The agency triumphed in a six-way pitch against incumbent Faulds Advertising, among other unnamed agencies.
The brief covers all Big City Network's stations, which are available in eight UK cities: Key 103 in Manchester; Metro Radio in Newcastle; Radio Aire in Leeds; Radio City in Liverpool; Hallam FM in Sheffield; Viking FM in Hull; and Rock FM in Preston.
Karmarama is to roll out regional campaigns from the autumn across each of the areas the stations cover.
Big City Network brand director Brendan Moffett said: "We want to continue building audiences with an innovative advertising programme focusing on the unique content and output of the individual stations. Karmarama has provided an exciting creative response."
The review of the account follows a lacklustre performance in the last set of Rajars.
The appointment does not effect the media communications planning account, which is held by Naked, or brand planning, handled by Sparkler.
Ramchandani, joint creative director of Karmarama, said: "Emap was on our list of companies we wanted to work for and we're looking forward to working with Big City Network. It's a great opportunity to deliver some unexpected creative solutions through a series of high-profile promotions."
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