It's academic as the decision hasn't been made.
However, a multiplex occupies a whole UHF channel and all channels in the 700 MHz band are occupied. 700 MHz clearance involves reallocating UHF channels 49-60 to mobile 4G services (a loss of 12 UHF channels). Additional space could be granted on UHF channels 31-38 (8 channels) to accommodate the services lost on the channels reallocated to 4G.
Obviously, taking account of the regionally organised channel spacing the full number of multiplexes previously carried on 12 UHF channels won't fit into 8 channels. Also bear in mind that one of those channels isn't assigned to broadcasting and a further channel has been assigned to local TV. That brings the total down to just 6 UHF channels.
12 regional multiplexes displaced from the 12 UHF channels won't fit into the 6 new UHF channels. That means fewer multiplexes will be available, as stated in my original post. Clearly, they could convert the new multiplexes to DVB-T2 and merge, say, 3 multiplexes into 2. But, as I originally stated, when they start squeezing so many streams onto a DVB-T2 mux, the picture quality will suffer. We could end up with the more efficient compression of DVB-T2 being used to cram in more channels rather than to give improved picture quality.
That's just one scenario, the entire transmitter network could be organised as SFNs but as the transmitters aren't actually designed for this the distance between transmitters won't be ideal. That would probably mean that the SFNs would cover less of the population than the current arrangement. Another option considered, of course, was to only transmit the 3 PSB muxes post 700 MHz band clearance.
It will be interesting to see how things develop.
Arqiva indicate that it would be possible to have 6 multiplexes after 7
00 MHz clearance.
- in some scenarios coverage may be reduced.
- while it is in theory possible, there may well be issues co-ordinating the UHF band in SE England. 700 MHz clearance would remove the majority of frequencies allocated to the UK in use from Dover. Frequencies would need to be borrowed or traded with France.
Given the hassle created by the need for new aerials for many more households and more filters, it will start to turn viewers off. Add to that low quality videostreams compared to improving web quality over the next decade you do wonder whether the multiplex operators are trying to make the most money while they can.