All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
Dean: Make sure you do a factory reset to clear out all existing stored channels. Your equipment could get confused with ArqB moving to C52 and ArqA replacing it on C67.
C52 has never before been used by the Mendip transmitter, so you need to check all legacy devices like VCRs to ensure that they're not outputting on a clashing channel. Clashes are possible on C52 itself, C51, C53 (due to inadequate filtering), and five or nine channels below, so C43 or C47 - though I would have expected more problems.
The power level is *very* slightly lower on C52 for the moment than it was on C67, but the much lower frequency should result in overall more signal being received for this multiplex. SDN having gone to full power on C48 means that the overall signal level is a lot higher, which could result in too much signal.
Just to confuse things further, the configuration of ArqB will be changed on 8 November - it's not clear whether this is to increase capacity or increase coverage. For you the result is a slightly lower probability of reliable reception, but it's still predicted to be a 98% chance.
Siston is a 'Freeview Light' transmitter and only provides the three PSB multiplexes.
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Nick: Money, and the design of the original licences to broadcast. See Will there ever be more services on the Freeview Light transmitters? | ukfree.tv - independent free digital TV advice for more.
The main transmitter they're using is probably Darvel. If you provide a full postcode we can check whether a full service is expected to be available from this or any other full-service transmitter.
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Briantist: I'd dispute that MPEG Audio Layer 2 audio is better than NICAM 728. Equivalent, possibly, at 256 kbps (the rate the BBC use) but not at 128 kbps as many of the commercial channels use.
Legacy mono audio was FM with a permitted deviation of plus/minus 50 kHz.
Freeview HD audio is AAC-LC (low complexity MPEG-4 Advanced Audio Codec) and I don't know what the bitrate is. Ofcom guessed, for the Second Invitation To Apply, that 192-384 kbps would be used, but bear in mind that this is for 5.1 audio rather than stereo. AAC is generally considered to require half the bitrate of MP3 for the same quality, and MP3 (MPEG-1 Audio Layer 3) itself substantially less than Layer 2.
The *volume* of the audio is nothing to do with it. Layer 2 and AAC can handle the same dynamic range. Indeed they work by hiding noise caused by low dynamic range - caused by saving bits - behind loud sounds. A loud sound at one frequency means that whole sub-band can be encoded with fewer bits.
As I understand it, differences in volume are generally caused by the downmix of 5.1 audio for stereo output. The audio stream carries metadata to tell the receiver what parts of which channel to combine to produce an output only for the front speakers. The crude version is of course to just take the front-left and front-right channels, omitting the contribution from rear-left, rear-right, front-centre and bass channels.
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jgked: Because the wallplates are rubbish? See Satellite, Television, FM, DAB, Aerial, Coaxial Cable, Plugs, Sockets, Connectors & Leads for one installer's opinion on using them and the sort that should be used, if you're going to.
Predicted reception from Wenvoe is already poor, probably due to interference on 42/45/49 from a nearby relay transmitter, and additional signal loss of the wallplate, or noise pick-up, could well push some channels into being too noisy to decode.
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Nicholas Wilmott: It's a '1'-series because its final intended service position is 19.2°E. It's only filling in at 28.2°E until the proper replacements, 2E, 2F and 2G, are built and launched over the next few years.
There is nothing analogue or digital about the satellites, they just relay whatever is transmitted up to them from the ground. The first digital tests at 28.2°E were from Astra 1D, moved there at the end of its service life for that purpose. Astra 1 satellites at 19.2°E (and 2C, which has had a history of being moved here there and everywhere) now carry a mix of analogue channels and digital multiplexes on the various transponders. The remaining analogue channels have been told to move to digital before being shut down next year.
As I said, 2C is at 19.2°E, and could presumably have been moved back to 28.2°E if it was still suitable. However, that only has a single pan-European beam, and the demand is for UK-only footprint. Presumably the UK spot beam got added some time in Astra 1N's construction, too late to push up 2E to an earlier launch.
We still don't know how many of 1N's transponders can use UK-only footprint. In frequency terms, several of the transponders would overlap with Eurobird 1 (28.5°E, close enough to effectively be part of the Sky and Freesat platforms) or with 2A or 2B.
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Gordon Davies: Make sure you're connecting the box to the TV with a digital link, such as HDMI, ONLY. If you connect SCART as well, the TV will often switch to the SCART input due to the box sending the Select signal. SCART is only SD.
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David: An aerial isn't specifically 'analogue' or 'digital', just designed for part or all of the UHF band, though there were some things not often done on cheaper aerials that are recommended for most reliable digital reception.
For HD reception on Freeview, you need a Freeview HD-labelled set-top box, PVR or TV. A PVR is typically required to record, although there are a few TVs you can now plug a USB hard disk into to record. Humax's 'set-top box' HD-FOX-T2 can also be turned into a one-tuner recorder by plugging in a hard disk.
For satellite, you can cancel your subscription to Sky and just use the Sky+ box to receive free-to-air and free-to-view channels. However, Sky will disable the recording and time-shifting functions. You also can't even watch things you previously recorded.
To get recording and timeshift features back, you can get a Freesat+HD PVR. You don't need an additional set-top box. You just plug it in in place of the Sky+ box.
If you're currently distributing the output of the Sky box to the bedrooms, you will also need a plug-in RF modulator as I'm not aware of any Freesat boxes that have one. As an alternative, you should consider getting an additional cable run from the dish to the bedrooms and put a Freesat box in there as well, allowing a viewer in the bedroom to watch something different from the main TV.
You can compare the channels available through a non-subscription Sky+ box ('Freesat-from-Sky'), switching to Freesat, or switching to Freeview, at Compare Freeview and Freesat TV | ukfree.tv - independent free digital TV advice .
If you provide a full postcode we can see whether an aerial change might be necessary to get all channels on Freeview.
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Coupland: Yes, these boxes only supported 2K mode and after switchover, all transmissions (except HD) are in 8K mode.
8K mode was always in the spec, the BBC were particularly keen on it as it allows larger single-frequency networks, but it requires more memory in the earliest stages of decoding so it was cheaper to make a box without it.
onDigital changed to be ITV Digital in 2001, and went into administration in 2002. So the box has to be at least nine years old.
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Duncan Brack: Freesat tuners need an independent connection from the dish to the box. That's because the tuner has to send some control signals back up the cable to the dish, to select low or high frequency range and horizontal or vertical polarization. To cram in more channels, both polarizations are used for different services.
Freesat PVRs usually have two tuners, so you can record one programme while watching another. That requires two connections to the dish. Since the TV itself supports Freesat, you could connect only one of the PVR's inputs if you're short of connections.
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Monday 24 October 2011 2:16PM
Briantist: The DTT Allocation Committee could still decide not to allocate any capacity this time around, but I think they'd have to have a very good reason for doing so.
This time, Channel 5 are offering a 24-hour simulcast of the Channel 5 Qualifying Service, although they do say "we wish to reserve the option of exploring possible ways for other providers to make use of some of the day time and late night hours". This was the sticking point last time, that they had said that 6am to 5pm would be an HD service provided by another broadcaster, without stating who that would be.
Of course, last time around, Five was still owned by RTL who were trying to get rid of it, while it's now owned by Richard Desmond's Northern and Shell.