All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
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Sandy Heath (Central Bedfordshire, England) Full Freeview transThursday 31 March 2011 1:53PM
Reading
Bain: Insulation does perish as the plasticizer chemical evaporates over time. If walls are damp that can allow water to get in, which changes the cable's behaviour. Generally you see some loss at low frequencies and higher losses as the frequency increases.
External cables are subject to wind, rain and UV light, which will usually make them wear out sooner.
For digital TV it's recommended that you use 'satellite grade' cable, which has a screen of dense braid over metal foil tape. The cable usually used for analogue TV tended to have a bare minimum of screening braid, which to be honest wasn't really sufficient to keep out electrical noise. Electrical noise on an analogue picture caused occasional bright lines. On a digital signal it causes errors, which - if there are enough of them - cause picture breakup and, rapidly, complete drop-out.
The longer the cable is, the more signal will be lost. Again, 'satellite grade' cable is intended to deal with very low signal levels and loses a lot less signal than so-called 'low-loss' coax.
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Sandy Heath (Central Bedfordshire, England) Full Freeview transThursday 31 March 2011 1:55PM
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Mrs L Hardy: Can you provide a full postcode please?
If everything worked before switchover, there's a chance that signals are now too strong rather than too weak. If you have any amplifiers, try removing them, or turning down if it's adjustable. If that doesn't help, or there aren't any, try adding an attenuator.
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Sonia Harvey: Was this a new box, or bought second-hand? If it was second-hand, check that it's not on the list of incompatible equipment at http://www.digitaluk.co.uk/2kequipment .
Do all the TVs (and the box) connect to the same aerial? If so, is the non-working box on a much longer cable than the others? Are the remaining analogue channels clear, or are they snowy, or any patterning on-screen?
Does the Freeview box work if you connect it to one of the other TVs, and does one of the other TVs work in the location that doesn't work?
Multi-room installations are harder to give simple answers to - it probably needs the attention of a professional to figure out what needs to be done. (RG47SH)
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If you have several TVs at home do you need separate decoders fThursday 31 March 2011 2:12PM
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Lin: You would only be able to watch whatever channel was selected on the Sky box. The 'magic eye' carries signals from the bedroom to the Sky box, so you can change the channel on the box, but you can't select one channel on the main TV and a different one in the bedroom, if there's a disagreement over what programme to watch.
To be able to watch different channels in the different locations at the same time, you would either need to get a Freeview box, and use the loft aerial (this may or may not work, and some aerial work might be needed) or as Les Nicol says, get another feed from the dish into the bedroom. Sky offer 'multi-room' installations with another Sky box, if you want to watch subscription channels, or you could go with Freesat for free-to-air channels only.
If you go with Freeview or Freesat, you can of course still use a 'magic eye' as well to watch whatever's on the main Sky box.
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Briantist: Windows Media Center only comes with some editions of Windows. For Windows XP you need the specific Media Center Edition. For Windows Vista, it's part of Home Premium and Ultimate only - it's *not* part of Vista Business. For Windows 7 you need Home Premium, Professional or Ultimate (or Enterprise, but that's only available through Volume Licensing and I don't expect anyone to have it at home!)
Phil Rogers: The problem here is that all devices connected to one port have to share the bandwidth. Lower-speed devices such as mice, keyboards, and ADSL modems reduce the available capacity for the tuner, which has to chuck several megabits per second to the PC. If it's throwing the whole multiplex to the PC to decode, that could be 24 Mb/s, or 40 Mb/s if it supports Freeview HD. If it's decoding the multiplex and just passing the single programme stream it's still up to 5 Mb/s or more.
The hub also has to be High-Speed compatible, but Windows should tell you if you plug the tuner into a port that doesn't support High-Speed.
Hubs can also be powered or un-powered. Unpowered hubs might not be able to give the tuner enough power, if it doesn't have its own power supply.
Plugging straight into the PC should ensure it has enough power, and will dedicate the entire capacity of that port to the tuner.
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Ivan: Those sound like very high signal levels. Many boxes have much more headroom on their meters than they can actually handle - they're calibrated for the maximum they can cope with on one single multiplex with no other signals being broadcast. On my Humax PVR-9200T, the CAI-recommended maximum signal level for one multiplex (65 dBuV) is 50%.
I suggest removing any amplifiers that you might have, and see if that helps. If not, try adding an attenuator.
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2011 switch-overs start today at Sandy Heath, Nottingham | SwiThursday 31 March 2011 2:44PM
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R. Graham: These channels are all carried on Multiplex A. The frequency for this multiplex has changed at the Waltham transmitter, which is the most common transmitter used in Leicester. You will need to retune the box to get these channels back.
If a retune doesn't help, please see the Single Frequency Interference page.
Another retune will be needed in two weeks, on the 13th of April, as Multiplex 2 is moving to a different frequency. These moves are to avoid problems when The Wrekin transmitter switches over, starting next Wednesday.
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Eastwood (Nottinghamshire, England) Freeview Light transmitterThursday 31 March 2011 2:56PM
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Ian, Notts: I believe Virgin Media are required to carry analogue versions of the main channels that you can tune into even if you aren't subscribing any more. It's possible that the cable head-end is fed from Nottingham - in which case they need to do some engineering to figure out how to continue supplying an analogue feed, if that continues to be required!
Best point of contact is Virgin Media themselves.
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Ashley: sounds like it could be too strong a signal, overloading an amplifier or the TV's tuner. If you have any amplifiers, try removing them or turning them down. If not, or that doesn't help, try adding an attenuator.
Many people have installed high-gain aerials who simply did not need them.
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Thursday 31 March 2011 1:26PM
k.hinshelwood: for retuning advice see TV Re-tune . They have one-sheet guides for most manufacturers. (RG47SH)