Created Sunday 30 April 2023
The National Weather Service (NWS), which is part of the National Oceanic and Atmospheric Administration (NOAA), operates a network of radio stations across the country that broadcast in narrow FM on seven different frequencies. The Canadian counterpart is called Weatheradio Canda, and broadcasts in English and French; the Mexican counterpart, called SARMEX broadcasts in Spanish, and there are also two English-language Caribbean stations based in Bermuda.
The mode and frequency choice was made to make these easy to incorporate into marine-band radios. In addition, they can be received on any police scanner and most 2m-capable ham radios.
The seven frequencies are:
162.400 162.425 162.450 162.475 162.500 162.525 162.550
There are channel numbers associated with these, but they don't go in order and are hardly ever used, so not really worth making yourself familiar with.
Basic alert capability
Generic radios, such as a scanner or ham radio will not have the ability to receive this, however, some purpose-built weather radios have the ability to receive a wake-up signal from the NOAA broadcasts, which will turn the radio on in the event of an emergency in the coverage area of whatever station it is monitoring.
SAME alert capability
Building on the basic alert capability, some weather radios can use a system called SAME, which stands for Specific Area Message Encoding. This is an extended alerting system in which the wake-up signal includes information about the specific area or areas of a station's coverage area are affected by an emergency alert, as well as information about the nature of the emergency.