Local Transmitters
Knowing where the TV signal comes from is useful since this determines what kind of Freeview service will be available after switchover. This page shows who will have the full Freeview (6 MUX) and who will get just a ½ Freeview (3 MUX) service, and why.
The Beacon Hill mast has had a significant amount of changes to its transmitting antennas, which has adversely affected digital reception for some viewers. The timing of the antenna changes is worth looking at if your digital reception doesn't seem as good as it used to be.
Beacon Hill Diary
The main terrestrial TV transmitter for Torbay and the South Hams is at Beacon Hill, on the road from Marldon to Totnes. According to Digital UK, the Beacon Hill transmitter provides 62% of the local population with their TV signals.
The other main transmitters that provide TV transmission for the South West are Stockland Hill (just outside Honiton, serving Exeter, east Devon and parts of Somerset and Dorset), Caradon Hill (4 miles north of Liskeard on the edge of Bodmin moor, serving Plymouth, west Devon and north Cornwall) and Redruth (serving south Cornwall). Huntshaw Cross is the main transmitter for North Devon.
Major changes have been made to the Beacon Hill TV transmitter mast since the summer of 2007 - the following photographs help to identify what's been happening:
August to December 2007
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The photo on the left (taken at the beginning of Aug 2007) shows the original UHF cylinder (long, white object) right at the top of the mast, which had been operating since 1973.
Just below the UHF cylinder is a white panel antenna array - the temporary UHF analogue antenna, allowing the UHF cylinder above to be removed without losing the analogue TV service locally.
Further down the mast, at about two-thirds height is the digital panel antenna array.
In August, the analogue signals were switched from the top antenna down to the temporary analogue antenna to enable the UHF cylinder to be removed. During this work, significant power reductions were noticed for the analogue service.
The middle photo shows the mast after the UHF cylinder had been removed (Oct 2007). The object at the top of the mast is a special crane with a very short jib to lift the cylinder off the mast top. This remained in place to allow the new panel antenna to be installed at the top of the mast in the same position as the old cylinder.
The photo on the right shows the mast at the end of Nov 2007, which looks similar to the first photograph. The black "blob" (just above the temporary analogue antenna) is the access "lift" with three riggers in it, about to work on the mast.
Just before Christmas 2007, the analogue TV service was connected to the new panel antenna at the top of the mast. This change coincided with a number of viewers observing their digital TV quality had degraded.
January 2008
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Into 2008, and work continued on the mast. Having switched the analogue TV signals to the top antenna, the temporary analogue antenna could be removed. The photograph above left (end Jan 2008) shows the mast after the temporary analogue antenna had been dismantled.
The middle photo shows the access lift for the riggers doing the antenna work as it climbed up one of the cable stays.
On the right is a close-up of the new panel antenna at the top of the mast. This will be used for analogue TV transmission until switchover, when it will become the main antenna for the digital TV signals.
February to March 2008
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At the end of February, the new reserve antenna was fitted where the temporary analogue antenna had been. These photos (19th March 2008) show the riggers still working on the mast, with the access lift just above the new reserve antenna.
The reserve antenna is designed to facilitate maintenance work on the top antenna. The transmitted TV signals can be transferred from the top antenna to the reserve antenna. Access is then possible through the centre of the reserve antenna whilst it is transmitting at full power, with no radiation hazard for the riggers.
April 2008
After just a few weeks, in early April 2008 the newly installed reserve antenna was removed! The following photographs show one half being lowered:
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Towards the end of April 2008 the reserve antenna was replaced. The rumour was that the original antenna had a "manufacturing problem", requiring it to be removed from the mast to be fixed. The photo below shows both halves of the reserve antenna back on the mast, with a small zig-zag gap remaining, prior to fixing in their final position:
May 2008
On the 22nd May 2008, the analogue signals were switched from the top antenna onto the reserve antenna. This degraded analogue reception in some areas due to the lower height of the reserve antenna. The analogue signals will remain on the reserve antenna for a month or two, until the changes to top antenna have been completed.
On the 29th May, the panels were dismounted from the new antenna at the top of the mast (the one installed in November 2007), leaving the lattice-work of its supporting structure visible:
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The photo above left shows two riggers removing the last couple of panels from the very top of the mast, giving an idea of the size of the structure they're working on.
The middle photo above shows the skeleton of the top antenna - inside the lattice-work structure are the cables for the feeds to the individual panels.
The photo above right is a close-up of the cage with the riggers bringing down the last couple of panels - the large size of the panels is apparent.
Work on these panels and feeds (and re-mounting back on the mast) is scheduled to take up most of June 2008. During this time, analogue signals will be transmitted from the reserve antenna, but will revert back to the top antenna once it has been re-assembled.
June 2008
The first week in June saw the panels for the top antenna being replaced (having been removed the previous week), starting from the top and working downwards:
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The photos above (June 6th 2008) show the top antenna with the first three rows of panels in place (the complete antenna has eight rows). The feeder cables can be seen inside the lattice support structure in the photo above right.
The following week all of the panels for the top antenna were back in place on the supporting structure. The photos below show the rebuilt antenna (photographed on 11th June 2008) with the analogue signals still being transmitted from the new reserve antenna just below:
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On 19th June 2008, the analogue signals were switched back up to the top antennna (from the reserve antenna). This should complete the changes on the Beacon Hill mast prior to the switchover proper in 2009. Further substantial changes will still be happening at Beacon Hill, updating the equipment inside the transmitter buildings that feed the signals to the mast.
Line of sight is important for signal propagation, and the height of the antenna on the mast is critical to the coverage that can be achieved. A higher antenna is more beneficial for coverage (especially in a hilly area) than a higher operating power, but the overall height has to be restricted for aircraft.
Since the digital antenna is significantly lower down the mast, the digital TV coverage has been less than analogue. Moving the digital signals up to the top antenna at switchover is intended to provide the same coverage that analogue TV had. It remains to be seen whether the lower digital antenna array will be removed, or will remain in place, possibly for some future expansion of the Freeview TV service.
The replacement antennas on the Beacon Hill mast are all made up from panels - each panel being a discrete UHF antenna on its own. The combination of panels in the array allows the overall transmission pattern to be "steered" both horizontally and vertically, by controlling the signal phase to each panel. In principle, this could allow a higher percentage of the emitted power to be used for Torbay for example, with transmission over to Totnes being reduced accordingly. Transmission across the sea towards France could also cause interference problems there, so it is likely that the transmission in some directions will be restricted.
Local Relays
An estimated 38% of the local population are unable to receive signals from Beacon Hill, caused by e.g. living in a valley with a hill blocking the view towards the Beacon Hill mast. Local terrain can make TV reception impossible: reception works best with a direct line of sight between the receiving aerial and the transmitter. A hill directly in the way between the aerial and the transmitter will reduce the signal strength - small hills midway between the transmitter and receiving aerial aren't so bad (since diffraction around the hill can still give an adequate signal), but a hill that's close to the receiving aerial can lose most of the signal.
In many such locations, where there is sufficient need, local relay transmitters are installed to "fill in" these areas with poor reception. A relay transmitter is typically located at sufficient height to be able to receive TV signals direct from Beacon Hill, and then re-transmit them (on different frequencies and at low power) down into a valley. The power is kept low to minimise interference with other relays, and typically has a very limited coverage, intended for that specific community alone.
The map below shows the location of the Beacon Hill transmitter, and associated low power local relays:
Other relays which might seem to be "missing" (e.g. Slapton and Dawlish) come under different main transmitters (Caradon Hill and Stockland Hill respectively). The Sidmouth relay, although geographically much closer to Stockland Hill, has a clear view over to Beacon Hill (the line of sight to the Stockland Hill transmitter is blocked by hills) - hence receives its signal via the Beacon Hill transmitter. The situation is exactly the opposite for Dawlish.
The following list shows important channel details for the local relay transmitters.
Note especially that only 3 MUXs will be provided after switchover, rather than the full set of 6 MUXs available from the Beacon Hill main transmitter.
| PSB 1 | PSB 2 | PSB 3 | Digital Aerial Group | Analogue Aerial Group | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| BBC A | D3&4 | BBC B | Analogue Channels | |||||||||
| Site Name | Grid Ref. | Channel | Channel | Channel | Power | Pol. | BBC1 | BBC2 | ITV | CH4 | ||
| Ashburton | SX758687 | 24 | 27 | 21 | 2W | A | V | A | 21 | 27 | 24 | 31 |
| Bovey Tracey | SX818787 | 52 | 48 | 56 | 3.6W | C/D | V | B | 39 | 45 | 49 | 42 |
| Brixham | SX921562 | 43 | 50 | 46 | 2W | B | V | B | 40 | 46 | 43 | 50 |
| Buckfastleigh | SX742664 | 41 | 47 | 44 | 2W | B | V | B | 51 | 44 | 41 | 47 |
| Chudleigh | SX876789 | 41 | 47 | 44 | 2W | B | V | B | 51 | 44 | 41 | 47 |
| Clennon Valley | SX885596 | 52 | 48 | 56 | 2W | C/D | V | B | 39 | 45 | 49 | 42 |
| Coombe | SX928736 | 24 | 27 | 21 | 2W | A | V | A | 21 | 27 | 24 | 31 |
| Dartmouth | SX875511 | 41 | 47 | 44 | 2W | B | V | B | 51 | 44 | 41 | 47 |
| Edginswell | SX886658 | 52 | 48 | 56 | 2W | C/D | V | E | 39 | 49 | 45 | 67 |
| Halwell | SX781528 | 47 | 41 | 44 | 2W | B | V | B | 51 | 44 | 41 | 47 |
| Harbertonford | SX780559 | 52 | 48 | 56 | 2W | C/D | H | B | 39 | 45 | 49 | 42 |
| Hele | SX912657 | 43 | 50 | 46 | 2W | B | H | B | 40 | 46 | 43 | 50 |
| Kingskerswell | SX873681 | 62 | 59 | 55 | 2W | C/D | V | C/D | 55 | 68 | 48 | 65 |
| Liverton | SX811734 | 62 | 59 | 55 | 2.5W | C/D | V | C/D | 55 | 68 | 48 | 65 |
| NewtonAbbot HP | SX851713 | 43 | 50 | 46 | 0.66W | B | H | B | 40 | 46 | 43 | 50 |
| NewtonAbbot VP | SX851713 | 43 | 50 | 46 | 2W | B | V | B | 40 | 46 | 43 | 50 |
| Occombe Valley | SX886625 | 24 | 27 | 21 | 20W | A | V | A | 21 | 27 | 24 | 31 |
| Sidmouth | SY136879 | 52 | 48 | 56 | 6W | C/D | V | E | 39 | 49 | 45 | 67 |
| South Brent HP | SX690607 | 43 | 50 | 46 | 0.3W | B | H | B | 40 | 46 | 43 | 50 |
| South Brent VP | SX690607 | 43 | 50 | 46 | 2W | BA | V | B | 40 | 46 | 43 | 50 |
| Teignmouth | SX936735 | 52 | 48 | 56 | 40W | C/D | V | E | 39 | 49 | 45 | 67 |
| Torquay Town | SX915637 | 41 | 47 | 44 | 40W | B | V | B | 51 | 44 | 41 | 47 |
| Totnes | SX805594 | 24 | 27 | 21 | 2W | A | V | A | 21 | 27 | 24 | 31 |
The first column shows the relay name - click on it to see the location in Google Maps (opens a new browser window - N.B. browser must have Javascript enabled to see the aerial photographs) and identify exactly where the relay is located.
The second column gives the national grid reference, which is useful for locating the relay on an O.S. map.
The next three columns give the channel numbers that will be used for the 3 PSB MUXs after switchover.
The fourth column shows the power for the digital transmission, which will typically be similar or slightly lower than the existing analogue transmissions.
The existing analogue channels are shown in grey on the right hand side of the table.
Many of the relays will utilise the same channel numbers as for analogue - these have the digital aerial group column shaded green. An existing aerial (working properly) will not require changing for the switchover.
A few of the relays will have channel number changes, but will remain within the channels specified for the existing aerial group. These are shown with yellow shading. Again, an existing aerial (working properly) will not require changing for the digital switchover.
Three relays have channel changes that are outside of the range for the existing aerial - these are shown with red shading. The existing aerials will only work if they are wideband aerials - otherwise they will require changing.
The column to the right of the Digital Aerial Group in the table above (headed Pol.) indicates the polarisation of the transmitted TV signal. Local TV relays mostly use vertical polarisation, as opposed to main transmitters which all use horizontal polarisation. The list of the Beacon Hill relays above shows four exceptions (Harbertonford, Hele, Newton Abbot and South Brent) where horizontal polarisation is used. The polarisation from the transmitter or relay determines which way up the TV aerial is mounted. Vertical polarisation requires the aerial directors (strips of metal on the main boom) to be positioned vertically, to match the transmitter. Horizontal polarisation has the aerial mounted with the directors correspondingly horizontal. This is an easy check to confirm whether your aerial is pointed at a local relay - if the directors are vertical, then it definitely is. Some local knowledge or a check on an Ordnance survey map can then reveal which relay is actually being used.
Photographs of many of the relay masts can be seen at tx.mb21.co.uk/gallery
Transmitter & Relay Coverage
Beacon Hill TV transmissions have a useful coverage of about 25 miles radius, but only for those locations with a direct line of sight to the transmitter, or with relatively small terrain obstacles in the way. Larger distances can be achieved theoretically, but would require a large aerial, mounted as high as possible.
Where houses are located in valleys that are shadowed from the main transmitter, they can be served by a relay transmitter (if one has been provided). All of the Beacon Hill relays are within a 25 mile radius of the main transmitter, and are typically positioned high up on a hill which enables the relay to receive signals direct from Beacon Hill, and re-transmit them (on a different frequency, and often with a different polarisation), down into the valley.
An estimate for the range for a very low power (e.g. 2W) relay transmitter would be approximately 600m (i.e. not very far!) assuming the transmission had a uniform circular coverage. Such a short range isn't practical for a relay, and doesn't match with the requirement to have the relay mast on a hill above a village. This problem is overcome by using directional aerials on the relay (similar to domestic TV aerials) that give the beam more energy in one specific direction. This can give a three-fold increase in range, extending a 2W relay to nearly 2km (a much more useful distance).
The following photograph shows the directional aerials on the Brixham relay:
Many of the relays use "crossed" aerials, giving a wider arc of coverage than produced by just a single aerial. Grouping the aerials in a stack of four reduces the vertical spread and extends the coverage further in the direction the aerials are pointing. The aerials at the top of this relay are the transmitting aerials and are all vertically polarised.
Further down the mast, a similar aerial on its own is horizontally polarised, and points directly at the Beacon Hill transmitter. This is the receiving aerial for this relay, feeding the TV signals down to the transponder at the base of the mast that provides the necessary gain and frequency conversion.