Aspidistra (transmitter)

Coordinates: 51°2′33.70″N 0°6′15.15″E / 51.0426944°N 0.1042083°E / 51.0426944; 0.1042083

Logo of the Aspidistra broadcasting station

Aspidistra was a British medium wave radio transmitter used for black propaganda and military deception purposes against Nazi Germany during World War II. At one time, it was the most powerful broadcast transmitter in the world. (The contemporary German Goliath transmitter was more powerful, but used only for radiotelegraphy.) Its name - after the popular foliage houseplant - was inspired by the comic song The Biggest Aspidistra in the World, best known as sung by Gracie Fields.

The transmitter was installed in 1942 at a purpose-built site near Crowborough in southeast England. This was equipped with other medium wave and short wave transmitters, which also used the Aspidistra name, being known as ASPI 2, ASPI 3, ASPI 4, etc. However, when the name Aspidistra was used on its own it always referred to the original medium wave transmitter (ASPI 1).

After the war, Aspidistra and other transmitters at Crowborough were used for BBC External Service broadcasts to Europe. The station closed in 1982.

Equipment and location

Aspidistra broadcast on medium wave AM with 600 kW of power. The transmitter (originally 500 kW) had been built by RCA for WJZ radio in Newark, New Jersey. But at the prompting of Congress spurred on by competition,[1] the Federal Communications Commission later imposed a 50-kW power limit on all US stations. RCA was therefore glad to sell it overseas and the British Secret Service bought it for £165,000.

In addition to its high power, Aspidistra could be re-tuned quickly to a new frequency (position on the dial). This was of great use in its secret wartime work and was unusual for a medium wave transmitter, as they generally operate on a fixed frequency throughout their working life.

Its antenna was three guyed masts, each 110 m (360 ft) tall. The 1940s Art Deco style transmitter building was in an underground shelter which had been excavated by a Canadian army construction unit. Power for the transmitter was supplied from a single large Crossley-Premier 16 cylinder heavy oil engine.[2]

The facility was at King's Standing, Maresfield, in the Ashdown Forest, near Crowborough, Sussex. The RCA transmitter used 3 class B modulators in parallel feeding 3 parallel 170 Kw (nominal) Power Amplifiers (PA's), one modulator dedicated to a specific PA. The PA units were operated in class C using 4 water cooled GL898 valves in each PA, 4 were also used in each modulator. the output of these PA's used a series combining scheme to feed the RF power into a 100ohm co-ax line. This fed the main mast, the other two being parasitic and providing the directional element necessary as the purpose was to get the maximum signal eastwards into Europe.


Alongside the original Aspidistra, other medium wave and short wave transmitters were installed over the years. These included two Doherty 250 kW medium wave units, whose outputs could be combined to give 500 kW on a single frequency.[3]

Two 100 kW short wave transmitters made by General Electric (USA) operated at the Crowborough site from 1943 until the 1980s.[4]

Wartime operations

Aspidistra went into service on 8 November 1942, and was in operation throughout the remainder of the war.

Impersonation

Main article: Operation Corona

Starting in 1943, Aspidistra was used to disrupt German night fighter operations against Allied bombers over Germany. German radar stations broadcast the movements of the bomber streams en route to targets during RAF Bomber Command's Battle of Berlin. As part of their strategies to misdirect the German fighters, German-speaking RAF operators impersonated these German ground control operators, sending fake instructions to the night fighters. They directed the night fighters to land or to move to the wrong sectors. This interference to enemy RT and WT was known as "Dartboard"[5] As German operational procedures changed to prevent impersonation so the British copied them, bringing in WAAFs when the Germans used female operators.[6]

Black propaganda

Aspidistra was also used for black propaganda operations, in which the propaganda material is issued from a disguised source. These activities were under the Political Warfare Executive, and directed by Sefton Delmer.

In particular, Aspidistra aired the broadcasts of Atlantiksender and Soldatensender Calais, which posed as official German military radio stations in France.[7]

Intrusion operations

During Allied air raids, German radio transmitters in target areas were switched off to prevent their use as navigational aids by the enemy. However, such transmitters were very often connected into a network, and broadcast the same content as other transmitters which were not switched off.

When a targeted transmitter switched off, Aspidistra began transmitting on its frequency, initially retransmitting the German network broadcast as received from an active station. This would cause German listeners to believe the original station was still broadcasting. Aspidistra operators would then insert demoralizing false content and pro-Allied propaganda into the broadcast. This content was considered especially effective, as it appeared to be coming from official German sources.

These intrusion operations were an early example of a "man in the middle attack".

The first such intrusion was carried out on 25 March 1945. On 30 March 1945 Aspidistra intruded on the Berlin and Hamburg stations, warning that the Allies were trying to spread confusion by sending false telephone messages from occupied towns to unoccupied towns. On 8 April 1945 "Aspidistra" intruded on the Hamburg and Leipzig stations to warn of forged banknotes in circulation. On 9 April 1945 there were announcements encouraging people to evacuate to seven bomb-free zones in central and southern Germany. All these announcements were false.

German radio stations tried announcing "The enemy is broadcasting counterfeit instructions on our frequencies. Do not be misled by them. Here is an official announcement of the Reich authority." However, Aspidistra broadcasts included similar announcements, leaving the listeners confused.[8]

Post-war operations

Although mainly intended for the military and propaganda transmissions described above, Aspidistra was also used during the war for some BBC broadcasts to Europe. After 1945, Aspidistra was used exclusively by the BBC. Frequencies used included 1122 kHz (1945-1950), 1340 kHz (1950-1962), 809 kHz (until 1978), 1295 kHz (1962-1978) and 1088 kHz (1972-1978). After reorganisation of the medium wave band in 1978, the frequencies used were 648 and 1296 kHz.[9]

From 1978, there was a phased transfer of Aspidistra's broadcasts to a new Foreign Office transmitting station at Orfordness on the Suffolk coast, which was better placed than Crowborough, which is inland.

Despite its exclusive post-war use by the BBC, the Crowborough station remained formally in the hands of the Foreign Office (from 1968, the Foreign and Commonwealth Office, FCO), and its staff were members of the Diplomatic Wireless Service (later known as the FCO's Communications Department and then the Communications Engineering Department) rather than the BBC.

Closure and fate

Aspidistra made its final transmission on 28 September 1982, the honour of pressing the "off" key for the last time going to Harold Robin, the Foreign Office engineer who had been responsible 40 years earlier for purchasing the transmitter in the USA and setting up the station at Crowborough.

The station was dismantled in 1984. Two years later, following extensive modifications, the bunker that housed the Aspidistra transmitter was commissioned by the Home Office as one of the 17 sites in England and Wales to be used as seats of regional government in the event of a nuclear attack.[10]

From 1988, Sussex Police used parts of the site, purchasing all of it in 1996 for use as a training facility.[11]

In 2007, Building No. 3 (known as "the cinema" because of its design similarities with pre-war Art Deco cinemas), which had once housed ASPI 3 and ASPI 6, was designated a Grade II listed structure because of its historic and architectural interest. The designation notes that it is "a remarkably intact and unaltered building through which one can understand its function as an early 1940s transmitter hall".[12]

A reported offer to donate the Aspidistra transmitter to London's Science Museum was not taken up and it was scrapped. A number of valves (tubes) and a large tuning coil were saved by FCO engineers and are now on display in the foyer of the Orfordness station.[13] A notice there says:

One of three RF output coupling coils from the Aspidistra 1 transmitter at Crowborough in Sussex.
ASP1 was a 600 kW medium wave transmitter which was installed and commissioned with great urgency by Harold Robin during the spring and summer of 1942 and which commenced broadcasting on 8 November 1942. The transmitter was in continuous service for the next 40 years, carrying "black" propaganda to the enemy in wartime and BBC External Services to Europe in peacetime. It ceased regular transmissions on 28 September 1982 and its services were transferred to Orfordness. It was dismantled in May 1984.
This coil is preserved as a memento of a transmitter which played a large part in the wartime activities of the Political Warfare Executive. In peacetime it became part of the expanding broadcast transmission facilities provided for the External Services of the BBC by the Diplomatic Wireless Service - now the Communications Engineering Department of the Foreign and Commonwealth Office.
October 1984

Notes and references

  1. ↑ WLW 500kW - and no Limiter! Some of the biography of forgotten visionary Powel Crosley, Jr., and his 500kW Super Station of 1934
  2. ↑ Bryan 'Bob' Boyle (2000). The Napier Way. Bookmarque Publishing. pp. 193, 197. ISBN 1-870519-57-4.
  3. ↑ Tricks of the Trade: Aspidistra and OSE5 Article by Dave Porter and Andy Matheson in Signal magazine, issue 12
  4. ↑ Transmitter Documentation Project Short wave radio transmittters in the UK
  5. ↑ http://www.rafupwood.co.uk/radarandradio.html
  6. ↑ http://www.bletchleypark.org.uk/content/archive/feb1944.rhtm
  7. ↑ Brown, Anthony Cave (1976). The Secret War Report of the OSS. Berkeley. ISBN 978-0-425-03253-4. Its high power and ability to rapidly switch frequency made it extremely useful for such activities; its power output alone gave it a reach well into Europe with a signal clarity that frequently confused German listeners, who thought it might be broadcasting from a local source.
  8. ↑ Rowen, Robert (18 April 2003). "Gray and Black Propaganda Against Nazi Germany". New York Military Affairs Symposium.
  9. ↑ Development of the BBC A.M. transmitter network Clive McCarthy, Revision 6a, May 2007
  10. ↑ The Biggest Aspidistra in Crowborough
  11. ↑ "Kingstanding installation". Sussex police.
  12. ↑ "Building No. 3 ('the Cinema'), Former King's Standing Radio Communications and Transmitter Station, Maresfield" British Listed Buildings
  13. ↑ Interview in 2003 with Andy Matheson, then manager of the Orfordness station, who had formerly worked at Crowborough

External links

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