Poldhu is a small area in south Cornwall, UK, situated on the Lizard Peninsula it comprises Poldhu Point and Poldhu Cove. It lies on the coast west of Goonhilly Downs , with Mullion 2 km to the south and Porthleven 7 km to the north. Poldhu means "black pool".

Poldhu Wireless Station

The site is famous as the location of Poldhu Wireless Station, Guglielmo Marconi's transmitter for the first trans-Atlantic radio message on December 12, 1901.

The station's fifty acre (200,000 m²) plot was bought in 1900 and contruction work ran from October 1900 to January 1901, to a design by John Ambrose Fleming. The initial twenty mast circular aerial set-up was destroyed in a storm on September 17, 1901. The station first received a signal on January 23, 1901 from the Isle of Wight. For Marconi's experiments a temporary installation of two 200 foot (61 m) masts was used. The station transmitted at roughly 13 kW and a wavelength usually given as 1.7 MHz. The original mast layout was not rebuilt, it was replaced with a four mast design, 215 feet (66 m) high and forming a 200 foot (61 m) square.

The site was also used for shortwave experiments in 1923 and 1924, with transmissions from Charles Samuel Franklin to the yacht Electra in the Atlantic.

The station continued to operate until 1933. The site was cleared in 1935 and six acres (24,000 m²) were gifted to the National Trust in 1937 with the rest of the site added in 1960. The site has a stone monument pillar and a number of concrete foundations and earth structures also remain. In 2001 the Marconi Centre, a new museum/meeting building, was opened close to the site by the efforts of the Poldhu Amateur Radio Club , the National Trust and Marconi plc.

The more substantial building near the site, originally the Poldhu Hotel, built from 1899 to house the Marconi workers is currently a care home.

Marconi also built a second wireless station nearby at Housel Bay - the Lizard Wireless Station.

The western Atlantic station is situated on Cape Cod Massachusetts, in the United States.