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Originally Posted by jfman

I’ve a DVB-C tuner.

Yes, each area has a different plan which is why I didn’t claim it was representative of the entire network. However space either side of the existing broadband frequencies is far more likely to be used for broadband than DVB-C TV services. Of course, you know this already.

Is the DVB-C tuner in a TV or a computer?

If you pay attention to the channel allocations on DBR you will see that the band of cleared frequencies, some of which are used for extra DOCSIS capacity (C037-C045) are not adjacent to the existing DOCSIS range (within the C004-C028 range). DBR uses Manchester data, so is a former Cable & Wireless network. I believe similar patterns exist across all former Cable and Wireless regions. As far as I know, some former Telewest regions use entirely different frequency ranges for DOCSIS, although most of the former Telewest regions do use a similar range for DOCSIS with the cleared capacity being adjacent to this range. There is no advantage to having such a wide band of adjacent frequencies. It is far too wide a range for all the channels to be bonded.

I’ve no reason to believe my area to be special in any way so I’d guess the same principle is happening elsewhere.

Fair enough for a guess but that isn't what is happening. A quick check of DBR channels would have proved that.

Obviously it relies upon the data at a given point but from my own observations and the graphs on DBR show a downward trend with far more red than live active streams at any given point.

I would expect to see a lot of red. The Vxxx names are assigned randomly. The clear names will have been in use at the time of the most recent scan. The red names will have been in use on previous scans. Often fairly recent scans. The amount of red would only show a trend if the Vxxx names were static but they aren't.

EDIT: If anyone got extremely bored and wanted to develop the frequency plan for their area it can be done, albeit in a time consuming way, with the technical menu of the V6. Channels will be grouped the same as on DBR, except regional variations, and it’ll report the frequency. The status page of your Superhub 3 will also tell you 24 of the broadband frequencies in use. Any “gaps” will be the cleared space or VOD.

If it’s a former Telewest area I suspect C001 on DBR is 115Mhz and rising at 8Mhz intervals until C080 at 747Mhz. So it does show where the gaps are too. I’d be interested to know what happens in 860Mhz areas as it was often proposed 860Mhz to 1Ghz (when the network was upgraded) would be better for DOCSIS 3.1 as it requires new kit anyway. The clearance makes more sense at the top than the bottom in these areas. That’s not to say they can’t swap it round later anyway.

That would be a very time consuming exercise. I've heard of Easter egg hunts but an Easter wild goose chase is a new one.

I believe that C001 is used for the first available channel above the FM band plus or minus the frequency offset used by Virgin in the local region. So your starting point is correct. The upper frequency differs between regions, with some going as high as 843Mhz. Maybe you should take a cautious approach and set the upper limit at 860MHz. That's only 94 frequencies for your Easter goose chasers to track.

Getting back on track, my point was that the trend you thought you saw might not be correct. The current MPEG4 conversions of SD channels makes sense as it is a more efficient use of the spectrum, maybe that's all it is.

Now the reason I asked if your DVB-C tuner is in a computer. If it is, you can use it to extract the frequency table from the NIT for multiple Virgin networks. It would probably only take a minute to complete the scan. But, if you prefer the labourious Easter goose chase, go for it!


So, coming soon, more efficient usage of the spectrum.