Fred Baumgartner is the former TV Product Manager for Nautel.
Fred started with AM in the 1970s, then FM, and now TV. Of all things in broadcasting, he loves transmission the most. He’s the guy with the 1954 1KW AM rig he’s slowly restoring for 160M Amateur operation; taking up the space normal people might have used for restoring a sports car. Fred loves a good idea, contemplating how to make this industry better, or an engineering puzzle.
Translators and ATSC 3.0
by Fred Baumgartner
Most television stations have any number of translators that repeat their signals into populated areas that the main transmitter can’t reach because of terrain or distance. A few of these are owned and operated by the station, often to reach communities and households that are metered. Most translators are owned and operated by other associations and organizations ranging from informal groups, governmental bodies to utilities.
I’m not the first one to observe that it’s unfortunate that the conversion to ATSC 3.0 (the new broadcast TV standard under development) won’t be concurrent with the loss to broadcasting of much of the UHF spectrum. One big reason to rush ATSC 3.0 along is that current TV translators often use the higher frequency UHF slots destined for repack and it will be difficult to relocate many of them into the shrinking spectrum.
Translators typically receive the mother station directly off-air and translate it to a different channel. These Multi Frequency Networks (MFN) are inherently spectrum inefficient. ASTC 3.0 offers a better solution in the form of Single Frequency Networks (SFN). While we usually talk about SFNs in terms of urban areas where the object is to reach devices and gateway routers deep within buildings; rural SFNs offer the ability to use the same frequency as the main transmitter over wide areas. Odds are pretty good that if a translator can operate on the same frequency as the main, that there will be a space on the dial for it.
There is some challenge moving translators to the same frequency as the main. Probably the most serious is that the translator’s program feed can’t come from receiving the main any longer. Fortunately, the availability of IP connectivity continues to expand and become more cost effective. ATSC 3.0 is inherently IP and the Studio Transmitter Links for SFNs lend themselves to IP connectivity.
The second challenge is, that if and where the main and translator signals overlap, the RF network design should minimize interference. There is a lot of room in ATSC 3.0 to adjust the timing, power and antenna patterns of the “translators” to maximize coverage while giving up little or nothing to destructive interference. Something that cannot be done with the current 8VSB DTV standard.
Translators have a way of growing in number to reach more people… if the spectrum is available. I think it safe to say that many a translator that might be on the air now, isn’t, because of the lack of an available slot. The ability to reuse spectrum as efficiently as ATSC 3.0 does is a powerful motivator to make the conversion to 3.0. Too bad ATSC 3.0 won’t be available until nearly the end of the projected repack cycle.
If you want to take a peek at what a TV translator might do for you, a tool that is helpful is Nautel’s FREE “Radio Coverage Tool” which covers UHF-TV as well as FM propagation. Create a free RF Toolkit account here, and once you’re in the Radio Coverage Tool and creating a coverage map select ATSC TV 41/48dBµV/M for North American TV, and select the default antenna and power or modify it for any location in the world.