RadioReference.com lists local police scanner frequencies in the United States and many other countries. The website also lists radio frequencies for municipal services, federal departments, airports, businesses and ham-radio stations, and it provides links to Internet rebroadcasts of certain police frequencies.
To find local police radio frequencies on RadioReference.com, click the Databases tab at the top of the homepage. Change the country, if necessary, using the Choose Country dropdown, and then click the desired location on the map. Use the search options below the map, such as Retrieve by State, Frequency Search by State or Search FCC Licenses by State, for more specific searches. RadioReference.com relies on user-submitted data, and its information may not always be complete or up to date.
There are various types of police radio scanners, according to Scanner Master, a scanner manufacturer. The three main types are analog conventional, analog trunking and digital. Conventional analog scanners are the simplest, and often the least expensive, but, as of 2015, most police forces use trunking analog or digital systems.
As of 2015, many police forces are also switching to encrypted systems, which prevent members of the public from listening to police frequencies, reports USA Today. For instance, the Metropolitan Police Department in Washington, D.C., switched to a encrypted system in 2011 after criminals used a police scanner to plan crimes around police movement.