Advice Needed Which are the satellites used for cable and freeview feeds?

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RichardCoulter

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Now that it's been confirmed that Horse & Country is leaving Sky, but remaining on Virgin Media, i've been wondering how VM will source their feed. I've been told that there are satellites that exist to provide feeds for cable and DTT and that perhaps it will go onto one of them.

Does anyone know anything about these satellites? I have heard about a satellite that has the PSB channels on it as a back up that are encrypted, but I think this is something else.
 
Adam792

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Mostly all over fibre in this country nowadays.

As far as I am aware, certainly most if not all of the HD channels carried by Virgin Media are supplied from the TV channels' playout via Fibre to VM where they then get encoded and multiplexed onto Virgin's network, without any satellite being involved.

A lot of SD channels were downlinked from the same satellite feeds at 28.2ºE as used by Sky/Freesat, but this may also have changed to fibre for at least some since they've switched to MPEG4 on Virgin's network (the MPEG2 SD feeds fed by satellite were passed into the VM network without re-encoding when they were MPEG2). They'll probably just get a feed via fibre from Horse & Country themselves.

Way back years ago, in the analogue cable and early digital cable days of NTL and Telewest, the channels they couldn't obtain via the Sky feeds or digital terrestrial tended to be carried on Intelsat 27.5ºW (incidentally, this is still where the encrypted PSB back-up for Freeview transmitters you've mentioned lives), as well as a few other satellites around 34.5ºW-37.5ºW. Channels like Tara TV from Ireland, Performance, and Bravo/Discovery (the longer hours analogue versions that weren't on Sky analogue) were carried on these satellites.

For Freeview, all the transmitters are fed by fibre too (main transmitters), with smaller ones just rebroadcasting a main transmitter off-air. The PSB back-up on 27.5ºW carries BBC-A (PSB1 Mux) and BBC-B (PS:cool: channels with a few limited regional variations (BBC One SD in Scottish, Welsh, NI and network England versions) that get used at some smaller transmitters if the main feed (off-air reception of the parent transmitter usually!) fails. The SDN multiplex (nowadays also referred to as COM4) used to be fed to the transmitters via satellite over Eutelsat 16ºE about 15 years ago but that's long since stopped.

Other countries (France, Spain, Italy, Greece, and some others) mainly use satellite to feed their terrestrial networks, which may be the satellites you're hearing about. These countries use satellite due to the use of large-scale single frequency networks over digital terrestrial - satellite is an easy way to provide all transmitters with an identical feed that can be synchronised. The UK national DAB radio multiplexes are actually fed via satellite (Astra 4.8ºE) for this reason too!
 
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RichardCoulter

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Many thanks for explaining this.

So, the back up satellite only carries BBC channels and nothing from ITV, Channel 4 or Channel 5? If i've got this right, what are their back up plans?

Are the DAB muxes on Astra 4.8°E encrypted too?
 
Analoguesat

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One ITV C4 & C5 are carried on 27.5W

FlySat Intelsat 907 @ 27.5° West - check 11495V

Incidently ever since the 28E UK spotbeams were tightened, the expats in Spain love this service as its fairly easy to open with the right receiver :-rofl2
 
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Adam792

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Many thanks for explaining this.

So, the back up satellite only carries BBC channels and nothing from ITV, Channel 4 or Channel 5? If i've got this right, what are their back up plans?
Yep, just PSB1 and PSB3 channels, so that does include the HD versions of ITV, C4 and C5 but only because they're carried on the BBC HD multiplex.

For the commercial channels and muxes, there aren't any back-up plans in this sense. If the feed fails at a small transmitter site for them then it fails until it gets fixed I guess! They don't want to fork out the expense for a satellite back-up.

Are the DAB muxes on Astra 4.8°E encrypted too?
Nope, they're free to air data streams on the 12303H transponder. There's actually some tools that can be run on a computer (with a PC satellite card) to listen to the radio stations (and see the associated text data like the DLS radio text) from them!
 
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Analoguesat

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Yep, just PSB1 and PSB3 channels, so that does include the HD versions of ITV, C4 and C5 but only because they're carried on the BBC HD multiplex.

For the commercial channels and muxes, there aren't any back-up plans in this sense. If the feed fails at a small transmitter site for them then it fails until it gets fixed I guess! They don't want to fork out the expense for a satellite back-up.
And with mobile phone operators readying for a massive spectrum grab on the dtt frequencies the tv transmitter network wont be needed much longer so these feeds will disappear in the next few years anyway.
 
Fisty McB

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Channel Five's analogue terrestrial network was (mostly) fed via satellite as well, pretty much from the start. IIRC they used two separate satellite positions out in the Atlantic, 18W & 37.5W if I'm right though they might have moved to a different nearby position at some point. At the time, they had advertising regions like Channel 4 with two regions on one satellite and the other two regions on the other. The satellite feeds were in DVB-S MPEG2 encrypted. A few weeks after they had launched, a thunderstorm near their main transmitter site serving Greater London (Croydon) affected reception of the satellite link, resulting in viewers there trying to watch a movie in the evening that kept breaking up. Sections of the press ridiculed Channel 5 for this even though the issue was (AFAIK) just confined to London, resulting in the broadcaster upgrading the link to Croydon to a landline connection not long after, likely fibre optic.
 
jeallen01

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Somewhere in England (possibly?)!
Fibre optic distribution is becoming more common nowadays - hence, e.g. the Andre Rieu concert distribution via 1W having apparently now disappeared for the last few months.
 
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RichardCoulter

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RichardCoulter

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Yep, just PSB1 and PSB3 channels, so that does include the HD versions of ITV, C4 and C5 but only because they're carried on the BBC HD multiplex.

For the commercial channels and muxes, there aren't any back-up plans in this sense. If the feed fails at a small transmitter site for them then it fails until it gets fixed I guess! They don't want to fork out the expense for a satellite back-up.



Nope, they're free to air data streams on the 12303H transponder. There's actually some tools that can be run on a computer (with a PC satellite card) to listen to the radio stations (and see the associated text data like the DLS radio text) from them!
Ahh right, I thought that they would somehow work by connecting a dish to a DAB receiver.
 
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RichardCoulter

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And with mobile phone operators readying for a massive spectrum grab on the dtt frequencies the tv transmitter network wont be needed much longer so these feeds will disappear in the next few years anyway.
So do you think that DTT is on It's way out?
 
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RichardCoulter

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Channel Five's analogue terrestrial network was (mostly) fed via satellite as well, pretty much from the start. IIRC they used two separate satellite positions out in the Atlantic, 18W & 37.5W if I'm right though they might have moved to a different nearby position at some point. At the time, they had advertising regions like Channel 4 with two regions on one satellite and the other two regions on the other. The satellite feeds were in DVB-S MPEG2 encrypted. A few weeks after they had launched, a thunderstorm near their main transmitter site serving Greater London (Croydon) affected reception of the satellite link, resulting in viewers there trying to watch a movie in the evening that kept breaking up. Sections of the press ridiculed Channel 5 for this even though the issue was (AFAIK) just confined to London, resulting in the broadcaster upgrading the link to Croydon to a landline connection not long after, likely fibre optic.
I remember Channel 5 eventually being put onto Astra analogue (transponder 64 I think it was). You'd have thought that when this started they would have used this as their back up to cut costs.
 
Adam792

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Ahh right, I thought that they would somehow work by connecting a dish to a DAB receiver.
They use a format called ETI which is a data format that can carry a full DAB multiplex (the encoded and multiplexed programmes) as a single data stream. The transmitters themselves will just accept ETI data as their input (no matter whether it comes in via satellite or fibre) and then modulate it for transmission.

You can broadcast it to your own DAB radios using a modulator device like a HackRF to create the signal on your computer from the ETI stream (just like the transmitters do). I’ve seen somebody in Germany doing this from these feeds with Digital 1 DAB!

For the BBC Freeview back-up transmissions on 27.5°W they use BISS encryption, but in a non-standard way as the actual DVB table data (the data that tells a receiver what channels are actually on the transponder and what the PIDs for their video, audio, subtitles, etc are) is also encrypted, to make it more difficult to view for unintended audiences! (Not impossible, although that’s shady ground and not something that can be spoken about in detail here of course!)
 
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Adam792

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And with mobile phone operators readying for a massive spectrum grab on the dtt frequencies the tv transmitter network wont be needed much longer so these feeds will disappear in the next few years anyway.
I think some form of Freeview is guaranteed until at least 2030 as far as I’m aware, and the BBC multiplexes as public service will probably be the last to go in any case!

Always a possibility that the satellite back-up could be gotten rid of at any point though, if the BBC decide it’s not worth the extra money for the redundancy it gives/has to make cost cuttings. As you’ve said before, for that reason it’d certainly be unwise to rely on it always being there!

As I’ve said before, I think we’ll end up with mobile broadband taking all of the spectrum eventually, but some kind of broadcast (maybe just news and live sport) being maintained over 5G/6G/whatever exists by then. 5G broadcast has already been trialled by European public broadcasters including the BBC.
 
Analoguesat

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I think some form of Freeview is guaranteed until at least 2030 as far as I’m aware, and the BBC multiplexes as public service will probably be the last to go in any case!

Always a possibility that the satellite back-up could be gotten rid of at any point though, if the BBC decide it’s not worth the extra money for the redundancy it gives/has to make cost cuttings. As you’ve said before, for that reason it’d certainly be unwise to rely on it always being there!
Indeed - I would put a lot of money on the main players (BBC / ITV especially) having some sort of fall over disaster recovery agreement with SES so if the craft carrying their muxes had a major on orbit incident thay are priority for relocation onto other frequencies. If so then the 27.5W backup could be seen as an unaffordable luxury......
 
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RichardCoulter

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I've read that the Astra signals are in the wrong format to be able to be used by the Freeview transmitters though, which is why they use 27.5W.
 
Analoguesat

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I've read that the Astra signals are in the wrong format to be able to be used by the Freeview transmitters though, which is why they use 27.5W.
I would have thought that coul;d easily be solved with the appropriate boxes of electronics at the head ends?? (No idea - Im not a transmission expert)
 
Adam792

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I would have thought that coul;d easily be solved with the appropriate boxes of electronics at the head ends?? (No idea - Im not a transmission expert)
It’s more the fact that that sort of thing would be very expensive to implement at each transmitter site. No doubt way more expensive than having this existing back-up on a little used satellite position that is presumably way cheaper than more in-demand capacity like UK Spot beam 28.2°E. That’s why I wouldn’t be surprised if when/if it gets switched off from 27.5°W it just won’t be replicated anywhere - with them just deciding that any downtime suffered at any small transmitters just has to be dealt with (as the commercial PSB SD channels have already decided!)

Basically, as it stands the BBC Satback feeds on 27.5°W are all encoded ready in the right formats and bitrates so that the digital data can be fed directly into the terrestrial transmitters when the back-up is required, without having to touch the actual video/audio/ancillary data itself (aside from decrypting it which doesn’t take much effort). The relay transmitters that use it are only equipped to modulate the digital data as a DVB-T/DVB-T2 signal on a UHF frequency, they don’t have the facility to actually re-encode any video or audio which would be required if they didn’t use a tailor-made feed. They just take in the pre-encoded digital multiplex data, and whether this comes in via a terrestrial signal from a parent transmitter (most of the time) or via the 27.5°W back-up, it’s already all in the right format ready for transmission. This keeps the equipment at these very small transmitters pretty cheap and basic (in the grand scheme of things)!

A lot of the more problematic relay transmitters that struggled with off-air reception of their parent transmitter (and thus would have relied on the BBC Satback feed more frequently) have gradually become fibre-fed for the BBC multiplexes over the last few years. Transmitters in mid Wales and rural Somerset. If that continues then that would likely be the point at which Satback gets switched off once it’s not worth it for the tiny fraction of transmitters that ever need it any more!
 
Fisty McB

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I remember Channel 5 eventually being put onto Astra analogue (transponder 64 I think it was). You'd have thought that when this started they would have used this as their back up to cut costs.
The Astra analogue service (which closed by the end of 2001) was effectively an infill for those outside of its terrestrial service area, and in any case would not have been a useful backup to the main satellite distribution as it is quite likely that were the main feed to fail due to external interference, then it's unlikely a feed from Astra 1D would have been useful either. Without knowing how they were arranged, it would appear to me that splitting the TX feeds over two different satellite positions was to allow a backup to be put in place, so if the feed from 18W failed at a particular site due to receiver failure then 37.5W could kick in and vice versa.

As to the suitability of using the intended DTH broadcasts from 28E for DTT use, the big issue here is that the TV channels on satellite will be stat-muxed and will therefore vary over time. To insert them into a DVB-T/T2 multiplex you'd either have to know what is the maximum allowed bitrate of the video stream so you can ensure all video streams can be accommodated on the multiplex without going over capacity, which would mean an awful lot of null bits being required and thus a lot of capacity wasted, or reencoding of the feed into the multiplex which obviously takes a hit on the output picture and audio quality - you want the lossy picture output to be first generation where possible. In the analogue days for cable providers this wasn't an issue, as many of the channels they provided were fed to them via Astra 1 that they could simply decode and insert into their network (some channels were fed via alternative satellite positions, 27.5W was once quite popular) but for DVB-C transmissions they could only take a direct satellite feed either as the entire content of a satellite transponder/multiplex from DVB-S to DVB-C and recode a new Network Information Table in the DVB-C signal, or take a channel whom was operating at a fixed bitrate for video as well as audio, this being predictable to insert into a DVB-C multiplex. Nowadays, most indivudal channels on Virgin Media's network provide the operator with either an uncompressed or lossless feed which VM encode into a multiplex before being sent for distribution.
 
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