BDA systems for firefighter radio coverage

Fire department radios often fail inside large or dense buildings. Concrete, steel, low-emissivity glass and basements block the signal. A BDA system fixes that with three parts working together:

• A donor antenna on the roof talks to the public safety radio tower.
• The bi-directional amplifier boosts the signal in both directions: down to radios inside the building, and up from those radios back to the tower.
• Indoor antennas, connected by coaxial or fiber cable, spread the signal through the floors.

The model fire code does not require every building to install one. It requires coverage. A building that already has good enough signal inside needs no amplifier. A building that cannot support the required coverage must add "systems and components to enhance the radio signals" until it does (IFC 2021 510.4.2.1).

The monitoring list in the model code has eight supervisory signals: loss of AC power, battery charger failure, donor antenna malfunction, failure of active RF devices, low battery at 70 percent reduction of capacity, failure of critical components, loss of the link to the fire alarm system, and oscillation (IFC 2021 510.4.2.5).

Local codes often go further. San Francisco requires the booster and its UPS in a 2-hour rated room and a remote connection that lets the City shut off the uplink (SFFD AB 2.01 Addendum G, II.G and II.N). Pierce County, Washington approves only Class A boosters (Pierce County ERRCS Handout). Check your local requirements page before anyone orders equipment.

Under the 2021 model code, a building has acceptable coverage when 95 percent of all areas and 99 percent of critical areas on each floor meet the signal requirements (IFC 2021 510.4.1). The inbound signal must be at least -95 dBm and give a Delivered Audio Quality (DAQ) of 3.0 or an equivalent signal-to-noise measure (IFC 2021 510.4.1.1).

Those are model numbers. Fire departments change them. San Diego and Palo Alto ask for DAQ 3.4, and Los Angeles' Requirement #105 uses 90 percent for general areas. Your fire code official's technical criteria document decides (IFC 2021 510.4.2.2).

A BDA rebroadcasts radio frequencies that belong to a licensee, usually the city, county or regional radio authority. Federal rules set three conditions that matter to owners:

• Consent. A building owner or contractor who is not the licensee must get the licensee's express consent before operating a booster, and keep it in a recordable format for the FCC (47 CFR 90.219(b)(1)(i)). Florida law repeats this for every new system or modification (F.S. 633.202(18)(d)).
• Registration. Class B signal boosters, those with a passband wider than 75 kHz, must be registered in the FCC signal booster database (47 CFR 90.219(a) and (d)(5)).
• Weak signal areas only. Boosters may improve coverage in weak signal areas but may not extend a station's normal range, and each retransmitted channel is limited to 5 watts ERP (47 CFR 90.219(d)(1) to (d)(3)).

The model code requires the designer and lead installer to hold a valid FCC general radio operator license and in-building system training from an approved organization or the equipment manufacturer, unless the fire code official accepts other proof of skill (IFC 2021 510.5.3).

Some cities add more:

• Houston requires ERCC plans sealed by a Texas Professional Engineer.
• Phoenix requires NICET In-Building Public Safety Communications certification for designers and lead installers.

Each city page lists its own rules.

1. Check whether your building likely needs coverage, with the source for each answer.
2. Read your state or local requirements for signal levels, bands and permit steps.
3. Learn what a system costs and how it is tested.
4. When you are ready, request up to 3 quotes. Your request goes to up to 3 vetted installers who serve your area. We send no texts and make no cold calls.

Confirm with your fire marshal (AHJ) before you design, permit or test anything.