UPDATE: 1st November 2013
After two years 'working' on this issue, Sling seem to have created a firmware update that addresses this problem. For now this firmware is only available as a private beta, but hopefully you'll see a general firmware release soon.
I have been waiting to connect my Slingbox HD-PRO to my rooftop aerial for some time. Today I finally got around to doing it and shared the disappointment of many other users on this forum with the setup process failing whilst trying to scan for channels.
To cut to the chase, the problem seems to be with the Slingbox tuning to any of the channels in the group COM4 (ITV2+1, ITV3, Quest, QVC, 5USA, and many more). This appears to be becuase of the number of services (TV + Radio + Data) that this multiplex provides. It seems that the Slingbox is unable to cope with more than 32 services on a single multiplex, despite the UK specification allowing 64.
This cause of this issue seems to have been identified back in January 2012, yet Slingbox still haven't fixed the issue.
Why have I reached this conclusion...
When doing a full "Digital Antenna" scan with the aerial unplugged the Slingbox quickly progresses through the scan 2% at a time. However when the aerial is attached the scan always stops and eventually fails at 10% (for me, receiving Freeview from the Crystal Palace transmitter - this fact is important - read on).
Some background to Freeview, or Terrestrial Digital Video Broadcasting (DVB-T)
DVB-T channels are transmitted in 'multiplexes' - These are digital data streams which occupy a channel of the radio frequency spectrum. The reason that DVB-T allows us to have more channels is that you can squeeze multiple channels in to a single multiplex. For example, all the BBC channels are transmitted on a single frequency. Everyone in the UK should be able to receive at least 3 multiplexes (These can be seen as PSB1, PSB2, and PSB3 on this multiplex listing page). These three multiplexes comprise what is know as "Freeview Lite" and are broadcast from over 1000 transmitters, including small local ones designed to 'fill in' the gaps in areas where reception is poor).
Most (but not all) of the population is able to receive a full Freeview service from one of the 80 'full service' masts. These carry additional multiplexes (COM4, COM5 and COM6 from this multiplex listing page).
The important bit... Because Freeview channels are broadcast in multiplex groups, the Slingbox (and your TV) only really tune in to up to 6 actually frequencies, and each of these frequencies will contain several channels - You might have noticed when you scan for channels on your TV they are found in groups of up to around 20 at a time.
Knowing this, we can take a closer look at how the Slingbox is tuning it to specific frequencies. When the Slingbox doesn't find a DVB-T signal on a particular frequency it is able to skip quickly to the next frequency (you will observe this when you scan with the aerial disconnected). However when the aerial is attached and the Slingbox finds a DVB-T frequency the percentage indicator will pause just a little longer than normal - this is because the Slingbox is working out which channels are within the particular multiplex it has just found.
How did I work out multiplex COM4 is the problem?
I know that from the Crystal Palace transmitter the following multiplexes are broadcast:
- Ch22 - COM5
- Ch23 - PSB1
- Ch25 - COM4
- Ch26 - PSB2
- Ch28 - COM6
- Ch30 - PSB3 (which is HD channels and the Slingbox can't receive these, so it will always skip these)
The eureka moment... When scanning for new channels I noticed that at 10% was the third time that the Slingbox took a while during it's 2% usual increments. This led me to believe that it was struggling with the third multiplex that it had found. I think we can assume it found it OK, but just didn't like something it found within the multiplex itself. Looking at the multiplex listing page, you can see that COM4 containts many more services than the other multiplexes and it seems that this is the cause of the Slingbox crashing. There are some reports than a while back COM4 did work for a brief period when fewer services were hosted within the multiplex. The critical number seems to be 32, more than that, the slingbox will fail. This is desipite Arqiva (The owners of some UK multiplexes) explaining that the UK digital TV standards allow for up to 64 services per multiplex.
Why do I think I'm right?
To test my theory, I did another channel scan and quickly unplugged my aerial when the progress bar reached 10% (so the Slingbox couldn't tune in to anything at that point). I then quickly plugged the aerial back in when it reached 12% and allowed the scan to continue.
Following the scan I had perfect reception on all channels apart from those within multiplex COM4. This tells me that the Slingbox was able to tune to and store four multiplexes, but always crashes when trying to store COM4.
So why does it fail at a different percentage for other people?
The percentage of the scan represents the channel frequency the Slingbox is scanning. Because each of the 80 full service transmitters broadcast multiplex COM4 on different frequuencies (to avoid interferrence) you will see the scan fail at a different percentage, depending on your location and therefore the frequncy that is used by COM4.
So why does it not fail for everyone?
Remember I said earlier that not everyone gets the COM4 multiplex? This would explain why not everyone has these issues when it comes to tuning.
Of course, with this in mind - If anyone has successfully retuned their Slingbox recently and it contains any of the COM4 channels, then I'll eat my hat and my theory is completely wrong. Otherwise... Slingbox - It's over to you. When are you going to fix this?
Message was edited by: mattbunce