Site Records

Site Name: Coldblow ACE HIGH relay station

Coldblow Lane
Thurnham, Kent
OS Grid Ref: TQ824585

Sub Brit site visit 9th January 2004

ACE HIGH is a tropospheric scatter/microwave link system which dates back to 1956, when SHAPE (Supreme Headquarters Allied Powers Europe) developed a plan for an exclusive communications system which would comprise the minimum essential circuits of early warning and alert and implementation of the 'tripwire' retaliation strike plan. The network, comprised 49 tropospheric scatter links and 40 line-of-sight microwave links, extending from northern Norway and through central Europe to eastern Turkey. The system had 570 voice, 260 telegraph and 60 data circuits.

Photo:Cold Blow ACE HIGH station before demolition of the dishes in 1985. The building and wooden mast in the foreground date from WW2.
Photo by Andy Emmerson

The principle of the tropospheric forward scatter system was to beam high-frequency signals against the troposphere (5 to 10 miles above the earth), pick up part of the reflected signal with highly sensitive receivers and beam it onward by the same means. This communications technique has many advantages. Its efficiency was not marred by atmospheric conditions; it had a computed circuit reliability of 99.9 per cent and signals could be transmitted in stages of from 50 to 250 miles. Reduction of the number of required relay stations through these longer stages also meant reduced operation and maintenance costs and personnel requirements.

With the development of new microwave at satellite communications technology in the 1980's, tropospheric scatter systems became redundant and the Ace High network was abandoned in the early 1990's

There were five sites in Britain:
  • Mossy Hill, Shetland Islands
  • Mormond Hill near Fraserburgh (Aberdeenshire)
  • Brizlee Wood near Alnwick (Northumberland)
  • Stenigot (Lincolnshire)
  • Coldblow near Detling (Kent)

The Ace High station at, Coldblow was located alongside an existing WW2 communications station on Coldblow Hill. The most prominent feature was two pairs of parabolic dish antenna, 60 feet in diameter supported on seven lattice steel girder legs. The transmitters, receivers and power supplies were located in a single storey brick building between the pairs of dishes. With the demise of the Ace High network the Coldblow station closed in the early 1980's was sold by auction in September 1986. The dishes, a local landmark, had been removed the previous year. A microwave tower on the site was retained by the Ministry of Defence and access rights to the tower were built into the sale agreement. The mast is currently used by the USAF in conjunction with the USAF radio stations at Dunkirk and Swingate in Kent.

Photo:From left to right standby set house with fuel tank compound, WW2 communications mast, portacabin/workshop, emergency water supply tank, transmitter building and behind it the current MOD site. The picture is taken from the roof of the dog kennels.
Photo by Nick Catford

Although the dishes were removed, all the buildings were retained and were included in the sale. By the time the site was sold for a second time in 2001 the main transmitter building had been wrecked by local vandals with a fire destroying a large section of the roof. The new owner has renovated the large standby set house which now houses a photographic studio and workshop now trading as 'The Radar Studio'

Plan of the Coldblow Ace High site

Most of the remaining buildings are unused and derelict. The owner considers the transmitter building is beyond economic repair and this will eventually be demolished. There are plans to build housing on the site.


For further information and pictures of the ACE HIGH relay station click here

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Last updated 23rd January 2004

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