Pennywell was the name of the BBC's low-power MW 'relay' transmitter for Edinburgh which operated from 1949 to 1978.
Edinburgh BBC MW Station - 1948 to 1978
When the Third Programme was launched on 29 September 1946 it was broadcast from just one national transmitter, at Droitwich in Worcestershire, England, on the longest medium wavelength at the BBC's disposal (514.6m/583kHz). Originally intended to radiate at a power of 120kW, days before launch Radio Latvia in Riga began operating on the same frequency with high power. The BBC respected their legality by reducing Droitwich's power to 25kW. However, this reduced the transmission area to a radius of just 100 miles, severely limiting reception.
To improve coverage the Government's White Paper on broadcasting suggested that additional low power filler stations be established in towns with populations over 120,000. Scotland was therefore given four such transmitters, in Glasgow (Bellahouston Park), Edinburgh, Dundee (Greenside Scalp), and Aberdeen (Redmoss). In the whole of Britain, there were around 20 such transmitters, all of which were synchronised on a wavelength of 203.5 metres (1474kHz).
The Edinburgh station entered service in 1948, changing its frequency to 647 kHz on 15 March 1950.
The aerial, which was supported by two 126-foot tubular masts, had a capacity top and a 100-foot vertical element.
With the arrival of Radio 1 in 1967 the old 1214 kHz "Light Programme Auxiliary Service" was pressed into service for the new Pop station, including the 50 kW transmitter at Westerglen. With the loss of this strong local Light Programme signal on 1214 kHz it was quickly discovered that the Radio 2 Long Wave signal in Scotland on its own left a lot to be desired, particularly in areas with high levels of electrical interference.
In late 1967 therefore the BBC made efforts to improve the situation, opening new medium wave transmitters for Radio 2 at the existing stations at Edinburgh and Glasgow just in time for Christmas, both running 0.5 kW, although this power was raised to 2 kW in July 1968.
For Aberdeen (Redmoss) and Dundee the response was less quick, and new MW relays (also on 1484 kHz) didn't open until October 1968.
So from 1969 to 1978 the Edinburgh station was used for both Radio 3 on 647 kHz with 2 KW, and Radio 2 on 1484 kHz with 2 KW.
In October 1978 the transmitters were still in service for both Radio 2 (1484 kHz) and Radio 3 (647 kHz), however in November 1978 they had been taken off air and replaced by high-power services from the Westerglen station near Falkirk, with Radio 2 on 909 kHz and Radio 3 on 1215 KHz.
There is some confusion re the precise location of the station over the years. The BBC Handbook 1950 has it listed at "Pennywell", which is in the Granton area of the city, at or near NGR NT218765 (i.e. the south-west corner of "Granton Park Recreational Ground" to be precise), however the BBC transmitter booklet from 1978 has it listed half-a-mile SE of this location at NGR NT227761.
The fact that Pennywell operated entirely unattended was seen as a novelty at the time of its opening in 1948. There were two transmitters there, one for service and one as stand-by, both of them remotely controlled from the BBC's studio centre at Queen Street, Edinburgh, about four miles away. At Queen Street the following control operations were capable of being carried out:
- Either transmitter could be switched on or off;
- The quality of the radiated programme could be checked and an indication of the radiated power obtained.
- The modulation depth could be measured; and
- Specific transmitter faults could be detected by a series of alarms.
- All information taken from mb21: The Transmission Gallery
- Speech by Sir Edward Appleton, 'Radio-Communication', 3 May 1949, BBC WAC R44/118.