How a BDA System Improves Radio Strength to Save Lives in Emergencies

By Andrew Erickson

December 16, 2022

A BDA (Bi-Directional Amplifier) system is a signal-boosting solution designed to enhance emergency responder radio coverage. This is an important technology for protecting first responders during an emergency. It's also increasingly mandated by state and local fire codes.

What is a BDA system?

Your BDA system enhances in-building radio coverage for two-way radio communication within buildings or other enclosed environments. This provides clearer and more reliable communication between responders. This allows them to communicate with one another without interference. Even when there are walls or other obstacles that can normally impede the signal.

What building types require radio amplification?

BDA systems are primarily used for facilities where fire, smoke, or hazardous materials would present a threat to human life. These situations require an emergency response from the fire department. These include public and private office buildings, schools and universities, hospitals, industrial plants, warehouses and manufacturing facilities. BDA systems can also be used in residential buildings as well.

Typical placement of bi-directional amplifier near top of a building

As shown in this cutaway, a BDA system is most commonly near the top of a building to amplify signals coming to and from the donor antenna on the roof. This increases signal strength heard by both first responders in the building and commanders and dispatchers outside.

Do notice, however, that fires aren't the only threat to public safety where perfect radio reliability is important. Police similarly need flawless communications when they enter a building during a shooting or terrorism scenario. EMTs (Emergency Medical Technicians) can save more lives when they can radio for additional support. The might also need to summon emergency medical transport to a nearby hospital.

What's the problem when you don't have a good amplifier installed in your building?

To understand why in-building radio is so important, first consider how radio works outdoors or in small buildings. Under normal circumstances, the signal from the nearest radio tower travels through the open air. It may perhaps cross through the exterior wall of a small home or office. There's not much in the way, so radio communication is generally unimpeded.

Now, think about how different things are inside of a skyscraper in a dense urban environment. Before public safety radio signals even get close to your building, they probably get weakened by surrounding buildings. Once inside, untold quantities of metal and concrete further degrade radio signals.

Imagine yourself as a firefighter, struggling to evaluate and beat back a raging fire. You need to be able to send and receive information in real-time. Patchy radio coverage is immediately frustrating and can even turn deadly.

What are the overall system components surrounding the Bi-Directional Amplifier?

A BDA system is composed of an amplifier, antennas, and cable connecting the outside of the building to the inside. The amplifier amplifies radio frequencies, allowing them to travel farther and through thicker walls. This improved coverage ensures emergency responders can remain in communication with one another while responding to an emergency situation.

Notice that this an enhancement to a standard in-building antenna system. Signals are already received by the "donor antenna" on the building's rooftop and distributed throughout the building. Now, the BDA will also actively boost the signal strength. All of the hardware performs better once you have installed a Bi-Directional Amplifier.

What are the advantages of a BDA system?

A BDA system has several advantages that make it an invaluable tool for protecting fire fighters and other first responders. Signal boosters the risk of “dead zones” within a building, areas where radio signals cannot reach. This allows responders to stay in contact even when they are separated by walls or floors. Additionally, it helps reduce interference with other communication systems that may be using the same frequencies, helping ensure reliable communication during an emergency.

A BDA system is an essential tool for protecting first responders in the event of a fire. By providing enhanced radio coverage and reducing interference, BDA systems protect live. They help ensure emergency responders can stay in communication with one another while responding to an emergency situation.

This improved building radio frequency (RF) signal strength supports better communication. It allows them to take decisive action quickly and helps keep them safe while they respond to the emergency. BDA systems are becoming increasingly mandated by state and local fire codes.

It's more important than ever for building owners to ensure they have a BDA system in place. Investing in this technology can help protect first responders and save lives.

What fire codes and building codes mandate BDA installation?

In recent years, BDA systems have become increasingly mandated by state and local fire codes. For example, the International Fire Code (IFC) Section 510.4 requires that BDA systems be installed in multi-story buildings over 75 feet tall. In addition to the IFC, many other building codes also require BDA installation for certain circumstances. You'll commonly see requirements for post-construction building surveys to verify a minimum dB level of -95 dB RSSI.

Interestingly, mandates thus far have existed primarily in local building codes rather than NFPA fire codes. That's not hugely significant, as any building owner already must have plenty of experience dealing with provisions in both. Just don't make the mistake of assuming that "because NFPA doesn't mention it", you're safe.

It's essential for building owners like you to stay up-to-date on the BDA requirements in their region. Without a BDA system, emergency responders cannot be sure of reliable radio coverage inside of a building. This can put them, and other building occupants, in danger. Investing in radio reliability is an important way that building owners can help protect first responders and save lives.

What areas within a building present the biggest problems for radio strength?

Radio signals can be particularly weak in elevators, stairwells and other areas with thick or reinforced walls. Multi-story buildings are also more likely to have “dead zones” than single-story buildings due to signal attenuation. This is caused by the number of floors between the BDA system and the donor antenna.

Basements are difficult for obvious reasons. It's tough to achieve line-of-sight to a radio tower when you're in a hole in the ground covered by a large building.

The amplification system is designed to amplify the signal throughout the building, but it cannot completely eliminate these dead zones. BDA systems can be particularly helpful in multi-story buildings with elevators and stairwells. They help ensure that radio signals are still able to reach all floors of the building.

In addition, BDA systems also reduce potential interference from other communication systems that are using the same frequencies. This can help ensure reliable communication during an emergency.

Who manufactures BDA systems that you can purchase?

BDA systems are typically manufactured by companies that specialize in fire safety, such as Fire-Lite Alarms or System Sensor.

There are a variety of bi-directional amplifier (BDA) manufacturers on the market, each offering different features and advantages for fire safety.

Fire-Lite Alarms is one of the most well-known BDA manufacturers. They've been in business since 1953. Their BDA systems are designed to amplify public safety signals within buildings, helping ensure uninterrupted communication during emergencies.

System Sensor is another BDA manufacturer, offering BDA systems that are designed to provide enhanced radio coverage and reduce interference from other communications systems. They also offer a variety of BDA accessories such as antennas and cables. If you're looking for systems for your building, be sure to do your research and choose one that meets your needs.

BDA systems are available for purchase through select suppliers. They should be installed by a professional to ensure they comply with local building codes.

BDA systems can also be integrated into existing fire alarm systems that include in-building radio. This allows you to easily upgrade your fire safety system. BDA systems are a valuable investment for protecting first responders. They should be considered by any building owner looking to improve the safety within their property.

What is a FCC GROL-certified technician, and why do I need one?

A FCC GROL-certified technician is someone who has passed a series of exams administered by the Federal Communications Commission (FCC). This person will then become certified in General Radiotelephone Operator License (GROL).

Having a BDA system installed and maintained by a professional is essential for ensuring it meets local fire codes. Any system you choose should be installed and maintained by a FCC GROL-certified technician to ensure it meets code requirements.

Your technician will also act as the liaison between you and the local Authority Having Jurisdiction (AHJ). They'll work with you in the event of any deficiency that must be corrected. As with most things, it pays to contract with an expert in the field.

What are the steps involved in a BDA system inspection?

In order for BDA systems to comply with local fire codes, they must be inspected by a professional on a regular basis. BDA system inspections involve two main steps: testing the system’s performance and ensuring that it meets code requirements.

The technician will first measure the BDA system's RSSI level (Received Signal Strength Indicator). This is a measure of the system's signal strength and, therefore, signal coverage for public safety radios. If this level is below specification, it indicates that the BDA system requires additional tuning or adjustment for optimal performance.

RSSI levels are measured first. Then, the technician will then check for any deficiencies in compliance with local building and fire codes. The BDA system must meet all requirements in order to be considered compliant.

After the BDA system inspection is complete, your technician will provide you with a detailed report of the system's performance and compliance status. This report should be kept on file for future reference.

The BDA system inspection process is essential for ensuring fire safety. It's important to have them inspected on a regular basis. BDA systems are an invaluable tool for protecting first responders. They should be well maintained with inspections performed by a certified technician.

By following proper BDA system inspection procedures, you can rest assured. Your BDA system will be in compliance with local fire codes and providing optimal performance. This will help keep your building and people safe in the event of a fire or other emergency.

What does a BDA system cost? How much do you have to pay?

The cost of BDA systems vary depending on the size, type and complexity of the BDA system being purchased. Generally speaking, BDA systems can range anywhere from a few hundred dollars to several thousand dollars.

In addition to the cost of purchasing a BDA system, there are other costs associated with a BDA system such as installation and inspection. Installation costs can also vary depending on the specific system being installed and the complexity of the installation process.

It generally costs at least as much to install a piece of business-grade equipment as it did to buy it in the first place. That's a standard reference rule for financial planning. Installing BDA systems, unfortunately, doesn't do much to break this budgeting rule.

BDA system inspections should be performed on a regular basis and cost an additional fee for each inspection.

Overall, BDA systems are a worthwhile investment for any building looking to improve fire safety. They can provide superior protection for first responders. Both the cost and the invaluable safety benefits of BDA systems should be taken into consideration when budgeting fire safety costs.

How does antenna gain (dB) work?

Antenna gain is one of the most important considerations when selecting a BDA system. Basically, antenna gain (or dB) refers to the amplification or increase in signal power that an antenna provides.

For BDA systems, it is important to choose an antenna with the right amount of gain for your specific application. Too much gain, and the system can be overpowered - while too little gain will result in poor coverage and performance.

In BDA systems, antennas are rated based on the number of decibels (dB) they are capable of producing or amplifying. The higher the dB rating of an antenna, the more signal power it is able to produce or amplify. Depending on your BDA system's needs, you may require an antenna with a higher dB rating than what is typically offered.

It is also important to consider the type of signal being transmitted when selecting an antenna gain for BDA systems. For example, some antennas are better suited for transmitting radio waves while others are better at sending signals over fiber optic cables. Take care when selecting an antenna for BDA systems. It's crucial to ensure that the dB rating and type of signal are compatible with your system's needs.

Ultimately, BDA systems require antennas with sufficient gain for proper performance and coverage. Understanding how antenna gain works is a critical piece of selecting the best BDA system for your needs. BDA system antennas should be carefully selected to ensure safety and optimal performance.

Checklist for buying in-building BDA systems:

When looking to buy an in-building BDA system, there are a few things you should keep in mind:

  1. Make sure the BDA system meets local fire code requirements. BDA systems must meet specific codes set by the AHJ in order to be compliant.
  2. Ensure that the BDA system will provide adequate coverage for all areas of the building. BDA systems should cover all areas in which public safety radios may need to be used.
  3. Look for BDA systems that are easy to install and maintain. Look for systems that are designed to be user-friendly and require minimal maintenance.
  4. Make sure the BDA system is compatible with all existing public safety radios. They must be compatible with all types of public safety radios in order to be effective.
  5. Consider BDA system inspection and maintenance costs. BDA systems should be inspected on a regular basis by certified technicians. It's important to factor in these costs when budgeting for BDA systems.

Following these guidelines will help ensure that you purchase the best BDA system for your building. You'll minimize costs associated with BDA system installation, maintenance, and inspections.

What other system reliability should I focus on improving in my building?

We're on the topic of vital systems that can save lives. It's good to take a moment to think about your fire alarm system. After all, that system must work before a BDA system becomes relevant at all. The fire department must be summoned before they need radio communication in your building.

In recent years, some fire alarm systems have transitioned to using mesh radio networks. Many of the same coverage considerations that apply to BDA systems will apply to your fire alarm system.

More broadly, fire alarm systems require good monitoring no matter how they communicate back to the head end. You need to select good fire alarm control panels (FACP). If you're running your own fire alarm monitoring locally, you need to select the right central server. It should have proven monitoring technologies and be a reliable device itself.

Call Digitize to discuss your next steps

We're experts in fire alarms at Digitize. This also gives us background knowledge on things like BDA systems. Give us a call at any time, whether or not you need our fire alarm monitoring equipment.

We're happy to help. After all, there's a good chance you work on a fire alarm system at some point. We also love to identify new technology segments for our engineers to pursue.

Call Digitize at 1-800-523-7232 or email

Andrew Erickson

Andrew Erickson

Andrew Erickson is an Application Engineer at DPS Telecom, a manufacturer of semi-custom remote alarm monitoring systems based in Fresno, California. Andrew brings more than 17 years of experience building site monitoring solutions, developing intuitive user interfaces and documentation, and...Read More