Mariachi was heavily involved in cultural promotion as a way to create a unified Mexican identity after the end of the Mexican Revolution. One of these efforts was the promotion of mariachi as an international symbol of Mexican identity, first with radio and sound recordings and later with films. Mexico built a nationwide radio broadcasting network in the 1920s such as XEB and XEW, which began broadcasting mariachi music as a media production, rather than as a music for social events. This music was already being modified in part due to the advent of sound recording. For example, most son jaliscense
WARC bands codified in official recommendations, such as the IARU Region 1 HF Manager's Handbook, which states: Contest activity shall not take place on the 10, 18 and 24 MHz bands. Non-contesting radio amateurs are recommended to use the contest-free HF bands (30, 17 and 12m) during the largest international contests. (DV05_C4_Rev_07) Canada is part of region 2 and as such is subject to the IARU band plan. Radio Amateurs of Canada offers the bandplan below as a recommendation for use by radio amateurs in that country but it does not have the force of law and should only be considered a