Accessed
"Radar Mostly" is a presentation, with vivid demonstrations of the scientific principles involved, on the history of the development of radar in England and Germany before and during World War II. Richard Brett-Knowles spent much of the War as a junior scientific officer at TRE (the Telecommunications Research Establishment in Malvern) where most British radar development took place. He also spent some time in occupied Europe engaged in intelligence work to discover the principles of German radar systems. Most of his professional career was spent working on radar and related systems. Although he is based in England Mr. Brett-Knowles is prepared to give this presentation anywhere in the World, provided his travel expenses are covered.
The introduction discusses the events which led to the British development of an operational radar system. After explaining the acronym "RADAR", echo ranging is demonstrated using audible sound. This is preferable to radio for a demonstration, since the sound and its reflection can be observed directly. Where necessary the lecture digresses at this point to discuss, and demonstrate, the cathode ray oscilloscope and -where time allows, digresses further to demonstrate the use of scanning in the production of a TV picture on a cathode ray tube.
The main thread continues with a demonstration, again using sound, of a "passive" radar system, similar to the German "Heidelberg" system which used signals from British radar systems to detect British aircraft.
It is not practicable to use sound to demonstrate PPI radar so this is demonstrated using a video recording. (PPI = Plan Position Indicator - this is the name of systems where radar is used to produce a map.)
The principles of thermionic valves are demonstrated (one is used as a DC amplifier to light a lamp bulb). A 3 metre oscillator using two such valves is demonstrated. One of the British breakthroughs in the development of radar was the magnetron, a specially designed vacuum tube which can produce very large amounts of power at very high frequencies. During WWII it revolutionised radar systems. Today, although still used in radar, it is commoner in microwave ovens. Magnetrons are discussed briefly and a low-power 3 cm CW magnetron is demonstrated in operation.
The low-level power needed for the demonstration of 3 cm döppler radar (similar to that used in radar speed traps) is generated with modern solid-state oscillator, a Gunn diode. This leads, briefly, to the discussion of detection and the superhet. The Gunn diode radar demonstration ends with illustrations of the use of polarisation to distinguish between rain drops and a target aircraft, and the use of small pieces of aluminium foil, or "chaff", to confuse radar.
The final active demonstration shows how, although light and radar travel in straight lines, it is possible to use the ionospheric reflection of longer electromagnetic radiation (short waves at [roughly] 3-30 MHz) to communicate around the World.
To close the lecture there is a display of the components used in radar, showing just how much the technology has developed over the last five decades.
In summary, "Radar Mostly" consists of a series of spectacular demonstrations with explanation appropriate to the audience. On different occasions it has been delivered at Preparatory Schools and Universities and at almost all levels between.
Richard Brett-Knowles died in early 2015. This web-page remains for reference, but of course the lecture is no longer available.
This is a page on James Bryant's Web-site.
Return to James Bryant's Home Page
Last modified
Number of visits to this page:
KEYWORDS FOR SEARCHES: lecture lecturer T.R.E. TRE Telecommunications Research Establishment Malvern R.R.E. RRE Royal Radar Establishment Malvern World War II WWII Second World War history of radar science science education scientific education technology history of technology scientific entertainment