In order to be able receive a particular signal with your TV tuner device you will need to tune/set it to the correct radio frequency used by that source transmission. Therefore, you (or, at least, the viewing application you are using) will first want to know which frequencies are used for transmission and thereby are tunable for your receiver at your location of residence. Frequency scanning utilities, listed below, perform such signal detection and, generally, provide a list of the frequencies upon which content is discovered, with which higher level applications can then in turn use for tuning purposes.
Note: Historically, the set of frequencies used under the older analogue systems have differed from one another, meaning that the particular frequencies used across North America, Europe, Asia, etc., etc., will differ depending upon the transmission standard adopted within each nation. When countries began to make the transition to digital TV systems, most have opted to continue to use their old channel frequency schemes so as to make the switch from analog to digital systems as seamless as possible for the end user.
Frequency Scanning Utilities
- scantv (part of xawtv package)
- apps with built in scanning ... tvtime, xawtv/motv (which call upon scantv), kdetv ...
One of the handiest tools for scanning frequencies is "(dvb)scan", a utility included within the LinuxTV dvb-apps package. (dvb)scan parses the information from a pre-configured initial scan file that is specific to a particular country/region/location/service_provider (many of which are contained within the dvb-apps package as well as being available within the wiki or elsewhere), then tunes into the frequencies and lists the names for all available PIDs.
- scan-s2 
- apps with built in scanning ... kaffeine, MythTV, Me TV
Digital For some other general sources (which may or may not be that useful) for finding local channel frequency lists, see: