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  • 1 Post By Terryl3

OTA bandwidth vs. picture quality question

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Old 12-06-2017, 11:10 AM   #1
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Default OTA bandwidth vs. picture quality question

I know that with ATSC tuners in TVs, the old standard 6MHz wide channel has been chopped up into 3 2MHz wide channels now? My question is why don't the broadcasters transmit in 1080i format on all 3 channels now? For instance, here in the Dallas/Ft. Worth area ABC transmits on channels 8.1, 8.2, & 8.3. But only 8.1 has a 1080i signal. The other 2 channels are 480i. This isn't a limitation because of bandwidth is it? Why doesn't ABC broadcast all 3 channels in 1080i?

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Old 12-07-2017, 11:16 AM   #2
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They can't it would by like trying to put 10 pounds of poop into a 5 pound bag.

And the TV channels are really 10 MHz wide, but you have guard bands to keep the channels that are close by from interfering with each other.

If you look at the local channel plan for your area you will see that there are no channels directly above or below each other.

Example: If there is a TV channel 40 there with be no TV channel 39 or 41 at the same location, the adjacent channel interference would wipe out both, also there can't be one above or below within a certain distance from the main, this to stop what is called inter-mod, this is where two or more strong closely spaced RF channels combine and create an unwanted third.(or more)
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Old 12-07-2017, 07:27 PM   #3
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Additionally, ABC stations broadcast 720p not 1080i. There is room for them to do 2 HD channels in 720p with dynamic allocation. Our ABC station has 2 HD subchannels.

2 SD channels (480p) is roughly the same bandwidth of a 720p channel.
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