Site of Marconi transmitting station, near Caernarfon

Link to Welsh translationbutton_lang_frenchSite of Marconi transmitting station, near Caernarfon

In 1913 the wireless pioneer Guglielmo Marconi opened Britain's first long-wave wireless transmitting station on this hillside. He visited the site many times during the station’s construction, staying at Caernarfon’s Royal Hotel. He had come to prominence in 1897 by sending the world’s first wireless transmission across water, near Cardiff.

The station provided a unique and vital facility in the First World War and later, enabling official communication with the USA and Australia and with ships on the North Atlantic. You can still see some of the foundations of buildings and masts today. The station closed in 1938.

waunfawr_marconi_wireless_station_mastAt the beginning of the 20th century, the Marconi Wireless Telegraph Company wanted to continue the profitable transatlantic service it had opened in 1907 at Clifden, Ireland, which had become inefficient due to land-line failures.

Land at 260m (850ft) above sea level on Cefn Du hill was purchased between 1912 and 1914 for £2,055 in total. A barracks, transmitter building and ten steel masts were built. The photo of the base of a mast (shown here courtesy of The Marconi Company Ltd) gives an idea of the structures’ scale.

Over 7,000 tons of materials were moved by train to Llanrug, then by traction engines and finally by a narrow-gauge railway which ran up the mountain (see our Welsh page for a photo of the railway). The facility became fully operational in July 1914 at a cost of £50,000.

The first wireless telegraph message to Australia was sent to Wahroonga, NSW, on September 22 1918. By March 1920 a commercial service from Caernarfon to New Jersey, USA, was operating successfully.

The station received improved technology, using valves, in the 1920s. However, technical advances elsewhere in the 1930s were the beginning of the end. Initially the station’s functions were downgraded. Then severe storm damage led to authority to close, and all the aerials and their structures were removed by the eve of the Second World War.

For detailed further information, see the Footnotes below and the book Marconi and his wireless stations in Wales, by Hari Williams, published by Gwasg Carreg Gwalch in 1999.

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waunfawr_marconi_wireless_station_valvesFootnotes: Details of the station

The original transmitter was a synchronous disk discharger powered by a 30kV three-phase supply generated by the North Wales Power Company’s Cwm Dyli hydro-electric station. The original aerial was supported by ten 120m (400ft) masts placed in 4 rows, 275m (900ft) apart. The first row was 137m (450ft) wide, the last 183m (600ft) wide.

In June 1916 the transmitters were replaced by timed disk dischargers. Poulson Arc transmitters were installed as a back-up in 1918 and put 100amps into the aerial.

Station efficiency was improved by the use of an “earth screen”, which replaced the original buried earth. 200kW Alexanderson alternators came into service by 1921.

It became evident that valves (shown in the photo courtesy of GEC-Marconi) would soon replace other transmitting systems and a 56-valve panel was installed. The valves were cooled by a current of air, while putting 340amps into the aerial. Marconi were reticent about valves for the commercial service, only using the 56 valves from September 1922.  A water-cooled valve transmitter, installed in May 1922, put 560amps into the aerial and entered commercial service in December 1923. In spring 1924 an additional 15 water-cooled valves were added. They were used for commercial working by October 1924.

See our Welsh page for another valve transmitter photo.