FCC rules just went into effect allowing FM stations to originate programming on boosters, effectively giving them the right to target ads to certain segments of their coverage area. The rule was approved in November 2024 but adopted in late July. 

In San Diego, Audacy’s KWFN 97.3 has a system with a main transmitter in Southeast San Diego and four independent boosters, each with HD capability. They could sell ads unique to booster coverage areas in La Jolla, Carlsbad, San Marcos, or Romona. The new rules allow up to three minutes per hour of independent broadcasting.

One limiting factor is with mobile receivers. When moving between coverage zones, a listener in an automobile would hear an ad being interrupted by a different ad. And with terrain shielding, as is likely in North County, these switches could occur frequently as one signal dominates another with movement. KWFN would have to file with the FCC to allow this operation. 

GeoBroadcast Solutions introduced the geotargeting concept, proposed the new rules, and developed the concept with several broadcasters, including KWFN. I was involved in helping to set up the boosters in 2021.  Precise timing with GPS helps to make synchronized boosters viable. Terrain helps isolate the booster from the main signal, but hills in the booster coverage area can make mobile reception tricky. Also, using boosters in a metro area like San Diego can be hindered by adjacent channel reception, especially when trying to maintain a digital HD sideband signal.