ATSC3 Frequencies

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scubajwd
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Joined: Fri Aug 23, 2013 10:31 am

ATSC3 Frequencies

Post by scubajwd »

Showing illiteracy here; why are all the ATSC3 channels at the
same frequency? In my case :563 MHz; I thought broadcast
signals needed separation; obviously my understanding of the
physics here is lacking..Merry Christmas or Happy Holidays to All

signcarver
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Re: ATSC3 Frequencies

Post by signcarver »

They are the same tv frequencies but a different frequency from other stations.... I believe you previously mentioned Vegas and 563 would be physical 29 which was your cw station which moved the 1.0 feed to 13 to convert 29 to atsc 3.0

bobchase
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Re: ATSC3 Frequencies

Post by bobchase »

scubajwd wrote: Fri Dec 25, 2020 9:04 am Showing illiteracy here; why are all the ATSC3 channels at the
same frequency? In my case :563 MHz; I thought broadcast
signals needed separation; obviously my understanding of the
physics here is lacking..Merry Christmas or Happy Holidays to All
The 3.0 "channels" that you see are not really channels at all. While they are labeled with channel numbers so that you can find them on your TV or device, they are actually multiple IP streams multiplexed onto/into one RF channel. In a few cases there is actually more than one 3.0 RF channel in a market, but even then, both physical channels will contain multiple streams typically using the existing 1.0 PSIP channel numbers to identify the individual streams.

scubajwd
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Re: ATSC3 Frequencies

Post by scubajwd »

Oh so..multiple ip streams..then all the majors in my market will
use 563Mhz as the container? NBC FOX ABC CW NBC CBS et al?
Does this scheme originate in one tower location? I keep wondering
why I'm missing Fox in my market?

signcarver
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Re: ATSC3 Frequencies

Post by signcarver »

Typically for "all" majors they will need (at least) 2 physical channels so another station will be needed and then convince "fox" to carry them (in HD if there isn't another major you are missing). For example here in Phoenix the cw station went to ABC's physical channel in HD, while it's subs went on fox's physical channel and the cw station (frequency) converted to atsc 3.0 and carries cw, abc, fox, and another, while the other atsc 3.0 station carries the Spanish language channels, CBS, NBC, pbs... however there is an issue with fox (and that other) in that data is missing to actually use it.

chris_in_texas
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Re: ATSC3 Frequencies

Post by chris_in_texas »

scubajwd wrote: Fri Dec 25, 2020 9:04 am Showing illiteracy here; why are all the ATSC3 channels at the
same frequency? In my case :563 MHz; I thought broadcast
signals needed separation; obviously my understanding of the
physics here is lacking..Merry Christmas or Happy Holidays to All

Don't get confused by RF channels and virtual channels. Also for a virtual channel X, if they have an ATSC3 transmitter and ATSC1 transmitter then they would be on different RF channels. The ATSC3 on RF Y and ATSC1 on RF Z.

Back in the analog days when you watched a channel that was the RF channel, however DTV changed all that. Now you can combine channels into a single RF transmitter but still select the channel you knew it by like Fox4 here in Dallas. Its all a single data stream now where all the sub-channels can live. Most of the time they are like virtual channel 4.1, 4.2, 4.3 etc on a single RF transmitter, however that isn't always the case. Now with ATSC3 multiple networks are being combined into a single RF channel, with vastly different virtual channels. They could be all on the same frequency.

Using that example of Fox4, which is the virtual channel that you see on your TV that you select to watch, but in reality the TV itself changes to RF channel 35 program 3 to broadcast ATSC1. If you want to watch Fox4.1 on ATSC3 it will tune to RF channel 34 program 4. With the ATSC3 tuner if it knows that there is a ATSC3 transmitter it will use that instead of the ATSC1. This is where SD is working on a fix to "select" which broadcast you receive either ATSC1 or ATSC3. It will fix the AC4 issues with a majority of the equipment that is out there today, that can't decode it.

scubajwd
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Re: ATSC3 Frequencies

Post by scubajwd »

Thanx Mr Texas..Happy New Years...stay safe down there

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