The BDA and the VRS

A good majority of the fire service community has at least heard of a Bi-Directional Amplifier (BDA) and a Vehicle Repeater System (VRS). But what exactly are they and why are they a valuable tool in the tactical fire communications toolbox?

A BDA is a booster of incoming (Rx) and outgoing (Tx) radio traffic. You can find them in most large, modern buildings, and in most below grade transportation systems. The actual BDA is typically in a room with other telecom equipment. A system of conduit, antennas, and radiating cables (also known as leaky-lines because they are stretched down tunnels and corridors and act as a long antenna) are installed in the areas where a radio system’s signal is weak or non-existent.

Most Authorities Having Jurisdiction (AHJs) have mandated, by building codes and law, the installation of BDAs in these compromised areas. An example would be Montgomery County, Maryland’s BDA requirement in new buildings greater than 25,000 square feet (the Metro system that runs through Montgomery County has an extensive system of BDAs and uses radiating cables stretched throughout the system’s tunnels). Also of note are the instances where companies with existing large buildings that have known communications problems have approached the building’s management, gotten the fire code compliance folks involved, and through positive dialogue convinced the building’s owner to install a BDA.

When a building with known communications issues does not have a BDA, a fire department can purchase and equip select units with a VRS to bridge the gap between the Public Safety Radio System (PSRS) and areas where there are issues. It’s essentially a repeater and an additional mobile radio installed in a vehicle that once on scene and operating, boosts the ability to transmit and receive in areas on an incident scene where communications are compromised. The VRS requires radio end users to switch to a repeater channel (talk group) on their portable radio in order for the system to work. It takes radio traffic on this local VRS talk group and ties it in to the PSRS, on the tactical talk group assigned at the time of dispatch.

Some fire departments outfit their command vehicles with VRS, while others, like the District of Columbia Fire Department, have VRS installed on 110 vehicles, including fire apparatus. You might be asking, “what happens when all these VRS units get on the scene and turn them all on?” As it turns out, so long as the vehicles aren’t close to one another, you’re good. In my department, the 1^st VRS equipped unit goes where the Battalion Chief parks their command vehicle. The 2^nd VRS equipped unit goes to the opposite side of the incident scene (if the 1^st VRS is on side A, the 2^nd one goes on side C). This does a good job of covering a building with compromised communications.

As with everything else in the fire service, these are merely tools in the toolbox, options for your next play. What makes these tools great is training with them, and educating your firefighters on how best to use these tools on the big one.

*Special thanks to DCF/EMS Captain Todd Bianchi for he correction on the number of VRS units on DC rigs.