A New Look at Low-VHF
Could extending the FM band work in Mexico?
Across Mexico, it sits in near-total silence.
Once upon a time, the low-VHF band was the beating heart of Mexican television. Channels 2 through 6 were prime real estate, often among the first channels to be activated in any given area. Mexico City had a 2, 4, and 5 before it had an 8 or 13. Mexico’s density of low-VHF stations made it a delightful and bewildering land for TV DXers, the very reason that this blog was started six years ago today. Even in the dawn of the last decade, with a digital transition looming, the Organismo Promotor de Medios Audiovisuales built the country’s last new low-VHF television stations, channel 2 Oaxaca and channel 5 Mérida. Those assignments had been freed up in prior years by channel shuffles designed to make maximum use of the VHF television spectrum, all while there were no primary UHF television stations in ten states.
That was then.
This is now. ATSC works best in UHF, and Mexico had the room to put almost every existing service on the band, even to repack stations on channels 38–51 entirely to other UHF channels. There’s been something of a high-VHF revival, despite the small challenges that sometimes face stations transmitting on channels 7 to 13, because it was wide open nationwide.
The problems that plague low-VHF digital television stations are well known from the United States. Even high-VHF outlets have sought UHF positions. While several public and social allotments have been set aside in the low-VHF band, there is just one authorized — and unbuilt — low-VHF television station in Mexico, Puebla’s XHCSBA-TDT 4.
Right now, this portion of the spectrum sits silent nationwide — aside from pirates coast-to-coast, border-to-border using 87.5 to 87.9 MHz for FM — awaiting a use. And it’s worth asking if, at least for two of the five low-VHF channels, television broadcasting is the highest calling.
FM Below 88?
The history of FM broadcasting below the present band of 88–108 MHz is longer than the history of the present FM band. Prior to 1945, it was 42 to 50 MHz where early FM radio resided. And in Japan and the Soviet Union, the used FM band wound up lower.
Japan’s FM band of 76–95 MHz, extended in 2013 from its former 76–90 MHz allocation to allow several AM stations to move to the FM dial after the country ended analog television service, is a critical reason why the idea of wiping out TV channels 5 and 6 (76–88 MHz) is feasible. It means tuners already exist for FM in that spectrum.
American Talk, Brazilian Action
The idea of extending FM to 76 MHz has been kicked around in some form or another in the United States since the digital television transition there, being most seriously considered around 2009.
No country, however, has embraced the idea with more gusto than Brazil. Freed up as television stations migrate to digital, the “extended FM” band of 76.1–87.3 MHz (Brazil assigns 87.5 to 87.9 to community stations) is being used to support a major metro AM-FM migration scheme (in less densely populated areas the standard band can accommodate migrants), and since 2017 new receivers have been required to support the full band of 76–108 MHz. This means there are receiver designs and hardware available to support a 32 MHz FM band. While no stations have yet moved, a public comment period about the process ended in September 2019 with more than 300 comments received.
Technical standards for such a band have been mooted before. REC Networks has made a number of proposals for extended FM in the United States, which are quite Japanese-inspired, include quite a lot of detail, and are also designed to help smaller AM broadcasters regain competitive parity.
Addressing Systemic Problems in Mexican Radio
Converting 76 to 88 MHz to primary radio use would add 60 new channels to the 100 available between 88 and 108. These channels could support a variety of new services:
- Public radio: Mexico does not have a national public radio service, and its existing public radio services do not add up to national coverage. A two-program public radio network could easily be assigned on 4 MHz (two MHz per program). (Financial feasibility is another topic.)
- Religious radio: If Mexico ever legalized religious radio, I warned in 2019, it would create a flood of demand for new station assignments. A portion of the extended FM band could be set aside for all religious services if the government were to ever allow religious associations to own concessions.
- AM-FM migration in additional cities: In Mexico City, Puebla (by errors still being litigated), Tijuana and Ciudad Juárez, there was not enough room to migrate at least one station from all operators to the FM band. In Juárez, all available frequencies identified in 2016 had to be reserved; in Tijuana, there were no available FM allotments at all. In border areas, likely half of the band would be available to Mexico and half to the United States.
- Additional community/indigenous stations and potentially room for new commercial services in the largest cities where demand exists. We’ve already seen one community station assigned on the AM expanded band operate as a pirate FM still (that’s XECSCA-AM 1670 Tarandacuao Gto., which went on 106.7 again and drew the ire of co-channel XHCSAL-FM in Contepec, Mich.)
Potential Problems
This isn’t all roses, though. While the benefits of expanding FM are rather apparent, there are also some drawbacks:
- You need receivers, and they need to be available. Mexico is not a technology leader: by virtue of free trade agreements and economic flows, it is a technology laggard and is quite locked into doing whatever the US does. (See: the 1990s DAB controversy, where Mexican stations feared they’d be frozen out of US audiences because the United States had no intention of using the standard seriously.) (Also see: at the last National Radio and Television Week, there was an ATSC 3.0 seminar.) So if the US doesn’t get on board, it makes it harder for Mexico to do likewise.
- International agreements with the United States would need to be amended to treat 76–88 MHz as FM radio space instead of television space and to create a table of allocations.
- RDS v1 does not support alternate frequencies below 88 MHz. But that’s why there’s… RDS v2. Thanks, RDS Forum.
However, given the poor suitability for low-VHF for 8VSB-modulated ATSC digital television, the lack of stations assigned to the channel, and the potential for more efficient use as 60 FM channels (adding 10 to 15 usable frequencies in each area) rather than two TV channels, extending the FM band may be an idea whose time is about to come in Mexico.
