The Idea of Radar
When Heinrich Hertz was carrying out his experiments on radio waves, he noticed that surrounding objects interfered with his radio waves. At the turn of the century, the phenomena of this interference was well enough known for scientists to theorize how to use this interference. In 1900, Nikola Tesla suggested a wireless system which would use reflected radio waves to locate objects and even to measure their distance. Tesla explained the concept of radar as:
“When we raise the voice and hear an echo in reply, we know that the sound of the voice must have reached a distant wall or boundary, and must have been reflected from the same. Exactly as the sound, so an electrical wave is reflected, and the same evidence can be used to determine the relative position or course of a moving object such as a vessel at sea.”
Unfortunately, Tesla was considered an anarchist and was never given funding for his ideas. His ideas were forgotten, only to be rediscovered time and time again in years to come.
As with any revolutionary theory, technical obstacles existed which had to be overcome in order to prove the validity of the concept. At the turn of the century radio suffered from the inability to generate sufficient signal power and amplify the faint signals received. The invention of the electron tube in 1904 provided the means to amplify the weak radio signals received on antennas and create increasingly more powerful radio transmitters. An equally important variant of the electron tube was the invention of the cathode ray tube in 1897 by the German, Karl F. Braun, who perfected the technique of presenting electronic beams on fluorescent-coated glass.
Incredibly, in 1904 a German inventor, Christian Hülsmeyer, was granted a British patent for a telemobiloscope, which was a “hertzian-wave projecting and receiving apparatus…to give warning of the presence of a metallic body such as a ship or a train.” On the morning of 10 May 1904, at the Rhine bridge in Cologne, he successfully demonstrated his apparatus. With rave reviews from the press, technical representatives from various shipping companies observed a convincing display of this new technology. He proved that a ship fitted with this system of transmitter and receiver could locate another ship and inform the captain of the approach of another vessel up to 5 kilometres away.
The shipping company representatives were enthusiastic, but hesitant to invest in this new technology and afraid of violating previous agreements with the Marconi Company. The shipping companies had trouble differentiating between wireless directional finding versus the idea of radio detection. In their minds it seemed to be spending twice for the same results. Hülsmeyer also sought the financial backing of the German Navy only to be rebuffed by Admiral von Tirpitz’s reply of, “Not interested. My people have better ideas!”. Only after a personal expenditure of 25,000 Marks and approaching bankruptcy did he abandon his idea to pursue more financially rewarding work.
What is important about this is the fact that as early as 1904 the concept of radar was demonstrated and patented. Hülsmeyer’s techniques revealed modern concepts which would not be rediscovered for another thirty years. His idea of mounting the assembly on the foremast of a ship to measure the range and bearing of an object did not reappear until the Second World War. It is also interesting to reflect how this invention would have changed history in the instance of the loss of the passenger ship Titanic and the World War I naval battle of Jutland.
Early Military Use of Radio At Sea
From the initial discovery of radio, navies were immediately interested in it as a way to revolutionize naval operations. Both Marconi and Telefunken worked on naval contracts to support their new businesses. By 1903 Marconi had reached an 11 year agreement with the British Admiralty for the use of his system, and one year later Telefunken had already installed 75 radio sets on German navy ships and at 11 naval coastal stations. The use of radio was considered to be revolutionary, but the navies did not appreciated the full range of its worth in naval combat. It was easy to appreciate its use as a ship to ship and ship to shore communication aid, but its effect on naval command and control was less well understood.
It was immediately clear that naval actions did not have to be coordinated with visual signals; but more importantly, land-based command could now stay in touch with the fleet and participate in offshore naval actions. This shore-based command and control gave a rebirth to the fields of cryptography and code breaking. Now, battles hung on the ability of how well one could decipher the other’s messages and the new methods of directional finding radios. This was the birth of signals intelligence.
At the beginning of the First World War, both Germany and England were leaders in radio technology. Both countries had built powerful home and overseas radio stations and realized the strategic value of the technology. In 1914, Britain started to build a chain of radio direction-finding stations around the country. This allowed the British to intercept and plot bearings and positions of unknown transmissions. The British were able to locate transmissions within a 10 kilometre box, and clandestinely operated a radio locating station in Oslo to get a better fix on the German naval ships in Kiel and Wilhelmshaven. The Germans on the other hand had developed an extensive system of radio-based command and control for their fleet operations. This radio traffic combined with British signals intelligence proved the key to keeping the German navy bottled up. The British fleet relied on critical, time sensitive, warning of the German fleet moving early enough to mass their own fleet decisively against them. Signals intelligence was so good that the British Admiral was briefed on the exact location of the German flagship every morning. Signals intelligence alerted the British fleet to sortie at just the right moment to thwart a breakout of the German fleet during of the battle of Jutand in May of 1916.
The Germans realized that their signals were being monitored, but they had trouble devising a way to limit the volume of radio traffic that accompanies a large fleet operation. The Germans, during the Battle of Jutland, experimented with radio deception by switching the flagship transmitter and transmitting false signals from port. The deception was successful, but the increased volume of transmissions still tipped the English off. The British, from their experience in World War I, saw the need for a sophisticated system of signals intelligence which was capable of breaking codes and tracking enemy movements through direction-finding stations. Signals intelligence was essential to British defence strategy which relied on sufficient early warning to sortie and mass the fleet (later aircraft) to counter enemy movements.
The role of radio in the great land battles of World War I is less well known. Unlike their naval counterparts, the British army did not embrace radio and preferred the cable linked telegraph system of the previous century. This is probably due to the army’s focus on maintaining small colonial garrisons and not on the problems associated with coordinating the movements of large continental armies. The Germans felt that radio could provide a dramatic advantage to a moving army which did not have to lay cable as it travelled. Unfortunately, the static trench warfare of the Western Front negated the advantages of radio and was perfect for the traditional establishment of a complex cable communications network, with the wireless relegated to the role of backup if the cable was severed.
On the eastern front, the German army’s use of wireless radio against the Russians on a more dynamic battlefield proved to be one of the key reasons for the Russian defeat. The Russians’ failure to use coded radio transmissions combined with quick coordinated movements by the German army led to the Russian defeats at Tannenberg and the Masurian Lakes.
In the Air
The use of aircraft and Zeppelins in World War I propelled the development of radio technology and created new applications. The size and length of the antennas of early wireless equipment relegated it to use only on large air vehicles, which could carry a radio operator and generate sufficient power. The Germans quickly saw the advantage of the combination of a Zeppelin and wireless radio for naval reconnaissance and for strategic bombing missions. The first use was to report intelligence and the second was radio navigation. The Germans quickly learned that accurate position information was vital to reconnaissance and night bombing missions. The Germans experimented with both ground and Zeppelin based locating equipment with varying degrees of accuracy. Fixes could be in error up to 100 kilometres due to their inability to correct for atmospheric conditions.
The British, on the other hand, realized that through their radio direction-finding stations they could track the movements of the Zeppelins and then launch intercept missions. During November of 1916, the British Marconi stations tracked and contributed to the destruction of a German Zeppelin over the Channel using the Zeppelin’s own transmissions.
Both countries learned valuable lessons from the radio in World War I. The British through their chain of radio direction-finding stations saw the value of tracking German fleet and aerial movements in order to coordinate defensive and offensive moves. The worth of signals intelligence to provide warning was equally highlighted. On the ground the British army missed the potential of radio in ground campaigns due to the stagnant nature of trench warfare. The use of radio on the Eastern Front confirmed the German army’s feeling that the wireless would be essential to mobile warfare and planted the seeds for Blitzkrieg doctrine. Both countries saw the need for radio telephony systems and developed it for their fighter aircraft.
Radio was a ubiquitous technology which was discounted, at times, as just a wireless telegraph or hailed as the key instrument to harness a nation’s military power in a revolutionary way. Signals intelligence performed many important military roles in the slower moving world of World War I and would continue to in the Second World War. Signals during World War I provided commanders with reliable positions of enemy fleets, tracked airborne bombers through their radio transmissions and provided critical intelligence. Radar in the Second World War would augment signals with precise short range tracking, but signals would continue to provide important intelligence on the enemy’s movements and intentions.
Radar would become the next logical step in the evolution of radio technology. The knowledge and theoretical basis for the building of radar existed prior to World War I and only needed someone’s desire to build it.