The Media Bureau of the FCC issued a Public Notice last week seeking comment on whether channel 6 analog LPTV stations should be able to continue to operate after the deadline to switch to digital.
Even after the 2009 TV broadcast transition to digital, the FCC allowed LPTVs to continue to broadcast in analog until 12 months after the completion of the post-incentive auction repack, due for a July 3, 2020 completion. This means LPTVs would have to make the digital switch by July 3, 2021.
This aural service on TV channel 6 has taken the pejorative term “Franken-FM” due to the distorted analog TV broadcast technology that boosts the power of the FM aural carrier, increases the modulation, sets the pre-emphasis to match that of the FM broadcast band, and usually runs a video slide show or fixed graphic in the visual portion of the signal. This is all done to add an FM station to the market. Venture Technologies, based in Los Angeles, has placed these stations all over the country, including KRPE-LP in San Diego, on Mt. San Miguel. Most home and car radios can receive this signal on 87.75 MHz, and such stations generate marketing materials promoting “87.7 FM.” Venture Technologies leases its signals to third-party programmers.
Comments must be in to the FCC 45 days after the comments solicitation is published in the Federal Register.
What Should be Done?
(Making Waves – Commentary) On one hand, there’s a high demand for aural broadcasting on the FM band, and 87.7 MHz is a desired channel for this. Broadcast engineers cringe every time another AM translator, FM low power, or rimshot station is added to the market. The noise floor continues to build, making it difficult for a receiver to discriminate between desired and undesired signals.
Do we need channel 6 for TV? If you see what LPTV broadcasters are doing in low-band VHF, I would maintain that we do not, that it should instead be turned over to an expansion of the FM band. In Japan, the FM band starts at 76 MHz, so we know radios can readily handle this.
However, forward-thinking engineers see the opportunity to use digital technology to expand aural services on TV channels. Why could you not have a car radio receive as many sub-channels on an ATSC-3 signal as you could fit in a 6 MHz, or even 12 MHz channel? How many could you fit in 57 Mbps of HE-AAC or VP9? Lots, right? With error-correction, appropriate compression levels, and stat-muxing, 500? 1,000?
A carrier, like AT&T, Pearl, Venture Technologies, SiriusXM, iHeartMedia, or Comcast could broker bandwidth to all takers. With the right error correction scheme, you could provide excellent service. Single-frequency networks with circular-polarization antennas could extend coverage regionally or even nationwide. Of course, the current stakeholders like iHeartMedia, Entercom, and other large groups might work against such a plan. If your objection is that we don’t have existing radios for this, you aren’t looking ahead. If we can build Xpiri or SiriusXM car radios, we can modify them to demodulate ATSC 3. And why not add all of the TV bands while we’re at it?
We engineers rightfully cringe at the prospect of wasting 5.8 MHz to broadcast an FM signal on TV channel 6. How about we allow a more efficient way of doing this?
(Gary Stigall is the editor of the SBE Chapter 36 and a contract engineer. Venture Technologies is a client of his company, Signal Wiz.)