EAW052580 ENGLAND (1953). Halstow, Cooling and Cliffe Marshes, St Mary Hoo, from the east, 1953

Curtis's and Harvey Ltd, explosives manufacturer. This site was originally set up in 1892 for the storage and blending of gunpowder by Hay, Merricks & Co Ltd, who shipped the gunpowder from their mill near Edinburgh. In 1898, they were merged into Curtis's and Harvey Ltd, who set about the manufacture of new, smokeless, chemical explosives. In the years up to the First World War, they were involved in the manufacture of 38 different explosives, fuses and primers on the site. By 1908, HM Inspector of Explosives was of the opinion that the works was one of the largest in the British Isles. During WW1, production of cordite increased dramatically. At the end of the War, demand collapsed and production ceased by 1921. Source: English Heritage Report 11-2011: 'Curtis's and Harvey Ltd Explosives Factory, Cliffe and Cliffe Woods, Medway. Archeological Survey and Analysis of the Factory Remains.' Rebecca Pullen, Sarah Newsome, Andrew Williams and Wayne Cocroft 2013. ISSN 1749-8775

HM Cordite Factory, built in 1916 to meet the demand for naval munitions. Production ceased after WW1. In November 1921, this site was sold to the War Office. The land is now owned by the Port of London Authority.

Faint vertical lines show the MUSA Antenna stretching across the marsh. Cooling Radio Station was at the UK end of a point-to-point, shortwave signal beamed from Lawrenceville, New Jersey. The site of the station was carefully selected as the antenna, MUSA (Multiple Unit Steerable Antenna), upon which it depended to receive the incoming transmission, had to be: directly aligned with Lawrenceville; two miles long; comprised of an array of 16 individual rhombic antenna; have an area of three miles in front of the MUSA that would be free from radio interference. The 16 rhombic antenna were strung between 60ft high telegraph poles; each side was 315ft long with internal angles of 140 degrees. The signal from each antenna was sent to the station via a core coaxial cable sheathed in a watertight copper tube and buried in a central trench. See : English Heritage Research Department Report Series No 110-2010, ISSN 1749-8775, COOLING RADIO STATION, HOO PENINSULA, KENT - An Archaeological Investigation of a Short-Wave Receiving Station by Derwin Gregory and Sarah Newsome.

Cooling Radio Station: ‘…the most advanced and technically complex radio ever built.’ (English Heritage Research Department Report Series No 110-2010) This vital communications link, between the US and British governments at the very highest level, operated from 1942 until the early 1960s. Although a transatlantic telegraph cable had been in use since 1866, there was no telephone cable until 90 years later, in 1956. An initial shortwave system was set up in 1929, but was of poor quality. The Post Office set up and ran Cooling Radio Station solely for the reception side of two way, shortwave, voice channels with the United States. Land was purchased in 1938 and the building was completed in 1939. The receiver used 1,079 valves and was considered to be the most complex radio built. It was connected to the adjacent MUSA (Multiple Unit Steerable Antenna) and could receive 4 incoming radio telephone channels. It was officially in use on the 1st July 1942. This may well have been because German intelligence services were able to break the scrambler / encryption device available in 1939. By 1943, Bell Laboratories in the US had developed SIGSALY, a far more secure scrambler system. (This system was so well screened and secure that German records captured at the end of WW2 showed that they were not aware that transmissions were person to person, direct voice contact.) SIGSALY was installed in the basement of Selfridges department store in Oxford Street with extensions to 10 Downing Street, the Cabinet War Rooms and the US Embassy amongst others. The US transmitter was located at Lawrenceville, New Jersey, while UK transmissions were made from Rugby to the US receiver at Manahawkin, New Jersey. For sources, see: English Heritage Research Department Report Series No 110-2010, ISSN 1749-8775, COOLING RADIO STATION, HOO PENINSULA, KENT - An Archaeological Investigation of a Short-Wave Receiving Station by Derwin Gregory and Sarah Newsome. A Multiple Unit Steerable Antenna for Short-Wave Reception by H. T. Friis and C.B. Feldman, Bell System Technical Journal 16, 3rd July 1937. https://archive.org/stream/bstj16-3-337#page/n0/mode/2up A Single Sideband Musa Receiving System for Commercial Operation on Transatlantic Radio Telephone Circuits by F. A. Polkinghorn, Bell System Technical Journal 19, 2nd April 1940. https://archive.org/stream/bstj19-2-306#page/n0/mode/2up https://en.wikipedia.org/wiki/SIGSALY

Cooling Station Y radio direction finding post was located in the field here, between August 1939 and November 1942. A small plot of land was purchased by the Admiralty in 1938 on the pretext of building an experimental radio station. The site was actually one of a number around the country listening for radio signals from German U boats to get a position fix on them.