Complete history of microwave technology (part 5). 1932 to 1939, discoveries by Sir Robert A. Waston-Watt (Radio Directional Finding), Dr. George C. Southworth, W. L. Barrow and Phillip Smith (The Smith Chart).

In 1932, Sir Robert A. Waston-Watt came up the idea of 'RDF', Radio Direction Finding. He wrote a paper (with A.F. Wilkins) describing this new technique of Radio Detection and Ranging giving it the code name of 'radar' in 1935. It was proved that the theory would work, but with a range of only eight miles using the state-of-the-art devices of the day. By the autumn of 1938, radar systems were in place along the south coast of Britain. Watson-Watt became scientific advisor to the British Air Ministry in 1940 and in 1941 went to the United States to set up radar systems there.

In addition, at Bell Telephone Labs in the 1930s, Dr. George C. Southworth discovered that radio waves could be transmitted efficiently through a hollow, water-filled copper pipe. He must have been a frustrated plumber. He and his team at Bell found that electromagnetic energy travelling through an enclosed structure moved in distinct patterns that we all know and love called 'modes', and that the optimum diameter for a wave-guide pipe was slightly greater than one-half wave length. They also experimented successfully with square, rectangular and oval wave-guides.

At the same time, W. L. Barrow had been studying antennas and reflectors of various shapes, which led him to experiment with hollow tubes. His successful propagation of waves through a tube 18 inches in diameter was published in May 1936. Today, the most common shape for wave-guides is rectangular, with dimensions about one-half wavelength by one-quarter wavelength at the center frequency.

By the end of the thirties, secret work was afoot in both the USA and the United Kingdom. At Bell Telephone's Radio Research Lab, Phillip Smith developed a circular chart form in 1939 that shows the entire universe of complex impedances in one convenient circle. The Smith Chart is still in wide use today.