At the same time I was putting together the vintage radio tutorial from earlier this week Jeff Devine just happened to be working on a scenario involving Arkham's first radio station. He was kind enough to send over this business card for it.
In the real world the WRKM call letters were unassigned until around 1960, when they went to a licensee on 1350 AM in Carthage, Tennessee. After getting an extension on their tower construction permit they appear to have gone on the air in 1963. That would suggest the owners of the Arkham station either went out of business or asked for new call letters sometime before that period.