How do they work: Conversion Boxes

[TexDX]

This may have been covered somewhere else at another time, so please excuse if this is 'old stuff'.

How, exactly, do conversion boxes re-map an ATSC signal and make it look like the 'old' NTSC channel is being tuned? Is that some sub-carrier that the station sends?

Will this phenomena continue in February when no NTSC stations remain? Or will we have to get used to (example) "CBS 48" instead of "CBS 2", and 'reprogram" our boxes? I have three up and running and am satisfied with look and 'feel' of them. Although I wish the remotes were larger in size.

What are cable and satellite outfits going to do that have local channels on the numbers we've had for 50 years? Re-map them to the new channels?

Sign me :confused:

73,

BILL

[w9wi]

This may have been covered somewhere else at another time, so please excuse if this is 'old stuff'.

How, exactly, do conversion boxes re-map an ATSC signal and make it look like the 'old' NTSC channel is being tuned? Is that some sub-carrier that the station sends?

Will this phenomena continue in February when no NTSC stations remain? Or will we have to get used to (example) "CBS 48" instead of "CBS 2", and 'reprogram" our boxes? I have three up and running and am satisfied with look and 'feel' of them. Although I wish the remotes were larger in size.

What are cable and satellite outfits going to do that have local channels on the numbers we've had for 50 years? Re-map them to the new channels?

Sign me :confused:

73,

BILL

Worry no more:)

There are provisions in the DTV standard for stations to "remap".

Actually, your analog TV is already remapping. "CBS 2" doesn't actually broadcast on channel 2 -- it broadcasts on 55.25MHz. If you punch up 2 on your analog TV's remote, the internal circuitry knows to tune to 55.25MHz. If you punch up 4, the internal circuitry tunes the TV to 67.25MHz.

The difference with DTV is that the station is able to inject itself into the process.

"CBS 2"'s digital signal broadcasts a stream of data bits. Some of this data represents the picture; some represents the sound. Some is "metadata" - data that describes the sound and picture signals. This "metadata" contains a data table that describes the station's "major_channel" and "minor_channel". These major and minor channels are what the station wants your TV to display.

CBS 2 transmits major_channel=2 and minor_channel=1. (if it has subchannels, they will have different minor_channel numbers)

When you scan in the channels, your TV builds the remapping table. Instead of 2 remapping to 55.25Mhz, CBS 2 has told your TV to have it remap to 674.31MHz. (the frequency we know in the analog world as "channel 48") When you punch in "2" on your remote, your TV tunes to 674.31Mhz.

If you were to take the TV to Chicago and scan in the channels again, the remapping table would be built differently: CBS 2 Chicago will tell your TV to tune to 60.31MHz when you punch in "2" on the remote.

There is nothing either technical or regulatory to force cable or satellite operators to change the channel numbers they use for the existing over-the-air stations. If CBS 2 is currently channel 2 on your cable system, it will still be channel 2 on cable after the transition.

So, after the transition, whether you're watching CBS 2 on cable, on satellite, or on over-the-air digital, you'll still punch "2" on your remote to get the station. And for that reason, CBS 2 won't be changing its branding. It will still call itself channel 2.

[Robert Grant]

What station is being referred to, here??

I though the CBS station in Ft Worth was KTVT, analog 11 and DT 19.

Rob

[w9wi]

Hypothetical. There is no CBS affiliate on DTV-48 & analog-2.

[TexDX]

Didn't the original message say (example)?

Maybe not.

:confused: