Greetings ...

From the very beginning back in the late 1940's, one of the key selling features of CATV (Community Antenna TV, as Cable-TV was originally called) was its ability to take each OTA channel - particularly UHF - and re-transmit it over-the-wire on a different frequency.

I (strongly) suspect that the same can NOT be done with digital TV channels. If such re-transmission is indeed not possible, please briefly explain why.

Thanx-A-Lot, Frank-0-Video

I (strongly) suspect that the same can NOT be done with digital TV channels. If such re-transmission is indeed not possible, please briefly explain why.

Hi there

Off hand I would guess that there is no reason why the carrier frequency could not be shifted. In other words, I disagree with you, and think it is possible.

The issue is, why bother? There was a time when TVs did not have UHF tuners, so block converting the UHF band to VHF made those channels accessible with a VHF tuner. What does moving a digital channel accomplish? The answer is nothing. You still need a digital tuner, which typically has a 3-band (VHF-lo, VHF-hi and UHF) TV tuner.

Regards

Aren't they already doing that? Before I cancelled my cable a year ago I could scan the frequencies and find local digital broadcasts at frequencies different than the broadcast OTA.

Or are you asking something else?

I (strongly) suspect that the same can NOT be done with digital TV channels. If such re-transmission is indeed not possible, please briefly explain why.

Thanx-A-Lot, Frank-0-Video

It's done everyday by cable companies..using off-the shelf QAM processors it's quite easily done.

It might make a comeback with cable upgrading to 1GHZ since few tuners go above 854MHZ. A STB for the STB, that's going to be fun.

It's done everyday by cable companies..using off-the shelf QAM processors it's quite easily done.
And it's not that awfully expensive, either.

Greetings ....

Thank you all for the replies.

A key item you did not address - the sub-channels. Would they be preserved in a frequency shift??

Thanx-A-Lot, Frank-0-Video

Nearly all broadcast channels carried on cable are frequency shifted, because, other than channels 2-13, the cable channels are at different frequencies than are the broadcast channels. Agile, heterodyne channel converters sell for under $1,000 each.

Broadcast digital signals are modulated using 8VSB modulation, which has been mandated for television transmission in the United States. But cable companies have determined that their interests are better served if the signals are QAM modulated, so the cable company in addition to changing the RF channel frequency, demodulates each the 8VSB channel and then remodulates it in QAM form. The most affordable equipment to do that costs close to $3,000 per channel. While converting to QAM is beneficial to the interests of cable companies, privately owned master antenna systems serving multiple dwelling unit buildings do not usually do that because they don't incur the same bandwidth congeation that cable companies do, and because the subsidized CECB decoder boxes cannot demodulate and process QAM modulated signals.

Any simple heterodyne channel conversion or demodulator-remodulator pair preserves the entire digital contents of the input broadcast channel, including sub channels and PSIP, so once TV tuner recognizes a frequency-converted channel, it will often display its "virtual channel number" regardless of what actual channel frequency it found it on, unless the conversion process does something deliberate to the program information to make the TVs number it otherwise.