Avon & Bristol Coverage Area Maps

BBC RADIO BRISTOL

BBC map showing the coverage area of the BBC Radio Bristol transmitters

The map above shows the coverage area of BBC Radio Bristol from the FM transmitter at Mendip and lower power relays at Ilchester Crescent and Bath. The map also shows the daytime medium wave coverage from the transmitters at Mangotsfield (1548 kHz) and Taunton (now operating on 1566 khz). Until late 2007 the station is operating a part time opt-out radio service for the county of Somerset, called BBC Somerset Sound, from the Taunton AM transmitter on 1566kHz medium wave.

It is anticipated that BBC Somerset Sound will split from BBC Radio Bristol on a full time basis and will gain a stand alone FM transmitter. In the summer of 2007 the BBC moved the Ilchester Crescent Bristol fill-in relay (94.9 MHz) to a new site on a tall tower high on Dundry Hill, at East Dundry Lane, overlooking the city. The Dundry Lane transmitter will provide a much enhanced coverage area compared to Ilchester Crescent.

This re-engineering of the 94.9 service appears to be the first stage in a plan for the BBC to re-allocate the 95.5MHz transmitter at Mendip to the new BBC Somerset Sound radio station. BBC Radio Bristol would continue on the enhanced 94.9 frequency for Bristol, South Gloucestershire and parts of North Somerset and also on 104.6 MHz from the Bath relay. A frequency of 103.6 MHz is also registered for BBC local radio at the Hutton transmission site, although unused at present, this could be utilised in the future to bring good reception to Weston Super Mare.

Once allocated full time use of 95.5 fromMendip, BBC Somerset Sound would have almost county wide coverage on vhf / fm. However there is a notable area of poor reception around Yeovil and this may be resolved by the installation of a low power fill-in relay transmitter. A frequency of 104.1 MHz is registerd with the ITU for this perpose. It is possible that Taunton may also be considered for a low power fill-in relay (possibly using 104.7, which has also been registered with the ITU), in which case the transmitter scheme would be similar to that of the Somerset ILR station (Orchard FM) except that the coverage area of Mendip for theBBC local radio service is of higher power and almost omnidirectional compared to the lower power and highly directional signal from Mendip used for the ILR station.

It is unknown at present, but the BBC could commission such relays at Cheddington for Yeovil, as used for ILR Somerset, or maybe a site closer to the town (e.g. Coker Hill). In Taunton the BBC investigated Staple Hill, as did the IBA for the ILR station, but it is more likely that a site closer to, or indeed in the town would be considered - as was the eventual case for the ILR station - if a relay transmitter is considered. Additionally there is a chance that the BBC could consider a relay for Minehead to in order to provide a truly county wide vhf / fm service, but all of this is speculation at this stage (summer 2007).

The map below shows the predicted coverage area (green) for good reception from the 94.9 Mhz transmission from the new site at East Dundry Lane. The transmitter uses an aerial located at the top of the tower using 500 watts with vertical polarisation and, unlike all the ILR services for this area, has an omnidirectional radiation pattern.

It is interesting to campare this plot with the one for ILR Bristol FM3 (Original 106.5 FM etc) which uses the same equivalent power, but with slant polarisation and a very directional yagi transmission antenna (see further down this page).

BBC Radio Bristol from East Dundry Lane. 500 watts omnidirectional, vertical polarisation.

The pixel plot above was made with the RadioMobile program and shows a 9kW omnidirectional service of BBC Radio Bristol from Mendip on 95.5 MHz. it is very close to the official BBC coverage map.

ILR BRISTOL FM1 - (Radio West - GWR FM etc)

IBA map for ILR Bristol with Wiltshire showing the combined coverage area of the Dundry, Naish Hill and Blundsdon v.h.f. transmitters.

The Dundry v.h.f. / fm transmitter has since been increased from 0.5 kW to 2kW and the coverage will be slightly wider, as the pixel plots from RadioMobile predict below:

N.B. In September 2007 GCap/GWR opened a new relay transmitter on 103.0 MHz to cover the town of Weston Super Mare which receives poor signals from the Dundry transmitter site.

Pixel plot showing Dundry Hill 0.5 kW - Green area of good reception

Dundry Hill 2000 watts

Pixel plot showing Dundry Hill 2.0 kW - Green area of good reception

Weston Super Mare relay at Worlebury Hill

In September 2007 GWR opened a new relay transmitter at Worlebury Hill to
bring coverage to Weston Super Mare, an area of the TSA that has always
suffered littleor no coverage from the main transmitter at Dundry Hill.
Power is 50 watts vertical plus 50 watts horizontal. Radiation pattern is
135 degrees from an aerial mounted 38 meters high on the Worelbury Hill tower.

I wanted to produce pixel plots for the regional Severn Estuary Independent Radio service (Vibe FM etc) and for the Somerset ILR service (Orchard FM etc). To kick off with I decided to produce a pixel plot for the omnidirectional 9kW BBC Radio Bristol service to see how a RadioMobile pixel plot would compare with the official BBC coverage map. The Radio Bristol Mendip plot can be seen towards the top of this page. As you will see it is pretty close. I therefore consider that the plots produced for the two Independent Radio stations should provide a reasonably good representation, especially as the plots use the detailed transmission parameters and data supplied by OFCOM. See plots below:

ILR SOMERSET / YEOVIL AND TAUNTON (Orchard FM etc)

The pixel plot above shows the very directional service (4kW max e.r.p.) on 102.6 MHz from Mendip for ILR Somerset (Orchard FM etc). The two low power fill-in relay transmitters at Taunton and Cheddington are also included in this map.

The very low power relay for Taunton is located at the Orchard FM studios on a small mast within their grounds. It is only 0.07 kW and re-inforces the signal in some parts of Taunton on 96.5 MHz. The other relay is at Cheddington and provides better reception in the South of the transmission area to the South and West of Yeovil It uses 97.1 MHz with a power of 0.4 kW.

ILR Somerset launched in 1989 with Orchard FM providing the radio service. Since their transmitter was also located at the Mendip mast, along with BBC Radio Bristol, some listeners may have been forgiven for thinking that the ILR station may have enjoyed similar coverage to Radio Bristol. However the effective radiated power is only 4kW maximum. (compared to 9kW for the BBC) and is highly directional towards to South West with a 17dB reduction towards Bristol in the North to avoid a programming overlap with the existing ILR station there. This arrangement also avoids possible interference to the ILR station in Oxford (Fox FM etc) which also uses 102.6 MHz.

Due to variable reception around Taunton and Yeovil, additional low power relay transmitters have been installed to reinforce coverage. The Taunton relay is located at the Orchard FM radio studio and uses 96.5 MHz at 0.07 kW, while the Yeovil area relay is at Cheddington on 97.1 MHz with 0.4kW.

See photographs of the Mendip mast at MB21.co.uk HERE
See photographs of the Taunton relay at MB21.co.uk HERE

SEVERN ESTUARY INDEPENDENT REGIONAL RADIO (Galaxy 101, VIBE FM, KISS FM etc)

Mendip 40kw directional coverage for Kiss 101

Pixel plot showing the highly directional service (40kW max e.r.p.) from Mendip on 101.0 MHz for the Severn Estuary Independent Radio service (Kiss FM etc). It can be seen that Bristol is poorly served and this is the reason for the low power relay on 97.2 from Pur Down for Bristol city centre.

The highly directional aerial radiation pattern for the Severn Estuary
regional radio service from Mendip

On paper the 40kW e.r.p. (effective radiated power) used by the regional Independent Radio station for the Severn Estuary looks extremely impressive. However the transmitting aerials have an extremely directional pattern that only allow the maximum 40kW to be directed in a beam towards Wales between a bearing of 300 and 320 degrees. All other ares receive a much lower signal. There are other smaller peaks at bearings of 20 to 40 degrees, 120 to 140 degrees and 220 to 230 degrees. In all other directions the effective radiated power is only about 0.4kW, a 20dB reduction over the main beam.

The 40kW beam to the North West is obviously designed to penetrate the Welsh valleys, and the drastic reduction in signal towards the London area in the East is to prevent interference to the INR1 transmitter at Wrotham on 100.9 MHz (Classic FM).

The poor signal in Bristol is overcome by a 0.2kW power relay station sited on the concrete BT link structure on Pur Down using 97.2 MHz. The predicted coverage from this low power relay is shown below:

Some areas of Bristol may receive a better signal from the Severn Estuary Independent Radio Station (Vibe FM etc) from this low power relay transmitter at the concrete BT tower on Pur Down. Power is 0.2kW mixed polarisation, frequency is 97.2 MHz.

ILR BRISTOL FM2 - (107.3 Star FM etc)

The transmitter used by the second Bristol ILR station (107.2 Star FM etc) is located on the concrete BT tower at Pur Down - together with relays for INR1 (Classic FM) and the Severn Estuary Regional station (Vibe FM etc).

For this service the transmitter uses 0.66 kW directional and the pixel plot above indicates where good reception may be possible in and around the city.

ILR BRISTOL FM3 (Original 106.5)

Coverage area of predicted good reception (green) for ILR Bristol FM3
Original 106.5 MHz FM.
This station uses the same site as BBC Radio Bristol at
East Dundry Lane but rather than an omni-directional aerial, the ILR transmitter
uses highly directional slant polarised yagi aerials to restrict coverage to the south.
Power is effectively 500w vertical plus 500w hortizontal.

ILR BATH (Bath FM etc)

The ILR station for Bath uses one of the broadcast towers located on Bathampton Down. There are two towers here, the main one is used to relay television signals and BBC national radio stations along with a relay for INR1 (Classic FM) and the FM1 ILR station (GWR). ILR Bath - Bath FM - also uses this tower. The aerial is mounted at a height if 41m a.g.l. and transmits a directional signal across Bath with a power of 0.1 kW mixed polarity.

Roddy Jenkins adds:

Thanks for your excellent Mendip coverage maps. I thought I might just add the following information. The Bristol ILR service of GWR FM can be picked up just South of the Mendip mast (ie the Safeway car park in Glastonbury!) on 96.3 MHz. Orchard FM's base above the M5 motorway outside Taunton, in what was once a large family residence, obviously has some sort of feed to the Mendip mast. I seem to recall a large satellite dish in the back garden facing South West, but seem to recall that this was for IRN (?)

The BBC Somerset Sound frequency was recently changed from the original frequency of 1323AM to 1566AM, to avoid interference from Voice of Russia. The link below gives the story:

http://news.bbc.co.uk/1/hi/england/2349767.stm

On the television front, Mendip's television coverage extends right down into mid Dorset with the Cerne Abbas relay, thus Dorset is served by three different regions West (Mendip and relays); South West (Stockland Hill and relays); and South (Rowridge and relays).

Also, when we lived in the foothills of the Mendips in the early to mid 1970s, we couldn't recieve signals from the Mendip mast; instead we had to pick up BBC and HTV Wales from Wenvoe outside Cardiff. Even today here in the south Somerset village of Keinton Mandeville, we can in effect pick up three regions - West, Wales, and South West. I suppose that if I was to erect a large mast on the roof and point an aerial towards the south coast I'd probably pick up BBC South and Meridian transmissions as well.