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Update on transmitter radiation patterns (BBC FOI request)

The BBC have responded to my request for an update to the sites that they have provided the "radiation patterns" for.

The BBC have responded to my request for an update to the sites
Published on by on UK Free TV

I wrote to the BBC under the "Freedom of Information Act" in 2009 to ask them to disclose the radiation patterns used by the transmitters in the UK. This information shows the level of signal reduction from each transmitter in each direction, as the signals are not always broadcast at their full power (the "ERP") in all directions.

The response, which I posted here on 5th September 2009 can be see here: www.ukfree.tv link icon BBC Freedom Of Information - transmitter radiation patterns and these are now included in the transmitter pages on UK Free TV, as shown in this example:



Also provided was some information on the pre-switchover patterns for certain transmitters, see www.ukfree.tv link icon BBC FOI transmitter data - first draft from 12th September 2009.

I recently wrote again to the BBC asking them to disclose the information for the masts that were "redacted" (withheld) in the original request. These masts are listed at the foot of this article.

The response from the BBC today is shown below:

British Broadcasting Corporation Room 2252, White City, 201 Wood Lane, London W12 7TS Telephone 020 8008 2883 Fax 020 8008 2398 Email foi@bbc.co.uk

Information Policy & Compliance bbc.co.uk/foi

6 March 2012

Dear Brian,

Freedom of Information Act 2000 - RFI20120153

Thank you for your request under the Freedom of Information Act (the Act) of 9 February 2012, seeking the information which we had withheld from our earlier response to your previous request under the Act of 3 August 2009 (our reference RFI20091165).

In our reply to RFI20091165, we stated that we expected international negotiations regarding coordination of certain of the antenna patterns which you had requested to continue until the end of 2012. I am advised, however, that Ofcom has informed our spectrum planning team that these negotiations have not yet concluded and may in some cases still have some months to run.

Since we last wrote to you regarding this matter, it has also become clear that a further clearance of spectrum currently allocated to DTT is to be expected, for which international negotiations may start shortly. Therefore, I am afraid that it appears to us that negotiations surrounding these have not concluded.

For that reason, therefore, I regret that we must continue to withhold the data for these sites under the exemption in section 27(1) of the Act ("International Relations").

As set out in our response to RFI20091165, the exemption referred to above is a qualified exemption, which means that it must be tested against the public interest in favour of disclosure.

We note that for a number of transmitter sites (that is, all those marked as "Redacted" in the spreadsheet accompanying our last response to you), the exact radiation pattern that is to be employed is still subject to, or is likely to require, negotiations between HM Government (represented by Ofcom) and the equivalent administrations in these neighbouring countries.

The arguments in favour of disclosure are:

  • the antenna systems used for television transmission are, in part, funded by public money through the BBC's transmission contracts with Arqiva and the public has an interest in understanding what that money has been spent on; and
  • disclosure of the antenna radiation patterns would enable certain members of the public with specialist knowledge to gain a more accurate understanding of reception conditions in their area.

However, the arguments against disclosure of the characteristics of particular antenna systems are:

  • disclosure of the antenna radiation patterns into the public domain could lead to these being available to foreign administrations, which would substantially weaken HM Government's negotiating position with respect to international frequency clearance;
  • a weaker negotiating position for HM Government may lead to additional cost for the broadcasters (where antenna systems have to be re-built as a result of international coordination) and lower coverage for viewers (where antenna systems have to be restricted in order to protect foreign transmissions); and
  • the BBC is required to provide coverage of its services on digital terrestrial television to a certain proportion of the population by the completion of switchover and a failure or suboptimal result from international co-ordination may harm the BBC's ability to meet this obligation.

Therefore, I am satisfied that in all the circumstances of the case, the arguments against disclosure outweigh the public interest in disclosure for some of the antenna radiation patterns.

Appeal Rights

If you are not satisfied with this response you have the right to an internal review by a BBC senior manager or legal adviser. Please contact us at the address below, explaining what you would like us to review and including your reference number. If you are not satisfied with the internal review, you can appeal to the Information Commissioner. The contact details are: Information Commissioner's Office, Wycliffe House, Water Lane, Wilmslow, Cheshire, SK9 5AF, telephone 01625 545 700 or see http://www.ico.gov.uk/

Yours sincerely,

Tom Everest
BBC Distribution


I am considering if making an appeal is the best course of action, or perhaps waiting until the end of 2012, when the mentioned negotiations may be complete.

Redacted masts

Aldeburgh Alderney Amlwch Angus Arfon Armagh Ballantrae Barrow Town Hall Barskeoch Hill Beacon Hill Beary Peark Beer Belcoo Belmont Benagh Berrynarbor Betws Y Coed Bevendean Bexhill Uhf Bilsdale Bincombe Hill Black Hill Black Mountain Blackwaterfoot Blaenplwyf Bluebell Hill Bowmore Hp Bowmore Vp Bow Street Brading Bridport Brighstone Brighton Central Brixham Broad Haven Brougher Mountain Budleigh Salterton Burnham Burnham On Crouch Bushmills Caernarfon Caldbeck Caldbeck Scotland Cambret Hill Camlough Campbeltown Caradon Hill Carmel Castlebay Castlederg Cemaes Cerne Abbas Chambercombe Charmouth Chartham Chatton Chideock Vp Clachan Clacton Claudy Clennon Valley Clettraval Coldean Combe Martin Conway Coombe Corfe Castle Countisbury Craigkelly Crystal Palace Dalton Darvel Darwen Dawlish Derrygonnelly Divis Dolybont Douglas Dover Dover Town Downderry Durris Eastbourne Eastbourne Old Town East Dean Ederny Eitshal Elham Emley Moor Exeter St Thomas Felixstowe Fenton Ffestiniog Findon Fishguard Folkestone Fremont Point Girvan Glenelly Valley Glengorm Glenmaye Gorey Gortnalee Gosforth Great Yarmouth Greenhill Guildford Gulval Hangleton Hannington Hartland Haslingden Hastings Hastings Old Town Haverfordwest Heathfield Hollington Park Horn Street Huntshaw Cross Hythe Ilfracombe Ipswich Stoke Isles Of Scilly Ivybridge Jurby Kendal Kilbride South Uist Kilkeel Killowen Mountain Kilmelford Kilvey Hill Kimmeragh Kingsbridge Kirkoswald Hp Kirkoswald Vp Lancaster Larne Laxey Leitrim Les Touillets Lethanhill Lewes Hp Lewes Vp Limavady Lisbellaw Llanddona Llandecwyn Llandrindod Wells Llandyfriog Llangranog Lochmaddy Hp Londonderry Long Mountain Looe Lowestoft Luccombe Lulworth Luscombe Valley Lydden Lyminge Margate Mendip Mevagissey Midhurst Millbrook Vp Moel Y Parc Morfa Nefyn Muldonagh Mynydd Pencarreg Newcastle Newhaven Newport Bay Newry North Newry South Newton Ferrers Occombe Valley Olivers Mount Overstrand Ovingdean Vp Oxford Patcham Penaligon Down Penmaen Rhos Penryn Perranporth Piddletrenthide Pinwherry Plumbridge Plympton Polperro Pontop Pike Poole Port Ellen Porthtowan Port Isaac Portnahaven Portpatrick Portslade Port St Mary Praa Sands Presely Preston Ramsgate Redruth Reigate Ridge Hill Ridge Hill West Roose Hp Rosemarkie Rosneath Vp Rostrevor Rothesay Rouncefall Rowridge Rowridge Vp Rumster Forest Rye Salcombe Salisbury Saltdean Sandy Heath Scoval Vp Sedlescombe Selkirk Sidmouth Skriaig Slapton South Knapdale St Austell St Brelades Bay St Davids St Dogmaels Steyning St Helier St Just Stockland Hill Stokeinteignhead Storeton Storeton Wales St Peter Port Strabane Stranraer Sudbury Sutton Coldfield Tacolneston Teignmouth The Wrekin Torosay Torquay Town Torteval Trefilan Trefin Trefor B Tunbridge Wells Ventnor Waltham Wells Next The Sea Wenvoe Westbourne West Kilbride West Kirby West Runton Westward Ho Weymouth Whitehaven Whitehawk Hill Winterborne Sticklan Winter Hill Woodbridge Woolacombe Woolwich Workington





Your comments: most recent posts are at the bottom


Your comments are always welcome. Please use the form below to add your thoughts or questions to this page. We will get back to you as soon as we can.

Noel
Wednesday 7 March 2012 8:45AM
Brian
Fantastic work on chasing the BBC on their radiation patterns.

I must say I do not understand the argument against release:
"...antenna radiation patterns into the public domain could lead to these being available to foreign administrations"
Since surely as part of the negotiations they must have informed counter parties of their coverage in order to agree the allocation? Are they suggesting that everyone sits around a table with no knowledge of how they will be affected and discuss frequency allocation on a best guess basis??
Mike Dimmick
Wednesday 7 March 2012 11:18AM
Noel: You can actually find the details of what we, and other nations, negotiated for in the ZIP file at www.itu.int link icon http://www.itu.int/ITU-R/terrestrial/broadcast/plans/ge06/dig_plan.zip . Warning: it's 280 MB, and contains the plans for all 121 European and African nations that participated.

At some point the ITU will notice that this should be behind their paywall.

There is one folder per country - our ITU region code is G. The rrc06_digital_plan_details.pdf file gives information about each DAB allocation (single-frequency network) and each TV transmitter above a certain power. Power is specified in dBW - divide by ten and then raise 10 to the resulting power (if using Windows Calculator there is a 10^x button) to get watts. The radiation patterns are given in section 23 and they are in effective height of the transmitting antenna in that direction. This is basically the height above the average height of surrounding terrain within a relatively short distance of the transmitter. Negotiations between countries are on the basis of these claims.

We've actually claimed far more than we're really using or going to use. As far as I can see, we've pretty much asked for omnidirectional patterns from all transmitters. You can compare using ITU's effective height calculator at www.itu.int link icon Calculation of Effective antenna heights using the SRTM3 database which uses height data from NASA's Shuttle Radar Topography Missions - we probably used Ordnance Survey data which is more precise and more accurate.

Do be aware that the co-ordinates and heights given are referenced to the World Geodetic Survey 1984 (WGS 84) co-ordinates, not the UK's National Grid. The notion of mean sea level can be substantially different.

We've only negotiated a couple of hundred transmitters, from the set of over 1,100. The smaller relays are not expected to substantially affect international coverage. Their allocations are essentially extracted from the negotiated ones - and this is why, quite often, the relays of a main transmitter clash with the commercial multiplex allocations of it or another relay, and why the commercial muxes can't actually transmit from all the relays. For example, Aldeburgh (though not one of the top relays in terms of population coverage) was allocated 8 channels at 10 kW

Even if a transmitter site is listed, it may have adopted another channel from another site, if the net interference to other countries will be the same or less. For example, Sheffield was not allocated C39, but ArqB is using it there. That channel *was* assigned to Emley Moor, but it's not used at that site, and Sheffield's coverage area is effectively contained within the area we claimed for Emley Moor.

What the BBC are saying is that if they published the full details of the compromises of how the main sites are *really* running, rather than how we told the rest of the world that they *would* run, we'd have problems negotiating those allocations in future.

The plans can be updated by negotiating with expected interferers (part 28-2 - note Emley Moor is shown interfering with Ireland!) and ultimately notifying ITU-R, who will include the update in the next Radiocommunications Bureau International Frequency Information Circular. BR IFIC (Terrestrial) can be found at http://www.itu.int/ITU-R/…g=en - look for GE06/nn updates. As far as I can see, though, we haven't sent through any updates for TV transmissions since the initial plan was finalized in 2006.
Mike Dimmick
Wednesday 7 March 2012 11:50AM
"the relays of a main transmitter clash with the commercial multiplex allocations of it or another relay" should read "of another main transmitter".

I didn't finish the comment about Aldeburgh. Aldeburgh got C21, C23, C25, C26, C28, C30, C32 and C33. We're clearing C31-C38 for new services (potentially) and therefore C32 and C33 can't be used, but that still leaves C21, C26 and C30 that it's not using. C26 and C30 were formerly analogue channels but C21 was a new allocation. However, as I said, the smaller relays had to be fit in somewhere. C21 was basically lost to Bramford. C26 is used at Ipswich Stoke, Linnet Valley and Thetford (Gorleston-on-Sea and West Runton were included in the ITU plan). I can't see clashes on C30, but without three spare channels they may not have bothered anyway.

Aldeburgh isn't a great example as it's only predicted to serve 9,500 homes. I have got a ranking spreadsheet of which relays serve the most households, extracted from consumers.ofcom.org.uk link icon http://consumers.ofcom.or….pdf . Top of the list is Rouncefall, which appears in the GE06 plan, and uses the same frequencies as its parent, Sudbury, anyway - it would add 51,000 households. The next two are Londonderry, 37,000 and Kidderminster, 33,000. I'm excluding Storeton (Wales), 41,000, as its purpose is to provide Welsh PSB services to people fully covered by Winter Hill, so most of them will already have commercial mux coverage from there. I haven't analysed the smaller relay clashes at Londonderry or Kidderminster.

If the commercial multiplex operators *had* indicated that they wanted to take up the additional 120 sites, or higher net coverage overall, the relay plans would have been fitted around that target. As it is, they haven't been, and now retrofitting the commercial muxes anywhere else is substantially more difficult. Bringing this back to the topic, that's one thing that we might have to negotiate with other countries.

The '600 MHz band', C31-C38, is also problematic because the actual frequency plan that's been worked out, using only three frequencies for each of layer 7 and 8 (9 is a Single Frequency Network on C36), doesn't match what we negotiated for those transmitter sites. Typically these were just conversions of the analogue frequencies previously used at those sites.
mst
Wednesday 7 March 2012 10:02PM
What international borders are challenged by the Oxford TX? Maybe is to do with the channels in/near 800MHz? Or maybe the reason here is that the work is just not finished, so they don't know...!
Mike Dimmick
Wednesday 7 March 2012 10:29PM
mst: Section 28-2 of the Oxford pages indicates that the allocations were negotiated with France.

Transmissions can stretch a very long way, particularly in unusual weather conditions. We have to be sure that we're not interfering unduly even under those conditions.

The 800 MHz clearance does require another round of negotiation. That's why the relays have typically had the necessary retunes incorporated into the main switchover plan - since about mid-2011 - while the main transmitters will have to be retrofitted.
Justin Smith
Wednesday 2 May 2012 4:41PM
Are you saying the`ve released more transmitter patterns but not all of them ? Even if one accepts their arguments why they haven`t (and I don`t, I think it`s a very weak argument compared with freedom of information), I can`t see any reason at all why they can`t release all the relay patterns. After all we`re only talking about TXs up to 50/100W, and most of those on the coast aren`t aimed out to sea anyway. Then there`s any TXs in the north or west of the UK (esp Scotland), how can their transmissions affect any other country ?

On the subject of Oxford, that`s a C/D transmitter, C/D transmissions, being higher frequency, don`t travel as far as A group transmissions. I think any argument about possible co-channel issues should bear that in mind.
Briantist
Friday 18 May 2012 3:41PM
Justin Smith: Just to clarify, the information in the original FOI request covers the relay transmitters, with a single exception.

You have to remember that it's not the "normal" conditions that have to be considered (as that's an easy computation) but the problems during "Inversion" where signals are carried much further than usual that have to form part of the process of allocation and co-ordination.
Mr P Watmough
Monday 21 May 2012 5:50PM
Why are some channels on waltham on low power very early in the morning ? Have you got co channel problems ?
Most noticed on Sky news, and about 0630 approx the signal strength sudendly doubles.
Checked at different locations with different aerial systems and different receivers. Explain and own up !
Mike Dimmick
Tuesday 22 May 2012 3:44PM
Mr P Watmough: They are not. Check that you are looking at signal *strength* and not signal *quality*. *Strength* should change gradually, it should only change sharply if an amplifier in the aerial system is switched on or off. If it really is, and you're using a communal aerial system, it's probably a fault in that.

Quality is a function of both the wanted signal strength and of the level of interference. The reported quality is usually some percentage of datablocks received without errors. The more interference, the more errors, but the error correction scheme automatically corrects as many as it can, up to the threshold of what's possible. Many boxes report only the rate of what couldn't be corrected. On these boxes, the aerial system should be set up so that the quality meter always reports 100%, even in the worst conditions.

Every frequency used for TV transmission in the UK is used at numerous different sites. They have been spaced far enough apart that they shouldn't interfere with each other, within the expected coverage area, for more than 1% of the time. However, for the COM muxes (SDN, ArqA and ArqB), there are usually more or closer interferers than for the PSBs (BBC A, D3&4, BBC B).

Changes in weather conditions cause changes in signal propogation. If signals usually change overnight, it can just be down to the regular daily warming or cooling of the atmosphere, which is termed 'tropospheric enhancement' as it enhances the signals from distant transmitters (i.e. interference).

If you really think you have discovered a fault, you should contact Sky or one of the other broadcasters on the affected multiplex. Arqiva do not take fault calls from the public, except for a small selected group of people who monitor their local transmitter. If the fault is occurring on one of the BBC multiplexes, you can report that through their engineering page at https://faq.external.bbc.co.uk/templates/bbcfaqs/emailstatic/interferencePage . Keep saying 'no' when it asks if this has answered your question, and eventually you'll get to a form that enables you to send an email.
Andy Ripley
Friday 15 June 2012 7:06PM Ripon
There's software out there that models propagation and gives a likely coverage, however they are not using a single omnidirection antenna, they are using array and they don't (as I have found) radiate evenly. It's this vital information that they hold back.
Yes it would be nice to have it, but it would show possibly a nice null on several of the muxes in my direction from Bilsdale. The signal strength is well down on several muxes even comparing them on the Spectrum Analyser connected to the antenna.
Tumbly
Monday 23 July 2012 5:51PM
I cannot understand eg Norfolk data being redacted seeing as Holland went Digital in 2007. I could understand Brougher vis a vis Republic of Ireland ...but Brougher was not redacted.
ron brown
Friday 14 December 2012 8:50AM Tamworth
I find it annoying, to say the least, to think of all the licence-payers (including so many pensioners who assume that they can truat their TV signal to be of consistent high-quality) who have paid lots of money to the "digital aerial" cowboys. Only to find in many cases that their received signal is only marginally improved by a more powerful aerial. becasue the power sent in their direction is nowadays too poor.
That the BBC, and perhaps Ofcom too, try to keep knowledge of the full details of all this from us is astounding.
We need Questions in Parliament. And pronto.
ron brown
Friday 14 December 2012 9:16AM Tamworth
I've downloaded the ITU spreadsheet. Thanks to Mike Dimmick for the URL which still works.

Which code applies to the UK?

Talk about obscure bureaucracy!!
Vast expense in making such documents (and making them almost unreadable) and then refusing to allow us Electors and Licence Payers knowledge of what's going on????
Amazing if it were not the norm.
Briantist
Friday 14 December 2012 10:57AM
ron brown: I do find it odd that you say "the power sent in their direction is nowadays too poor" when you are in an exceptionally good reception area for one of the most powerful transmitters in the country (at Sutton Coldfield).

Can I suggest you have a look at www.ukfree.tv link icon Freeview signals: too much of a good thing is bad for you | ukfree.tv - 10 years of independent, free digital TV advice ?
ron brown
Friday 14 December 2012 11:39AM Tamworth
Briantist: Thanks for your reply.

I own a variable attenuator too.....and a choice of aerials.
>>The received signal is poor.<<

It is abundantly obvious that my particular part of Tamworth suffers from poor reception (now). Pre-digital (in fact, pre-HD turn-on too) we could receive TV on a coat-hanger improvised aerial.
Then the "experts" decided to "improve" things.....

All around me, neighbours have had to put up fringe-area, multi-element aerials - at huge expense - just to get a watchable signal. Everyone agreed that this was all their OWN fault for not having a "digital Aerial"....

I am 6 miles from the transmitter!!!!
Many neighbours - after spending fortunes to fix "their" poor aerial systems switched to cable, Sky or Satellite to resume normal service.

Too often, people jump in and say we're wrong.. "There's nothing wrong with the transmitted signal"."What you need is a proper Digital aerial" and so on...

All of us, so wrong, ALL of the time???
I smell cover-up.


Michael
Friday 14 December 2012 1:29PM
ron brown: Your switchover was in September last year - have you had problems since then?

Can I assume you've had a qualified aerial installer/engineer out to check on this problem? And with all of your neighbours also having problems, you have got in touch with the BBC (via www.radioandtvhelp.co.uk) link icon http://www.radioandtvhelp…uk)?

And I do hope you realise there's no such thing as a digital aerial...
ron brown
Friday 14 December 2012 7:10PM Tamworth
I was being satirical...
I have a doctorate in physics... and I can tell an installation engineer form a "you need a digotal aerial" cowboy. Pity the old folks around here can't.

BBC ignore all such complaints, won't even give an email address you can reply to to state your case. Too busy paying 200+ people more than we pay the PM !!!!!
That says it all.

It's their "no reply" website email or nothing.
Some Licence Fee value....
My MP is starting to listen though.....
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