Channel Television

But apparently they do get ITV3 (SD).

I wonder whether the lack of ITV HD could be because the HD mux is fed from the satellite backup, which only contains the London variant? Analogue BBC services were fed from Astra so it would not surprise me if they did that either due to fibre capacity or cost.

Possibly, but then why would the HD Mux be supplied that way when the other BBC Mux isn't?

I remember a discussion about this here a while back about whether ITV HD reaches the islands and is blanked by the service data, or the channel is just not there at all. I can't remember the conclusion though. I'm pretty sure it's purely an editorial thing and a seperate version of the Mux is deliberately created for the islands

The more pressing question surely why is Sewing Quarter on the PSB commercial mux?

We all do, it’s on PSB 2. However it was on COM 4 until this year, but in the CIs it was was already on PSB2 displacing ITV+1

You could apply that logic to any mainland region though ? All three muxes are delivered by the same
fibre network from the mainland mux farms, as the other 79 Tx sites. It's hardly a massive amount of bandwidth, 30-40 Mb/s per mux, so less than 100 Mb/s in total. Some people could support that with their domestic broadband line !

Because the other BBC mix requires BBC One CI which isn't on the satellite.

On the mainland that mux contains a different version of ITV HD in each region and I think different BBC One HD in the nations, services which are not carried on the satellite backup.

Fair point that it's not a lot of data, I don't know how much capacity the fibre has and whether it's cost effective to use it.

PSB 3's transport streams (for all the regions) are assembled centrally at the BBC's CCMs on the mainland.
It makes absolutely no difference to the bandwidth required whether or not ITV or any other service
is absent from that version of the mux, because you still have to 'pad out' the TS with null packets to replace them.

I don't follow your logic regarding D-Sat back up ?

It's probably that the Satellite backup service (not Sky DSat but the PSB 1 and 3 backups on Intelsat 907 that feed main transmitters as a backup for the redundant fibres) only carries one ITV HD variation, STV HD and UTV HD (If that's still the case post UTV becoming part of ITV plc)

https://en.kingofsat.net/tp.php?tp=1524 (Pretty out of date as BBC HD was replaced by BBC Two HD a while back, and I expect that transponder now contains CBBC HD too.)

This is OK for backup purposes in England but I doubt ITV Channel's advertisers would want PSB3 ITV HD permanently to carry no commercials sold to the Channel Islands communities (plus there may be legal issues with that ITV HD region going out in the Channel Islands - ISTR advertising compliance issues in the old days of TVS?) I think the point was being made that if PSB3 was derived from this satellite backup source, it would be an option to remove ITV HD (or not include it) rather than broadcast the 'wrong' ITV HD.

You could still achieve that, because the SI tables in a back up situation are generated at the individual Tx sites, and it would just be a case of 'not pointing' to the ITV HD stream (just as you wouln't point at BBC 1 HD Scotland etc) ?

I think we're at crossed purposes.

The suggestion was that if the CI TX sites were fed by Satback they couldn't get an ITV HD feed with CI adverts in it, so would blank it. This was used as a reason to suggest the CI TX sites weren't fibre fed. (Assumption being that fibre fed TXes could have a specific ITV HD feed)

However another suggestion was that generating an ITV HD Channel Islands feed at RedBee wasn't cost effective, and/or coding and muxing it to create a CI PSB3 mux wasn't, even if the transmitters are fed fibre.

Yes, my suggestion was that the HD mux *only* might be generated locally using satback, given the BBC's history of not using the fibre to feed the analogue channels using it back in the day, implying it might be cost prohibitive.

The other muxes are CI specific so would be handled in a more conventional way.

I'll seek clarification from someone that will definitely know chapter and verse, but I'm sure there are gigs and gigs and gigs of fibre bandwidth to and from the CIs now (think of all the banks there !)