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

[Analoguesat]

Theoretically in that case the 27.5W feed could just be switched to a spare tp on 28E on the UK beam? About time they started turning off the SD DVB-S stuff anyway

 

[Fisty McB]

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!

As far as I know, there is at least one relay station that uses SATBACK as its primary DTT feed for the PSB1 & 3 multiplexes that is based on the Isle of Barra on the Western Isles of Scotland, basically because the only RBL feed after digital conversion has been unreliable. PSB2 (ITV/C4/C5) is still fed by RBL but if the feed fails, then it goes until conditions return to "normal" again.

In terms of distribution either for main or backup, cost will factor - but as a backup it is arguably now even more important because of the 700MHz clearence - the more common reuse of UHF frequency allocations increase the risks of interference at a site for either RBL (used at relays) or RBS (used at sites as a backup link) for either to be reliable. As an example, the Strabane relay station in NI has had to change its RBL twice since DSO, originally for analogue & DTT it was fed via the Limavady transmitter but this was shortly changed to being fed via Brougher Mountain, while after the 700MHz clearence in September last year, its RBL feed is now due to change to the L/Derry relay which itself was originally RBL fed from Limavady but now has its own fibre feed.

 

[Fisty McB]

Theoretically in that case the 27.5W feed could just be switched to a spare tp on 28E on the UK beam? About time they started turning off the SD DVB-S stuff anyway

In theory, it's possible but in practice it would be complicated and messy. The 27.5W feed uses a transponder Symbol Rate (45000 IIRC) that none of the craft at 28E is capable of handling. Then you come to the issue of regional variations - not an issue for COM5 and COM6 but it can be for the others. It used to be the case, especially Pre-DSO, on the main BBC multiplex that in England the capacity was "split" into two blocks, one to carry the local BBC One region at a fixed data rate, and the second block to carry all remaining BBC TV "national" services that were collectively stat-muxed in this data block - the "national" channels were distributed to local DVB-T multiplex encoders to be inserted into them alongside the local BBC One region before being sent to transmission sites.

In the likes of France & Italy where one PSB channel is regionalised (France 3 & RAI Tre) the satellite distribution to terrestrial TXs involves the regional channel being sent via its own "stream" while the rest of the nominal multiplex content is sent via an alternative stream. At the transmission site both of these streams would be combined into one DVB-T/T2 multiplex to then transmit/broadcast, not dissimilar to the method for early BBC DVB-T distribution mentioned above. It's for technical reasons like that that (for example) at 5W the multiplexing of services for the French DTT networks and the Fransat platform are kept separate.

It's possible that the SATBACK broadcast could move to a new satellite in the not too distant future, especially if it worked out cheaper - the Intelsat 907 satellite at 27.5W is already operating beyond its expected service life of 13 years having launched in February 2003 and I've heard no announcement from Intelsat about a potential replacement. Over the Atlantic there are two somewhat close by orbital positions that have UK targeted footprints which could provide continuity of service (allowing for dishes to be realigned, of course!) from Telstar 12 Vantage at 15W and Intelsat 32e (aka Sky Brasil 1) at 43E, the latter at first appearing as though it would be too low on the UK horizon but in northern & western parts of the UK wouldn't be much different to that for 28E in the same location. I think there might be one or two more Intelsat positions even further out west with Ku-Band spot beams aimed at the UK but they would risk not being above the horizon in some tricky locations.

Incidently, Q Radio in Northern Ireland use 27.5W these days to distribute their audio feeds to their transmitters (outside of those TXs serving Greater Belfast), but use a symbol rate of only 500 thus not possible to receive on most domestic DVB-S2 receivers.

 

[Adam792]

As far as I know, there is at least one relay station that uses SATBACK as its primary DTT feed for the PSB1 & 3 multiplexes that is based on the Isle of Barra on the Western Isles of Scotland, basically because the only RBL feed after digital conversion has been unreliable. PSB2 (ITV/C4/C5) is still fed by RBL but if the feed fails, then it goes until conditions return to "normal" again.

In terms of distribution either for main or backup, cost will factor - but as a backup it is arguably now even more important because of the 700MHz clearence - the more common reuse of UHF frequency allocations increase the risks of interference at a site for either RBL (used at relays) or RBS (used at sites as a backup link) for either to be reliable. As an example, the Strabane relay station in NI has had to change its RBL twice since DSO, originally for analogue & DTT it was fed via the Limavady transmitter but this was shortly changed to being fed via Brougher Mountain, while after the 700MHz clearence in September last year, its RBL feed is now due to change to the L/Derry relay which itself was originally RBL fed from Limavady but now has its own fibre feed.

Ahh interesting! I didn’t realise it was actually the main feed for anything, although in those far-flung Scottish islands it does make sense.

As you say, the 700MHz clearance most likely makes it more necessary rather than less to have an alternative feed too.

 

[Fisty McB]

As far as I know, there is at least one relay station that uses SATBACK as its primary DTT feed for the PSB1 & 3 multiplexes that is based on the Isle of Barra on the Western Isles of Scotland, basically because the only RBL feed after digital conversion has been unreliable. PSB2 (ITV/C4/C5) is still fed by RBL but if the feed fails, then it goes until conditions return to "normal" again.

Found it - it's the Bruernish relay site...

mb21 - The Transmission Gallery

If you compare the four sets of photos (the second page has two sets) you can see its evolution over from analogue relay to digital. It looks like at DSO there was originally two different RBL aerial set ups, one working as a pair and another as a single that looked decidedly battered with missing elements. Shortly afterwards a new "trough" receiving aerial was added and the old single RBL aerial taken down later on. Even then the work didn't stop as an old-school prime-focus satellite dish was added to allow PSB1 & PSB3 to be fed via SATBACK instead of RBL and with it the erection of a fence surrounding what was one of the very few such unguarded DTT sites, presumably not so much to protect against vandalism rather than to help shelter the dish from the strong Atlantic wind!

 

[Fisty McB]

Ahh interesting! I didn’t realise it was actually the main feed for anything, although in those far-flung Scottish islands it does make sense.

As you say, the 700MHz clearance most likely makes it more necessary rather than less to have an alternative feed too.

The main disadvantage of relying on SATBACK is that the only regional variations it carries is the BBC One opt outs for Scotland, Wales & NI, therefore for viewers relying on the Brunerish relay there's no BBC Scotland (and prior to that, BBC Two Scotland), STV is SD only (HD is ITV London) as is BBC One Scotland (the English BBC One feed instead). However considering the population amount covered I'd say those slight inconveniences are better than putting up with the mercy of the RBL.

As a side note, there surely must come a time quite soon when the likes of the BBC, ITV C4 etc. Will be looking to reduce transmission costs and decide that at least a small amount of relay stations either serve very few users directly these days, or that they are now surplus to requirements e.g. Relays installed in the days where the main TX suffered issues of ghosting, which is not much of an issue for DTT. Anything between say 100 to 200, many of whom might have no other services on the tower or mast. The likes of Bruernish must be a good example given that those in such less-populated locations are more likely to use satellite as their primary TV source. The 700MHz clearence programme could have been a good chance to verify wherever some of these very small PSB muxes only relays were worth keeping going with any affected viewers offered a free or subsidised Freesat installation, or a new UHF Aerial aligned at an alternative DTT source (where possible) where most if not all of the funding could be recouped by the lower resulting transmitter network fees paid to Arqiva. Alas, that was a wasted opportunity.

 

[RichardCoulter]

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!

Thanks, that explains what I meant much more comprehensively.

Yes, the commercial channels have obviously decided that the cost of putting all of their channels onto 27.5°W exceeds any loss of advertising revenue from any downtime (i'm assuming that the commercial channels on 27.5°W pay the BBC for their capacity).

Having said that, i've read that Film 4 +1 is on there, which seems very odd. Why would this channel (and it's timeshift at that) be singled out for special treatment?

Some time ago (in the analogue era) I read that, in the case of a national emergency such as a nuclear war, BBC1 and Radio 4 would be taken over by the Government to give instructions and advice to the population. It was to have been named the 'Wartime Broadcasting Network', but I believe that this has now been superceded by something else. As such, BBC1 & Radio 4 were the most protected networks on the system.

If this is still the case, maybe these encrypted PSB services will remain indefinitely??

Is it possible for people in the UK to receive these services with the right equipment? This is purely an acedemic question as in practice they would simply use the FTA services on Astra!

Would it be possible for these services to use a UK spotbeam so that the BBC could save money by switching off the BISS encryption?

 

[Fisty McB]

Having said that, i've read that Film 4 +1 is on there, which seems very odd. Why would this channel (and it's timeshift at that) be singled out for special treatment?

Film 4+1 is no longer on SATBACK and has been replaced by TBN, this is because TBN (and previous to it, Film 4+1) broadcast on Freeview on the PSB3 multiplex. The HD versions of ITV London, Channel 4 & Channel 5 are also carried on SATBACK for the same reason.

 

[RichardCoulter]

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.

I guess Channel 5 on transponder 64 was switched off as soon as digital terrestrial coverage was in place.

I also remember radios 1-5 going onto Astra and it being said that, whilst the public could use them, they were intended for cable operators. ISTR that when the BBC decided to suddenly close them, this was the explanation given to domestic users. I've tried to search for more info but can only find a post saying that some BBC radio stations were broadcast on the audio subcarriers of CNBC for Dutch cable operators.

If this was correct, I wonder why cable operators didn't simply use the SATBACK for them? Also, why wouldn't the Dutch cable operators simply use the feeds on the audio sub carriers of UK Living etc?

 

[RichardCoulter]

Film 4+1 is no longer on SATBACK and has been replaced by TBN, this is because TBN (and previous to it, Film 4+1) broadcast on Freeview on the PSB3 multiplex. The HD versions of ITV London, Channel 4 & Channel 5 are also carried on SATBACK for the same reason.

Cheers, that makes sense.

Maybe the commercial channels don't pay the BBC for their SATBACK capacity then as their back up feeds might be part and parcel of the service provided for DTT.

 

[Analoguesat]

As a side note, there surely must come a time quite soon when the likes of the BBC, ITV C4 etc. Will be looking to reduce transmission costs and decide that at least a small amount of relay stations either serve very few users directly these days, or that they are now surplus to requirements

For some of the piddly little relays it would probably be cheaper to get satellite dishes installed & give everyone a couple of Freesat receivers.

 

[Adam792]

I guess Channel 5 on transponder 64 was switched off as soon as digital terrestrial coverage was in place.

I also remember radios 1-5 going onto Astra and it being said that, whilst the public could use them, they were intended for cable operators. ISTR that when the BBC decided to suddenly close them, this was the explanation given to domestic users. I've tried to search for more info but can only find a post saying that some BBC radio stations were broadcast on the audio subcarriers of CNBC for Dutch cable operators.

If this was correct, I wonder why cable operators didn't simply use the SATBACK for them? Also, why wouldn't the Dutch cable operators simply use the feeds on the audio sub carriers of UK Living etc?

I’m pretty sure Satback has only existed since digital switchover started (2008 onwards?) at the earliest, because it was only at that point that any off-air relay transmitters started broadcasting Freeview at all.

Before that, all the transmitters carrying Freeview were the main transmitters that had pre-DSO DTT since the OnDigital days, which was fed by fibre since the beginning (except for the SDN multiplex which was delivered via satellite until around the same time in the mid-late 00s via 16°E as mentioned earlier in the thread).

 

[RichardCoulter]

For some of the piddly little relays it would probably be cheaper to get satellite dishes installed & give everyone a couple of Freesat receivers.

I imagine that the self help transmitters have diminished or gone entirely too for the same reason. It would now be easier for most people to install a satellite dish!

 

[RichardCoulter]

Film 4+1 is no longer on SATBACK and has been replaced by TBN, this is because TBN (and previous to it, Film 4+1) broadcast on Freeview on the PSB3 multiplex. The HD versions of ITV London, Channel 4 & Channel 5 are also carried on SATBACK for the same reason.

This site says that TBN wasn't originally encrypted, but now is. I can't see any rights issues for a channel showing religious programming, perhaps the BBC didn't want to effectively provide them with free extra satellite coverage?

BBC-SATBACK – Astra 2

Intelsat 907 and the Freeview - Satellite Backup This service is a backup for Freeview and carries PSB channels from the BBC, ITV and Channel 4, it is often referred to as BBC Satback It is a a backup of Freeview multiplexes PSB 1 and PSB 3, it is not intended for direct-to-home (DTH) reception...

www.astra2sat.com

It also says that STV & UTV are present, but not viewable. Does anyone know why not? It says that they are listed as data channels, but so are all the rest! I'm assuming that as the channels are configured for the Freeview transmitters, that they are classed as data streams rather than normal satellite channels.

Also, does anyone know what the non radio data feeds (at the bottom) are used for? Fat CSI, 301, 302 and 'SIPSI In-band configurations'. A search for SIPSI says something non satellite related in connection with French employees!

 

[RichardCoulter]

Thanks, that explains what I meant much more comprehensively.

Yes, the commercial channels have obviously decided that the cost of putting all of their channels onto 27.5°W exceeds any loss of advertising revenue from any downtime (i'm assuming that the commercial channels on 27.5°W pay the BBC for their capacity).

Having said that, i've read that Film 4 +1 is on there, which seems very odd. Why would this channel (and it's timeshift at that) be singled out for special treatment?

Some time ago (in the analogue era) I read that, in the case of a national emergency such as a nuclear war, BBC1 and Radio 4 would be taken over by the Government to give instructions and advice to the population. It was to have been named the 'Wartime Broadcasting Network', but I believe that this has now been superceded by something else. As such, BBC1 & Radio 4 were the most protected networks on the system.

If this is still the case, maybe these encrypted PSB services will remain indefinitely??

Is it possible for people in the UK to receive these services with the right equipment? This is purely an acedemic question as in practice they would simply use the FTA services on Astra!

Would it be possible for these services to use a UK spotbeam so that the BBC could save money by switching off the BISS encryption?

Found out that the BBC already does use a UK spotbeam, but that there is still some overspill, so they have to encrypt. Also, people in the UK could theoretically pick up these channels, but it's pointless faffing about with them when we can get them from Astra. It's only worth doing if you're abroad and out of range of the Astra signals.

 

[Adam792]

This site says that TBN wasn't originally encrypted, but now is. I can't see any rights issues for a channel showing religious programming, perhaps the BBC didn't want to effectively provide them with free extra satellite coverage?

BBC-SATBACK – Astra 2

Intelsat 907 and the Freeview - Satellite Backup This service is a backup for Freeview and carries PSB channels from the BBC, ITV and Channel 4, it is often referred to as BBC Satback It is a a backup of Freeview multiplexes PSB 1 and PSB 3, it is not intended for direct-to-home (DTH) reception...

www.astra2sat.com

It also says that STV & UTV are present, but not viewable. Does anyone know why not? It says that they are listed as data channels, but so are all the rest! I'm assuming that as the channels are configured for the Freeview transmitters, that they are classed as data streams rather than normal satellite channels.

Also, does anyone know what the non radio data feeds (at the bottom) are used for? Fat CSI, 301, 302 and 'SIPSI In-band configurations'. A search for SIPSI says something non satellite related in connection with French employees!

STV and UTV HD aren't viewable on Satback because only the name label for both of them is present in the stream (even after decrypting it). There's no audio or video stream linked with them. I'm not sure why they're there.

The other data feeds contain stuff like the Freeview bouquet information (like all the transmitter group names across the country). There's also full Freeview EPG data carried, but encrypted like the channels and on a non-standard PID. Any transmitter taking the feed will be able to filter and use the PIDs it needs.

 

[woborny]

It's possible that the SATBACK broadcast could move to a new satellite in the not too distant future, especially if it worked out cheaper - the Intelsat 907 satellite at 27.5W is already operating beyond its expected service life of 13 years having launched in February 2003 and I've heard no announcement from Intelsat about a potential replacement.

Intelsat 901 is being prepared with Intelsat MEV (Mission Extension Vehicle) to extend it lifespan, then moved to 27.5 to take over from I907 "ealry 2020)...a few reports and links elsewhere on this here forum,

 

[Adam792]

Found it - it's the Bruernish relay site...

mb21 - The Transmission Gallery

If you compare the four sets of photos (the second page has two sets) you can see its evolution over from analogue relay to digital. It looks like at DSO there was originally two different RBL aerial set ups, one working as a pair and another as a single that looked decidedly battered with missing elements. Shortly afterwards a new "trough" receiving aerial was added and the old single RBL aerial taken down later on. Even then the work didn't stop as an old-school prime-focus satellite dish was added to allow PSB1 & PSB3 to be fed via SATBACK instead of RBL and with it the erection of a fence surrounding what was one of the very few such unguarded DTT sites, presumably not so much to protect against vandalism rather than to help shelter the dish from the strong Atlantic wind!

Seemingly, Bruernish does still rely on its off-air feed for a lot of the time! But falls back to Satback on a regular basis when that fails.

If you look here - Bruernish (Eilean Siar, Scotland) Freeview Light transmitter

In the comments they're showing a feed of the BBC Reception transmitter fault information for the transmitter. You can see the exact times where Satback is being used (pretty often!) by all the faults logged as "Wrong regional programme due to a fault" (for the reasons you've mentioned already - no STV HD, no BBC Scotland/BBC Alba, and BBC One England HD instead of Scotland). Presumably outside of these fault times it's managing to receive the correct feed via its receiving aerial.

It's amazing some of these Western Isles transmitters seem to be able to get a feed from mainland transmitters at all considering the long sea-paths!

 

[RichardCoulter]

Does this mean that people will no longer be able to use Satback?

Biss-ca is coming

Saw this article this morning: https://www.svgeurope.org/blog/headlines/eurovision-services-to-implement-biss-ca-encryption-next-year/ Sounds pretty unhackable... All good things must come to an end I guess :(

www.satellites.co.uk

 

[Analoguesat]

Biss-CA may be coming but we have no idea as far as Im aware if 27.5W will be using it