Mounting A Terrestrial TV Aerial

3  Aerial Alignment Calculator (with internet mapping)

The author of this page apologises to users for its current non-functioning.  This has been caused by Google's withdrawing functionality without updating their documentation, and hopefully will be of short duration.

At its simplest, for anywhere in the world this page calculates and displays on a map the direction (bearing or azimuth) to point (align) a terrestrial TV aerial towards a distant transmitter, and can display on an internet map the required azimuth (bearing or direction), or calculate the compass or grid bearing for use with a printed map.  However for countries in the British Isles including Eire, particularly for those within the UK, it can do significantly more.  To realise its full potential, first time users are advised to read the General Help.

General Help

Page loading is staged  -  as soon as possible the calculator's form unlocks so that you can begin entering data, further options becoming enabled as the code to support them completes loading.  The options available also depend on the chosen receiver location as follows:

  • Anywhere  -  Google Map displays a direction line for aligning the aerial, while the calculator shows the true azimuth (degrees clockwise from True North), and another azimuth corrected either against Grid Variance (Grid Convergence, Grid Angle) for use with a printed map, or against Magnetic Variance (Magnetic Declination) for use with a compass.  As accurately as possible, enter locations for the receiver and transmitter, click the map button, and if required drag the marker(s) to more precise locations.

    The map has two choices of base layer selectable by the buttons in the top right hand corner.  Satellite pictures can take significantly longer to load, so it's quickest to use Map to get as close as possible to the intended final location and zoom level before switching to Satellite.

    Satellite images are often subject to perspective distortion, occasionally to an extent significant in the context of aligning a TV aerial, thus making their results potentially less reliable than the initial impression given by their simplicity.  Although it may seem counter-intuitive, you should work entirely from ground level  position the marker at the point on the ground beneath the proposed aerial siting, and choose as aiming point a landmark the base of which is crossed by the line.

  • British Isles and Eire  -  Signal Profile displays a vertical elevation along the signal path.  UK users can choose a transmitter via one of the various UK lists and the transmitter's location and height will be entered automatically.  Users from Eire will need to determine and enter manually not just the transmitter's location but also the height of its antenna above sea level.

    The signal profile is shown as a straight line (allowing for refraction conventionally by assuming a radius of Earth 4/3 × the real one), with 60% (red) and 100% (orange) Fresnel zones, and intervening clutter (brown), terrain (green), and possibly curvature of the Earth (black).

    If you are within range and have a clear Fresnel zone, then you should get a good signal, but obstructions will progressively weaken it, blocking it when they cross the line of sight.  Obstructions into the orange zone will probably not be serious, but any into the red might require sensitive aerials and/or amplification to get a good enough signal.  If the signal is blocked, then you can only receive it indirectly, perhaps by reflection off other buildings or refraction over or around obstacles.  In marginal cases, you might be advised to consult a reputable CAI installer with good local knowledge, or to consider Freesat.

    If the relevant maps have been created, clicking in the top third of the display will centre the Google map on an area of the signal path, the bottom third the OS map, and the middle third both.

  • UK Nations (including the CI, the IoM, and NI The calculator has transmitter data for the entire UK, including locations, antennae heights, transmissions, channel numbers, etc.  Further details are given in UK Transmitter Help.

  • UK Mainland Nations & the IoM  -  UK OS Map displays the signal path (default) or the locations of the transmitters in the calculator's current list.  Click the buttons beneath the navigator bar to swap between the two modes.

    Coordinate conversion between Lat/Lon and E/N doesn't use OSTN02™, so coordinate readouts should only be considered accurate to around 5m.

    OS's OpenSpace® on-line mapping covers UK mainland down to street level (other UK nations are covered by other agencies and are either only available via OS at low-scale or not at all).  If, despite the coordinate vetting, you manage to create a map of somewhere not actually covered, the map may just show nothing, or stick on an area on the north east coast, in which case Ctrl-Click the map button to remove it, and just use the Google one. 

If you plan to print either map, please read the Notes.

If some of the terms or techniques mentioned here are unfamiliar, you are advised particularly to read General Introduction  -  see also the navigator bar at the top of the page, and the list of useful links at the bottom.

If you are unsure of the format for inputting data, hovering the pointer over an input will bring up a short message describing the format expected.  In general:

  • Latitudes, longitudes, grid and magnetic variances can be entered as decimal degrees or DD:MM:SS.  In both cases, southern and western values can be entered as negative or by appending S or W, northern and eastern as positive or by appending N or E.
  • All other data such as grid references and post codes should be entered in their normal format.  Irish grid references should be flagged with a leading I.  For example, that for Divis transmitter would be entered as IJ287750, although as it happens this transmitter is in the area of overlap between the two systems, so the nearest UK equivalent of NW412309 will also work.

UK Place Name look up covers UK mainland only, except that the transmitter version also searches the UK transmitter list.  UK Post Code look up should find codes for the entire UK, but to reduce the chances of usage capping by Google, does so by searching the OpenSpace UK mainland database first, only trying Google on failure.  Other post codes and places, for example Eire, can be looked up using the World Place Name option, but the database is very US-centric, so append an appropriate country name, for example ,Eire.

When you are satisfied with your settings, you can save them by pressing Submit and then bookmarking, marking as a favourite, the resulting URL, the parameters in which will recreate your original settings in the calculator.  You may wish to do this once you have positioned a map exactly on your aerial site as described above (though then you will have to wait for everything to reload).

Clicking on a map button fixes latitude and longitude as the method of designating the receiver location.  Dragging a marker to a new location updates the calculator and may also recentre the map(s).  Likewise, where necessary, changes in the calculator will be reflected in the map(s).  After creating a map, changing settings other than receiver latitude & longitude, or choosing a different transmitter, is not recommended and may not be possible.

UK Aerial Help

GroupChannel RangeCap colourSchematic showing aerial group overlap
A21 - 37RedGroup A Cap ColourSchematic showing aerial group overlap
B35 - 53YellowGroup B Cap Colour
C/D48 - 60GreenGroup C/D Cap Colour
E35 - 60BrownGroup E Cap Colour
K21 - 48GreyGroup K Cap Colour
W21 - 60Black or noneGroup W Cap Colour
PolarisationAlignment Of Elements

Note that where a transmitter uses a semi-wideband group (E or K), Ofcom often suggest wideband (W) as an alternative, resulting in E/W or K/W.  However, for performance reasons, I suspect that in such cases most professional installers would recommend the narrowest group aerial that can accommodate the signals required, and not a wideband.

UK Channel / Mux Help

The following channels are currently being broadcast in the UK:

Mux LCN Channel Name Genre CI E NI S W
PSB11BBC OneGeneral Entertainment**   
PSB11BBC One NIGeneral Entertainment  *  
PSB11BBC One ScotlandGeneral Entertainment   * 
PSB11BBC One WalesGeneral Entertainment    *
PSB12BBC TwoGeneral Entertainment**   
PSB12BBC Two NIGeneral Entertainment  *  
PSB12BBC Two ScotlandGeneral Entertainment   * 
PSB12BBC Two WalesGeneral Entertainment    *
PSB17BBC AlbaGeneral Entertainment   * 
PSB19BBC FourGeneral Entertainment*****
PSB1130BBC NewsNews*****
PSB1131BBC ParliamentNews*****
PSB1200BBC Red ButtonText services*****
PSB1600BBC RB 0Interactive*****
PSB1601BBC RB 1Interactive*****
PSB1700BBC Radio 1Radio*****
PSB1701BBC R1XRadio*****
PSB1702BBC Radio 2Radio*****
PSB1703BBC Radio 3Radio*****
PSB1704BBC Radio 4Radio*****
PSB1705BBC R5LRadio*****
PSB1706BBC 5SXRadio*****
PSB1707BBC 6 MusicRadio*****
PSB1708BBC Radio 4 ExRadio*****
PSB1709BBC Asian NetworkRadio*****
PSB1710BBC World ServiceRadio*****
PSB1719BBC Local RadioRadio**   
PSB1719BBC Radio ScotlandRadio   * 
PSB1719BBC Radio UlsterRadio  *  
PSB1719BBC Radio WalesRadio    *
PSB1720BBC Local RadioRadio *   
PSB1720BBC Radio nan GidhealRadio   * 
PSB1720BBC Radio CymruRadio    *
PSB1720BBC Radio FoyleRadio  *  
PSB1721BBC Local RadioRadio**   
PSB1722BBC Local RadioRadio *   
PSB1734BBC Local RadioRadio *   
PSB1735BBC Local RadioRadio *   
PSB23ITVGeneral Entertainment**   
PSB23ITV WalesGeneral Entertainment    *
PSB23STVGeneral Entertainment   * 
PSB23UTVGeneral Entertainment  *  
PSB24Channel 4General Entertainment**** 
PSB24S4CGeneral Entertainment    *
PSB25Channel 5General Entertainment*****
PSB26ITV 2General Entertainment*****
PSB27Channel 4General Entertainment    *
PSB210ITV3General Entertainment*    
PSB213Channel 4+1General Entertainment*****
PSB214More 4General Entertainment*****
PSB215Film4General Entertainment*****
PSB224ITV4General Entertainment*****
PSB228E4General Entertainment**** 
PSB233ITV +1General Entertainment * **
PSB233STV+1General Entertainment   * 
PSB233UTV+1General Entertainment  *  
PSB2100Freeview InformationGeneral Entertainment*****
PSB2726U105Radio  *  
PSB345Film4+1General Entertainment*****
PSB3101BBC 1 Scotland HDHD   * 
PSB3101BBC 1 Wales HDHD    *
PSB3101BBC One HDHD**   
PSB3101BBC One NI HDHD  *  
PSB3102BBC Two HDHD*****
PSB3103ITV HDHD * * 
PSB3103ITV Wales HDHD    *
PSB3103STV HDHD   * 
PSB3103UTV HDHD  *  
PSB3104Channel 4 HDHD*****
PSB3105Channel 5 HDHD*****
PSB3123CBBC HDChildren's*****
ARQ A11PickGeneral Entertainment ****
ARQ A12DaveGeneral Entertainment ****
ARQ A17ReallyGeneral Entertainment ****
ARQ A23Create & CraftGeneral Entertainment ****
ARQ A29E4+1General Entertainment ****
ARQ A32Sony Movie ChGeneral Entertainment ****
ARQ A41Food NetworkGeneral Entertainment ****
ARQ A43Gems TVGeneral Entertainment ****
ARQ A46ChallengeGeneral Entertainment ****
ARQ A48movies4menGeneral Entertainment ****
ARQ A49TJCGeneral Entertainment ****
ARQ A65TBN UKGeneral Entertainment ****
ARQ A68truTVGeneral Entertainment ****
ARQ A69truTV+1General Entertainment ****
ARQ A72YourTVGeneral Entertainment ****
ARQ A126Tiny PopChildren's ****
ARQ A132Sky NewsNews ****
ARQ A173ADULT smileTV3Adult ****
ARQ A176ADULT BlueAdult ****
ARQ A177ADULT Babestn2Adult ****
ARQ A207Kiss Me TVText services ****
ARQ A208Proud DatingText services ****
ARQ A723talkSPORTRadio ****
ARQ A730RNIB ConnectRadio ****
ARQ B184MusicGeneral Entertainment ****
ARQ B19YesterdayGeneral Entertainment ****
ARQ B22Ideal WorldGeneral Entertainment ****
ARQ B25HomeGeneral Entertainment ****
ARQ B31SpikeGeneral Entertainment ****
ARQ B35QVC BeautyGeneral Entertainment ****
ARQ B36QVC StyleGeneral Entertainment ****
ARQ B38QUEST+1General Entertainment ****
ARQ B40Rocks & Co 1General Entertainment ****
ARQ B42Travel ChannelGeneral Entertainment ****
ARQ B474sevenGeneral Entertainment ****
ARQ B59BT ShowcaseGeneral Entertainment ****
ARQ B64CBS ActionGeneral Entertainment ****
ARQ B73YourTV+1General Entertainment ****
ARQ B76Jewellery MakerGeneral Entertainment ****
ARQ B78Sewing QuarterGeneral Entertainment ****
ARQ B79Dave ja vuGeneral Entertainment ****
ARQ B125POPChildren's ****
ARQ B135RTNews ****
ARQ B172ADULT smileTV2Adult ****
ARQ B174ADULT BabestnAdult ****
ARQ B199ADULT SectionAdult ****
ARQ B711The Hits RadioRadio ****
ARQ B712KISS FRESHRadio ****
ARQ B713KissRadio ****
ARQ B714KISSTORYRadio ****
ARQ B715MagicRadio ****
ARQ B716heatRadio ****
ARQ B717Kerrang!Radio ****
ARQ B718Smooth RadioRadio ****
ARQ B725Premier RadioRadio ****
ARQ B731Classic FMRadio ****
ARQ B732LBCRadio ****
SDN10ITV3General Entertainment ****
SDN16QVCGeneral Entertainment ****
SDN20DramaGeneral Entertainment ****
SDN215 USAGeneral Entertainment ****
SDN26ITVBeGeneral Entertainment ****
SDN27ITV2 +1General Entertainment ****
SDN28E4General Entertainment    *
SDN305STARGeneral Entertainment ****
SDN34ITV3+1General Entertainment ****
SDN37QUESTGeneral Entertainment ****
SDN39The StoreGeneral Entertainment ****
SDN44Channel 5+1General Entertainment ****
SDN54My5General Entertainment ****
SDN58ITVBe+1General Entertainment ****
SDN61True EntertainmentGeneral Entertainment *** 
SDN62ITV4+1General Entertainment ****
SDN66CBS RealityGeneral Entertainment ****
SDN70Horror ChannelGeneral Entertainment ****
SDN83BlazeGeneral Entertainment ****
SDN84Blaze+1General Entertainment ****
SDN85HochandaGeneral Entertainment ****
SDN95Children's SectionChildren's ****
SDN96Ketchup TVChildren's ****
SDN122CITVChildren's ****
SDN170ADULT SectionAdult ****
SDN171Television XAdult ****
SDN182ADULT Xpanded TVAdult *** 
SDN185ADULT Studio 66Adult ****
SDN201365 TravelText services ****
SDN226CCTVStreamed channels ****
SDN231Racing UKStreamed channels ****
SDN234CONNECT 4Streamed channels ****
SDN239SonlifeStreamed channels ****
SDN244VisionTVStreamed channels ****
SDN246JSTVStreamed channels ****
SDN247kykNETStreamed channels ****
SDN249Huda TVStreamed channels ****
SDN250Revelation TVStreamed channels ****
SDN255Box NationStreamed channels ****
SDN257Arise NewsStreamed channels ****
SDN258LoveworldStreamed channels ****
SDN724CapitalRadio ****
SDN727Absolute RadioRadio ****
COM7 HD565USA+1General Entertainment ****
COM7 HD57VIVAGeneral Entertainment ****
COM7 HD67CBS Reality +1General Entertainment ****
COM7 HD71CBS DramaGeneral Entertainment ****
COM7 HD77Rishtey EuropeGeneral Entertainment ****
COM7 HD81TalkingPictures TVGeneral Entertainment ****
COM7 HD82Vintage TVGeneral Entertainment ****
COM7 HD87Keep It CountryGeneral Entertainment ****
COM7 HD106BBC Four HDHD ****
COM7 HD107BBC News HDHD ****
COM7 HD108Al Jazeera English HDHD ****
COM7 HD109Channel 4+1 HDHD ****
COM7 HD1104seven HDHD ****
COM7 HD113RT HDHD ****
COM7 HD124CBeebies HDChildren's ****
COM7 HD245Planet KnowledgeStreamed channels ****
COM7 HD733Trans World RadioRadio ****
COM8 HD555STAR+1General Entertainment ****
COM8 HD63CommunityGeneral Entertainment ****
COM8 HD86More4+1General Entertainment ****
COM8 HD88Rishtey CineplexGeneral Entertainment ****
COM8 HD91Front RunnerGeneral Entertainment ****
COM8 HD112QVC Beauty HDHD ****
G-MAN50mov4men+1General Entertainment *   
G-MAN75Chart Show TVGeneral Entertainment *   
G-MAN80ShowBiz TVGeneral Entertainment *   
G-MAN89Clubland TVGeneral Entertainment *   
G-MAN128POP+1Children's *   
G-MAN129Tiny Pop+1Children's *   
Local7Local TVGeneral Entertainment **  
Local8Local TVGeneral Entertainment * **
Local60True CrimeGeneral Entertainment ****
Local74True MoviesGeneral Entertainment ****
Local127KixChildren's ****
NI Mux51TG4General Entertainment  *  
NI Mux52RTÉ OneGeneral Entertainment  *  
NI Mux53RTÉ TwoGeneral Entertainment  *  
NI Mux729RTÉ RnaGRadio  *  
Mux LCN Channel Name Genre CI E NI S W
This data changes quite frequently, for the latest information see the data source at
Digital UK - Channel / Mux Listings ©.

The following multiplexes muxes are currently being broadcast in the UK:

NameAlternate Name(s)OperatorSpecificationsComment
64 QAM, code rate 2/3, 8K FFT
Standard Definition
PSB2D3&4, Mux 2Digital 3 & 4DVB-T:
64 QAM, code rate 2/3, 8K FFT
Standard Definition
256 QAM, code rate 2/3, 32K FFT
High Definition
64 QAM, code rate 3/4, 8K FFT
Standard Definition
COM5Arqiva A, COM B, Mux CArqivaDVB-T:
64-QAM, code rate 3/4, 8K FFT
Standard Definition
COM6Arqiva B, COM C, Mux DArqivaDVB-T:
64-QAM, code rate 3/4, 8K FFT
Standard Definition
COM7Mux E, Arq 600 MHz Multiplex*ArqivaDVB-T2:
256 QAM, code rate 2/3, 32K FFT
High Definition
COM8Mux E, Arq 600 MHz Multiplex*ArqivaDVB-T2:
256 QAM, code rate 2/3, 32K FFT
High Definition
GIMuxGeographically Interleaved Spectrum Multiplexes
(Manchester & Cardiff)
Entertainment Television Ltd (Manchester)
Cube Interactive (Cardiff)
DVB-T: 16QAM, rate 3/4, 8K FFT
Cardiff not currently broadcasting
LTVMuxLocal TV Multiplex*Comux UK LtdDVB-T:
QPSK, code rate 3/4, 8K FFT
Standard Definition
NIMuxNorthern Ireland MultiplexMultiplex Broadcasting Services NI LtdDVB-T2:
QPSK, code rate 2/3, 32K FFT
Standard Definition
(but needs UK High Definition receiver)


  • DVB-T2 (HD) broadcasts cannot be received by DVB-T (SD) receivers
  • * Some data included here for planned sites not yet broadcasting.

UK Transmitter Help

UK transmitters are arranged in groups with main transmitters, here shown in bright white, covering general geographical areas, and relays (sub-transmitters), here shown in off white, filling holes in the coverage of the main transmitters.  Most main transmitters and some relays transmit all six main digital muxes, some of which also transmit further local muxes, but most relays only transmit the three PSB muxes.  Transmitter information is available here for the entire UK, including the CI, the IoM, and NI.  Sources are primarily Ofcom, but also Digital UK, and the BBC, see the links at the bottom of the page.  Note that I am aware of some data conflicts between sources, and while I have endeavoured in good faith to resolve these correctly, it's unlikely that I have succeeded in every case, and while I apologise in advance for any errors that may be here, I accept no responsibility for their consequences.

For receiver locations within the UK, transmitters can be selected:

  • Alphabetically from the entire UK List.  For slow browsers on very slow machines, unavoidably this option may take a long time to appear after being chosen  this is because it takes such a time to load so many transmitters into the page element  so if the browser times the script out offering to cancel it, if you are prepared to let it run on at least two or three times, you will probably find that it will eventually complete and thereafter the page will work normally.
  • Alphabetical list of transmitters broadcasting all of the six main digital muxes.
  • By ITV region.
  • By transmitter group.
  • In distance order out to 100km, approximately 62 miles, default selection will be nearest main transmitter.
  • By searching to find those transmitters nearest to the receiver  up to five nearest each of relays, transmitters broadcasting all digital muxes, and mains  likely to give the strongest signals.  Before using this feature, it's recommended to open the Google Map and exactly position the receiver marker (green).  Thereafter, the marker can be adjusted up to 15m before terrain data will be refetched from the server.

    It's important to understand that the accuracy of such predictive calculations will be limited by the completeness with which many factors (explained further in the General Introduction) are taken into account.  The official Digital UK Postcode Checker has access to the best data, yet is considered 'pessimistic' because of the strictness of its correction for availability over time, and because the interpretation of its results on a per post code basis leads to post codes with mixed reception being marked out of coverage, even for individual addresses within them that may be within coverage.  By contrast, this one is probably too optimistic because, although it works from the actual location of the receiving aerial, it lacks transmitter radiation patterns and any correction for availability over time.  Thus, although the predictions of either checker are a useful pointer, neither should be taken as fact, and wherever possible should be checked against other such information, preferably against actual measurement.  In particular, signal levels given here should be regarded as likely relative rather than absolute.  For comparison, minimum useable signal levels at the aerial are around 47dBµV/m for digital tuners.

    Note that, during the search, the form and the markers on the map are locked, and occasionally and randomly, internet traffic or other problems may prevent completion and unlocking.  In this situation there are several means of escape:

    • A Cancel button is displayed whenever the calculator is locked;
    • The search script has a timeout;
    • Many browsers throw up a dialog box to allow breaking out of a script that has hung;
    • A few older browsers may hog the CPU so much that cancellation has no effect, and then there will be no alternative to reloading the page, to aid which this option cannot be set via a URL parameter, it will be changed to the previous option on reload.
  • Additionally, UK Place Name can be used to search for a transmitter of which the exact name is uncertain.  Any transmitters so found will be inserted at the top of the results denoted by (Tx), and a dialog box will offer to select the first one found as the chosen transmitter.  When a transmitter is chosen from the results, UK National List and the chosen transmitter are set.

Each transmitter broadcasts either 3, or 6 or more, digital muxes, each carrying many digital channels within the same spectrum space as formerly occupied by a single analogue channel.  Five of the six standard muxes  PSB1, PSB2, COM4, COM5, & COM6  are SD (DVB-T), PSB3 and the extra muxes COM7 & COM8 are HD (DVB-T2), while the NIMux, although SD, is also DVB-T2, and none of these latter can be decoded by SD (DVB-T) tuners.

Channels above 60 were released for 4G mobile data use during DSO, leaving 21 to 60 as the current range, but between 2017 and 2020 further channels above 50 @ 700MHz are to be released for mobile use.  As with DSO, these ongoing changes will cause 'retune events' requiring local residents to retune equipment to pick up changes, some may even need new aerials.  From 14/2/2017, just two weeks before the first channel release at Selkirk, further information should be available from the Freeview Advice Line on Freephone 0808 1000288, and from the Digital UK & Ofcom links at the bottom of this page.

It should be noted that there is great uncertainty as to whether and by how much 4G & 5G services will affect reception in those areas where TV continues to be broadcast on immediatly neighbouring channels.  Homes can be provided with filters to be fitted to the aerial downlead, but some have doubted whether filters will really be able adequately to differentiate between the wanted TV signals and the unwanted mobile signals, as well as to what arrangements will be made to distribute these filters and whether and in what circumstances they will be chargeable to homeowners.


  • Magnetic variance is computed by the 2015 World Magnetic Model, with estimated error less than 1° until 2020.  Thereafter it will display in red, indicating the model's increasing unreliability over time, in which case you should attempt to get a more recent estimate for your location and enter it manually:
  • Browser compatibility notes (see also the next note about printing):
    • ALL  -  Maps gobble up resources.  If you create both types of map together without letting one complete before starting the other, or, after creating maps, many times change settings in the calculator or drag and zoom forcing continual redrawing, you may find that the Google map becomes blank, or there are jumbled tiles or holes in the OS map, or markers disappear from it, perhaps first from the print preview, then from the map proper.  Such problems may resolve themselves given enough time, but now there is also an option to remove a broken map or signal profile by Ctrl-Clicking the relevant button, so it can be then be clicked again to redraw from scratch.  However, particularly as Google Maps do not document a destroy function, it is questionable whether all the resources used are reclaimed when a map is removed, and, especially if you want to print the maps, you may have to reload the page with your chosen final settings, most easily done by clicking Submit on them, before creating one map at a time, allowing each to load fully before creating the next.
    • FF  -  The oldest legacy versions cannot be supported, but any version including and after 12 that has been tested has been proved to work.
    • IE  -  Google's policy of only supporting the latest three versions of any browser means that any version of IE prior to 8 cannot run this page.
    • Opera  -  The oldest legacy versions cannot be supported, but v12 seems to work as long as an Opera inbuilt extension is turned off  about:config, Extensions, EcmaScriptJIT needs to be disabled.  Of the newer Webkit versions, only 43 has been specifically tested and shown to work, but Webkit browsers generally are known to work.
  • Each map is designed to print on a single page of A4 or Letter with top and bottom margins of about 15mm and side margins of about 10mm.  This site has better map printing support than many, but generally printing web content is too often neglected, not least by those who create browsers, and maps particularly so.  In the past I've reported problems to Microsoft, Opera, Google, and OpenLayers, yet problems remained long outstanding, though recent testing has shown a marked improvement in some browsers.
    • ALL  -  Print the Google Satellite Base Layer without the labels.  The latter tend to look fine in Print Preview but prevent the map printing properly.  IE8+ & FF3+ may print them properly, but legacy browsers tend to print only the label & map overlay, without the satellite imagery.
    • FF3  -  Printing individual map pages results in blank maps, you have to print the entire document to get the maps to print properly. Fixed in v3.5.1.
    • IE  -  continues its abysmal history printing maps  of the versions still actually supported by Google, IE8/9 won't print either map correctly, IE10/11 will only print the Google map correctly.
    • Chrome  -  Earlier versions may insert spurious blank pages.
    • Safari  -  Earlier versions may not print the Google Map  please upgrade to the latest version.
    • Opera  -  Legacy version map printing was abysmal; Webkit versions have not been specifically tested, but see the notes above about Chrome and Safari.

Apologies for these inconveniences.

Use decimal degrees or Degrees : Minutes : Seconds?

Where is the receiving aerial?
Where is the transmitter?
How to find azimuth?
Transmitter Settings
GridMag Azim:
Dist (mi):
Dist (km):
Transmitter Type:
Signal path profile


Black LineSignal Path.
Red60% Fresnel Zone - Obstructions into this probably WILL significantly affect the signal.
Orange100% Fresnel Zone - Obstructions into this probably will not significantly affect the signal.
BrownClutter - Natural and artificial surface features such as trees and buildings (resolution ~1km2).
GreenTerrain - Topographic features such as hills and valleys (resolution ~90m2).
BlackCurvature of Earth's surface (may not be visible over short distances).

Many thanks to:

Significant updates to this document
Date Description
21/06/2020 Fixed SNAFU by Google that was preventing their components loading.
26/04/2017 Added ability to set transmitter frequency for Fresnel path analysis.
12/03/2017 Updated page help on browsers, minor supporting script changes.
12/02/2017 Updated with the latest Ofcom & Digital UK data.  Updated Google Maps authentication.
03/04/2015 Updated server terrain and loss calculation script to give more even sampling of terrain, and remade again the Shetland tiles not originally covered fully by the original SRTM data.
20/12/2014 Updated World Magnetic Model script with WMM2015 coefficients and test answers.  Added navigation history controls to Ordnance Survey map.
07/12/2014 Updated site OpenLayers script to allow future implementation of navigation history controls.
26/07/2014 Fixed clicking signal profile crashes instead of maps panning to area of signal path.  Added support for legacy transmitter URL parameters where the NGR of the TX has since changed.
04/07/2014 Corrected Ordnance Survey map panning problem for all browsers except IE.
28/05/2014 Updated with and adapted to the latest Ofcom data.  Added channel / mux help.  Fixed bug in Transmitter Group selector, and another in Find Nearest selector.
19/03/2014 Restored proper printout in IE10+, and, by setting IE7 standards, to IE8/9.
27/02/2014 Updated with latest Ofcom data, including offsets, & added tooltips to channel details to give alternate mux names, and mux frequencies taking account of offsets.  Corrected: legacy IE markers, world place names not looking up properly, degree symbol in DMS mode.
06/02/2014 Corrected printing problems, updated Notes concerning Internet Explorer problems.
01/02/2014 HTML5, Google, OpenLayers, & OpenSpace map updates, data and form script updates.
11/02/2013 Final update of Ofcom / DigitalUK DSO data.
15/03/2012 Updated with latest Ofcom / DigitalUK data.
06/11/2011 Updated with latest Ofcom / DigitalUK data.  Bugfix to allow spaces in grid references.
11/09/2011 Remade from OS Panorama Open Data the SRTM terrain tiles covering the Shetlands, fixing missing data and sea noise.
05/09/2011 Updated with latest Ofcom / DigitalUK data.  Improved form option locking when maps are drawn.  Refinements to site OpenLayers script and SRTM void data handling.
17/08/2011 Updated with latest Ofcom data.  Improved date handling for DSO start and end days.  Added Signal Profile key, improved Help, and buttons & printing of OpenLayers map.
19/07/2011 Updated with latest Ofcom data.  Updated URL parameter handling to be more memory efficient.
12/01/2011 Updated with latest Ofcom data.  Added knowledge of transmitters broadcasting all digital muxes.
27/10/2010 Updated data for Camperdown, C5 relays, corrected The Wrekin pre-DSO.  Fixed bug loading DMS values from URL.
11/10/2010 To reduce risk of Google usage capping, altered UK Post Code search to try OpenSpace first, then Google.  Released September's major upgrade betas as live.  Cut down OpenLayers script and enabled compression for faster loading.
21/09/2010 Corrected Ofcom data.  Converted to use SRTM terrain and UMD clutter data.  Fixed bugs: no signals found for remote islands; no signal profile for manually entered transmitter details.  Significant rewrite of asynchronous script loading.
08/08/2010 Fixed bug in redrawing signal profile when transmitter changed.
19/07/2010 Updated data files as per latest Ofcom publications.
June 2010 Fixed bugs:  IE data file reading anomalies.  Reading URL parameters when DMS set.  Find operations  Form & marker update and lock/unlock during & after, and not ending for marginal signals.  Aerial Schematic and Signal Path Profile charts not appearing with some browser / operating system combinations.  Improved scales on signal profile.  Support for Chrome and Safari, inc updated browser Notes and covering Opera 10 hang up.
28/04/2010 Added advanced transmitter choice and find options, and corresponding map functionality.  Greatly improved support for IE8 wrt map drawing and printing.  Updated transmitter data including HD / DVB-T2 transmissions.  Updated site scripts for better form handling and asynchronous data loading.  Added this update record.
01/12/2009 Updated transmitter data.  Added transmission display for each transmitter.  Updated site script handling forms.
13/08/2009 Google Map converted to use Google API, rather than OpenLayers API.  Upgraded Ordnance Survey map to use OpenLayers v2.8.  Fixed problem with colours in <Select> elements in the forms in Opera and IE8.  Improved marker dragging and update of calculator.
07/05/2009 First major useable version in its current form, including a signal path profile.