DTV station identification; are local TV stations still analog on digital cable?

[Jeffhs]

Originally Posted by andy

It works because your cable system is still sending standard NTSC analog TV signals down the wire. These are the same type of signals that were used over the air, except they are sending them through a coaxial wire. The digital signals are on the same wire, but at a different frequency.

It's possible for analog and digital cable to share the same wire in much the same way analog and digital TV shared the same airwaves. They get along fine, as long as each channel is on a different frequency.

How can anyone still be transmitting analog when every television station in the US has turned off its analog signal? Television stations, and I think cable companies as well, are not allowed to transmit or otherwise use those signals anymore--it is all supposed to be digital or nothing as far as full-power television stations and cable companies are concerned. A lot of TV stations will find themselves in deep trouble with the FCC over this, and cable companies could find themselves in violation of some FCC statute as well for carrying analog TV signals.

[peverett]

Andy is correct. Also, I do not know of any law forbidding the transmission of NTSC analog via cable TV. The DTV law applies to over the air broadcasting(and only to high power stations). I am sure that local stations can provide their analog signals to the cable companies via cable, not via broadcast. Since they are not broadcast, the cost will be very low.

At one time, I worked on an ADSL system where analog phone signals and high speed digital data signals were sent via the same pots(plain old telephone service) lines using different frequencys. Although complex, it worked fine.

In fact I get my analog TV, high speed internet, and telephone signal via one cable at present-no problems.

[MelodyMaster]

Originally Posted by Jeffhs

How can anyone still be transmitting analog when every television station in the US has turned off its analog signal? Television stations, and I think cable companies as well, are not allowed to transmit or otherwise use those signals anymore--it is all supposed to be digital or nothing as far as full-power television stations and cable companies are concerned. A lot of TV stations will find themselves in deep trouble with the FCC over this, and cable companies could find themselves in violation of some FCC statute as well for carrying analog TV signals.

Others have given much more detailed answers, but to sum up..

(1) The signal that is sent over cable is NOT in any way the same signal that is sent over the air by the station transmitter, it is a brand new signal originated by the cable company, in whatever standard best serves the customer. Since this doesn't "Radiate" it is not regulated by the FCC. Though of course there are standards for channel numbering etc.

(2) The cable company generally doesn't even PICK UP the signal over the air, but by some closed-circuit means such as microwave or fibre, so whatever format the broadcaster uses is irrelevant to the cable company. However, if baseband/closed circuit reception is not available the cable companies have been already often been using the broadcasters' digital service for reception rather than analog, because the quality is better.

Satellite is just the same, it picks up the station, then retransmits it using its own methods, then the customer has a box to convert it to what the customer's TV needs, which has generally been VHF RF, if not composite or component video.