All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
AWED: Try without the boosters. You shouldn't need them any more.
The loop-through RF output on the PVR usually has slightly more gain than is lost by the PVR itself, so you can end up with more level, going over the TV's limits. Or it could simply be that the TV can't handle as much signal as the PVR can.
The meters can often be deceptive. On my Humax PVR-9200T, the Confederation of Aerial Installers' recommended range of signal levels (before switchover) appeared as 35% to 50%.
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Andrew Harris: Could you get ITV1 West on analogue before switchover?
The ITV1 West mini-mux is broadcast from a separate antenna much further down the mast, and aimed into the Cheltenham and Gloucester area - it doesn't have the same radiation pattern as the other multiplexes.
It's also only on one-quarter the power of the others, until mid-October. (Oxford is using the channel for low-power Mux D until 28 September.).
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Derrick: The spec always had 2K and 8K modes, but Sanyo only implemented the 2K mode. Try contacting them via http://uk.sanyo.com/Contact-Us/Contact/ You can still use the TV as a TV, but you will need an external Freeview box. Again, if you complain, Sanyo may provide one.
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m hughes: You may be using Ridge Hill, which completed switchover on Wednesday morning. You would need to retune the box. Do a 'first time installation', 'factory reset' or 'default setting'.
However, you're predicted to get better results from Sutton Coldfield, both now and after switchover. Although Ridge Hill is closer, line-of-sight is blocked by Oxenton Hill to your west.
I'm not aware of any work at Sutton Coldfield, so if you are using that transmitter, check whether analogue is also poor. If it is, a cable has probably broken or become disconnected.
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m hughes: Note that if the aerial is pointing to Sutton Coldfield and you did retune, it's possible that your box has stored the weakly-detected signals from Ridge Hill rather than the stronger ones from Sutton Coldfield - many boxes just store the first version they find.
Somewhere in the box's menu system it should show you the RF channels being used. If BBC One is shown as being on C28, it's tuned in Ridge Hill. You should delete all the channels, then manually tune in the frequencies from Sutton Coldfield - see that page for details. See Digital Region Overlap for other suggestions.
You may find that Mux D on C29 doesn't work very well - Ridge Hill transmits a special ITV1 West service on this frequency.
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Angelina Hadlington: Samsung have never made a box called a DV3. I think this is the DVB project's logo. There should be another label on it somewhere with the model number - probably next to the serial number.
There's a Samsung box on the list of equipment that doesn't support the 8K mode. If it's an SIRU200i, I'm afraid you'll have to replace it.
8K mode was always in the DVB-T specification, but up until switchover the UK has used 2K mode. 8K mode is more robust, allows the use of Single Frequency Networks (e.g. The Wrekin, Bromsgrove and Lark Stoke work together as one, using the same channels), and every other country is using it.
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Peter Bates: You *must* do a full reset, a first time installation, a default setting. If you do an automatic scan without deleting the existing channels, or resetting to an empty channel list, many boxes will simply remember where the channels were before and completely ignore the new location.
Please check TV Re-tune for a guide to how to do this on your box.
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Nathan: yes, I'm afraid the Sony 28DX20 is on the list of equipment that doesn't support the 8K mode. You'll have to add a Freeview box.
You could try complaining to Sony, see if they'll give you a free box.
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Steve: The useful time that any given pattern of carrier data ('symbol') is on the air is either 2,048 or 8,192 time units. In 8 MHz-wide channels as used in the UK, a time unit is 7/8ths of 125 nanoseconds. The useful time is 224 microseconds (s) for 2K mode. For 8K mode it's 896s. It's a modulation rate of 1.116 kHz for 8K and 4.464 kHz for 2K.
The number is quite closely related to the number of carriers within the 8 MHz bandwidth of a channel: in 2K mode, there are 1,512 useful carriers and in 8K, 6,048. There are also a number of extra 'pilot' carriers that indicate the edges of the band and carry information about how the data is encoded, bringing it up to 1,705 for 2K mode and 6,817 for 8K. Why this number? It works better for the mathematical process that works out what the value of each carrier is.
The more carriers there are, the more memory the digital signal processor needs to perform the Fast Fourier Transform algorithm to determine the amplitude and phase of each carrier. The 8K mode would cost more to implement, so some early receivers only implemented 2K mode. The 8K mode is more resilient, though, as narrow-band interference knocks out fewer carriers, and because of the longer duration, is more tolerant to echoes and reflections.
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Friday 22 April 2011 2:23AM
LRC: ArqA is on C29, ArqB is on C34. SDN is on C33. Before switchover started, Mux 1 was on C34, but the post-switchover ArqB requires twice as much signal as Mux 1 did.
The definitive source is Digital UK's postcode checker. The broadcasters have been making some very late changes and the regulator (Ofcom) isn't keeping up with the official licence documents.
This website can't cope with the multiple post-switchover changes. It generally shows the final state that the transmitter will be in when all the changes are complete, with a note below indicating any temporary channels. This note comes from Ofcom's documents, which are now out of date.
The postcode checker shows 99-100% chance, which usually indicates high signal levels. If you have a booster or amplifier, you should remove it - too much signal causes signal from one channel to bleed into another, and adjacent channels are the worst affected.