LPTV stations on Channel 6 will have until July 13, 2021 to complete their digital transition, according to the FCC’s Incentive Auction Closing and Channel Reassignment Public Notice, released 13 April 2017.
This appears to put an end date on the “Franken-FM’s” on 87.76 MHz, but only as we currently know them. They still may be permitted alongside ATSC 3.0 in a future FCC decision (and probably closer to 87.9, given the physical limitations of ATSC 3.0).
FM stations use a 75 KHz of deviation standard, and ATSC 3.0 would end at 87.76. Using tight spacing with that standard, there would be a tiny guard band between TV 6 and the FM band.
My Engineer Commentary:
There are a few options here. Like I said above, they could just try tight spacing, but that does not seem the most viable.
ATSC 3.0 is made to withstand a certain amount of interference. If the FM signal is (considerably) lower power and as close to the edge of the channel as possible, this may work. There can be no harmful interference.
Another option would be to use vertical polarization for the FM (while the TV is horizontal). But it would be a different antenna pattern transmitting different content. At what point would the FCC consider that to be a different station?
A 4th option may be to use narrowband audio, possibly combined with the “lower power” concept or vertical concept.
Can’t wait to see what happens here!
Franken FMS should be allowed in the future as an extension of the FM dial to 87.5 and no longer required to be low power TV stations. New car radios do have 87.5, 87.7 and 87.9 on them. Existing stations on all three frequencies should be restricted as Class A, B-1 or C-3 stations and licensed to broadcasters that now operate them without going through the bidding process. The licenses of all ‘new stations’ seeking these three frequencies should be granted through the bidding process. Existing owners should not be penalized by having to bid on the licenses of stations in which they have put thousands of dollars.
Rather than having to bid, let’s say existing owners can retain the existing license by paying the FCC an amount based on its revenue from the previous year. This way the FCC still gets $$$$ and existing owners do not risk losing their licenses to a higher bidder.
Because of cable, people are unlikely to miss Channel 6. All Franken FM stations should operate as FMs, both commercial and non-commercial, depending who wins the bidding process for the new stations not already on the air. Also, they should licensed as Class A, B-1 or C-3 stations. The 60 dBu signal of a Class B-1 is 27 miles, C-3’s about 25 miles and a Class A 17 miles. None of the stations on these frequencies would be allowed in a city with a station on 88.1 unless their towers are placed at the FCC’s required minimum separation distance from that station on 88.1 The distances vary depending on the Class and power of the station seeking a CP.