[1][2] Petránek was a journalist for Czech Radio, the public radio broadcaster, at the time of the Prague Spring and the Warsaw Pact invasion of Czechoslovakia in 1968.
[2] He was fired by Czech Radio's management shortly after the invasion, but resumed underground, independent broadcasts during the country's Normalization period.
[1][2] In the late 1980s, Petránek also became involved with the samizdat publication of the Lidové noviny newspaper, which had been banned by the Communist government since the 1950s.
[2] Petránek became the editor of the Lidové noviny once the newspaper was legalized following the Velvet Revolution.
[1] In 2015, President of the Czech Republic Miloš Zeman awarded Petránek the Medal of Merit.