All posts by Michael Perry
Below are all of Michael Perry's postings, with the most recent are at the bottom of the page.
rob:
Let us know what happens when you fit the 'booster'.
I would be very surprised if you need that amplification as you are only 7.4 km from the Oxford transmitter. Usually having too strong a signal causes the sort of problems you are reporting. Generally it seems that 70-80% strength gives better quality with fewer, if any interruptions/disturbances.
I note that there are mobile signal masts between Oxford Road and Bicester Road, not far from your location. It doesn't appear that any are 4G, but it may be worth contacting at800 (see https://at800.tv/) and asking if they are aware of any problems being caused in your area.
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Strikes me that all the careful planning that went into the UHF analogue broadcasting plans is now being totally wasted with the bathwater. Not everyone will have access to fast enough broadband, the current requirements only require a 2 Mbps service minimum but many rural users will have to wait quite a long time for even that speed, let alone any fibre type service. So TV over the Internet is, in my opinion, a 'pipe dream' for many rural viewers. And not everyone even wants an internet service either.
A great many people are already fed up to the back teeth with all the changes done already and will throw away the Freeview TVs with so many more changes. All they want is a working and reliable system that they can watch what they consider to be decent programmes. It doesn't look as if they are going to get that.
The headlined testing of 'terabit' fibre means we will not get it for use outside of high commercial value locations so again rural loses out and I doubt they will ever see anything approaching that sort of service, they'll be lucky to see gigabit services - if ever.
Am I cynical? Of course I am because the planners are not looking at what the customer wants, only looking at the business demands - which are not the same at all. Plus many people have limited budgets so all this expensive equipment they will need to watch TV in the future will not appear in many front rooms. It seems as if it is all change for changes sake as long as we make yet more profit - which is what drives the mobile operators.
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If, and it's a very big 'if', *everyone* were to be guaranteed an internet connection that was a minimum of 5 Mbps and at not cost, then there *may* be an case for transferring TV from RF broadcasting to fibre. But, not everyone will get FTTH or FTTP and many will have FTTC followed by good old copper - the length and quality of which is a serious determining factor on available throughput speeds (that is the critical measure and not the sync speed).
History of broadband rollout shows that urban areas tend to get the better speeds sooner than anyone in a rural area. A great many urban broadband connections are underground with a few older areas provided via wires on poles. Rural areas have always been provided with slower connections via existing copper, mostly overhead and hence subject to the vagaries of our wonderful weather. So typical rural broadband speeds have seriously lagged behind urban and suburban areas. Further, the exchange equipment in many urban areas is now 21CN standard yet a great many rural exchanges are still 20CN, so we cannot even get ADSL2 let alone ADSL2+! Plans to provide fibre services to rural areas are so far behind that many 'intervention' areas still have no date given for the work to start. My are is being told there is no planned date yet but it is unlikely to be before 2018 and probably later.
So that leaves large areas of the country poorly served for internet services and hence any transfer of TV from RF to internet before all that is completely resolved is highly premature.
Any forward planning *must* have a touch or reality built in and must address all the delivery issues well before any such transfer is attempted. I cannot see all that happening for at least another 20 years. The technology may be available but governments, government departments and local councils move amazingly slowly and no amount of wishful thinking will speed them up.
So we should not plan to disrupt TV viewing for the vast majority of the general public who only want to watch the programmes and don't want to be constantly retuning, buying new equipment when what they have still works well nor should they be forced unwillingly to have such a major change thrust upon them.
Technology is not meant to be the driving force but to be an enabler.
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Rob
Are your splitters of the passive type (do not require any power) or of the active type needing a power supply?
Reason I ask is that passive splitters rely upon having all the outputs connected all the time to maintain correct impedance matching throughout the system. If you unplug just one output from a passive splitter it will seriously disturb the signal distribution to the extent that the signal delivered to a connected input will be seriously reduced perhaps by as must as making a quarter or less of what it should be! (The mathematics is complex, but it is essential that correct impedance matching is maintained throughout the system, so every input is matched to its supply at 75 ohms.)
An active (powered) splitter, on the other hand, has buffer amplifiers built in so each output is 'independent' of all the others so impedance matching is always maintained no matter how many outputs are connected.
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Rob
Forgot to add that a signal strength of 100% is not good! You can have too much of a good thing and 100% is too much. Typically you look for around 70-80% maximum.
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Briantist:
The WWW is not entirely 'self healing'. Having discussed at great length with my friend in Openreach and Virgin Media, the topology of the web at an international and national level is as a web of interconnected systems, so at that level it is 'resilient' and can automatically re-route data connections if some/several are lost or disrupted. However, at a lower and more local level things are different. Each main exchange (or distribution centre) is fed by several connections so that has a degree of resilience. Residents lucky enough to be connected directly to the main exchange can benefit from that but each subscriber is connected in a 'star' pattern to the main exchange and that 'final mile' is a single connection so cannot be resilient. At the next level down, the sub-exchange that serves smaller towns, they rarely have more than a single connection to the main exchange and subscribers on those sub-exchanges are also on a star topology, so no resilience. I happen to connected to a sub-sub-exchange which has a single connection to the sub-exchange which has a single connection to the main exchange. So I, and many rural subscribers and others are on a star+star topology and there is no resilience at all! If one exchange in the link fails, there is no internet. If the link to my house fails, there is no internet. If my exchange is flooded, there could be no internet. No internet will mean no TV in the scenario you mention. (I have checked my thoughts with a friend working for Openreach just before composing this response.)
As for reliability of DTT, I have to agree it does not appear to be anywhere near as robust as analogue was. The key part of the link in not the distribution side, that is from studio/playout centre to transmitter but the link between transmitter and TV screen& speakers. Just looking at the pages on your website here shows that a significant, but probably small, proportion of viewers have significant problems receiving the programme services they are led to expect. In the early day of analogue, there were many problems and most were connected with the reception equipment. My suspicion is that the same is currently holding true for DTV. Some installations at homes experience little or not problems, but others experience very significant problems and hence causing severe frustration. Part of the problem is perhaps poorly design/manufactured home equipment, part is poorly designed/installed aerial systems. Part is poorer understanding by both the industry and the viewer of what is actually feasible with the technology we currently use. So it seems that most have no problems with DTV services, but most also don't appreciate all the 'retuning' that has been needed to accomodate changes and will be rather more vociferous in future if the current ideas come to fruition. But others are having significant problems that cannot just be 'swept under the carpet'. I know that is not your intention and hence the reason, or at least one of them, for this website that can be very helpful to the non-technical as we who have some knowledge and experience in these matters can offer suggestions.
As someone with a scientific background (electronics and physics are my main degree subjects) I know thisnge are always changing, but the viewers' main interest is watching the programme content largely for entertainment.
Keep up the good work with the website but we need to see things from the customer perspective too.
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Briantist
Look again at the technicality involved with the internnet and stop being picky. WWW relies upon the internet.
What I said is absolutely true. I am talking of the hardware and not the software/appware. No connection means no TV in the scenario envisioned. The internet at a local level is NOT imune to problems.
How many wires are there arriving at your home carrying telephone and internet (broadband by ADSL*) services? Just two! Two because that is the minimum need to create a circuit. As there are only two you do not have redundancy at all. Same at your local exchange, especially if it is a sub- or sub-sub-exchange. Redundancy provides the immunity for the internet and the protocols are irrelevant to how the hardware connections are made. That redundancy is absent in the 'last mile' connection. You have to look at the reality of what is installed to connect a subscriber. That the networks yiou worked on included redundancy is irrelevant to the 'network' connections provided to the consumer. They do not include any redundancy so if a single wire in that last link fails there is no connection.
Also remember that no customer is able to determine what form the connection to their home will be, irrespective of whether they have fibre, ADSL or satellite connection to the internet. They cannot tell BT/Openreach or Virgin or whoever to install a dual connection to provide any redundancy. The standard Openreach Master Socket can only take two incoming connections so cannot include any redundancy so no resilience to interuptions. That is the reality for the consumer.
What your seem to be talking about is the national/international connectivity which *does* have redundancy as I stated.
Please also bear in mind that I have been using netorked systems for more than 25 years and know what all the mnemonics mean.
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Charles
Well spotted, a spot of finger trouble!
I did state that Mendip aerials have the rods horizontal.
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Brian Gregory
That's what I was alluding to in my original post! The connections between servers are mostly well protected with redundancy to spare, but there are sections of the 'backbone' that appear not to be. Evidence of unexpected connection failures on a large scale shows that you are right.
Looking at the suggested scenario from the customers' perspective, any interruption of their internet service delivery, for what every reason or cause, will mean they lose TV as well as internet and probably telephones as well, except for mobiles of course (but a power outage can affect the mobile masts as well!).
That the core elements of the internet are well enough designed and connected to be 'resilient' is a good thing, but the connections branching out from that to feed individuals or even groups can be affected by flooding power failures, equipment faults, etc, etc. Any failure there will also cause 'No Signal' behaviour I expect.
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Wednesday 22 January 2014 9:09PM
Briantist
Most people think of the Digital Switchover as being when UK terrestrial domestic TV transmissions becoming all digital (Freeview), a change that ended with the closure of the last terrestrial analogue TV transmitters. What happened last year was a re-arranging of how the multiplexes used the available spectrum to free up the frequencies above 800MHz (channels 62 to 68, vision carrier at 799.25 to 847.25 MHz [sound at +6 MHz]) so that that part of Band 5 became available to 'sell' to 4G operators. The next step being discussed is to further re-arrange the spectrum usage so that the 700-800 MHz range (affecting channels 49 to 61) can be used for further mobile services use. That has potential to make DTT reception even more troublesome for more people, bearing in mind how sensitive DVB-T2 transmissions appear to be to variations in strength and quality, or other sources of interference.