All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
NICK ADSL UK: Incidentally, I noticed that the signal level of the BBC A multiplex, the last two evenings, was much lower than expected: only 34% on my Humax PVR, when it's usually around 60%. I'm out in Reading. The levels of the other four SD multiplexes were what I expected, around 60%. It was back to expected levels this morning.
It could of course be weather conditions or some device of my neighbours' interfering: the cable to my flat goes via a booster/splitter in theirs! Still, I wouldn't expect that to affect the strength of just one multiplex, particularly since BBC A is adjacent to ArqA (which was fine) and only two away from SDN (also fine).
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Owen Hesford: The owner of this website, Brian Butterworth (Briantist), has asked the BBC several times for the radiation patterns. Their most recent response is at Update on transmitter radiation patterns (BBC FOI request) | ukfree.tv - independent free digital TV advice .
For the frequencies used by Llandyfriog, we have actually told the international community that we will be broadcasting on them from Blaenplwyf (near Aberystwyth) at 40 kW. We are using them at Blaenplwyf, but only at 10 kW, so we can reuse them at a number of other sites in west Wales: see UK TV Frequency map - channel C22 (482.0MHz) before switchover map | ukfree.tv - independent free digital TV advice for the map. If Ireland were to officially discover that we weren't really using them to the extent we negotiated for, it might cause problems when renegotiating.
As for your wind farm, Llandyfriog currently uses a single log-periodic antenna to receive the signal from Presely. I would expect that use of trough antennas or arrays of logs, and/or diversity reception, should overcome any reduction of signal level. If all else fails, the data can be delivered to the relay site via fibre-optic cable rather than off-air, although this imposes an additional cost to the broadcasters.
The National Planning Policy Framework says, in section 44, "Local planning authorities [...] should ensure that [...] they have considered the possibility of the construction of new buildings or other structures interfering with broadcast and telecommunications services." The local authority could insist that the wind farm operator pays for any work required to restore broadcasting, if it does cause enough of a problem.
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Terry Ward: The frequency offsets mean that the centre of the signal is moved about 2% above or below the proper centre frequency (167 kHz in a channel bandwidth of 8,000 kHz). If one transmitter has a - offset and another a + offset on the same channel, there's still 96% of the signal overlapping (actually, more, because the transmissions don't go quite up to the edge of the channel bandwidth).
That means that the services on C23, C24, C26, C27 and C29 will all be knocked out. You'd be left with the HD services from Caldbeck (English and Scottish, though ITV1 Granada/Border HD, not STV HD), BBC England SD and ITV1 Border SD, and UTV from Divis (plus the other channels on those multiplexes). After switchover, C23, C26 and C29 will carry the commercial multiplexes from both transmitters, but because they're so far apart, they won't be synchronized and will cancel each other out rather than reinforcing. You cannot get most of these channels from Freesat.
The only way you could do this is if you had selective filters that only picked the services you want from each transmitter. Single-channel filters are quite expensive! They're usually only used in distribution systems for large buildings, e.g. tower blocks.
STV HD is available free-to-air on satellite, it's just not currently in the Freesat EPG. This was due to a conflict with ITV plc, I believe. Your box should have an 'Other Channels' or 'non-freesat channels' option. You can find the frequency and other tuning information at http://www.lyngsat.com/28…html - it's currently on 10936 MHz, V polarization, symbol rate 22000 baud, FEC 5/6.
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JORDAN: ArqB's capacity increase should have occurred on 21 November last year. If your box handled that, it should handle the upcoming changes to SDN and ArqA. Those are scheduled for 1 May, next Tuesday.
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Phil H: If you mean via Freeview, through an aerial, see CI+ Landing
You will need a CI+ rather than CI compatible CAM slot. From the channels' perspective, traditional CI was a problem because the decrypted data stream was completely open and could therefore be recorded or streamed over the Internet. CI+ protects the decrypted data stream to prevent this.
Top-Up TV briefly sold CI-compatible CAMs for use with ESPN, but Sky would not permit their channels to be accessed via a CAM.
On satellite, Sky will not permit anyone else to use their decryption scheme. You have to have a Sky box and a Sky subscription.
On cable you have to use the cable provider's supplied box.
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Nick, Paddy: RT channels *are* available on the satellite cluster at 28°E, but are encrypted. To decrypt, you need a Sky box with a Sky Ireland viewing card.
Saorsat requires a dish pointing at 9°E, or a multi-LNB dish set up so that signals from 28°E converge on the Astra LNB, and those from 9°E on the Saorsat LNB. (The Saorsat signals will be using circular polarization rather than linear.)
The KA-SAT satellite's beams are intended to reuse the same downlink frequencies in cells all over Europe - see http://www.boards.ie/vbul…1281 . It may well not be receivable in England due to interference from the reuse of the blue frequencies over northern Scotland and France.
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sarah: It still comes through the satellite dish. There are some channels available on Freeview - TV through an aerial - that are not available on Sky's free service or the Freesat-branded service, and vice versa. There are a couple of channels available on Sky's free service that aren't on the Freesat-branded service, and again vice versa.
See the 'Compare TV' section at Compare Freeview and Freesat-from-Sky TV | ukfree.tv - independent free digital TV advice to figure out what's available on what system.
If you do cancel your Sky subscription, you would lose the recording and time-shifting capabilities of the Sky+ box, if you have one. You either have to keep paying at least £10/month (reportedly - if you ask Sky just to keep the recording features), or replace the box with a Freesat-branded recorder.
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Yorkiebar: There are satellite receivers on the market that haven't signed up to Freesat's EPG and branding. They simply implement the basic DVB-S/S2 and MPEG-2, MPEG-4 video decoding specifications. Because they don't download a broadcaster-provided EPG, you have to tune them in yourself. They can show any service that conforms to the standards, which is broadcast unencrypted (aka 'free-to-air').
A Freesat-branded receiver does all that the generic free satellite box does, but also downloads Freesat's EPG, therefore automatically tunes in all the services that Freesat advertise, at the channel numbers that Freesat advertise. A Sky box downloads Sky's EPG and does the same, plus passes encrypted channel streams to the viewing card to be decrypted. (Actually, Freesat boxes often have CAM slots to allow a decryption module to be plugged in, and would pass any encrypted channel to that CAM, but Sky will not allow CAMs for their encryption scheme, and no UK channel is encrypted with any other scheme at present.) Both EPGs carry not only the next several days of programme information, but also content-delivery flags that signal a recorder to start recording when a programme actually starts.
For German channels there is no advantage to using a Freesat-branded receiver. Since the dish is pointing to a different part of the sky, it won't be able to pick up the Freesat EPG. Some Freesat receivers do have a 'non-Freesat' mode where you just tune it yourself, but others won't work at all if they can't find the Freesat EPG.
There are other free EPG providers in Germany, for example tvtv. Boxes sold in Germany are designed to download the EPG from one of these providers. They may also support the 'HD+' service, which are encrypted but have a much cheaper annual access fee. The cost of the first year is included in the cost of the box.
More advanced receivers support the DiSEqC (Digital Satellite Equipment Control) standard, to control switches and even motorized dishes. That can allow you to connect both a dish pointed to the UK satellite cluster and one pointed to the central-European cluster to the same box. You can also set up one dish with multiple LNBs to collect the signals from more than one satellite cluster (the dish and LNBs have to be positioned so that the signals from one cluster bounce off the dish to one LNB, and from the other cluster to the other LNB).
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Alan Shearing: If you're getting Norwegian and Spanish channels your dish is very likely pointing to the satellite cluster at 19.2°E. You will need to have it moved to 28.2°E.
There may still be Sky-supplied dishes pointing to 19.2°E, as the old analogue Sky service was broadcast from this cluster. That service closed in 2001. The new orbital position was used as there wasn't enough capacity at 19.2°E to run both the analogue and digital services. There are many people who are also interested in receiving foreign channels, either through heritage, migration or general interest.
The 19.2°E position is often called "Astra 1" because most of the names of the Astra satellites there start with "1", and 28.2°E is often known as "Astra 2" for the same reason. However, just to confuse you, Astra 2C was designed to go to 28.2°E but has now ended up at 19.2°E, while 1N, designed for 19.2°E, is temporarily filling in at 28.2°E.
The Freesat EPG information is carried on 11426 MHz, Horizontal polarization (this transponder is actually on Eutelsat 28A, formerly known as Eurobird 1, not any of the Astra satellites). The symbol rate is 27500 and the FEC rate is 2/3. I'm not sure if the EPG data is carried as a data stream on a specific Service ID, or just as Event Information Table data (which is part of the overall datastream, not a specific service).
If this is not a Freesat-branded device, see Astra 1N / Astra 2A / Astra 2B / Astra 2D / Eutelsat 28A (28.2°E) - All transmissions - frequencies - KingOfSat for the tuning information. 10773 MHz at 28.2°E carries the London, West, Cambridge and Channel Islands versions of BBC One, the England variant of BBC Two, and CBBC/BBC Three (these two services share a slot, effectively, as neither is on-air at the same time as the other).
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Friday 27 April 2012 3:28PM
NICK ADSL UK: 100% for strength almost certainly indicates too much signal. It's likely that conditions yesterday meant that the levels received were *lower* than usual.
Too much signal causes the amplifiers inside TVs, PVRs and set-top boxes to leave their linear region - where the output of the amplifier is an exact multiple of the signal going in. Instead the signal is distorted, which starts to introduce errors in addition to the errors caused by noise and interference from other transmitters. The error-correction built into the signals can only handle so many errors: once that threshold has been exceeded, the picture and sound start to break up and, as the number of errors increases, very rapidly disappear completely.
The first thing to look at is to turn down or remove any additional amplification. You're distributing the signals to multiple rooms, so you may need to replace the distribution amplifier with a passive splitter. Unfortunately, masthead amplifiers often won't pass the signals through if you just unplug the power supply, you actually have to bypass the connection.
If the signal levels are still very high, you will need to add attenuation to bring them back into spec.