All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
ALL: Note that transmitters are officially off-air from midnight to (at least) 6am. You may find some services go off and on before the advertised completion time, but it is not guaranteed to be complete until then.
At Sudbury, the Multiplex A service moves to Multiplex 1's old frequency (C49) *tonight*, rather than in two weeks.
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Sudbury will be OFF-AIR from shortly after midnight until 6am (officially). Services may come and go during this time. It's recommended that you retune after 6am when all work should be complete. See Digital UK - Relay transmitter switching times for progress reports.
While maximum digital power is lower than maximum analogue power, the reduction is much less than at other sites, and the increase from pre-switchover power levels is substantial. If you had reliable digital reception before switchover started, and you have problems afterward, you could have too much signal. Remove any boosters or amplifiers, and if that doesn't help, add an attenuator.
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Felixstowe will be OFF-AIR from midnight. It is expected to be up-and-running again by mid-morning (the advice to installers says 9am). Ensure that the transmitter is fully running again before tuning in your digital box.
You can find progress reports at Digital UK - Relay transmitter switching times .
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Ipswich Stoke will be OFF-AIR from midnight. It is expected to be up-and-running again by mid-morning (the advice to installers says 7am). Ensure that the transmitter is fully running again before tuning in your digital box.
You can find progress reports at Digital UK - Relay transmitter switching times .
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Somersham will be OFF-AIR from midnight. It is expected to be up-and-running again by mid-morning (the advice to installers says 6am). Ensure that the transmitter is fully running again before tuning in your digital box.
You can find progress reports at Digital UK - Relay transmitter switching times .
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Wivenhoe Park will be OFF-AIR from midnight. It is expected to be up-and-running again by mid-afternoon (the advice to installers says 12 noon). Ensure that the transmitter is fully running again before tuning in your digital box.
You can find progress reports at Digital UK - Relay transmitter switching times .
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Woodbridge will be OFF-AIR from midnight. It is expected to be up-and-running again by mid-afternoon (the advice to installers says 12 noon). Ensure that the transmitter is fully running again before tuning in your digital box.
You can find progress reports at Digital UK - Relay transmitter switching times .
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Brian: If the old aerial works, I wouldn't replace it. Going by Justin Smith's aerial tests at Gain (curves), Again , a small log periodic (shown there as 'DM Log') should have more gain in Group A, for the PSB multiplexes, but will have less above C48, where the commercial multiplexes live.
The log periodic is supposedly more resilient to impulse interference, though, so if you find your reception breaks up when cars go past, it may help.
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Steve: DO NOT USE WOLFBANE. It is inaccurate, signal strengths shown are far lower than calculated by the ITU-R line-of-sight equation for known line-of-sight paths. I use Field Strength Calculator which shows a field strength of 81.3 dBuV/m at 66km from a 20kW transmitter on C67. Multiply the field strength shown in V/m by one million, take the base 10 logarithm ['log' on most calculators, not 'ln'] then multiply by 20.
We need a full postcode to see whether there is anything preventing line-of-sight. The Digital UK postcode checker considers how signals travel over the terrain and has factors for buildings and trees.
Bob Archer: If channels on higher frequencies break up when it rains, it often indicates that water is getting into the cables. Check that the seals on any outdoor boxes (such as a masthead amplifier or splitter) are intact and not letting water penetrate. Some aerials have a connection box on the aerial itself, where the cable connects to the aerial, again this needs to be watertight. If the cable has been up for a long time (over 10 years), the outer insulation may have perished due to ultraviolet light exposure and that again allows water to penetrate into the cable.
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Tuesday 5 July 2011 11:15PM
abby gillespie: The Humax PVR 9150T is a full Freeview digital box as well as a recorder. However, it only has one tuner, so you can't necessarily watch one channel while recording another (although my 9200T allows you to watch channels that are part of the same multiplex as one being recorded).
Even if the box does not add its output so it can be tuned in as an analogue TV station - the component is called an 'RF modulator' - it usually does reproduce the input on an output socket so you can chain devices together. It should be possible to plug the RF output of one box into the input of another, you should have received a cable ('fly lead') with the box. If not you can buy a fly lead.
Alternatively you can buy a splitter to split the signal from one outlet to multiple boxes. This often produces slightly better results.