But to accommodate local sales, all of those “networks” from the past had to have fixed length stop sets in order to allow local abilities. The end result was many hours with unpaid PSAs for lots of PI spots inserted to fill unsolved timeCompanies such as TranStar and Satellite Music Networks were able to deliver 24/7 national formats in the 1980s without any timing or flow issues. They were tracked by Arbitron;s RADAR system for national sales.
The advantage of a “national station“ is that it can determine with flexibility the amount of commercial time needed to fill the requirements of sales. For example, on lighter sales days or later day parts extended music sweeps can be scheduled on extremely short notice as late as the afternoon prior. There is no need to consider local sales and Its potential need for commercial time which may not always be sold.