Y - stations Y - stations were British Signals Intelligence collection sites initially established during World War I and later used during World War II . These sites were operated by a range of agencies including the Army , Navy and RAF plus the Foreign Office ( MI6 and MI5 ) , General Post Office and Marconi Company receiving stations ashore and afloat . The " Y " stations tended to be of two types , Interception and Direction Finding . Sometimes both functions were operated at the same site with the direction finding ( D / F ) hut being a few hundred metres away from the main interception building because of the need to minimise interference . These sites collected traffic which was then either analysed locally or if encrypted passed for processing initially to Admiralty Room 40 in London and during World War II to the Government Code and Cypher School established at Bletchley Park in Buckinghamshire . In World War II a large house called " Arkley View " on the outskirts of Barnet acted as a data collection centre at which traffic was collated and passed to Bletchley Park , it also acted as a " Y " station . Many amateur ( " ham " ) radio operators supported the work of the " Y " stations , being enrolled as " Voluntary Interceptors " . Much of the traffic intercepted by the " Y " stations was recorded by hand and sent to Bletchley on paper by motorcycle couriers or , later , by teleprinter over post office land line s . The term was also used for similar stations attached to the Intelligence Corps ' India outpost , the Wireless Experimental Centre ( W . E . C . ) outside Delhi . Direction finding Y stations . In addition to wireless interception , specially constructed Y stations also undertook direction finding on enemy wireless transmissions . This became particularly important in the Battle of the Atlantic ( 1939 – 1945 ) where locating U - boats became a critical issue . Admiral Dönitz told his commanders that they could not be located if they limited their wireless transmissions to under 30 seconds , but skilled d / f operators were able to locate the origin of their signals in as little as 6 seconds . The design of land based d / f stations preferred by the allies in World War II was the U - Adcock system , which consisted of a small , central operators hut surrounded by four 10 m high vertical aerial poles usually placed at the four compass point s . Aerial feeders ran underground and came up in the centre of the hut and were connected to a direction finding goniometer and a wireless receiver that allowed the bearing of the signal source to be measured . In the UK some operators were located in an underground metal tank . These stations were usually located in remote places , often in the middle of farmers ' fields . Traces of World War II d / f stations can be seen as circles in the fields surrounding the village of Goonhavern in Cornwall . Beeston Bump “ Y ” Station . During the Second World War Beeston Bump was the location of one of the top secret listening stations . The concrete remnants of this top secret facility can still be seen on the summit of the hill . The remains consist of an octagonal concrete base that measures 3850mm across with a channel running west to east across the middle . On the southern edge of the octagon is a raised area of concrete which is 225mm higher than the rest of the base . Around the edge of the octagon are the remnants of what was one a reinforced parapet which has long been removed . There are also signs of a fletton brick wall running westward away from the raised area . During an episode of the BBC1 series " Coast " Joy Hale , a former WREN operator at the station , was interviewed . The octagonal shape of the base indicates that a direction - finding station operator ' s hut stood there . It would have consisted of a double - skinned wooden structure in which the cavity was filled with shingle designed to make them " splinter proof " or " bulletproof " . Two Y stations were operated in Sheringham in World War II , one run by the RAF and the other by the Navy .