 18.3.3.1; IFC 510.5.1). A donor antenna malfunction is a required supervisory signal (IFC 510.4.2.5 item 3).

Why it happens. Roofers, HVAC crews, cell site crews and storm prep all happen near rooftop antennas. An antenna knocked out of alignment can lose its link to the radio site it was aimed at; the codes require fixed mounting "to maintain proper alignment with the system designed donor site" (NFPA 1225 18.3.3.1).

The fix. Have the vendor re-aim and re-test it. Then protect it: add the sign if it is missing, and put "do not touch the BDA antenna" in every roof work order. Miami-Dade notes the donor antenna's orientation "shall be determined in coordination with the AHJ," so a re-aim may need the fire marshal's sign-off.

What the code checks. A test is required not only every year but "where structural changes occur, including additions or remodels that could materially change the original field performance tests" (IFC 510.6.1). In Florida, the fire marshal can require a new coverage assessment sooner than the usual 3 or 5 years after a Level III alteration or rehabilitation, or reconstruction (F.S. 633.202(18)(c)2a, b).

Why it happens. New walls, ceilings, metal studs, low-e or impact glass, and tenant build-outs can all change how radio moves through a building. Indoor antennas get removed, painted or boxed in. Cables get cut or rerouted. A Fort Lauderdale commissioner quoted by the Sun-Sentinel described a building that failed after putting in high-impact windows.

The fix. Before the project starts, send the drawings to your BDA vendor. After it ends, have the affected floors grid-tested. If coverage dropped, the vendor adds or moves indoor antennas and retests.

What the code checks. Systems must be able to be modified or expanded when the FCC or the agency changes or adds frequencies (IFC 510.4.2.6; NFPA 1225 18.11.2.1), and the owner pays for that work: "The building owner shall modify or expand ... at his or her expense" (IFC 510.6.2). Earlier approval on old frequencies does not exempt the building.

Why it happens. Counties upgrade radio systems, add channels or move to new technology. The BDA was tuned for the old ones.

The fix. Watch for the notice. Florida requires the local authority to give owners of existing systems at least 180 days' notice before requiring changes (F.S. 633.202(18)(f)). Forward it to your vendor right away; the change needs the license holder's consent like any other modification (F.S. 633.202(18)(d)).

Systems also fail on paperwork. If the acceptance test gain values are lost, the owner can be required to rerun the acceptance test (IFC 510.5.4 item 6), and fire marshals ask for the licensee's consent and the FCC registration. Our inspection checklist lists what to keep.

If you need repair quotes, you can ask installers who serve your area through ERRCSCheck. Your request goes to up to 3 vetted installers who serve your area, with no texts and no cold calls.

Confirm any repair plan with your fire marshal (AHJ).