Picking up good vibrations

Share this article: Share Tweet Share Share Share Email Share

During World War II the Cape sea route was strategically important to the British war effort and the British government encouraged Commonwealth and Allied governments to develop technology to detect and destroy enemy surface ships and submarines. By 1935 two British scientists had proved that radar was feasible. The meaning of “radar” is a radio wave-based electronic system for determining the direction and distance of objects. Pulses of radio waves are sent from a transmitter, bounced off a target object and reflected back to the transmitter. By measuring the time it takes for the reflected waves to return, the object’s exact distance can be calculated.

In other words, two radar stations targeting the same object can accurately determine its exact location by triangulation.

South African scientists were briefed by British radar experts and encouraged to develop their own equipment.

A dedicated corps of South African engineers and scientists subsequently made a significant contribution to the war effort.

The first experimental radar set in South Africa, JB1 Radar Transmitter, was built in 1939 by a team under the leadership of Dr Basil Schonland at the University of the Witwatersrand in Joburg, later formed into the South African Corps of Signals.

They developed a transmitter, initially using components available from amateur radio shops, which operated at a frequency of 90MHz with a peak power of 5KW in a 20-microsecond pulse. It proved to be highly successful.

An improved version of the JB1 transmitter was subsequently developed and saw service, not only in South Africa but also in East and North Africa.

Although the maximum frequency and power of this unit was limited by the radio valves available locally during World War II, it outperformed the larger and more cumbersome British radar units on the battlefield and was used throughout the war.

After World War II, South Africans continued to make significant contributions to radio technology.

One of South Africa’s most prolific inventors was Dr Trevor Wadley, who was born in Durban in 1920.

He served in the Signals Corps in England during World War II, and made several major contributions to the design of radar equipment.

Wadley joined the Telecommunications Research Laboratory (TRL) of the CSIR in Joburg in 1946, where he perfected the Wadley Loop Receiver, a unique circuit for cancelling frequency drift.

While working for the TRL, Wadley also developed one of the first practical broadband radios in the world, the Barlow-Wadley Broadband Radio (1947).

In 1947 he invented an improved Ionosonde, a device for probing the ionosphere with radio waves.

In 1948 Wadley stunned the telecommunications world by inventing the first crystal-controlled radio in the world, based on the Wadley Loop.

It could be accurately and consistently set to any frequency between 0 and 30 MHz, and avoided the “fading” that was typical of most of its competitors.

This was achieved using a single 1 MHz crystal and some clever circuitry.

Wadley’s All-Wave Communications Receiver was made by Racal in the UK and became the standard high frequency radio for the British Navy for many years.

A special model was designed by Wadley for the South African Post Office.

In 1958, Wadley designed a transistorised version of this radio, called the Wadley Transistorised Receiver.

This model was cheaper to construct than the valve versions, and became a best seller internationally.

One version, the Barlow-Wadley XCR30n (1958), was manufactured by Barlows SA and became popular among amateur radio enthusiasts worldwide.

In 1960 Wadley developed a Rack-Mounted Wadley Receiver, which was made by Racal in the UK for professional telecommunications, military, civil defence and broadcasting applications.

This famous receiver was used by the BBC for transcontinental commercial radio broadcasts between London and South Africa in the 1960s.

l Mike Bruton was the founding director of the Cape Town Science Centre and is director of imagineering at MTE Studios. He wrote Great South African Inventions (Cambridge University Press). - Cape Argus