All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
D White: Digital UK's advertising is maddeningly simplistic.
Yes, analogue is switched off - in order to replace the analogue signals with far higher-power digital ones. See the 'Comparison of analogue and digital signal levels' above. The actual digital power levels will be lower than current analogue levels, but if anything the coverage areas are expected to be larger than current analogue coverage.
Basically, if you have good analogue reception, you should have good digital reception after switchover.
It looks like the pre-switchover digital power from Midhurst may be concentrated in one direction. All directional restrictions are removed at switchover, with transmissions moving to the main antenna that analogue transmissions use now, which may mean that the effective increase in your direction is even larger.
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Charlie Carruthers: It is actually at 12.5kW. It is still scheduled to go up to 100kW on the 21st of September, the same day that the channel clash with Sutton Coldfield is resolved (Sutton Coldfield completes switchover on that date).
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Frithe: You would actually get slightly fewer channels with a Freesat box, and the possibility that your local ITV1 region would change (some ITV1 regions are encrypted, requiring a Sky box and viewing card to decode). However, you would be able to purchase a Freesat+ recorder - recording and timeshifting requires a minimum £10/month payment to Sky if you have a Sky+ or Sky+HD box - and the EPG will only show the channels you can actually watch.
There is a comparison of channels at Compare Freesat and Freesat-from-Sky TV | ukfree.tv - independent free digital TV advice .
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Matt: Channel 5 from Croydon, covering roughly the same area as Crystal Palace, uses C37. If you can already receive Channel 5, you are unlikely to have trouble receiving any new services.
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"In particular the ArqA and ArqB multiplexes will be at restricted power for several weeks after the "end" of switchover - see below."
I think you cloned this from the Belmont page? At Sheffield, only ArqB is affected, while at Chesterfield, all three COM muxes are affected.
As for why Chesterfield is held back, it's really unlikely to be international clearance at only 400 watts. Chesterfield was included in the submissions to the Regional Radio Conference in Geneva in 2006, but it doesn't show an interaction with any other country. I suspect the block on running at full power is that Emley Moor will continue to use some of the frequencies for low-power DTT until 21 September.
There are a number of other retune events going on the following week, so many in fact, and across the country, that some are scheduled for the Tuesday (27th September) rather than Wednesday 28th. Some of Waltham's relays get a retune on the 5th of October and Derby gets HD for the first time. I can't see any other block on using 43/46/50 between the end of September and 12th of October so I assume it's just a resourcing issue, getting the staff to make the change.
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jak: The most likely explanation for problems when it rains is that rainwater is getting into the system somewhere, which changes the performance of the cables, increasing the amount of signal lost along the cable. Higher frequencies are affected worse than lower ones - mux 1 and D are the highest frequencies carrying digital channels.
If Channel 4 analogue appears more 'snowy' when it rains, or you have more problems with Teletext, then this is most likely the problem.
Water could either be getting into a junction box or an external amplifier, the connection point on the aerial, or through the insulation of the cable itself. All junction boxes should be fitted with the lid and cable entry points on the underside, so that water is less likely to enter and can drain out. The edges of the cover should be sealed, as should all cable entry points. Any unused connections should be sealed up.
Cables should be secured at regular intervals as they travel over brickwork and tiles - if the cable can move, the insulation will be abraded by rubbing against this, and that can let water in. Cables that are on a sunny wall will lose their flexibility and go brittle, with prolonged exposure to ultra-violet light. If the cables haven't been renewed for more than 10 years, it may be worth doing this anyway.
Eventually the aerial itself will become damaged with exposure to weather - check that it appears to be intact.
The increased power levels after switchover will probably mean that the problem goes away for a while, but depending on the type of cable, it may be possible for water to run down the inside of the cable and damage your TV or set-top box.
There is a natural variation of signal levels - the amount of signal lost as it goes from the transmitter to you increases and decreases - so if the average levels are marginal, channels will come and go.
A well-functioning set-up at your distance from the transmitter should really have near-perfect analogue reception, so if it isn't, it may be worth getting it sorted out now.
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viv ryan: Are you using an indoor, loft or rooftop aerial? What is the full postcode? Is this a shared, communal aerial? If not, is one available?
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Roger Scales: The Pace Twin cannot handle 8K mode and Pace are no longer offering support. It will not work once switchover is complete. It's likely that it's using a 2K signal from a distant transmitter rather than the one you really want. See http://www.digitaluk.co.u…ment and
Digital Switchover UK - Pace
for more information.
The DHD4000 is known to store the first version of the signals that it finds, rather than the strongest, but Belmont should be on the lowest channels in the vicinity. Check that the aerial is actually pointing to Belmont.
If it is, the most likely explanation is too much signal. If you have a booster, remove it or turn it down. If not, you may have to add an attenuator.
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jb38: unless the signal level at the aerial terminals is too much for the masthead amplifier, in which case the signal will already be degraded before it gets to the receivers. In this case you would need to put attenuation in front of the masthead amp, change the aerial for one with less gain, change the amplifier for one which can handle more signal, or replace with a passive splitter.
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Wednesday 17 August 2011 6:51PM
Colin: Yes, probably you would need to retune the Sky box output. It's probable that it is now on or adjacent to a channel being used for digital TV.
The moves were: Mux B from C58 to C66; Mux C from C61 to C68. These changes were made to avoid interference from high-power services from the Waltham transmitter.
You may have to do this again when Tacolneston switches over in November. Obviously the other five channels will disappear then because all analogue is switched off, with digital services starting up in place of three of them.
I would recommend using a frequency at the low end of the range somewhere between 21 and 30, so it avoids Tacolneston completely.