After KPBS-TV abandoned channel 15 during the digital conversion in June 2009, the FCC allocated that spectrum to first responders in the Los Angeles and Orange Country for use in mobile 2-way voice communications, otherwise known as “T-band” public service spectrum. Past UHF-TV channels 14, 16, and 20 are also so designated in the L.A. metro area.
Fast forward to 2017. FCC and Mexican authorities hashed out a TV band plan for the border region in the era that would follow selling the 600 MHz TV spectrum to U.S. telecom operators. In that plan, Mexico got channels 15, 21, 27, and 30 for their displaced channels 44 and 46 (Tijuana), and 47 (Tecate).
The FCC reserved for Mexico the channel positions in the border region by entering into their database as much information about a theoretical station as they could. Interestingly, channel 15 is reserved, but for Ensenada, at a safe distance from the T-band activity in Orange County and Los Angeles.
It’s not clear exactly when it happened, but Canal Once (a Mexican public broadcasting network) affiliate XHTJB-TDT moved from channel 46 to 15, apparently with its signal emanating from Cerro Colorado, a hill south of the Otay border crossing and east of Mte. San Antonio, where most other TV transmissions emanate from. This, of course, is many kilometers north of Ensenada.
A flurry of emails went out from radio technicians in the L.A. basin August 17 to broadcast engineering consultants in San Diego asking for more information about their new, interfering neighbor. It remains to be seen what can be worked out between public service radio management up north and Mexican representatives of the government and Instituto Politécnico Nacional, owners of XHTJB. As of this writing, the station remains on channel 15 (virtual channel 11-1 and 11-2) at what appears to be its full 79 kW assigned power output.