The broadcast imperative is to be on the air and available at all times, especially during emergency situations. Most facilities possess redundant capabilities and signal paths in order to maintain their over-the-air and cable feeds. In larger markets, more robust measures are employed. These are usually "case-hardened" facilities that include multiple power feeds from diverse power generation stations, full backup power generators at the studio and transmitter sites, multiple signal paths from studio to transmitter sites, redundant transmitters /antennas and direct feeds to cable and satellite operators. All of these minimise the number of single points of failure that could keep vital information from being broadcast.
Some humanitarian agencies have "radio in a suitcase" kits on standby, which are used to re-establish FM radio services when these are destroyed or damaged. Used in conjunction with a small petrol-driven generator, the equipment can enable an FM radio station to be on-air within hours of a disaster occurring. The idea is usually not to set up a completely new radio station, but to operate a special radio service on the FM frequency and broadcasting licence of a local partner station that is no longer able to broadcast from its own studios and transmitters.
In the United States, the FCC's Communications Security, Reliability and Interoperability Council (CSRIC) was formed to provide recommendations to the FCC to ensure, among other things, optimal security and reliability of communications systems, including broadcasting, during terrorist attacks, natural disasters and all other threats or attacks nationwide. The FCC's Media, Security and Reliability Council (MSRC) for radio and television broadcasting developed Best Practices, which were updated by the CSRIC. The Best Practices include recommendations for detecting, preparing for, preventing, protecting against, responding to and recovering from terrorist threats, natural disasters or other attacks upon national infrastructure and people.
The 2011 CSRIC report on Best Practices can be accessed at http://transition.fcc.gov/pshs/docs/csric/WG2B-MSRC-Best-Practice-Update-Final-Report.pdf
The following Annex provides examples of operational methods used to assure continued broadcast service:
Annex 3A: BBC Media Action - Use of emergency equipment.