All posts by Michael Perry
Below are all of Michael Perry's postings, with the most recent are at the bottom of the page.
Chris
One problem is due to the signals being digital all the way from camera/microphone to your TV set or recorder (similar effects used to happen in the days of analogue transmissions too, but were often slightly less noticeable). The sound signals are originally pressure waves (analogue) that are received by the microphone. Either in the mic or very soon after the signal is converted into digital 'words' by time division sampling. There is a finite time needed to do that conversion into a series of digital 'words'. The same is true of the picture except that the camera uses a CCD normally, somewhat like your own digital camera, and that produces the digital signal already. Note that each conversion from analogue into digital takes a finite time period, very short but still finite. Next comes the studio equipment (or the OB setup) and the two signals, sound and vision, progress through those systems as separate but paired signals. Then they are distributed digitally, still as separate signals paired in many cases, to eventually arrive at your local transmitter. There they are combined with others to create the multiplex of signals combined on an RF carrier signal that is then transmitted. Your aerial receives these signals and decodes (which also takes finite time) the digital signal complex into several programme pairs (sound and vision) which are then processed to be displayed, the vision part, or converted back to analogue to drive the loudspeakers in your TV or sound bar. I've simplified it rather, believe it or not! But that is the gist of what happens and at every stage there are numerous chances for the pair of signals to get 'out of sync' slightly.
That they are generally reasonably well 'in sync' is good but they can slip out of sync - and that happened in the old analogue days as well.
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Cavan Adolphe
The fact that some services are still present shows there is no problem with your dish and probably not with your receiver either, thought there is a slight possibility of a problem.
On my system, new Sky+HD box with 60cm Dish and quad LNB, I get the same issues but merely changing programme often brings back the wanted signals. Else I wait a few minutes and it returns anyway. That suggests a temporary interruption of the received signal, which may be because of the uplink to the satellite being interrupted, the downlink from the satellite being interrupted (possibly by aircraft if you are on/new a flightpath), or even a bird sitting on the arm holding the LNB! One other factor could be excessive rain in the downlink path or covering the input to the LNB, that will give the same effect. You can do nothing about any of those factors.
I have seen this happening for over 24 years since the early Sky analogue satellite broadcasts started. Rain is a known factor as is snow as the signals used are at extremely high frequencies and are susceptible to water absorption effects.
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Briantist
I like your refreshing approach - well done.
Sadly, as someone else here says, not all website providers consider the end user experience. For example, the BBC News website uses several 'trackers' and image inserts that are not on the same server as the News site, so sometimes you have to sit and wait for items (often irrelevant) to load before you can read the real story of interest. One example is their use of www.emf.bbc.co.uk which is, as far as I can ascertain, a data gathering service that runs even if you have set uyour browser to not respond to such - and if you have allowed the response the delay can still be several minutes! Not good for use mere news readers!
But this site loads very well now on both laptop, desktop and Galaxy Tab2.
Thanks and well done.
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Conor:
Channel 4 and Channel 5 are entirely independent of the ITV organisation. As such, they select which transmitters to be available on, if at all, and what type of service they provide. As they are commercial operations, the potential for income from advertisers is a key factor in their thinking. Each service costs them cash to operate so they will want an income stream large enough to cover their costs.
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Ian
So it is appearing on Logical Programme Number 64 and not Channel 64, that's now in the spectrum being used for 4G.
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Neil Larmour
My Sky+HD box decided to show no programmes at all the other day - just a blank screen. No amount of pressing buttons on the remote made any difference, though the light showed it was receiving the commands. I disconnected the mains supply for 1 minute and reconnected it, waited for the box to restart (takes around 2 minutes) and then pressed the button to turn it on. And we had all our pictures back! Have you tried anything like that?
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Michael
All depends on how the various signals are multiplexed together to form the broadcast stream. Many SD services have used the 64QAM method (works with DVB-T tuners) but HD and newer SD multiplexes use 264QAM which needs a DVB-T2 tuner. So it gets much more data into the same bandwidth data stream.
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And with experiences of many this winter, internet delivery is unreliable. I know of several areas in Wiltshire that have either had protracted power outages, which either means no TV in the home or no transmissions of TV and/or radio services, or no internet service at all. At the weekend, we had no power for 15.5 hours due to a damaged supply line about six miles away and then no phones due to loss of connection to the exchange (so no ADSL either) and then BT (our ISP) had a major system fault meaning large areas were without any internet connections.
So not TV in those circumstance and no access to other services at times. That means we could not receive any emergency messages either. So putting all our eggs into the one internet basket is a foolish idea.
We managed to keep warm and have hot drinks only because I had bought a decent generator before the winter.
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Thinking aloud, surely those areas that were difficult to provide with UHF TV in the past (the 0.2% unserved by main or relay transmitters prior to DSO) will still be difficult to provide with signals? The primary reason was terrain, followed by big buildings and then distance to sparse populations. So those factors are still there and making DTT difficult in those same areas. Plus it is many of those areas that will be last to be provided, if ever, with an internet connection capable of giving viewable TV. Current DTT coverage is variously stated as being 98% or 99.2% (I'm not sure which is right, if any) so there is still a long way to go before DTT coverage is as much as it was claimed to be for analogue. So those unserved areas will not benefit from 'White Space' technologies if they can't get the transmissions anyway! What technology can achieve improves but that doesn't mean it will reach everyone. Example is that a great many medium and small villages and most hamlets are still on ADSL, let alone ADSL2+!
I think there is a very long way to go to have anything approaching a 'universal' provision. What is possible in more populated areas is inevitably slower to arrive in the less populated areas, hence Freeview 'Light' transmitters, and the very sparsely populated areas may never see such wonders either. And satellite does not always resolve the supply problem, again because of shielding by terrain and/or buildings or even forests!
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Tuesday 4 February 2014 8:58PM
Tracey
You would need a satellite distributions system to achieve what you want.
Have a look at Labgear HDU681/S Home Distribution Unit 8-Way | eBay to see what kind of unit would be required (there are other makes and specifications available) and note that you will need different wall plates that can accommodate the additional connections.
Hope that helps?