How is the transtion to 1.0 different from 3.0 other than some major station groups have proposed a voluntary transition 3.0 has more bandwidth with more efficent video compression and does not even interfere with 1.0,
The difference is that there will be a lot less channels available to begin with. Upon completion of the DTV transition, 18 channels were wacked from the top of the TV band. It seems likely that more will be removed one way or the other (I'm thinking VHF low) in the not too distant future. At the same time, quite a few more subchannels have appeared so the net bandwidth usage hasn't gone down. In my market, channel consumption has actually gone up by two channels.
1.0 stations do not need to share bandwidth with 3.0 stations what is being proposed for the trasition to 3.0 is one or a few stations will switch to 3.0 and one or a few stations will carry those stations with 1.0 in that market
The explaination is that both 1.0 stations and 3.0 stations will broadcast each other
This where the lie happens. The standards absolutely do have to share the bandwidth pie. Because ATSC 3.0 is substantially incompatible with ATSC 1.0, the ATSC 1.0 stations don't change anything and, at least initially, consume the same bandwidth that they do today. ATSC 3.0, in order to drive adoption, must duplicate all of the same programming using bandwidth that isn't currently in use. This takes additional bandwidth out of a smaller pie than the previous transition. Many of the compression and modulation efficiencies will be eaten up by additional services that are added to make ATSC 3.0 attractive.
At 2:1 savings, it is 50% more bandwidth than we're using now. It doesn't matter one iota how the stations cooperate as at least initially, they will be two separate systems independently broadcasting all the same content in a TV band that is at best 27% smaller now than it was seven years ago. At some point, they'll start removing subchannels from ATSC 1.0, but without a mandate, how is that cut-off timed?
While you may have been hoodwinked by elegant answers to a few key questions, the public is a huge mass that moves very slowly when it comes to their TV content (look how long it took VHS to die and how slowly Blu-ray has progressed). The people won't adopt a new standard based on promises.