Appleton noticed that a "ghost image" sometimes appeared on the signals received from the 30-line Baird transmissions which were being broadcast by the BBC from Brookmans Park. From a television point of view this was just a nuisance, but for Appleton it was a useful experimental tool. He concluded that the two images had arrived via two separate routes, 'direct' and 'reflected from the ionosphere' the displacement distance between the two images on the screen related directly to the difference in the time of their arrival. It was therefore a simple process for Appleton to calculate how far the reflected signal had travelled from the object before reaching the screen (relating to the position of the ionosphere). The calculation was based on the number of picture elements between any identical feature on the 'direct' image and its counterpart on the reflected or 'ghost' image as shown in Figure 2 [7]. Later in 1931 Appleton progressed to using a pulsed emitter and CRT receivers, in place of the transmitted TV signal and a Televisor, but the principle was the same [8]. Fifty years later, the idea of television as a form of continuous-wave radar resurfaced in an article for children in a Christmas number of New Scientist [9].
Operational Radar and "Chain Home"
The detection of large objects by reflected radio waves was first documented in 1904 when Christian Hulsmeyer of Germany had used a spark gap pulsed transmitter to detect ships located several miles away, although he never managed to measure their range. By the early 1930s, much better results were being reported on the reflection of radio waves by moving objects, by organisations such as the U.S.Naval Research Laboratory in Washington and the Telefunken company in Germany [3,4]. These reports were buried in the patent literature and technical journals they did not grab the attention of the general public in the same way as television. Nor were governments much interested in radar from an operational point of view, until 1935.
In that year, Britain was the first country to start developing radar operationally. A government committee on air defence, chaired by Sir Henry Tizard, recommended the development of what was then known as radio-location. The project was given the code name Chain Home and it was led by Robert Watson Watt, a career civil servant who had worked on cathode ray tube direction-finding. Watson Watt had collaborated with Appleton in advising Baird Television Ltd. on cathode ray tubes in 1931.[5] Appleton himself joined the Tizard committee in late 1936 and he was then briefed on the Chain Home project, of which he had no previous knowledge.
A wall of secrecy surrounded the Chain Home project and the radar research station at Bawdsey Manor, near Felixstowe, directed by Watson Watt. In September 1936, he used a modified EMI-Marconi television receiver as a pulsed 25 image per second radar receiver on the B.B.C. television wavelength of 7.6 metres, for the first national trials of pulsed radar. Here again was a use of television in ranging, although this time the receiver came not from Baird Television Ltd. but from their successful rivals in the competition to provide the BBC’s first high-definition television service.
It is hard to pin down definite links between Baird Television Ltd. and the development of radar, but it is known that in the late 1930s one of the company’s consultants was Professor F.A. Lindemann, who had served on Tizard’s air defence committee and was Winston Churchill's scientific advisor.
Although the British public was unaware of radar, there were a few gaps in the wall of secrecy. In October 1936 the founder of the Luftwaffe, Erhard Milch, arrived in Britain on an official visit and alarmed his hosts by blandly asking them how their radiolocation project was coming along.[3,4] Two years later, at the time of the Munich crisis, the technical journal Television and Short Wave World published an editorial on "… a television system which could detect planes as far out as 200 miles" and further disclosing the British operating wavelengths for the system[10]. Perhaps this was a deliberate release of information with government approval equally, it may have been simply a security slip.
Radar Goes Public
Awareness of radar and its crucial role in World War II only reached the general public in 1945, as victory was achieved. Among the historical articles published at this time was one by R.L. Smith-Rose [11], head of the radio section in the National Physical Laboratory. He drew attention to Appleton's utilisation of CRTs [8] as being the basis of modern radar. This theme was not taken up by others and Appleton's name is just a footnote in the official radar histories, although his purely scientific work on the ionosphere was recognised when he received the Nobel prize in physics in 1947.
The name of Robert Watson Watt is firmly linked with radar in the public mind, not only as the leader of the operational team after 1935, but also as the inventor of radar. Watson Watt saw himself in this role when he appeared in 1951 before the The Royal Commission on Awards to Inventors. He received a tax-free award of £52,000, worth about £2 million in today's terms, but considerably less than the amount he had claimed. Moreover the RAF controller of patents denied that Watson Watt was the inventor of radar there was simply too much prior art in the area.
JLB had no public place in any of this. He had offered his services to the war effort in 1939, but no reply came [1] even though many former staff of Baird Television Ltd. were drawn into radar work. JLB spent the war years developing advanced systems of colour and stereoscopic television, at his own expense. In 1945, with his savings almost gone, he was busy starting a new television company for the post-war market. His diary for 1945 provides clues on his response to the radar disclosures. An entry on October 16 reads "secret patent radar" and a later entry reminds him to contact his patent agents for "radar renewals". In December an unsigned editorial in Wireless World [12] commented on the remarkable resemblance between patent GB 292,185 and the airborne radar system "H2S" which gave pilots images of the terrain they were flying over. The writer was probably the editor, N. Maybank, whose name appeared several times in JLB's diary at the time. It is open to speculation whether JLB would have gone on to press his claim in a more direct way, but he fell seriously ill in February 1946 and he died four months later, at the age of 57. For the next 25 years his reputation declined while a concerted effort was made to publicise the Marconi-EMI company's development of electronic television.[5]
Meanwhile a US Patent (R.H. Rines, US 2,696,522) for a scanned radar with an insulated particle screen had appeared in 1954 almost unnoticed. At the head of the list of prior art was Baird's 1930 US patent 1,699,270, the technical equivalent of GB 292,185. In his US patent, JLB had described the system as "extremely valuable in case the invention is used during a war, for instance, where it is desired to view the enemy's position without detection." Although the resolution of images deteriorates when reflected radio waves are used instead of light, the range of radio waves is far greater than that of light. Baird's radio wave version of the "noctovisor" in the mid 1920's therefore had great potential as a defense system. From this is can be argued that GB 292,185 could not operate with the same resolution as early television but rather it was designed as a form of radar.
Controversy --- and a challenge to NBTVA
It was not until the mid 1970s that the overlap between JLB's experiments and radar became generally known, through the researches of Dr. Peter Waddell. In 1979 Professor Russell Burns [13] described GB 292,185 as a "rudimentary form of radar". In 1986 McArthur and Waddell published their biography of JLB [3] and in 1990 they brought out a sequel [4] with new data pointing to definite links between JLB and radar. In the late 1990s Adrian Hills produced several publications and a CD under the auspices of the University of Strathclyde, linking JLB with radar [14]. However in 2000 a technical biography of JLB by Burns [15] flatly denied that JLB's work had anything to do with radar. In 2002 a further biography by Kamm and Baird [5] took the middle ground and tried to point out, for the non-technical readers, the areas of overlap between the two technologies. Within the past 3 years a series of articles in Transmission Lines, by Peter Waddell and Brandon Inglis, has presented new information some of which has been included in this short overview.
Although much historical work has been done and more is in progress, the controversy about the connections (or lack of them) between early television and early radar is unresolved. It is strange that no one since Appleton appears to have made any experimental observations in this area. Here is a challenge for NBTVA members who have unique practical expertise in JLB's early technology. The challenge is to reconstruct equipment as close as possible to the specifications in JLB's early patents and then evaluate it in terms of range, quality of images, etc.
The authors will be happy to answer questions of detail and provide copies of any of the cited papers or patents for NBTVA members who are seriously interested in taking up this challenge.
