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All posts by Mike Dimmick

Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.

jb38, Nick H: It means that the satellite is in geostationary orbit above the point on the earth at 0°N latitude, 28.2°E longitude - geostationary orbits are always directly above the equator.

The angles needed to set up your dish depend on your location. Try - Satellite Dish Alignment / Setup Calculator 2.0 to calculate the settings required.

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Another factor is that all high-power sites have to be negotiated with our neighbours, due to the mutual interference. Signals can travel a surprisingly long way, for example Mendip had to be cleared with both Ireland and France.

The question is whether these 20 sites will be subject to a new round of negotiations, or whether the plan is simply to use the allocations we already have. If the latter, it could lead to some very weird results as to who gets what, with some low-coverage transmitters appearing and some high-coverage ones not. There's not even a guarantee that all sites will get both multiplexes.

Checking the sites with two allocations in the 31-37 range in the Geneva 2006 plan, I get this list, in descending order of 6MUX population coverage:

Crystal Palace
The Wrekin
Ridge Hill
Lark Stoke/Bromsgrove/The Wrekin (SFN)
Stockland Hill
Caradon Hill
Kilvey Hill
Tunbridge Wells
Pendle Forest
Rumster Forest
Brougher Mountain

27 sites, sum of gross 3PSB coverage 17,862,000 households, sum of gross 6MUX coverage 13,361,000 households. Top 20 give PSB coverage of 17,749,000 households and 6MUX of 13,277,000 households. The TV population is usually given as 24.8 million households, so assuming PSB coverage levels (which they should be, as the band is clear!) you get 71% population coverage, or 53.5% for 6MUX coverage levels.

Those with one allocation:

Sutton Coldfield
Emley Moor
Black Hill
Sandy Heath
Moel Y Parc
Whitehawk Hill

Many other sites have additional unused allocations outside this band - we negotiated 8 'layers' per site for mainland UK and Northern Ireland. In many cases those allocations have had to go to neighbouring sites, where a site wouldn't have had six multiplexes after the 800 MHz allocations were removed, or have had relays carved out of them. Still, there *could* be scope for putting one of the multiplexes somewhere else, or borrowing a neighbouring allocation *from* a high-power relay that isn't one of the 6MUX sites (though it would inevitably be at lower power, to stay within the envelope of the original allocation). For a concrete example of that, see how Sheffield has borrowed C39 from Emley Moor.

There are of course massive omissions from this plan, particularly Winter Hill, Sutton Coldfield, Emley Moor and Black Hill. Some negotiation is likely to be required!

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It's far easier for Sky's 'barker' channels to convert a Freesat user to a Sky subscriber, than a Freeview user to a Sky subscriber. In the former case, they just have to get the customer to plug in a Sky box to the existing cabling. In the latter, they have to get the customer to get all-new dish and cabling installed. That's been a stumbling block for them.

It may be that they see Freeview -> Freesat -> Sky as an easier upgrade than directly Freeview to Sky, but that the absence of their channels from Freesat puts Freeview viewers off choosing that.

It is an interesting change in dynamic, now that switchover is complete: no longer are they trying to grab a greater share of analogue viewers, they're now truly head-to-head with each other.

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I don't expect there will be much all-new content on these multiplexes. I expect them to carry more HD simulcasts of existing services, probably services that are already available in HD on satellite, though the BBC's service(s) will be new.

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Just to clarify, when I said 'new', I meant that it would be HD simulcasts of existing BBC channels: just not ones that are currently broadcast in HD. There is no chance whatever in this climate that the BBC Trust and DCMS would approve an entirely new service.

David: That story dates from the end of 2010, just after the real-terms cut in funding and additional mandatory spending were announced, when the BBC had not announced how they planned to deal with it. Now they have. BBC Three and Four will remain, but "play supporting roles to the two bigger channels", BBC Three being aligned with BBC One, and Four with Two. BBC - Inside the BBC - Delivering Quality First

BBC HD's replacement by BBC Two HD is in order to save the, actually quite small, cost of its separate scheduling, continuity, branding and playout. This is around £2.8m per year. It's almost an accounting trick actually, because all the necessary HD infrastructure for BBC Two will then be divided among BBC Two's much higher viewer base and result in a lower cost per viewer hour, the standard that the BBC use to assess value for money.

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Mike: You say 'accommodation'. Is this a shared dish? If so, you should contact your landlord, agent or residents' association, whoever manages the property. My guess is that there is a fault on the multiswitch. Can your neighbours get the free channels on satellite? If so, it's likely just a fault on your link, but if others are having problems it's probably a problem with the low-frequency output on the LNB.

You should be aware that you CANNOT split a satellite feed, to feed more than one input or more than one box. Each input sends control signals to the LNB or multiswitch, to select the frequency range (LO or HI) and the polarization (H or V). If you split a feed, clashing control signals can be sent to the LNB/switch and you get unexpected results. The exact behaviour depends on what each signal is controlling.

If you only have one feed into your accommodation, you should plug that into the LNB1 input, and leave the LNB2 input disconnected. This does mean you can only record a programme and watch another, or record two programmes, when the programmes are on channels with the same frequency range and polarization (both LO or both HI range, and both H or both V polarization).

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DAB local radio gaps | Digital radio
Wednesday 19 December 2012 12:05PM

michael: The BBC are reserved space for each local radio station covered by each local multiplex. They must wait for the commercial operators to launch their multiplex, and to extend service by adding new transmitters. The law doesn't actually say that the BBC is not allowed to bid, nor does the Royal Charter, but practically speaking, there are already licensees for all of the areas that the ITC and, subsequently, Ofcom have chosen to offer. The problem is that they haven't launched, and those that have launched haven't matched coverage. This is despite the Broadcasting Act 1996 section 49(1):

"In exercising their powers to grant local radio multiplex licences, the Authority shall reserve to the BBC such digital capacity as the Authority consider appropriate in all the circumstances with a view to enabling every BBC local radio service and every BBC radio service for Wales, Scotland or Northern Ireland to be received in digital form within a coverage area which, so far as reasonably practicable, corresponds with the coverage area for that service as provided otherwise than in digital form."

The operative words there are probably 'reasonably practicable'. The multiplex operators simply don't want to spend any more money than they are compelled to, as long as there is enough ad revenue coming in (same problem, of course, as the commercial TV multiplexes). The BBC has no power to require extension of coverage and won't want to - possibly isn't allowed to - fund an extension from which the commercial services will benefit.

The government will have to accept that to achieve a radio switchover, they must *require* the multiplexes to extend their coverage. Until they introduce that mandate, and probably offer some funding, it won't happen.

There is no great social benefit to a digital radio switchover - the FM band isn't really crowded enough to stop new community radio stations launching, and there is no other practical purpose for that radio spectrum.

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James Hillsdon: As free-to-air services migrate to the Astra 2F satellite, you are likely to need a larger dish and may not be able to receive them at all. The broadcasters specifically intend that people outside the British Isles cannot (easily) receive them. They pay less for content if broadcasts are restricted to the British Isles (for practical purposes, it is impossible to eliminate the Republic of Ireland from the footprint).

The Astra 2F footprints are at
. The BBC, ITV and Channel 4 services use the UK Ku Spot Beam.

The services are currently on Astra 1N
. It's become clear that the "UK spot beam" on that satellite is actually a dish designed for Europe or African coverage that has been tilted up so it's centred on the UK, and the power has been reduced. Once services have been transferred to the 2F satellite, 1N is expected to move to its proper orbiting position at 19.2°E.

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Wednesday 19 December 2012 12:25PM

Philip Lane: It's worth checking if there are any firmware updates for your TV. The encoders for Freeview HD can switch between interlaced and progressive modes for each Group of Pictures (GoP), depending on how well that GoP compresses in each mode. Some TVs don't cope well with a change of mode, resetting all the hardware, causing a break in audio as well as video. (They expected mode changes to only occur when switching channels or sources.)

Because the mode switches depend on the content transmitted, they will occur apparently at random, even within a programme, and different channels will be affected at different times.

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David Penfold: The Ofcom Radio Tech Parameters spreadsheet only lists Farthinghoe and Beckley (Oxford) at present. The legal requirement is only what they outlined in their Technical Plan when they applied for the licence: Beckley, Boars Hill and Oxford. Ofcom | Radio Multiplex Licence Award: Oxfordshire

Only five years late launching...

The Arqiva document that Briantist referred to was created for Ofcom's DSO consultation titled "An approach to DAB coverage planning". In the post-consultation Interim Statement, Ofcom said:

"The options we proposed do not constitute a definitive or final view on any post-switchover DAB network but will inform the Governments decision about whether to proceed with digital radio switchover. We noted that further technical work on network planning, and public policy decisions by Government on the issues raised, would be necessary."

No-one has yet figured out who is to pay for increasing the DAB coverage to the same level as FM. The commercial stations don't want to do it as additional coverage comes at an ever-increasing cost per additional listener, typically less than the additional fees that could be charged for advertising. The multiplex operators will only do it if their customers ask, and pay, for it. The BBC can't afford it and currently isn't required to do it (for local radio; for national radio the current licence fee settlement requires them to get to 97% population coverage, still short of the 99% FM is estimated to reach).

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