All posts by Michael Perry
Below are all of Michael Perry's postings, with the most recent are at the bottom of the page.
Despite what Briantist wrote way back in 2011, digital TV has been shown to experience a number of reception problems, some are a natural phenomenon of transmitting RF signals in the UHF bands and some are particular to the nature of digital transmission and reception and then decoding.
RF signals will always be affected by natural atmospheric events, such as those caused by a temperature inversion which tends to cause troposhperic tunnelling and hence signals travelling further than is usual and if they are on same/similar frequencies they will interfere with each other, with digital this often appears to cause an apparent loss of signal but in reality the decoding is not able to sort out which signal is the correct one so gives a 'no signal' error message. Rolling was an artifact of the TV design rather than reception though there were a few instances of loss of the vertical sync pulses obscured by noise pulses.
With Digital signals, they are received in exactly the same way as the 'old' UHF TV signals (hence no requirement for a so-called 'digital aerial') but the programme content is carried as digitally encoded modulation. That has to be decoded, error correction applied and then arranged to be displayed on the screen. It is in the reception and decoding that most problems occur and usually appear as pixillation (the little blocks of incorrect imagery within the picture) at first. If the reception/transmission problems get worse then it can lead to apparent total loss of signal, the TV being unable to work out what to decode and display, so you get the 'No Signal' message, which is often very misleading as the signal is there but cannot be sorted out from within the mess caused by interference, etc.
Unlike analogue reception, there is a threshold for satisfactory digital reception. Signal levels below that are either unstable or non-existent. You need at least a minimum level of signal strength, often around 50-60%, to get reasonable to good reception. HD signals also seem to have an upper limit, signals above 80-90% seem to be prone to problems and may be unviewable. Elsewhere on this site is a discussion about having too much signal being as bad as having too little.
Clearly, as signals are radiated all round main transmitters, the strength falls off with distance so the further away you are the more loss of signal strength there is - and so a possible loss of displayed programme quality afftecting both sound and picture.
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rob:
It has been reported that sales of analogue vinyl records has increased by 18% in the last few months. So not everyone likes digital signals and more and more are coming to realise that analogue still has something to offer.
In technocal terms, analogue is more accurate than digital - but both suffer from intereference problems, though in different ways.
It has become very clear that reception of digitally encoded signals, such as Freeview or DAB, have inherent problems and may not be a complete solution.
Therefore it is vital that we retain AM and FM broadcasts.
(I am given to understand by a friend working in the aircraft industry that though many communications use digital encoding, the emergency systems are all analogue as reception is apparently more reliable, especially with high speed [military] aircraft!)
Personally I prefer the tonal qualities available with analogue, digital suffers from the Nyquist limitations.
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Briantist
No misconception on my part - I don't like the look of what is being shown as it is unsuitable for a laptop/desktop. It may be fine on a smartphone but not otherwise. The 'selkection' method is clearly not working as I again have the 'smartphone version showing which I find both unappealing and restricted on my Windows 7 Pro laptop as well as my Ubuntu desktop.
I suspect the coding needs a further look.
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Briantist:
It does not look as you suggest! The look of the pages and navigation are the main problems.
In FF 33.1 and IE 11 under W7Pro it is severely lacking in the content we are accustomed to. It lacks the 'tables' on the right side and trying to find the latest comments is a bit of a nightmare as the back button returns to a top level screen and not the previous one! So as I like to view a range of posts, I have to go throught four steps instead of one!
In FF under Ubuntu, the same problem is present and the pages are not good to look at. It may suit a smartphone but not a laptop or desktop at all.
Please can we have the 'old' look and feel back please? Then people can find where to put their post code in for example, see some posts especially from MikeB for more.
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But it is not so good for those in areas where the internet provision is only 2 Mbps at best or even non-existent. A number of the more rural areas are not being covered by the Government promoted provision of fibre-based services and the minimum service expectation, it is not a requirement, is just too slow for streaming live TV - especially if the house occupants try to do something else on the internet at the same time.
At least UHF terrestrial signals reach the vast majority of the population, even though some don't get the COM services coverage due to the restricted numbers of people to see the advertising which pays for the services. I know a few areas have topographical problems (such as hills and mountains or big buildings in the way) preventing UHF reception but many of those, not all though, can get a satellite based TV service such as Freesat.
The issue is about the lack of 'universal' coverage at a data rate good enough for TV streaming as well as other normal usage at the same time (Mum and Dad watching TV while children play on-line games, etc).
People have come to expect a universal TV service covering virtually the whole UK land mass, the internet does not do that (my friend in Sutherland is too far away from a town to get internet but does get TV) so the service could not be 'universal'.
Add to that the fact that there are people who do not want and will not have anything to do with internet services, partly because of the extra costs involved and they see no usage for it in their household. 'Techies' will wonder if such people exist - I can assure them they do and in larger numbers than some care to admit.
Internet is not, in my considered view, the future for TV services.
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Michael
The Sky Conditional Access system allows them to control what your box, normally supplied 'free' by Sky, can display. The record and playback functions are also controlled via that system so they turn such features off when your subscription ceases. You can, I understand, pay extra to keep usage of the previously recorded programmes for a time. You should check on the Sky website for more information.
The Sky Viewing Card determines which regional variations you can receive within the 'normal' progtramme number range, out of area services often being placed in the 800+ programme number range.
The term 'scrambling' was widely used and still is by some to describe the effects of the Conditional Access system, but the actuall operation differs with the digitally encoded signals compared to the analogue ones. Those often looked like a jumbled set of lines that did allow a partial sighting of the content if you studied it very closely. With digital encoding and CA you don't see anything unless your box is authorised to display it.
The 'pirate' cards that used to allow viewing of Sky services were not only illegal but Sky took firm legal action against the sellers/providers of such - they guard their service and revenue stream very carefully.
Not sure why you are unable to watch Dave, my Sky +HD box does show it and I enjoy some of the programmes. I know that some programme channels are not available if you do not subscribe to a particular viewing package. We don't have access to the Sky Movies, Sky Sports, etc as we just don't watch them enough to warrant the extra expense. What you are able to view does depend on your chosen Sky package.
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Dr Shirley Firth
I suspect your comments are not meant for this website. This is intended for assistance with technical problems, mainly relating to reception difficulties and associated problems with the Freeview and Freesat services with some additional items covering Sky services.
I suspect you wanted to communicate with UK TV whose website is at
Homepage | UKTV
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MFPA:
If each flat were to have their own separate aerial, then one for each flat means six will be needed. I suspect that would tend to be rather unsightly unless they can be positioned in such a way as to be not visible from the ground or surrounding areas.
The real issue is why the aerial distribution system is powered from the electricity supply for one of the flats, so that means they have been paying for everyone in the other flats to view TV services! The owner of the flats should be contacted to ask them to change how the TV system is supplied so that all the 6 flats are not affected by the loss of mains power when the money in the meter od the one flat runs out. Plus it would save the occupier of that flat the expense of powering the system for everyone else. I'm sure they will appreciate that small saving, it would not be much but over a year could add up to a couple of pounds or so.
Peasedown St John is only about 17 km away from the Mendip transmitter with no obstructions visible to cause problems so individual aerials would not need any amplification at all and any communal system does not need any significant gain, merely enough to overcome splitting and distribution losses.
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Patricia/jb38:
My BT YouView box does not have an 'aerial out' socket. The aerial lead from the wall socket goes directly to the YouView box's aerial input socket. That connects to the TV via an HDMI cable. The YouView box also needs an Ethernet connection to your internet router - I use a powerline socket pair to provide that without running a lengthy Ethernet cable between them.
The design of the YouView box assumes that viewers will use that alone to select and watch the various Freeview programmes without using the tuner in the TV set at all. As I am not entirely comfortable with that situation, I have placed a small powered 'splitter' with the aerial lead from the wall socket connected to the input of that, with two leads then feeding the YouView box and the TV. The type I use is similar to this: TV Freeview Aerial Amplifier Booster Splitter 1 input 2 outputs Adjustable Gain | eBay and I have set the gain to the minimum possible as I do not need much gain, only enough to overcome the splitting losses (I am on Mendip at about 20 km so have very good signal strength and don't need any more than overcoming the 6 dB spliting losses). That solution is better than a non-powered splitter as that requires all the outputs to be connected all the time to prevent unwanted impedance mismatches.
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Saturday 29 November 2014 9:44AM
Ian:
One problem often seen at present is that the server used by the provider of either your broadband connection or that of the programme provider may not be able to cope with the volume of traffic demand by all users exceeding its capability - hence the buffering even on a reasonably fast internet connection. I've recently moved and had FTTC installed, giving around 39 Mbps, but some services still suffer buffering! Where I used to live we had a 1.9 Mbps service at best and it was impossible to view any 'live downloads' of TV programmes. With the new service still suffering from buffering, but less so, it still makes viewing 'live on line' rather disturbing.
That is an issue that providers of broadband services and TV programmes on-line need to address and is being ignored by Ofcom in their future planning.
The only solution you can impliment is to use off-air services either using Freeview (terrestrial), Freesat or Sky (via satellite) or have a cable TV provision (like Virgin Media for example, there are others) if that is available in your locality.