Towers of the Swingate Chain Home radar site stand before the clouds.

Swingate Chain Home Radar Station

Chain Home Radar

Chain Home radar towers

The Swingate Chain Home radar station was built in the late 1930s and used heavily during World War II. It was part of the Chain Home network of early radar systems. Elements of the Chain Home network remained in service through 1955. Wikipedia has a list of Chain Home sites.

The transmitting array was formed of wire strung between 110 meter towers with a beamwidth of about 100°. The receiving array was a pair of antennas on towers about 70-75 meters high and at right angles to each other. Range was measured by time delay of the echo, azimuth by relative strength of signals at the two receive antennas. Elevation was measured by comparison to a second pair of receive antennas closer to the ground, at least where local terrain allowed. The tower at BAE Systems at Great Baddow in Essex, which originally stood at Canewdown, is said to be the only Chain Home tower still in its original, unmodified form.

The data from the Chain Home network and others was collected in a facility in tunnels carved into the White Cliffs overlooking the Dover Harbor.

Abandoned tunnels first excavated in the cliffs during the Napoleanic Wars were converted into a naval facility starting in 1939, and they were further extended following the fall of France in 1940.

That naval facility became the new Combined Operations Headquarters for the Royal Navy, Royal Air Force and the Army, jointly charged with protecting the Straits of Dover and the coast of Kent. Sensor data including radar was collected, organized, and analyzed, and commands for intercept fighter missions and artillery fire were then issued. See my other page for more details and pictures of that facility, now partially open to the public.

World War II radar systems included the following. The Chain Home system operated at relatively low frequency, in the high HF through low VHF range. It ran relatively high power.

WWII Radar Systems
Country, first use System Number built Max Range Peak Power Frequency Pulse Length, μsec PRF, Hz Use
U.K. 1937 Chain Home ? 100 km 350—750 kW 20—46 MHz 5—45 12.5, 25, 50 Early warning
U.S. 1940 SCR-270 930 240 km 100 kW 106 MHz 10—20 625 Early warning
U.S. 1941 SCR-268 3100 37 km 50—75 kW 195—215 MHz 5 4098 Anti aircraft
U.S. 1944 SCR-584 1600 29—55 km 300 kW 2700—2900 MHz 0.8 1707 Anti aircraft
Germany 1938 Freya >1000 160 km 20 kW 57—187 MHz 3 500 Early warning
Germany 1940 Würzburg Model D 3000—4000 20-30 km 7—11 kW 483—566 MHz 2.0 3750 Anti aircraft
Germany 1940 Giant Würzburg 1500 40-60 km 7—11 kW 517—566 MHz 2.0 1875 Anti aircraft
Germany 1942 Mannheim 400 25-40 km 15—20 kW 483—566 MHz 1.5 3570 Anti aircraft
Japan 1942 Tachi-6 350 300 km ? 68—80 MHz 25—30 500, 1000 Early warning
Japan 1943 Tachi-1 30 17 km 5 kW 200 MHz 2.0 1000 Anti aircraft
Japan 1945 Tachi-31 70 35 km 50 kW 187—214 MHz N/A N/A Anti aircraft
All anti-aircraft radars were also used for searchlight control, except for Giant Würzburg and SCR-584. Giant Würzburg was also used for night fighter control. From IEEE Spectrum, Aug 1987, referencing "The History of U.S. Electronic Warfare" by Alfred Price for German and Japanese systems; the Historical Electronics Museum and "Radar: A Reluctant Miracle" by John B McKinney for U.S. systems; and "Technical History of the Beginnings of Radar" by S.S. Swords for the U.K. See my other page for pictures from my visit to the Historical Electronics Museum.

The Swingate station is adjacent to the World War I Swingate airfield. The airfield was used after World War II and throughout the Cold War as a Royal Observer Corps (ROC) base, a hardened facility to monitor and locate nuclear detonations.

The ROC was formed in 1925 and lasted through the end of 1995. It was staffed mainly by civilian spare-time volunteers who wore a Royal Air Force style uniform and who eventually came under the administrative control of RAF Strike Command and operational control of the Home Office.

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The Cold War era ROC posts were hardened against nuclear blast effects and radiation. 870 underground monitoring posts were constructed roughly ten miles apart all over Britain and Northern Island in 1960-1968. The posts were excavated down to twenty-five feet, a reinforced concrete structure was poured and waterproofed, and the whole thing covered by a compacted soil mound. The post was entered down vertical shaft with a steel ladder. The post consisted of one main room for work and accommodation plus a separate toilet compartment. Air was circulated from ventilators at both ends, and electricity was provided from a 12 V battery system periodically recharged by a portable generator. Instrumentation included:

Communication links were buried landlines. For more on the ROC see the Subterranea Britannica web site and the Wikipedia article on the Royal Observer Corps.

If you are interested in recent history and an antenna geek (I have a ham radio license), this seems like a perfectly reasonable tourist attraction...

Below are some maps from the extremely useful U.K. Ordnance Survey site. First, Dover's relative location along the coastline in Kent:

Dover and the Kent coast.
Dover and the nearby coast.

Below at left: 1:50,000, and at right, 1:25,000 maps. The castle is immediately north and overlooking the center of the harbor. If you arrive by train, see Priory Station in the 1:50,000 map. The Swingate Chain Home radar site is shown as two or three radio masts to the north-east of the castle. It's marked on the 1:25,000 map as "W T Sta" for "Wireless Telegraphy Station". "C G Sta", or "Coast Guard Station", is a relatively smaller facility near the edge of the cliffs.

Dover and its harbor.
Dover.

A cluster of smaller antennas is 500 to 600 meters to the north-east of the prominent site, almost due north of the Coast Guard station.

Dover and the Chain Home antenna locations.
Dover and the Chain Home antenna locations.
Dover White Cliffs, and a hiking path.

There are some great hikes along the White Cliffs in either direction out of Dover.

This is along the White Cliffs Path, along the 16.6 km segment from Walmer to Dover.

The White Cliffs are up to 110 meters tall. They're made up of soft, white, very fine-grained chalk formed mainly from the calcium carbonate from coccolithophores, single-celled planktonic algae whose remains sank to the bottom of the sea during the Cretaceous period, which was 145-66 million years ago. There are some streaks of black flint within the chalk.

The chalk was part of a land bridge joining what is now southeastern Britain to northern France. Two major floods, about 425,000 and 225,000 years ago, cut through the chalk and started the formation of what the English call the Strait of Dover within the English Channel, and the French call Pas de Calais within la Manche.

The chalk is soft, and erodes at a rate of about one centimeter per year on average. That's the overall average, large chunks collapse from time to time. Don't get too close to the edge!

Dover White Cliffs, a lighthouse, and the Marconi site.

South Foreland lighthouse is near the edge of the cliff, overlooking some Second World War observation posts.

On 24 Dec 1898 Guglielmo Marconi made the first shore-to-ship and international radio contacts from here, with a ship in the Channel and with a station in Wimereux, France

Chain Home WWII radar towers.

Here I am approaching the Chain Home station from the south-west. The station is located approximately at UK Grid location TR 334 428 and is clearly shown on Ordnance Survey maps.

Chain Home WWII radar towers.

At right is a view from the road immediately to the south of the Chain Home site.

Chain Home WWII radar towers and remains of some runways.

At left is a view across the end of the WWI airbase. You can see the remains of some asphalt runways.

Chain Home WWII radar towers and a WWI air base.

At right is a view across the end of the WWI airbase.

Chain Home WWII radar towers, and Cold War communications sites.

This picture is zoomed to show the odd mesh pyramid and the multiple layers of fence and berms.

Chain Home WWII radar towers with modern UHF and microwave antennas.

This picture is zoomed to show the various UHF and microwave antennas still in use on the towers.

Chain Home WWII radar towers, and the ROC nuclear watch bunkers from the Cold War.

A view across the former airfield. I think that the ROC nuclear watch facility was in the bunkers at right in the distance.

Chain Home WWII radar towers, and the ROC nuclear watch bunkers from the Cold War.

We're looking across the former airfield toward the assumed ROC facility. Notice the remaining concrete in the pictures at right and below.

Chain Home WWII radar towers, WWI air base, and the ROC nuclear watch bunkers from the Cold War.

Looking across the former airfield toward the Chain Home station.

Chain Home WWII radar towers, WWI air base, and the ROC nuclear watch bunkers from the Cold War.

Looking across the former airfield toward the Chain Home station.

Chain Home WWII radar towers, WWI air base, and the ROC nuclear watch bunkers from the Cold War.

Looking across the former airfield toward the Chain Home station.

ROC nuclear watch bunkers from the Cold War, used until the early 1990s.

Here is the facility that I think is the former ROC nuclear watch station. The ROC sites were largely in use until the early 1990s.